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Fig. 3. Raman functional group indexes for the PB microstruc- ture of HIPS subjected to multiple processing: (Ml) trans-1,4; (O) cis-1,4; (@) vinyl-1,2.

Figure 3 Raman functional group indexes for the PB microstruc- ture of HIPS subjected to multiple processing: (Ml) trans-1,4; (O) cis-1,4; (@) vinyl-1,2.

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Figure 1.1. Plastic demand by end-use application sector in Western Europe, 2004 applicability of polymeric materials in wide markets [1]. Polymer demand in Western Europe has been continuously growing during the past decade, reaching a total demand volume of 43,50 million tonnes in 2004. In terms of end-use applications, packaging is by far the sector with highest polymer demand (37%), followed by building and construction applications (20%), automotive industry (7,5%) and electric and electronic equipment (7,5%); these results prove the versatility and applicability of polymeric materials in wide markets [1].
Figure 1.1. Plastic demand by end-use application sector in Western Europe, 2004 applicability of polymeric materials in wide markets [1]. Polymer demand in Western Europe has been continuously growing during the past decade, reaching a total demand volume of 43,50 million tonnes in 2004. In terms of end-use applications, packaging is by far the sector with highest polymer demand (37%), followed by building and construction applications (20%), automotive industry (7,5%) and electric and electronic equipment (7,5%); these results prove the versatility and applicability of polymeric materials in wide markets [1].
Figure 1.2. Plastic waste management options in terms of the life cycle of polymeric products The current environmental policy considers the material efficiency during service life and the reduction o f the environmental impact throughout their entire life cycle. Suitable waste management recovery options for plastic waste streams therefore contribute to the sustainable deve closing the mate opment of our societies taking into account a life cycle perspective, by rial and energetic life cycle loop and enhancing the conversion of waste materials into va uable resources (Fig. 1.2). The current environmental policy considers the material efficiency during service life and 1e dirrerent avaliable Options ror plastic waste recovery, 1n contraposition to lanadril sposal, include material recycling and energy recovery procedures. As a whole, recycling ocesses (mechanical and feedstock recycling) involve material recovery from plastic iste streams, whereas combustion procedures for heat production with controllec uissions are included into energy recovery options. Mechanical recycling consist: sically on the re-melting of plastic waste into new plastic products; this process can be tformed on homogeneous waste streams of on waste streams consisting on a mixture different plastic materials (mixed waste streams). By feedstock recycling, plastic waste: e cracked and depolymerised by chemical means into a series of petrochemica oducts or monomers, which can be later transformed again into new polymeri oducts by synthesis. Finally, energy recovery employs polymeric waste streams as fue ft energy production, since 1 tonne of plastic offers approximately the same amount o: ergy as 1 tonne of crude oil in the combustion process.
Figure 1.2. Plastic waste management options in terms of the life cycle of polymeric products The current environmental policy considers the material efficiency during service life and the reduction o f the environmental impact throughout their entire life cycle. Suitable waste management recovery options for plastic waste streams therefore contribute to the sustainable deve closing the mate opment of our societies taking into account a life cycle perspective, by rial and energetic life cycle loop and enhancing the conversion of waste materials into va uable resources (Fig. 1.2). The current environmental policy considers the material efficiency during service life and 1e dirrerent avaliable Options ror plastic waste recovery, 1n contraposition to lanadril sposal, include material recycling and energy recovery procedures. As a whole, recycling ocesses (mechanical and feedstock recycling) involve material recovery from plastic iste streams, whereas combustion procedures for heat production with controllec uissions are included into energy recovery options. Mechanical recycling consist: sically on the re-melting of plastic waste into new plastic products; this process can be tformed on homogeneous waste streams of on waste streams consisting on a mixture different plastic materials (mixed waste streams). By feedstock recycling, plastic waste: e cracked and depolymerised by chemical means into a series of petrochemica oducts or monomers, which can be later transformed again into new polymeri oducts by synthesis. Finally, energy recovery employs polymeric waste streams as fue ft energy production, since 1 tonne of plastic offers approximately the same amount o: ergy as 1 tonne of crude oil in the combustion process.
Figure 1.3. Evolution of plastic recovery options and total post-consumer plastic waste volume The rate of plastic waste recovery has been continuously increasing since the mid-90’s due to the implantation of mechanical recycling and energy recovery facilities all over Europe; feedstock recycling remains still as a minor alternative. As a result of thes developments and despite the increasing post-use plastic waste volumes, the amount o: residual waste sent to landfill disposal seems to have stabilised. Decoupling between th« volume of plastic consumption and the associated amount of residue generation i currently being achieved in the countries with a developed waste managemen infrastructure [1]. Figure 1.3 proves this progressive decoupling between the plastic wast growth and the volume sent to disposal, due to enhanced plastic waste recovery options. erowth and the volume sent to disposal, due to enhanced plastic waste recovery options. Analysing plastic recovery by end-use applications [3], the largest volume of recoverec plastic waste corresponds to municipal solid waste, with a total volume of 5.45 MTonne: in 2002. Sectors like agricultural applications exhibit the highest recovery rates (ove: 50%), though with lower waste volumes. However, the automotive sector and electrica and electronic equipment showed lower plastic recovery rates in 2002; this situation i: expected to be continuously improving due to the implementation of the corresponding European Directive 2000/53/EC on end-of-life vehicles ( 2002/96/EC on waste of electrical and electronic equipment (W/ ELV) and European Directiv Gb F) E). es es Analysing plastic recovery by end-use applications [3], the largest volume of recovered
Figure 1.3. Evolution of plastic recovery options and total post-consumer plastic waste volume The rate of plastic waste recovery has been continuously increasing since the mid-90’s due to the implantation of mechanical recycling and energy recovery facilities all over Europe; feedstock recycling remains still as a minor alternative. As a result of thes developments and despite the increasing post-use plastic waste volumes, the amount o: residual waste sent to landfill disposal seems to have stabilised. Decoupling between th« volume of plastic consumption and the associated amount of residue generation i currently being achieved in the countries with a developed waste managemen infrastructure [1]. Figure 1.3 proves this progressive decoupling between the plastic wast growth and the volume sent to disposal, due to enhanced plastic waste recovery options. erowth and the volume sent to disposal, due to enhanced plastic waste recovery options. Analysing plastic recovery by end-use applications [3], the largest volume of recoverec plastic waste corresponds to municipal solid waste, with a total volume of 5.45 MTonne: in 2002. Sectors like agricultural applications exhibit the highest recovery rates (ove: 50%), though with lower waste volumes. However, the automotive sector and electrica and electronic equipment showed lower plastic recovery rates in 2002; this situation i: expected to be continuously improving due to the implementation of the corresponding European Directive 2000/53/EC on end-of-life vehicles ( 2002/96/EC on waste of electrical and electronic equipment (W/ ELV) and European Directiv Gb F) E). es es Analysing plastic recovery by end-use applications [3], the largest volume of recovered
Figure 1.4. Key properties for quality assessment of recycled plastics S a a“ * has lead to the identification of three key properties for the quality assessment of recycled plastics: the degree of mixing (composition), the degree of degradation and the presence of low molecular weight compounds (additives, degradation products, and contaminants) (Fig.1.4) [17]. These key properties are necessary to fully guarantee the applicability of recyclates for the manufacture of new products. The degree of mixing (composition) is related to the presence of polymeric impurities in the recycled polymers resulting from impure plastic waste streams and poor separation in the recycling plant. The degree of degradation of recyclates considers the degradation processes to which polymeric materials are subjected during their processing, service life, and further recovery. Finally, the identification of low molecular weight compounds (contaminants, additives, and degradation products) present in recycled polymers is essential to verify that the products are compliant with legislation on the presence of hazardous substances. that the products are compliant with legislation on the presence of hazardous substances.
Figure 1.4. Key properties for quality assessment of recycled plastics S a a“ * has lead to the identification of three key properties for the quality assessment of recycled plastics: the degree of mixing (composition), the degree of degradation and the presence of low molecular weight compounds (additives, degradation products, and contaminants) (Fig.1.4) [17]. These key properties are necessary to fully guarantee the applicability of recyclates for the manufacture of new products. The degree of mixing (composition) is related to the presence of polymeric impurities in the recycled polymers resulting from impure plastic waste streams and poor separation in the recycling plant. The degree of degradation of recyclates considers the degradation processes to which polymeric materials are subjected during their processing, service life, and further recovery. Finally, the identification of low molecular weight compounds (contaminants, additives, and degradation products) present in recycled polymers is essential to verify that the products are compliant with legislation on the presence of hazardous substances. that the products are compliant with legislation on the presence of hazardous substances.
Figure 1.5. Analytical strategies for degradation studies in polymers (drawn after [22]) degradation processes in polymers [22-24]. Different strategies can be considered to investigate the degree of polymer degradation, depending on the changes at a macroscopic or microscopic scale (Fig. 1.5) [22]. Common approaches to determine degradation effects include analysis of the alterations in chemical functional groups (using vibrational spectroscopy or nuclear magnetic resonance), crystallinity and thermal properties (using thermal analysis), morphology (using electron microscopy), mechanical properties (mechanical testing), and molecular weight distribution and composition (using size exclusion chromatography and mass spectroscopic techniques). Additionally, investigation of degradation products and additives using chromatographic tools have proved to be useful for monitoring ongoing degradation processes in polymers [22-24].
Figure 1.5. Analytical strategies for degradation studies in polymers (drawn after [22]) degradation processes in polymers [22-24]. Different strategies can be considered to investigate the degree of polymer degradation, depending on the changes at a macroscopic or microscopic scale (Fig. 1.5) [22]. Common approaches to determine degradation effects include analysis of the alterations in chemical functional groups (using vibrational spectroscopy or nuclear magnetic resonance), crystallinity and thermal properties (using thermal analysis), morphology (using electron microscopy), mechanical properties (mechanical testing), and molecular weight distribution and composition (using size exclusion chromatography and mass spectroscopic techniques). Additionally, investigation of degradation products and additives using chromatographic tools have proved to be useful for monitoring ongoing degradation processes in polymers [22-24].
Figure 1.6. Microstructural isomeric units of polybutadiene The resulting material can be structurally defined as a multiphase system in which PE rubber granules are dispersed in a continuous rigid polystyrene (PS) matrix. The rubbe: phase contains the three typical microstructural isomeric units of PB: vinyl-1,2, cis-1,4 and trans-1,4 (Fig. 1.6). This multiphase structure confers HIPS its improved fracture resistance properties (impact strength, elongation at break, and fracture toughness together with a reduction in transparency, modulus and tensile strength if compared witk unmodified PS [43]. The introduction of a rubbery phase alters, however, the stability of the polymer blends towards degradation, enhancing the sensitivity of the material to the degradative agents. Degradation processes ate complex phenomena that usually involve different mechanisms and initiating agents, such as temperature, chemical agents, mechanical stress, or radiation. In this chapter a brief review on the degradation aspects related to HIPS and other rubber-modified styrenic polymers will be given, with special focus on photo-oxidative, thermo-oxidative and thermo-mechanical degradation.
Figure 1.6. Microstructural isomeric units of polybutadiene The resulting material can be structurally defined as a multiphase system in which PE rubber granules are dispersed in a continuous rigid polystyrene (PS) matrix. The rubbe: phase contains the three typical microstructural isomeric units of PB: vinyl-1,2, cis-1,4 and trans-1,4 (Fig. 1.6). This multiphase structure confers HIPS its improved fracture resistance properties (impact strength, elongation at break, and fracture toughness together with a reduction in transparency, modulus and tensile strength if compared witk unmodified PS [43]. The introduction of a rubbery phase alters, however, the stability of the polymer blends towards degradation, enhancing the sensitivity of the material to the degradative agents. Degradation processes ate complex phenomena that usually involve different mechanisms and initiating agents, such as temperature, chemical agents, mechanical stress, or radiation. In this chapter a brief review on the degradation aspects related to HIPS and other rubber-modified styrenic polymers will be given, with special focus on photo-oxidative, thermo-oxidative and thermo-mechanical degradation.
II. Reactions of cis-1,4 and trans-1,4 isomers nvolves the creation of free radicals and the formation of hydroperoxides; the second stage includes the decomposition of the hydroperoxides and the formation of different oroducts containing oxidised groups. Further reactions are responsible for the formation of stable crosslinked structures, extensive damage in the polymeric chains by chain scission and the disunification of the polymer graft between butadiene and styrene units. Different reaction mechanisms have been proposed by several authors for the thermo- and photo-oxidation of PB-modified styrenic polymers (Fig. 1.7) [44, 45, 47, 52, 59].
II. Reactions of cis-1,4 and trans-1,4 isomers nvolves the creation of free radicals and the formation of hydroperoxides; the second stage includes the decomposition of the hydroperoxides and the formation of different oroducts containing oxidised groups. Further reactions are responsible for the formation of stable crosslinked structures, extensive damage in the polymeric chains by chain scission and the disunification of the polymer graft between butadiene and styrene units. Different reaction mechanisms have been proposed by several authors for the thermo- and photo-oxidation of PB-modified styrenic polymers (Fig. 1.7) [44, 45, 47, 52, 59].
Figure 1.7. Reaction mechanisms proposed for the PB phase during the thermo-and photo-
Figure 1.7. Reaction mechanisms proposed for the PB phase during the thermo-and photo-
Figure 1.8. Crosslinked gel structures after prolonged exposure of PB-modified styrenic polymer ether gel, and saturated gel structures [45, 54].
Figure 1.8. Crosslinked gel structures after prolonged exposure of PB-modified styrenic polymer ether gel, and saturated gel structures [45, 54].
Figure 1.9. Proposed reactions for the oxidation of the PB-PS grafting sites scission of the PB-PS graft [45, 47, 54]. Further oxidation of the PS phase in PB-modified styrenic polymers is promoted by the free radicals formed during degradation of the rubber phase, compared to the oxidation of pure PS [47]. It is well known that the initiation of PS oxidation takes place by the oxygen attack to the a-hydrogens found on the backbone of the PS chain, leading to the formation of hydroperoxides as the initiation products [60, 61]. Aromatic and aliphatic ketones, peroxyesters, carboxylic acids, and anhydrides are some of the oxidised structures that can be found in PS subjected to thermo- and photo-oxidation; molecular compounds as benzoic acid, benzophenone, acetophenone, benzaldehyde, benzoic anhydride, and dibenzoylmethane are also formed as degradation products [60, 62, 63].
Figure 1.9. Proposed reactions for the oxidation of the PB-PS grafting sites scission of the PB-PS graft [45, 47, 54]. Further oxidation of the PS phase in PB-modified styrenic polymers is promoted by the free radicals formed during degradation of the rubber phase, compared to the oxidation of pure PS [47]. It is well known that the initiation of PS oxidation takes place by the oxygen attack to the a-hydrogens found on the backbone of the PS chain, leading to the formation of hydroperoxides as the initiation products [60, 61]. Aromatic and aliphatic ketones, peroxyesters, carboxylic acids, and anhydrides are some of the oxidised structures that can be found in PS subjected to thermo- and photo-oxidation; molecular compounds as benzoic acid, benzophenone, acetophenone, benzaldehyde, benzoic anhydride, and dibenzoylmethane are also formed as degradation products [60, 62, 63].
Figure 1.10. Chemical structures of the different families of brominated flame retardants The increasing environmental concern about BFRs is based on their persistence,
Figure 1.10. Chemical structures of the different families of brominated flame retardants The increasing environmental concern about BFRs is based on their persistence,
Figure 3.1 Procedure for modelling the life cycle of recycled plastics: a) modelling processing processing, service life and mechanical recycling by multiple processing and thermo- and mechanical recycling by multiple processing; b) modelling service life by thermo-oxidation.
Figure 3.1 Procedure for modelling the life cycle of recycled plastics: a) modelling processing processing, service life and mechanical recycling by multiple processing and thermo- and mechanical recycling by multiple processing; b) modelling service life by thermo-oxidation.
the sample materials employed in the analyses. HIPS samples were collected for analysis at different points of the mechanical recycling process (Acteco, Spain). Figure 3.2 shows the mechanical recycling flow diagram and the points at which the different samples were taken: Scrap HIPS employed as raw material in the recycling process, intermediate samples after grinding and washing, and different grades of final recycled HIPS material. Virgin HIPS, commercial grade Polystyrol 486M (BASF Espafila S.A., Spain), was employed as reference material. Table 3.1 describes the sample materials employed in the analyses. Table 3.1 Description of the HIPS materials sampled from the large-scale
the sample materials employed in the analyses. HIPS samples were collected for analysis at different points of the mechanical recycling process (Acteco, Spain). Figure 3.2 shows the mechanical recycling flow diagram and the points at which the different samples were taken: Scrap HIPS employed as raw material in the recycling process, intermediate samples after grinding and washing, and different grades of final recycled HIPS material. Virgin HIPS, commercial grade Polystyrol 486M (BASF Espafila S.A., Spain), was employed as reference material. Table 3.1 describes the sample materials employed in the analyses. Table 3.1 Description of the HIPS materials sampled from the large-scale
Figure 3.2 Sampling of the HIPS materials through the large-scale mechanical recycling process 3.1.3 Reference HIPS samples containing brominated flame retardants
Figure 3.2 Sampling of the HIPS materials through the large-scale mechanical recycling process 3.1.3 Reference HIPS samples containing brominated flame retardants
Table 3.2 Composition of the standard polymeric samples from waste electrical and electronic 3.2 CHARACTERISATION TECHNIQUES
Table 3.2 Composition of the standard polymeric samples from waste electrical and electronic 3.2 CHARACTERISATION TECHNIQUES
Figure 4.1. Influence of reprocessing on the melt mass-flow rate (MFR) of HIPS.
Figure 4.1. Influence of reprocessing on the melt mass-flow rate (MFR) of HIPS.
Figure 4.2. Tensile properties of the virgin HIPS subjected to multiple processing: a) tensile properties at break: (@) elongation at break; (9) stress at break; b) Young’s modulus. Figure 4.2. Tensile properties of the virgin HIPS subjected to multiple processing: a) tensile properties at break: (@) elongation at break; (©) stress at break; b) Young’s modulus. slightly more brittle material with lower ductility. The influence of reprocessing and thermo-oxidation on the mechanical properties (elastic modulus, elongation at break and stress at break) was analysed by tensile testing. Figure 4.2 shows the evolution of tensile properties during consecutive extrusion cycles. The elastic modulus remains practically unaffected; the stress and elongation at break are on the other hand clearly influenced by the successive processing steps, with a progressive diminution of the elongation at break and an increase of the stress at break. Each processing step induces the thermo-mechanical degradation of the HIPS materials, which may introduce alterations in the chemical structure of the polymeric chains, resulting in a slightly more brittle material with lower ductility.
Figure 4.2. Tensile properties of the virgin HIPS subjected to multiple processing: a) tensile properties at break: (@) elongation at break; (9) stress at break; b) Young’s modulus. Figure 4.2. Tensile properties of the virgin HIPS subjected to multiple processing: a) tensile properties at break: (@) elongation at break; (©) stress at break; b) Young’s modulus. slightly more brittle material with lower ductility. The influence of reprocessing and thermo-oxidation on the mechanical properties (elastic modulus, elongation at break and stress at break) was analysed by tensile testing. Figure 4.2 shows the evolution of tensile properties during consecutive extrusion cycles. The elastic modulus remains practically unaffected; the stress and elongation at break are on the other hand clearly influenced by the successive processing steps, with a progressive diminution of the elongation at break and an increase of the stress at break. Each processing step induces the thermo-mechanical degradation of the HIPS materials, which may introduce alterations in the chemical structure of the polymeric chains, resulting in a slightly more brittle material with lower ductility.
detail from the results of vibrational spectroscopy and dynamic-mechanical analysis. As a conclusion, HIPS seems to be a promising material for mechanical recycling, sinc the processability of the recyclates is guaranteed by the small variation of the MFR after. large number of recycling steps. On the other hand, elongation at break appears as th mechanical property that should determine the second market application for HIP‘ recyclates. Reprocessing up to nine cycles does not affect to high extent the mechanica properties of HIPS, while thermo-oxidation at 90°C may be considered to be quite sever for the mechanical nronerties of HIPS As a conclusion, HIPS seems to be a promising material for mechanical recycling, since for the mechanical properties of HIPS.
detail from the results of vibrational spectroscopy and dynamic-mechanical analysis. As a conclusion, HIPS seems to be a promising material for mechanical recycling, sinc the processability of the recyclates is guaranteed by the small variation of the MFR after. large number of recycling steps. On the other hand, elongation at break appears as th mechanical property that should determine the second market application for HIP‘ recyclates. Reprocessing up to nine cycles does not affect to high extent the mechanica properties of HIPS, while thermo-oxidation at 90°C may be considered to be quite sever for the mechanical nronerties of HIPS As a conclusion, HIPS seems to be a promising material for mechanical recycling, since for the mechanical properties of HIPS.
xidative stability of reprocessed and thermo-oxidated HIPS samples was assessed b ie determination of the oxidation induction time (OIT) and the oxidation temperatur "4): Table 4.1 presents the OIT and the T., average data obtained by the DS(¢ leasurements for the HIPS samples. As it can be observed, the stabilising syster nployed in the material is clearly affected by the reprocessing cycles and by therma xidative degradation, while the largest changes are observed in the aged samples. Eac! processing step caused a progressive consumption of the stabilisers in the materia ainly during the first three extrusion cycles. In the case of the thermo-oxidated samples ie decrease in the stabilising activity is even more fast and dramatic, with a decrease a ie 57% in the value of the OIT after 1 day of exposure at 90°C and a total decrease a 9% of the OIT value after 16 days of ageing. Table 4.1. Oxidation temperature (Tox) and oxidation induction time (OIT) for high-impact polystyrene subjected to multiple processing and thermo-oxidation at 90°C.
xidative stability of reprocessed and thermo-oxidated HIPS samples was assessed b ie determination of the oxidation induction time (OIT) and the oxidation temperatur "4): Table 4.1 presents the OIT and the T., average data obtained by the DS(¢ leasurements for the HIPS samples. As it can be observed, the stabilising syster nployed in the material is clearly affected by the reprocessing cycles and by therma xidative degradation, while the largest changes are observed in the aged samples. Eac! processing step caused a progressive consumption of the stabilisers in the materia ainly during the first three extrusion cycles. In the case of the thermo-oxidated samples ie decrease in the stabilising activity is even more fast and dramatic, with a decrease a ie 57% in the value of the OIT after 1 day of exposure at 90°C and a total decrease a 9% of the OIT value after 16 days of ageing. Table 4.1. Oxidation temperature (Tox) and oxidation induction time (OIT) for high-impact polystyrene subjected to multiple processing and thermo-oxidation at 90°C.
Figure 4.4. Curve fitting of the virgin HIPS Raman spectra to 5 individual bands for the determination of the three individual PB conformers: 1550-1700cm-1 region.
Figure 4.4. Curve fitting of the virgin HIPS Raman spectra to 5 individual bands for the determination of the three individual PB conformers: 1550-1700cm-1 region.
Figure 4.5. Chemical changes induced by reprocessing on the structure of HIPS by vibrationa
Figure 4.5. Chemical changes induced by reprocessing on the structure of HIPS by vibrationa
carbonyl regions. Figure 4.6 shows the FTIR spectra for the HIPS samples subjected to thermo-oxidative ageing at 90°C through the hydroxyl region (between 3600 and 3100cm'), carbonyl region (between 1800 and 1620cm'), and the double bond region (between 1000 and 880cm"'). Thermo-oxidation induces, in contrast with the heterogeneous effects reported by reprocessing, quite progressive changes in the analyzed functional group indexes; a marked decrease in the unsaturated groups (trans-1,4 and vinyl-1,2 groups) can be observed employing FTIR, while broad bands appear both in the hydroxyl and the catbonyl regions.
carbonyl regions. Figure 4.6 shows the FTIR spectra for the HIPS samples subjected to thermo-oxidative ageing at 90°C through the hydroxyl region (between 3600 and 3100cm'), carbonyl region (between 1800 and 1620cm'), and the double bond region (between 1000 and 880cm"'). Thermo-oxidation induces, in contrast with the heterogeneous effects reported by reprocessing, quite progressive changes in the analyzed functional group indexes; a marked decrease in the unsaturated groups (trans-1,4 and vinyl-1,2 groups) can be observed employing FTIR, while broad bands appear both in the hydroxyl and the catbonyl regions.
Figure 4.7. Chemical changes induced by thermo-oxidation at 90°C on the structure of HIPS:
Figure 4.7. Chemical changes induced by thermo-oxidation at 90°C on the structure of HIPS:
Figure 4.8. Isocronal representation of the storage modulus E’ (lower plot) and loss modulus maximum of the loss modulus, which is usually assumed as the glass transition where FE”, is the maximum of the loss modulus; ~ is the Fuoss-Kirkwood parameter;
Figure 4.8. Isocronal representation of the storage modulus E’ (lower plot) and loss modulus maximum of the loss modulus, which is usually assumed as the glass transition where FE”, is the maximum of the loss modulus; ~ is the Fuoss-Kirkwood parameter;
reprocessing and thermo-oxidation, respectively. Table 4.2. Influence of multiple processing on the viscoelastic parameters related to the glass transition relaxations of PB and PS phases in HIPS according to the free volume theory
reprocessing and thermo-oxidation, respectively. Table 4.2. Influence of multiple processing on the viscoelastic parameters related to the glass transition relaxations of PB and PS phases in HIPS according to the free volume theory
Table 4.3. Influence of thermo-oxidation at 90°C on the viscoelastic parameters related to the properties reported in other works [67, 69, 110]. glass transition relaxations of PB and PS phases in HIPS according to the free volume theory.
Table 4.3. Influence of thermo-oxidation at 90°C on the viscoelastic parameters related to the properties reported in other works [67, 69, 110]. glass transition relaxations of PB and PS phases in HIPS according to the free volume theory.
Figure 4.10. SEM micrographs of HIPS samples: a) virgin HIPS: b) reprocessed HIPS (9 cycles); which show the evident deterioration of the morphology under thermo-oxidation. he complex effects of multiple processing and thermo-oxidation on the microstructure od morphology of HIPS can be verified in the micrograms obtained by scannin P sy 8 y 2 lectron microscopy (S| FM). The typical double phase distribution in HIPS can be bserved in virgin HIPS microgram (Fig. 4.10a) where the PB granules are dispersed in 1e PS matrix. The PB granules exhibit heterogeneous shapes with a particle size in the rder of 5-10 um. After multiple processing (Fig. 4.10b), shrinkage in the shape of the B granules can be observed together with a clear modification in the surface of the ranules; cracks, channels and wrinkles are also appreciated in the PS matrix. The rogressive effect of thermo-oxidation on the morphology of HIPS can be followed with 1e exposure time. For shorter exposure times (Fig. 4.10c), the PB granules seem tc rease and contract, showing a rough outer surface; for longer exposure times, however. B phase appears to have partially lost the granular microstructure, though smallet article can still be detected (Figure 4.10d). Cracks can be also observed in the PS matrix. ee
Figure 4.10. SEM micrographs of HIPS samples: a) virgin HIPS: b) reprocessed HIPS (9 cycles); which show the evident deterioration of the morphology under thermo-oxidation. he complex effects of multiple processing and thermo-oxidation on the microstructure od morphology of HIPS can be verified in the micrograms obtained by scannin P sy 8 y 2 lectron microscopy (S| FM). The typical double phase distribution in HIPS can be bserved in virgin HIPS microgram (Fig. 4.10a) where the PB granules are dispersed in 1e PS matrix. The PB granules exhibit heterogeneous shapes with a particle size in the rder of 5-10 um. After multiple processing (Fig. 4.10b), shrinkage in the shape of the B granules can be observed together with a clear modification in the surface of the ranules; cracks, channels and wrinkles are also appreciated in the PS matrix. The rogressive effect of thermo-oxidation on the morphology of HIPS can be followed with 1e exposure time. For shorter exposure times (Fig. 4.10c), the PB granules seem tc rease and contract, showing a rough outer surface; for longer exposure times, however. B phase appears to have partially lost the granular microstructure, though smallet article can still be detected (Figure 4.10d). Cracks can be also observed in the PS matrix. ee
Figure 4.11. Total ion chromatogram (TIC) from the MAE extracts of virgin HIPS, HIPS
Figure 4.11. Total ion chromatogram (TIC) from the MAE extracts of virgin HIPS, HIPS
Table 4.4. Relative abundance and chromatographic properties of identified low molecular weight compounds in reprocessed HIPS samples.
Table 4.4. Relative abundance and chromatographic properties of identified low molecular weight compounds in reprocessed HIPS samples.
* Identification by injection of standard substances; > Proposed identification by comparison to the NIST database; ¢ Proposed identification through bibliographic reference [127]; ¢ Proposed identification through bibliographic reference [124]; ¢ Relative quantification respect 4-methylstyrene (LS.); f Relative quantification respect o-terpheny] (LS.) Styrene (peak 1) shows a dramatic reduction in its relative abundance during short time
* Identification by injection of standard substances; > Proposed identification by comparison to the NIST database; ¢ Proposed identification through bibliographic reference [127]; ¢ Proposed identification through bibliographic reference [124]; ¢ Relative quantification respect 4-methylstyrene (LS.); f Relative quantification respect o-terpheny] (LS.) Styrene (peak 1) shows a dramatic reduction in its relative abundance during short time
polypropylene contaminations, respectively, in these materials. The presence of mixed polymeric fractions as impurities in recycled polymeric material: clearly affects the macroscopic performance of recyclates. The employment of therma analysis is suitable for the characterisation of the properties of the material in the bulk Polymeric contaminations in the recycled materials were detected by DSC. Figure 4.12 shows the thermograms corresponding to the second heating segment for the differen HIPS samples, where it can be observed that all the samples exhibit the slope chang corresponding to the glass transition of the polystyrene phase at around 90°C. Smal melting peaks at temperatures of 120°C and/or 160°C can be observed, however, fo: samples HIPS2 and HIPS7, which indicate the presence of polyethylene anc polypropylene contaminations, respectively, in these materials.
polypropylene contaminations, respectively, in these materials. The presence of mixed polymeric fractions as impurities in recycled polymeric material: clearly affects the macroscopic performance of recyclates. The employment of therma analysis is suitable for the characterisation of the properties of the material in the bulk Polymeric contaminations in the recycled materials were detected by DSC. Figure 4.12 shows the thermograms corresponding to the second heating segment for the differen HIPS samples, where it can be observed that all the samples exhibit the slope chang corresponding to the glass transition of the polystyrene phase at around 90°C. Smal melting peaks at temperatures of 120°C and/or 160°C can be observed, however, fo: samples HIPS2 and HIPS7, which indicate the presence of polyethylene anc polypropylene contaminations, respectively, in these materials.
which indicates that the morphology of the samples seems to be similar. DSC was employed to calculate the glass transition temperature of the PS matrix and to assess the oxidative stability of the different HIPS samples (Table 4.6). In polymeric materials, the glass transition temperature (T’,) is particularly related to the mobility of the polymeric chains and determines the transition between the glassy and the rubbery polymeric state. Variances in the glass transition temperature may be due to several structural effects of the polymers, such as molar mass, degree of crosslinking, chain branching, or physical ageing phenomena [128]. The different samples present comparable T, values between 90 and 95°C for the polystyrene (PS) phase of HIPS, which indicates that the morphology of the samples seems to be similar. Table 4.6. Thermal parameters of differential scanning calorimetry (DSC): Glass transition temperature of the polystyrene phase (T,), oxidation induction time (OIT), and oxidation
which indicates that the morphology of the samples seems to be similar. DSC was employed to calculate the glass transition temperature of the PS matrix and to assess the oxidative stability of the different HIPS samples (Table 4.6). In polymeric materials, the glass transition temperature (T’,) is particularly related to the mobility of the polymeric chains and determines the transition between the glassy and the rubbery polymeric state. Variances in the glass transition temperature may be due to several structural effects of the polymers, such as molar mass, degree of crosslinking, chain branching, or physical ageing phenomena [128]. The different samples present comparable T, values between 90 and 95°C for the polystyrene (PS) phase of HIPS, which indicates that the morphology of the samples seems to be similar. Table 4.6. Thermal parameters of differential scanning calorimetry (DSC): Glass transition temperature of the polystyrene phase (T,), oxidation induction time (OIT), and oxidation
Table 4.7. Results from thermogravimetric analysis: Onset temperature of thermal degradation han the virgin material, with HIPS2 and HIPS7 showing the highest residue levels. (Tonset), decomposition temperature range, temperature of maximum decomposition rate (Tmax)
Table 4.7. Results from thermogravimetric analysis: Onset temperature of thermal degradation han the virgin material, with HIPS2 and HIPS7 showing the highest residue levels. (Tonset), decomposition temperature range, temperature of maximum decomposition rate (Tmax)
Figure 4.13. FTIR spectra of the HIPS samples: a) hydroxyl region (3100-3600cm); b) carbonyl the vinyl-1,2 and trans-1,4 peaks in the recycled materials can be qualitatively observed. The regions corresponding to the hydroxyl group, the carbonyl groups, and the double bond groups from the PB phase corresponding to the peak of trans-1,4 and vinyl-1,2 groups were analyzed in detail employing FTIR. Figure 4.13 represents the absorbance spectra of the HIPS samples in the hydroxyl, carbonyl, and unsaturated regions. The recycled samples show, in general, higher absorbance in the hydroxyl and carbonyl regions than the virgin material, because of the presence of humidity and other oxidative moieties. Considering the unsaturated region from the PB phase, a general decrease of the vinyl-1,2 and trans-1,4 peaks in the recycled materials can be qualitatively observed.
Figure 4.13. FTIR spectra of the HIPS samples: a) hydroxyl region (3100-3600cm); b) carbonyl the vinyl-1,2 and trans-1,4 peaks in the recycled materials can be qualitatively observed. The regions corresponding to the hydroxyl group, the carbonyl groups, and the double bond groups from the PB phase corresponding to the peak of trans-1,4 and vinyl-1,2 groups were analyzed in detail employing FTIR. Figure 4.13 represents the absorbance spectra of the HIPS samples in the hydroxyl, carbonyl, and unsaturated regions. The recycled samples show, in general, higher absorbance in the hydroxyl and carbonyl regions than the virgin material, because of the presence of humidity and other oxidative moieties. Considering the unsaturated region from the PB phase, a general decrease of the vinyl-1,2 and trans-1,4 peaks in the recycled materials can be qualitatively observed.
Figure 4.14. FTIR functional group indexes (hydroxyl; carbonyl; trans-1,4; vinyl-1,2) figure 4.14 represents the FTIR hydroxyl, carbonyl, trans-1,4, and vinyl-1,2, functiona rroup indexes for the analysed HIPS samples. The diminution of the unsaturatec unctional groups (vinyl-1,2 and trans-1,4) and the increase of the hydroxyl and carbony rroups in the real recycling samples, compared to the virgin material, may prove th« »ccurrence of PB oxidation during previous life and recycling of HIPS, resulting in < wide variety of oxidised structures in the polymeric chains [44, 45, 53]. The calculation o: he hydroxyl, carbonyl, vinyl-1,2 and trans-1,4 indexes could therefore be employed tc verify the degree of degradation in recycled plastics and to assess the content o: insaturated groups in recycled HIPS. samples from the large-scale mechanical recycling process. Conventional Raman
Figure 4.14. FTIR functional group indexes (hydroxyl; carbonyl; trans-1,4; vinyl-1,2) figure 4.14 represents the FTIR hydroxyl, carbonyl, trans-1,4, and vinyl-1,2, functiona rroup indexes for the analysed HIPS samples. The diminution of the unsaturatec unctional groups (vinyl-1,2 and trans-1,4) and the increase of the hydroxyl and carbony rroups in the real recycling samples, compared to the virgin material, may prove th« »ccurrence of PB oxidation during previous life and recycling of HIPS, resulting in < wide variety of oxidised structures in the polymeric chains [44, 45, 53]. The calculation o: he hydroxyl, carbonyl, vinyl-1,2 and trans-1,4 indexes could therefore be employed tc verify the degree of degradation in recycled plastics and to assess the content o: insaturated groups in recycled HIPS. samples from the large-scale mechanical recycling process. Conventional Raman
Figure 4.15. Raman functional group indexes (vinyl-1,2; cis-1,4; trans-1,4) for the HIPS samples.
Figure 4.15. Raman functional group indexes (vinyl-1,2; cis-1,4; trans-1,4) for the HIPS samples.
The presence of low molecular weight compounds in recycled HIPS was assessed by microwave-assisted extraction followed by analysis of the extracts using GC-MS. Figure 4.16 presents a total ion chromatogram (TIC) from the extract of recycled HIPS as ar example of the resulting chromatograms for the analysed materials. At a glance, differen zones can be observed: A first zone until approximately 800s where the volatile organic compounds (VOCs) appear; a second zone around 900s where styrene dimers (residue: from polymerisation) elute; a third zone around 1400s where different peaks from the styrene trimers (residues of polymerisation) appear; and, finally, a fourth zone at longer: elution times where different aliphatic compounds can be found. elution times where different aliphatic compounds can be found. Figure 4.16. Total lon Chromatogram (TIC) of the low molecular weight compounds extracted
The presence of low molecular weight compounds in recycled HIPS was assessed by microwave-assisted extraction followed by analysis of the extracts using GC-MS. Figure 4.16 presents a total ion chromatogram (TIC) from the extract of recycled HIPS as ar example of the resulting chromatograms for the analysed materials. At a glance, differen zones can be observed: A first zone until approximately 800s where the volatile organic compounds (VOCs) appear; a second zone around 900s where styrene dimers (residue: from polymerisation) elute; a third zone around 1400s where different peaks from the styrene trimers (residues of polymerisation) appear; and, finally, a fourth zone at longer: elution times where different aliphatic compounds can be found. elution times where different aliphatic compounds can be found. Figure 4.16. Total lon Chromatogram (TIC) of the low molecular weight compounds extracted
«Proposed identification by comparison to the NIST database; > Proposed identification through bibliography [121]; * Proposed identification through bibliography [124]
«Proposed identification by comparison to the NIST database; > Proposed identification through bibliography [121]; * Proposed identification through bibliography [124]
The optimisation of the spectrometric detection was achieved by injection of standard solutions of the analytes in tetrahydrofurane in the range 1 — 1000 ug/ml into the HPLC- UV. The initial chromatographic parameters (column, mobile phase, mobile flow, temperature) were first directly chosen from previous bibliographic results [85], and further adjustments were performed to satisfy the requirements for successful se and detection. Different wavelengths for the DAD detection were tested and wavelength of 220 nm was selected. The retention times, limit of detection (LO paration finally a D), limit of quantification (LOQ), and the linearity range for TBBPA and Deca-BDE have been calculated for the developed HPLC-UV method and are presented in Table 4.9. calculated for the developed HPLC-UV method and are presented in Table 4.9. Table 4.9. Limit of detection (LOD), limit of quantification (LOQ) and linearity of the analytical
The optimisation of the spectrometric detection was achieved by injection of standard solutions of the analytes in tetrahydrofurane in the range 1 — 1000 ug/ml into the HPLC- UV. The initial chromatographic parameters (column, mobile phase, mobile flow, temperature) were first directly chosen from previous bibliographic results [85], and further adjustments were performed to satisfy the requirements for successful se and detection. Different wavelengths for the DAD detection were tested and wavelength of 220 nm was selected. The retention times, limit of detection (LO paration finally a D), limit of quantification (LOQ), and the linearity range for TBBPA and Deca-BDE have been calculated for the developed HPLC-UV method and are presented in Table 4.9. calculated for the developed HPLC-UV method and are presented in Table 4.9. Table 4.9. Limit of detection (LOD), limit of quantification (LOQ) and linearity of the analytical
The optimisation of the MS sensitivity was per formed by direct infusion of the standard analytes in acetonitrile into the APCI mass spectrometer. Figure 4.17 shows the full scan mass spectra of TBBPA, HBCD, and Deca-BDE. According to these fragmentation results, the MRM signals corresponding to m/z 543-79 and m/z 543-481 for TBBPA, m/z 641—+79 and m/z 641-81 for the three HBCD congeners, and m/z 487-79 and m/z 487-81 for Deca-BDE, were selected and compared in terms of LOD, LOQ and linearity, to detect and quantify the flame retard ant content in the extracts. linearity, to detect and quantify the flame retardant content in the extracts.
The optimisation of the MS sensitivity was per formed by direct infusion of the standard analytes in acetonitrile into the APCI mass spectrometer. Figure 4.17 shows the full scan mass spectra of TBBPA, HBCD, and Deca-BDE. According to these fragmentation results, the MRM signals corresponding to m/z 543-79 and m/z 543-481 for TBBPA, m/z 641—+79 and m/z 641-81 for the three HBCD congeners, and m/z 487-79 and m/z 487-81 for Deca-BDE, were selected and compared in terms of LOD, LOQ and linearity, to detect and quantify the flame retard ant content in the extracts. linearity, to detect and quantify the flame retardant content in the extracts.
Figure 4.17. Full scan mass spectra of the BFRs acquired in the APCI negative mode by direct infusion of standard solutions in acetonitrile: a) TBBPA; b) HBCD; c) Deca-BDE.
Figure 4.17. Full scan mass spectra of the BFRs acquired in the APCI negative mode by direct infusion of standard solutions in acetonitrile: a) TBBPA; b) HBCD; c) Deca-BDE.
Figure 4.18. Chromatogram for the superposed MRM signals corresponding to TBBPA
Figure 4.18. Chromatogram for the superposed MRM signals corresponding to TBBPA
Che limit of detection (LOD) and limit of quantification (LOQ) for the studied flame etardants were calculated from the reference solutions for each compound and juantification MRM ion pairs (Table 4.10). HBCD has a relatively higher LOD and LOQ compared to TBBPA and Deca-BD! EF, due to the relatively low ionisation efficiency in \PCI. Other studies have pointed out the idoneity of electrospray ionisation (ESI) for he analysis of more polar flame retardants such as TBBPA and HBCD [129-132] olybrominated diphenyl et , but hers generally cannot be analysed using | ESI, which is why \PCI was selected. The linearity range of each analyte is also shown in Table 3.8; the lynamic range of Deca-BD! E, was lower compared to the other compounds. Regardless of these differences, the quantification of the extracts was performed adjusting the ‘oncentration to the linearity range of the flame retardants in the HPLC-MS/MS nethod. In general, the MRM signals obtained from both Br, and Br,, isotopes at the hird quadrupole (Q3), can be used for the determination of the selected BFRs, with imilar LOD, LOQ, and line arity conditions. Table 4.10. Limit of detection (LOD), limit of quantification (LOQ) and linearity of the
Che limit of detection (LOD) and limit of quantification (LOQ) for the studied flame etardants were calculated from the reference solutions for each compound and juantification MRM ion pairs (Table 4.10). HBCD has a relatively higher LOD and LOQ compared to TBBPA and Deca-BD! EF, due to the relatively low ionisation efficiency in \PCI. Other studies have pointed out the idoneity of electrospray ionisation (ESI) for he analysis of more polar flame retardants such as TBBPA and HBCD [129-132] olybrominated diphenyl et , but hers generally cannot be analysed using | ESI, which is why \PCI was selected. The linearity range of each analyte is also shown in Table 3.8; the lynamic range of Deca-BD! E, was lower compared to the other compounds. Regardless of these differences, the quantification of the extracts was performed adjusting the ‘oncentration to the linearity range of the flame retardants in the HPLC-MS/MS nethod. In general, the MRM signals obtained from both Br, and Br,, isotopes at the hird quadrupole (Q3), can be used for the determination of the selected BFRs, with imilar LOD, LOQ, and line arity conditions. Table 4.10. Limit of detection (LOD), limit of quantification (LOQ) and linearity of the
Table 4.11. Calculated accumulative concentration of BFRs in the standard HIPS samples usin:
Table 4.11. Calculated accumulative concentration of BFRs in the standard HIPS samples usin:
Table 4.12. Calculated accumulative concentration of BFRs in the standard HIPS samples using ultrasound-assisted extraction under different conditions.
Table 4.12. Calculated accumulative concentration of BFRs in the standard HIPS samples using ultrasound-assisted extraction under different conditions.
Table 4.13. Calculated accumulative concentration of BFRs in the standard HIPS samples usin, the three HBCD congeners. MAE offers almost complete recovery of TBBPA and HBCD using isopropanol/n- hexane as solvents at 130°C for 60 minutes, with calculated concentrations similar to the initial BFR composition of the standard HIPS samples, whereas lower calculated concentrations are obtained for Deca-BDE (Table 4.13). The effect of microwaves and high temperatures may cause isomerisation of the B- and y-HBCD congeners into the more thermally stable a-HBCD, as shown by the anomalous concentration results for the three HBCD conoenets. microwave-assisted extraction under different conditions.
Table 4.13. Calculated accumulative concentration of BFRs in the standard HIPS samples usin, the three HBCD congeners. MAE offers almost complete recovery of TBBPA and HBCD using isopropanol/n- hexane as solvents at 130°C for 60 minutes, with calculated concentrations similar to the initial BFR composition of the standard HIPS samples, whereas lower calculated concentrations are obtained for Deca-BDE (Table 4.13). The effect of microwaves and high temperatures may cause isomerisation of the B- and y-HBCD congeners into the more thermally stable a-HBCD, as shown by the anomalous concentration results for the three HBCD conoenets. microwave-assisted extraction under different conditions.
Figure 4.19. Comparison of the extraction yield of PLE, MAE, and PLE for the different BFRs
Figure 4.19. Comparison of the extraction yield of PLE, MAE, and PLE for the different BFRs
Figure 4.20 shows the chro The sample ABS-GVL2-07 BDE (tg=20.6 min), other minor peaks that may correspond with other PBDI es matograms of the extracts for the standard WEEE samples. shows, in addition to the main peak corresponding to Deca- UI congeners with lower bromination degree at tp=20.0 min, tg=19.4 min, and tg=18.9 min, either originally contained in the technical Deca-BDE grade used in the manufacture of the plastic component, or due to the debromination of the BFR during service life and further recycling (Figure 4.20a). Sample ABS-GVL2-11 shows a single clear peak corresponding with TBBPA at tz=11.1 min, proving that the flame retardant has been successfully extracted from the polymeric matrix (Figure 4.20b). Finally, different peaks can be observed in the chromatogram corresponding to sample SB-GVL2-07; the main peak assigned to Deca-BD] EH at tg=20.6 min and other peaks that may be attributed to other PBDE congeners at tp=19.9 min, tg=18.9 min, and tg=18.4 min (Figure 4.20c). other PBDE congeners at tg=19.9 min, tp=18.9 min, and th=18.4 min (Figure 4.20c).
Figure 4.20 shows the chro The sample ABS-GVL2-07 BDE (tg=20.6 min), other minor peaks that may correspond with other PBDI es matograms of the extracts for the standard WEEE samples. shows, in addition to the main peak corresponding to Deca- UI congeners with lower bromination degree at tp=20.0 min, tg=19.4 min, and tg=18.9 min, either originally contained in the technical Deca-BDE grade used in the manufacture of the plastic component, or due to the debromination of the BFR during service life and further recycling (Figure 4.20a). Sample ABS-GVL2-11 shows a single clear peak corresponding with TBBPA at tz=11.1 min, proving that the flame retardant has been successfully extracted from the polymeric matrix (Figure 4.20b). Finally, different peaks can be observed in the chromatogram corresponding to sample SB-GVL2-07; the main peak assigned to Deca-BD] EH at tg=20.6 min and other peaks that may be attributed to other PBDE congeners at tp=19.9 min, tg=18.9 min, and tg=18.4 min (Figure 4.20c). other PBDE congeners at tg=19.9 min, tp=18.9 min, and th=18.4 min (Figure 4.20c).
Oxidation temperature (T,x) and oxidation induction time (OIT) for high-im- pact polystyrene subjected to multiple processing and thermo-oxidative ageing at 90 °C
Oxidation temperature (T,x) and oxidation induction time (OIT) for high-im- pact polystyrene subjected to multiple processing and thermo-oxidative ageing at 90 °C
Scheme 1. Procedure employed for the modelling of the second life for plastics, (a) modelling of processing and mechanical recycling; (b) modelling of service life.
Scheme 1. Procedure employed for the modelling of the second life for plastics, (a) modelling of processing and mechanical recycling; (b) modelling of service life.
Fig. 1. Influence of reprocessing on the melt mass-flow rate (MFR) of HIPS. From a recycling point of view, HIPS seems to be a prom- ising material for mechanical recycling, since the MFR values only increase approximately 2% in the first reprocessing step and a total of 45% after nine extrusion cycles. This small var- iation of the MFR with a large number of recycling steps would guarantee the processability of the recyclates during the mechanical recycling processes.
Fig. 1. Influence of reprocessing on the melt mass-flow rate (MFR) of HIPS. From a recycling point of view, HIPS seems to be a prom- ising material for mechanical recycling, since the MFR values only increase approximately 2% in the first reprocessing step and a total of 45% after nine extrusion cycles. This small var- iation of the MFR with a large number of recycling steps would guarantee the processability of the recyclates during the mechanical recycling processes.
Fig. 2. Tensile properties of the virgin HIPS subjected to multiple processing, (a) tensile properties at break: (@) elongation at break; (O) stress at break; (t Young’s modulus.
Fig. 2. Tensile properties of the virgin HIPS subjected to multiple processing, (a) tensile properties at break: (@) elongation at break; (O) stress at break; (t Young’s modulus.
Fig. 3. Tensile properties of the virgin HIPS subjected to thermo-oxidative ageing at 90 °C, (a) tensile properties at break: (@) elongation at break; (©) stress at break; (b) Young’s modulus. The absorbance spectra of the surface of the HIPS samples subjected to multiple processing and thermo-oxidative ageing at 90 °C were recorded and studied. In particular, the regions corresponding to the hydroxyl groups (between 3100 and 3600 cm—'), carbonyl groups (between 1620 and 1780 cm~'), and the unsaturated groups from the polybutadi- ene phase of HIPS corresponding to the peak of trans-1,4 (966 cm!) and vinyl-1,2 (911 cm ') were analyzed in detail. The peak corresponding to the cis-1,4 double bond group from the polybutadiene phase (around 730 cm ') could not be stud- ied because of the overlapping peak from the C—H out- of-plane vibration of the styrene units in polystyrene at 754 cm! [13]. Moreover, in order to obtain a quantitative pic- ture of the structural changes caused by reprocessing and age- ing, the relative absorbance ratios of the peaks corresponding to the maximum of the hydroxyl region (3287 cm™'), the max- imum of the carbonyl region (1729 cm™'), trans-1,4 group (965 cm_'), and vinyl-1,2 group (907 cm’) were determined, As a conclusion, the elongation at break appears to be the mechanical property that should determine the recycling pos- sibilities and the second-market application for high-impact polystyrene recyclates. It was observed that reprocessing up to nine cycles does not affect to any high extent the mechanical properties of HIPS, with a decrease of 15% in elongation at break after three extrusion steps, and a total decrease of around 38% in the elongation at break after nine cycles. On the other hand, the thermo-oxidative ageing at 90 °C may be considered to be quite severe for the mechanical properties of HIPS, since it remarkably affects the elongation at break values of HIPS, with a decrease of 85% after only 4 days of exposure.
Fig. 3. Tensile properties of the virgin HIPS subjected to thermo-oxidative ageing at 90 °C, (a) tensile properties at break: (@) elongation at break; (©) stress at break; (b) Young’s modulus. The absorbance spectra of the surface of the HIPS samples subjected to multiple processing and thermo-oxidative ageing at 90 °C were recorded and studied. In particular, the regions corresponding to the hydroxyl groups (between 3100 and 3600 cm—'), carbonyl groups (between 1620 and 1780 cm~'), and the unsaturated groups from the polybutadi- ene phase of HIPS corresponding to the peak of trans-1,4 (966 cm!) and vinyl-1,2 (911 cm ') were analyzed in detail. The peak corresponding to the cis-1,4 double bond group from the polybutadiene phase (around 730 cm ') could not be stud- ied because of the overlapping peak from the C—H out- of-plane vibration of the styrene units in polystyrene at 754 cm! [13]. Moreover, in order to obtain a quantitative pic- ture of the structural changes caused by reprocessing and age- ing, the relative absorbance ratios of the peaks corresponding to the maximum of the hydroxyl region (3287 cm™'), the max- imum of the carbonyl region (1729 cm™'), trans-1,4 group (965 cm_'), and vinyl-1,2 group (907 cm’) were determined, As a conclusion, the elongation at break appears to be the mechanical property that should determine the recycling pos- sibilities and the second-market application for high-impact polystyrene recyclates. It was observed that reprocessing up to nine cycles does not affect to any high extent the mechanical properties of HIPS, with a decrease of 15% in elongation at break after three extrusion steps, and a total decrease of around 38% in the elongation at break after nine cycles. On the other hand, the thermo-oxidative ageing at 90 °C may be considered to be quite severe for the mechanical properties of HIPS, since it remarkably affects the elongation at break values of HIPS, with a decrease of 85% after only 4 days of exposure.
Glass transition temperatures (T,) of the polybutadiene (PB) and the polysty- rene (PS) phases of the high-impact polystyrene thermo-oxidised samples Table 2 related to the height of a reference peak at 1601 cm ', in order to make their results comparable and to eliminate the effect of the thickness of the films [6].
Glass transition temperatures (T,) of the polybutadiene (PB) and the polysty- rene (PS) phases of the high-impact polystyrene thermo-oxidised samples Table 2 related to the height of a reference peak at 1601 cm ', in order to make their results comparable and to eliminate the effect of the thickness of the films [6].
Fig. 4. FTIR absorbance spectra at the region between 1800 and 1400 cm! for HIPS samples subjected to different steps of multiple processing. Fig. 5 represents the spectroscopic results of the analyzed functional group indexes as a function of the reprocessing steps. It can be observed that repeated processing steps induce
Fig. 4. FTIR absorbance spectra at the region between 1800 and 1400 cm! for HIPS samples subjected to different steps of multiple processing. Fig. 5 represents the spectroscopic results of the analyzed functional group indexes as a function of the reprocessing steps. It can be observed that repeated processing steps induce
Fig. 5. Evolution of the (©) vinyl-1,2 ratio, (MB) trans-1,4 ratio, (A) carbonyl ratio and (@) hydroxyl ratio, with the reprocessing steps for HIPS. Pigs. O snOWS We WNTarea speCuld LOT UI FAIS sdliples suD- jected to thermo-oxidative ageing at 90 °C through the hy- droxyl region (between 3600 and 3100 cm’), carbonyl region (between 1800 and 1620 cm’!), and the double bond region (between 1000 and 880 cm7'). In addition, a quantita- tive study of the selected functional groups was performed and the evolution of their indexes with the ageing time was then plotted in Fig. 7. Figs. 6 and 7 demonstrate that thermo-oxida- tive ageing induces, in contrast with the heterogeneous effects reported by reprocessing, quite progressive changes in the an- alyzed functional group indexes. As a whole, thermo-oxidative ageing caused a marked decrease in the unsaturated groups (trans-1,4 and vinyl-1,2 groups), while broad bands appear both in the hydroxyl and the carbonyl regions. These results are in agreement with previous studies performed on the photo- and thermo-oxidation of HIPS and other styrene/buta- diene copolymers by FTIR spectroscopy [14—16]. The trans-1,4 group index showed a slight decrease at the initial ageing time due to the protective effect of the antioxidants, but after the fourth day of thermo-oxidative ageing, the reduc- tion was considerable. This phenomenon is in accordance with the results of Israeli et al. [14], which reported that the thermal oxidation of HIPS shows an induction period, followed by 9 fast oxidation of nolvbutadiene and then bv a slow oxidation
Fig. 5. Evolution of the (©) vinyl-1,2 ratio, (MB) trans-1,4 ratio, (A) carbonyl ratio and (@) hydroxyl ratio, with the reprocessing steps for HIPS. Pigs. O snOWS We WNTarea speCuld LOT UI FAIS sdliples suD- jected to thermo-oxidative ageing at 90 °C through the hy- droxyl region (between 3600 and 3100 cm’), carbonyl region (between 1800 and 1620 cm’!), and the double bond region (between 1000 and 880 cm7'). In addition, a quantita- tive study of the selected functional groups was performed and the evolution of their indexes with the ageing time was then plotted in Fig. 7. Figs. 6 and 7 demonstrate that thermo-oxida- tive ageing induces, in contrast with the heterogeneous effects reported by reprocessing, quite progressive changes in the an- alyzed functional group indexes. As a whole, thermo-oxidative ageing caused a marked decrease in the unsaturated groups (trans-1,4 and vinyl-1,2 groups), while broad bands appear both in the hydroxyl and the carbonyl regions. These results are in agreement with previous studies performed on the photo- and thermo-oxidation of HIPS and other styrene/buta- diene copolymers by FTIR spectroscopy [14—16]. The trans-1,4 group index showed a slight decrease at the initial ageing time due to the protective effect of the antioxidants, but after the fourth day of thermo-oxidative ageing, the reduc- tion was considerable. This phenomenon is in accordance with the results of Israeli et al. [14], which reported that the thermal oxidation of HIPS shows an induction period, followed by 9 fast oxidation of nolvbutadiene and then bv a slow oxidation
Fig. 7. Evolution of the (©) vinyl-1,2 ratio, (MB) trans-1,4 ratio, (A) carbonyl ratio and (@) hydroxy] ratio, with the time for HIPS subjected to thermo-ox- idative ageing at 90 °C.
Fig. 7. Evolution of the (©) vinyl-1,2 ratio, (MB) trans-1,4 ratio, (A) carbonyl ratio and (@) hydroxy] ratio, with the time for HIPS subjected to thermo-ox- idative ageing at 90 °C.
Scheme 1. Polybutadiene microstructures: trans-1,4; cis-1,4; vinyl-1,2 groups.
Scheme 1. Polybutadiene microstructures: trans-1,4; cis-1,4; vinyl-1,2 groups.
Fig. 1. Curve-fitting of the virgin HIPS Raman spectra to five individual bands for the determination of the three individual PB conformers: 1550-1700 cm™! region.
Fig. 1. Curve-fitting of the virgin HIPS Raman spectra to five individual bands for the determination of the three individual PB conformers: 1550-1700 cm™! region.
Fig. 2. Raman spectra of the PB microstructure region of selected HIPS samples subjected to multiple processing. Fig. 2 shows the effect of multiple processing on polybutadiene microstructure in selected HIPS sam- ples; PB microstructure is, to some extent, affected by the repeated extrusion cycles, since the intensities of the bands slightly decrease with the successive reprocessing steps. The influence of multiple pro- cessing on the Raman indexes can be observed in Fig. 3; in general, the normalised areas for the three microstructures decrease slightly under the consecu- tive extrusion cycles. The thermo-mechanical degra- dation produced by the processing steps may induce chemical reactions in polybutadiene that could cause crosslinking of the rubber phase and alter
Fig. 2. Raman spectra of the PB microstructure region of selected HIPS samples subjected to multiple processing. Fig. 2 shows the effect of multiple processing on polybutadiene microstructure in selected HIPS sam- ples; PB microstructure is, to some extent, affected by the repeated extrusion cycles, since the intensities of the bands slightly decrease with the successive reprocessing steps. The influence of multiple pro- cessing on the Raman indexes can be observed in Fig. 3; in general, the normalised areas for the three microstructures decrease slightly under the consecu- tive extrusion cycles. The thermo-mechanical degra- dation produced by the processing steps may induce chemical reactions in polybutadiene that could cause crosslinking of the rubber phase and alter
Fig. 4. Raman spectra of the PB microstructure region of selected HIPS samples subjected to thermo-oxidation.
Fig. 4. Raman spectra of the PB microstructure region of selected HIPS samples subjected to thermo-oxidation.
Fig. 5. Evolution of the Raman functional group indexes with exposure time for the PB microstructure of HIPS subjected to thermo-oxidation at 90 °C: (Ml) trans-1,4; (O) cis-1,4; (@) vinyl- 1,2.
Fig. 5. Evolution of the Raman functional group indexes with exposure time for the PB microstructure of HIPS subjected to thermo-oxidation at 90 °C: (Ml) trans-1,4; (O) cis-1,4; (@) vinyl- 1,2.
Fig. 6. Isocronal representation of the storage modulus E’ (lower plot) and loss modulus E’ (upper plot) for virgin HIPS: (¥) 0.1 Hz; (x) 0.25Hz; (MM) 1Hz; (©) 3.98 Hz; (@) 10 Hz; (8) 39.81 Hz.
Fig. 6. Isocronal representation of the storage modulus E’ (lower plot) and loss modulus E’ (upper plot) for virgin HIPS: (¥) 0.1 Hz; (x) 0.25Hz; (MM) 1Hz; (©) 3.98 Hz; (@) 10 Hz; (8) 39.81 Hz.
Fig. 7. Viscoelastic properties as a function of temperature for selected HIPS samples subjected to multiple processing; (a) storage modulus (£’) and (b) loss modulus (£’): (@) virgin HIPS; (CO) HIPSr1; (©) HIPSr4; (p>) HIPSr6; (Ml) HIPSr9.
Fig. 7. Viscoelastic properties as a function of temperature for selected HIPS samples subjected to multiple processing; (a) storage modulus (£’) and (b) loss modulus (£’): (@) virgin HIPS; (CO) HIPSr1; (©) HIPSr4; (p>) HIPSr6; (Ml) HIPSr9.
Fig. 8. Viscoelastic properties as a function of temperature for selected HIPS samples subjected to thermo-oxidation at 90 °C; (a) storage modulus (£’) and (b) loss modulus (£’’): (@) virgin HIPS, (C4) aged 2 days, (©) aged 4 days, (p>) aged 8 days, (O) aged 12 days, (Ml) aged 16 days.
Fig. 8. Viscoelastic properties as a function of temperature for selected HIPS samples subjected to thermo-oxidation at 90 °C; (a) storage modulus (£’) and (b) loss modulus (£’’): (@) virgin HIPS, (C4) aged 2 days, (©) aged 4 days, (p>) aged 8 days, (O) aged 12 days, (Ml) aged 16 days.
* Parameters calculated from the Fuoss—Kirkwood plot at a frequency of 1 Hz. Influence of multiple processing on the viscoelastic parameters related to the glass transition relaxations of PB and PS phases in HIP‘ according to the free-volume theory Table 1
* Parameters calculated from the Fuoss—Kirkwood plot at a frequency of 1 Hz. Influence of multiple processing on the viscoelastic parameters related to the glass transition relaxations of PB and PS phases in HIP‘ according to the free-volume theory Table 1
* Parameters calculated from the Fuoss—Kirkwood plot at a frequency of 1 Hz. Influence of thermo-oxidation on the viscoelastic parameters related to the glass transition relaxations of PB and PS phases in HIPS according to the free-volume theory Table 2
* Parameters calculated from the Fuoss—Kirkwood plot at a frequency of 1 Hz. Influence of thermo-oxidation on the viscoelastic parameters related to the glass transition relaxations of PB and PS phases in HIPS according to the free-volume theory Table 2
Fig. 9. Arrhenius maps for the PB and PS glass transition relaxations for selected HIPS samples subjected to multiple processing: (@ virgin HIPS; (4) HIPSr1; (©) HIPSr4; (p>) HIPSr6; (Ml) HIPSr9.
Fig. 9. Arrhenius maps for the PB and PS glass transition relaxations for selected HIPS samples subjected to multiple processing: (@ virgin HIPS; (4) HIPSr1; (©) HIPSr4; (p>) HIPSr6; (Ml) HIPSr9.
Fig. 10. Arrhenius maps for the PB and PS glass transition relaxations for selected HIPS samples subjected to thermo-oxidation: (@) virgin HIPS, (LC) aged 2 days, (©) aged 4 days, (p>) aged 8 days, (O) aged 12 days, (I) aged 16 days.
Fig. 10. Arrhenius maps for the PB and PS glass transition relaxations for selected HIPS samples subjected to thermo-oxidation: (@) virgin HIPS, (LC) aged 2 days, (©) aged 4 days, (p>) aged 8 days, (O) aged 12 days, (I) aged 16 days.
Fig. 11. SEM micrographs of HIPS samples: (a) virgin HIPS (low magnification); (b) virgin HIPS (high magnification); (c) reprocessed HIPS (9 cycles); (d) thermo-oxidated HIPS (4 days); (e) thermo-oxidated HIPS (8 days) and (f) thermo-oxidated HIPS (16 days). peratures with increasing exposure time to thermo- oxidation, and is especially noticeable for longer exposure times (Fig. 10). The chemical reactions induced by oxidation are associated with an increase in the glass transition temperature of polybutadiene [8,28], which can be related to the changes in the PB microstructure. On one hand, oxidation causes extensive crosslinking in the PB phase, which restricts the mobility of the polymeric chains. On the other hand, as confirmed by Raman spectros- copy, oxidation affects the cis-1,4 and trans-1,4 con- formers more severely than it does that of vinyl-1,2; this leads to oxidised HIPS samples with higher vinyl content than the original ones, which exhibit higher glass transition temperatures. The free-vol- ume parameter, however, shows a slight decrease This contrasting behaviour for short and long exposure times to thermo-oxidation becomes more evident for the PS phase. The Arrhenius plots for the PS glass transition shift to higher temperatures for shorter exposure times, but drastically shift to lower temperatures for longer times; similarly, the
Fig. 11. SEM micrographs of HIPS samples: (a) virgin HIPS (low magnification); (b) virgin HIPS (high magnification); (c) reprocessed HIPS (9 cycles); (d) thermo-oxidated HIPS (4 days); (e) thermo-oxidated HIPS (8 days) and (f) thermo-oxidated HIPS (16 days). peratures with increasing exposure time to thermo- oxidation, and is especially noticeable for longer exposure times (Fig. 10). The chemical reactions induced by oxidation are associated with an increase in the glass transition temperature of polybutadiene [8,28], which can be related to the changes in the PB microstructure. On one hand, oxidation causes extensive crosslinking in the PB phase, which restricts the mobility of the polymeric chains. On the other hand, as confirmed by Raman spectros- copy, oxidation affects the cis-1,4 and trans-1,4 con- formers more severely than it does that of vinyl-1,2; this leads to oxidised HIPS samples with higher vinyl content than the original ones, which exhibit higher glass transition temperatures. The free-vol- ume parameter, however, shows a slight decrease This contrasting behaviour for short and long exposure times to thermo-oxidation becomes more evident for the PS phase. The Arrhenius plots for the PS glass transition shift to higher temperatures for shorter exposure times, but drastically shift to lower temperatures for longer times; similarly, the
* Identification by injection of standard substances; ” Proposed identification by comparison to the NIST database; ° Proposed identification through bibliographic reference [24]; ‘ Proposed identification through bibliographic reference [27]; ° Relative quantification respect 4-methylstyrene (I.S.); ‘ Relative quantification respect o-terpheny] (1.S.)
* Identification by injection of standard substances; ” Proposed identification by comparison to the NIST database; ° Proposed identification through bibliographic reference [24]; ‘ Proposed identification through bibliographic reference [27]; ° Relative quantification respect 4-methylstyrene (I.S.); ‘ Relative quantification respect o-terpheny] (1.S.)
~ 1aenutication Dy injection Of Standard substances; § rroposed 1aenulicauon Dy CoOMparison to the Niol database; ° Proposed identification through bibliographic reference [24]; * Proposed identification through bibliographic reference [27]; ° Relative quantification respect 4-methylstyrene (I.S.); ' Relative quantification respect o-terpheny] (1.S.)
~ 1aenutication Dy injection Of Standard substances; § rroposed 1aenulicauon Dy CoOMparison to the Niol database; ° Proposed identification through bibliographic reference [24]; * Proposed identification through bibliographic reference [27]; ° Relative quantification respect 4-methylstyrene (I.S.); ' Relative quantification respect o-terpheny] (1.S.)
Scheme 1 - Key parameters for the quality assessment of recycled plastics.
Scheme 1 - Key parameters for the quality assessment of recycled plastics.
Scheme 2 - Sampling of the different HIPS materials through the mechanical recycling process Polymeric materials suffer degradation processes in each step of their life cycle, mostly in processing and service life, which modify their mechanical properties and long-term stability [2]. An experimental approach entailing multiple pro- cessing and thermo-oxidation has been proposed, to model the degradation processes undergone by recycled polymers during their life cycle [5]. Different strategies can be employed for the characterisation of polymer degradation: analysing the changes in the chemical, physical and mechanical proper- ties; studying the variations in molar mass and composition; or determining the degradation products [6]. An integrated analytical approach considering the macroscopic properties, HIPS samples were collected for analysis at different points of the mechanical recycling process (Acteco, Spain). Scheme 2 shows the mechanical recycling flow diagram and the points at which the different samples were taken: Scrap HIPS employed as raw material in the recycling process, intermediate samples
Scheme 2 - Sampling of the different HIPS materials through the mechanical recycling process Polymeric materials suffer degradation processes in each step of their life cycle, mostly in processing and service life, which modify their mechanical properties and long-term stability [2]. An experimental approach entailing multiple pro- cessing and thermo-oxidation has been proposed, to model the degradation processes undergone by recycled polymers during their life cycle [5]. Different strategies can be employed for the characterisation of polymer degradation: analysing the changes in the chemical, physical and mechanical proper- ties; studying the variations in molar mass and composition; or determining the degradation products [6]. An integrated analytical approach considering the macroscopic properties, HIPS samples were collected for analysis at different points of the mechanical recycling process (Acteco, Spain). Scheme 2 shows the mechanical recycling flow diagram and the points at which the different samples were taken: Scrap HIPS employed as raw material in the recycling process, intermediate samples
were carried out in a Mettler-Toledo SDTA/TGA851 (Columbus, OH). Approximately 10 mg of sample was heated from 40°C to 700°C at a heating rate of 10°C min“, under a nitrogen gas flow of 50mLmin-}. after grinding and washing, and different grades of final recy- cled HIPS material. Virgin HIPS, commercial grade Polystyrol 486M (BASF Espanola S.A., Spain), was employed as reference material. Table 1 describes the sample materials employed in the analyses.
were carried out in a Mettler-Toledo SDTA/TGA851 (Columbus, OH). Approximately 10 mg of sample was heated from 40°C to 700°C at a heating rate of 10°C min“, under a nitrogen gas flow of 50mLmin-}. after grinding and washing, and different grades of final recy- cled HIPS material. Virgin HIPS, commercial grade Polystyrol 486M (BASF Espanola S.A., Spain), was employed as reference material. Table 1 describes the sample materials employed in the analyses.
Table 2 - Thermal parameters of differential scanning calorimetry: glass transition temperature of the polystyrene phase (Tg), oxidation induction time (OIT), and oxidation temperature (Tox) lene and polypropylene contaminations, respectively, in these materials.
Table 2 - Thermal parameters of differential scanning calorimetry: glass transition temperature of the polystyrene phase (Tg), oxidation induction time (OIT), and oxidation temperature (Tox) lene and polypropylene contaminations, respectively, in these materials.
Fig. 1 - Determination of polymeric impurities in the HIPS samples by DSC: thermograms of the second melting ramp.
Fig. 1 - Determination of polymeric impurities in the HIPS samples by DSC: thermograms of the second melting ramp.
able 3 - Results from thermogravimetric analysis: onset temperature of thermal degradation (Tonset), decomposition >mperature range, temperature of maximum decomposition rate (Tmax), and residue percentage
able 3 - Results from thermogravimetric analysis: onset temperature of thermal degradation (Tonset), decomposition >mperature range, temperature of maximum decomposition rate (Tmax), and residue percentage
Fig. 2- TGA mass-loss thermograms resulting from the thermal decomposition of the HIPS samples.
Fig. 2- TGA mass-loss thermograms resulting from the thermal decomposition of the HIPS samples.
Fig. 3 - FTIR spectra of the HIPS samples: (a) hydroxyl region (3100-3600 cm~‘); (b) carbonyl region (1620-1800 cm-~*); (c) unsaturated region (880-1000 cm~*).
Fig. 3 - FTIR spectra of the HIPS samples: (a) hydroxyl region (3100-3600 cm~‘); (b) carbonyl region (1620-1800 cm-~*); (c) unsaturated region (880-1000 cm~*).
Fig. 4 -— FTIR functional group indexes (hydroxyl; carbonyl; trans-1,4; vinyl-1,2) for the HIPS samples.
Fig. 4 -— FTIR functional group indexes (hydroxyl; carbonyl; trans-1,4; vinyl-1,2) for the HIPS samples.
Fig. 5 - Curve fitting of the Raman spectra for the determination of the three individual PB conformers in the 1550-1700 cm-? region: (a) virgin HIPS; (b) HIPS1; (c) HIPS3; (d) HIPS5; (e) HIPS6.
Fig. 5 - Curve fitting of the Raman spectra for the determination of the three individual PB conformers in the 1550-1700 cm-? region: (a) virgin HIPS; (b) HIPS1; (c) HIPS3; (d) HIPS5; (e) HIPS6.
Fig. 6 - Raman functional group indexes (vinyl-1,2; cis-1,4; trans-1,4) for different HIPS samples.
Fig. 6 - Raman functional group indexes (vinyl-1,2; cis-1,4; trans-1,4) for different HIPS samples.
Fig. 7 - Total ion chromatogram (TIC) of the low molecular weight compounds extracted from virgin HIPS.
Fig. 7 - Total ion chromatogram (TIC) of the low molecular weight compounds extracted from virgin HIPS.
Figure 2
Figure 2
Figure 3
Figure 3
Liquid Chromatography
Liquid Chromatography
Calculated BFR accumulative concentration (mg/g)
Calculated BFR accumulative concentration (mg/g)
Figure 2. Schematic drawing of microenvironment chamber for accelerated ageing tests. Wallstrom et al., Microbiological growth testing of polymeric materials: an evaluation of new methods, Polym. Test. 24, 5,557, Copyright Elsevier (2005); Printed with permission.
Figure 2. Schematic drawing of microenvironment chamber for accelerated ageing tests. Wallstrom et al., Microbiological growth testing of polymeric materials: an evaluation of new methods, Polym. Test. 24, 5,557, Copyright Elsevier (2005); Printed with permission.
Figure 3. Procedure for modelling the life cycle of recycled plas- tics: a) multiple processing; b) thermo-oxidation. Vilaplana et al., Degradation of recycled high-impact polystyrene. Simulation by reprocessing and thermo-oxidation, Polym. Degrad. Stab. 91, 9, 2163, Copyright Elsevier (2006); Printed with permission.
Figure 3. Procedure for modelling the life cycle of recycled plas- tics: a) multiple processing; b) thermo-oxidation. Vilaplana et al., Degradation of recycled high-impact polystyrene. Simulation by reprocessing and thermo-oxidation, Polym. Degrad. Stab. 91, 9, 2163, Copyright Elsevier (2006); Printed with permission.
Recent research carried out by our group on the char- acterisation of recycled polymers has lead to the identi- fication of three key properties for the quality assessment Figure 4. Key properties for quality assessment of recycled plas- tics. Vilaplana et al., Analytical strategies for the quality assess- ment of recycled high-impact polystyrene: A combination of thermal analysis, vibrational spectroscopy, and chromatography, Anal. Chim. Acta 604, 1, 18, Copyright Elsevier (2007); Printed with permission.
Recent research carried out by our group on the char- acterisation of recycled polymers has lead to the identi- fication of three key properties for the quality assessment Figure 4. Key properties for quality assessment of recycled plas- tics. Vilaplana et al., Analytical strategies for the quality assess- ment of recycled high-impact polystyrene: A combination of thermal analysis, vibrational spectroscopy, and chromatography, Anal. Chim. Acta 604, 1, 18, Copyright Elsevier (2007); Printed with permission.
Figure 7. DSC analysis of oxidative stability of reprocessed and recycled HIPS using OIT measurements at 160 °C.
Figure 7. DSC analysis of oxidative stability of reprocessed and recycled HIPS using OIT measurements at 160 °C.
Figure 8. Monitoring the FTIR functional group indexes in waste HIPS samples throughout the mechanical recycling process.
Figure 8. Monitoring the FTIR functional group indexes in waste HIPS samples throughout the mechanical recycling process.
Figure 9. Comparison of the efficiency of brominated flame retardant extraction using different extraction procedures.
Figure 9. Comparison of the efficiency of brominated flame retardant extraction using different extraction procedures.
Table 1. Continued.
Table 1. Continued.
Related topics:
Analytical ChemistryPolymer ChemistryVibrational SpectroscopyMicrowave-assisted extractionInfrared Spectrometry
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