Melt rheology of polymer blends from melt flow index

Polymer Science Series A, 2015

The aim of this work is to study the rheological properties of PVDF/LDPE blends in the molten state, in relation to shear rate, shear stress and temperature. Blends of LDPE and PVDF at different compo sitions, namely PVDF/LDPE = 0/100, 30/70, 50/50, 70/30, 100/0 were realized. The blends were prepared by using brabender plastograph and measurements were carried out by using capillary rheometer. For study ing the viscous properties non Newtonian index n, true viscosity η and the flow activation energy E were determined. The melt elasticity has been studied in term of die swell ratio B. The results show that PVDF/LDPE blends behave in pseudo plastic manner (n < 1), plots of true viscosity versus blending ratio go through a minimum nearly at blending ratio (50/50), and the flow activation energy decreases with increasing shear rate at the wall γ but it increases with increasing true shear stress τ. The results of die swell ratio show that, B increases linearly with increasing true shear stress τ, while B decreases with increasing L/R. It was also found that a maximum of elastic properties is observed at certain blending ratio. This phenomenon can be attributed to the amount of elastic deformation energy stored in the melt flow and its transition due to the viscoelastic difference between the two phases.

Polymer Engineering & Science, 2007

The rheological, thermal, and mechanical properties of blends consisting of a linear high melt flow rate polypropylene (PP) and two branched PPs are characterized in detail. Blends containing branched PPs display evidence of miscibility in the melt state and exhibit high melt elasticity together with significant strain hardening in extensional deformation while retaining good flow properties. Out of the two blend systems examined the blends containing linear and branched PPs with similar melt flow rates have better mechanical properties, higher crystallization temperatures, and higher crystallinities.

Rheologica Acta, 1996

A series of melt blended commercial linear and branched polyethylenes are used to explore the generality of blending laws. The

In this work, rheological properties of poly(lactic acid) (PLA), low density polyethylene (LDPE) polymer blends were investigated in the molten state. The experiments were carried on a capillary rheometer. The effect of shear stress, temperature and blending ratio on the flow activation energy at a constant shear stress and melt viscosity of the blends are described. The results showed that the PLA/LDPE polymer blends are pseudo plastic in nature, where there viscosity decreases with increasing shear stress. Also it was found the melt viscosity of the blends decreases with increasing PLA content in the blend.

Journal of Applied Polymer Science, 2002

Phase morphology development in immiscible blends of polystyrene (PS)/nylon 6 was investigated. The blends were prepared by melt blending in a twin-screw extruder. The influence of the blend ratio, rotation speed of the rotors, and time of mixing on the phase morphology of the blends was carefully analyzed. The morphology of the samples was examined under a scanning electron microscope (SEM) and the SEM micrographs were quantitatively analyzed for domain-size measurements. From the morphology studies, it is evident that the minor component, whether PS or nylon, forms the dispersed phase, whereas the major component forms the continuous phase. The 50/50 PS/nylon blend exhibits cocontinuous morphology. The continuity of the dispersed phase was estimated quantitatively based on the preferential solvent-extraction technique, which suggested that both phases are almost continuous at a 50/50 blend composition. The effect of the rotor speed on the blend morphology was investigated. It was observed that the most significant breakdown occurred at an increasing rotor speed from 9 to 20 rpm and, thereafter, the domain size remained almost the same even when the rotor speed was increased. The studies on the influence of the mixing time on the blend morphology indicated that the major breakdown of the dispersed phase occurred at the early stages of mixing. The melt rheological behavior of the blend system was studied using a capillary rheometer. The effect of the blend ratio and the shear stress on the melt viscosity of the system was investigated. Melt viscosity decreased with increase in the shear stress, indicating pseudoplastic behavior. With increase of the weight fraction of PS, the melt viscosity of the system decreased. The negative deviation of the measured viscosity from the additivity rule indicated the immiscibility of the blends. The domain size versus the viscosity ratio showed a minimum value when the viscosities of the two phases were matched, in agreement with Wu's prediction. The morphology of the extrudates was analyzed by SEM. From these observations, it was noted that as the shear rate increased the particle size decreased considerably.

A series of blends of Acrylonitrile-Butadiene-Styrene (ABS) and Polycarbonate (PC) and another series of polyvinylidene fluoride, PVDF, and low density polyethylene, LDPE, were prepared and characterized for some of their rheological properties. The blends of a series were prepared by mixing the components, with different weight % composition, in a molten state using Brabender Plastograph. Visco-elastic parameters were measured using the capillary rheometer (Melt Index 3/80). Die-swelling rate, (B), was determined for different composition samples and correlated with the end pressure drop, (Pend), the end correction, (e), the apparent shear rate, (a), the apparent shear stress, (a), and the length-radius ratio, (L/R). The effects of blending composition on the die-swell rate, (B), the end correction, (e), and the shear strain, (SR) were also studied for the prepared series of blends.

Arabian Journal of Chemistry, 2015

Reactive melt blending of low-density polyethylene LDPE with a low molecular weight poly (acrylic acid) PAA in the presence of benzoyl peroxide (BPO) free radical initiator was studied by means of a HAAKE torque rheometer and a capillary rheometer FTIR spectroscopy and was used to characterize the structure of LDPE/PAA blends. The rheological behavior of blends has been investigated at different temperatures (170, 190, 210 and 230°C) and shear rates (5.43, 18.1, 54.3, 181 and 543 S À1). With a rise of temperature and increasing shear rates the shear stress of blends increases nonlinearly. The melt viscosity increases with the increase in the PAA proportion but decreases with the increasing shear rate and shear stress. The melts of all the blends are pseudoplastic in nature. The flow behavior index (n) of the blends decreases with the increase in the PAA proportion and with the increase in the temperature. The temperature sensitivity of the flow behavior of the blends is studied using Arrhenius plots. The system exhibits relatively low activation energy which means less sensitivity to temperature with an increase in the PAA ratio.

Petroleum & Petrochemical Engineering Journal, 2019

Two polymer blends were prepared. The first one was Poly methyl methacrylate (PMMA) and Poly vinyl acetate (PVAc), and the second was Poly vinyl chloride (PVC) and Polystyrene (PS). The first blend prepared by mixing two polymers (PMMA, PVAc) with co-solvent (Chloroform) at different weight percentages (0/100, 20/80, 40/60, 50/50, 60/40, 80/20, 100/0). The second blend prepared by mixing two polymers (PVC, PS) with co-solvent N,N dimethylacetamide (DMAC) at different weight percentages (0/100,20/80,40/60,50/50,60/40,80/20,100/0). Two processes were used for preparation; dissolution process was used at a room temperature (25°C) and (1atm.) pressure using co-solvent. Viscosity test was performed for stock solutions (1%wt/v=1g/dL) and other concentrations (0.75, 0.6, 0.5, 0.4, 0.3 g/dL) these concentrations are obtained by dilution of stock solution. The obtained data were collected and substituted accordance to equations (Huggins Equation) and certain criteria (Interaction parameters ΔB,μ) to identify the miscibility (or compatibiliIty).To get polymer blends in solid state, The same procedure to prepare the stock solution of diluted solutions followed but the stock solutions of polymer blends were at concentration (10%wt/v) for all different compositions and then followed solvent casting (evaporation then drying). The solid state samples were taken to hold tests of DSC and FTIR. The aim of the present work was to study the thermodynamic behavior of polymer blend via determination of miscibility. Miscibility (or immiscibility) tests are performed in three techniques: viscometry method, DSC analyzer and FTIR to test polymer blend in solid state. It was found from the viscosity method that for first blend (PMMA/PVAc), the interaction parameters (ΔB,μ) are positive for all compositions therefore the system is miscible whilst the second system (PVC/PS) is immiscible where the interaction parameters (ΔB,μ) are negative.

Polymer, 1998

The effects of composition and resulting morphology on rheology of blends of polyethylene and polyamide 12, two immiscible polymers having the same Newtonian viscosity but different elasticity, were studied in the whole range of volume fraction. The composition dependence of zero shear rate viscosity ~/0 and first normal stress difference N~ show a positive deviation from the additivity law: ~/0 and Nt increase gradually at low and moderate volume fraction of the dispersed phase, but remain almost constant in the phase inversion region. The variation of zero shear rate viscosity has been analysed, in relation to morphology observations, by an emulsion model as developed by Oldroyd in the case of droplet-type morphology and by a layer model which takes into account the simultaneous presence of droplets and fibres when the morphology is partially fibrillar. If the volume fraction of the dispersed phase is not too low, the first normal stress difference is proportional to shear rate, in agreement with the prediction of Doi-Ohta theory, as a result of morphology modifications during flow. The linear viscoelastic behaviour has been analysed using Palierne's model and the interfacial tension between the two polymers has been determined by fitting the dynamic moduli with this model.

Journal of Applied Polymer Science, 2012

The dynamic rheological behavior of low‐density polyethylene (LDPE)/ultra‐high‐molecular‐weight polyethylene (UHMWPE) blends and linear low‐density polyethylene (LLDPE)/UHMWPE blends was measured in a parallel‐plate rheometer at 180, 190, and 200°C. Analysis of the log–additivity rule, Cole–Cole plots, Han curves, and Van Gurp curves of the LDPE/UHMWPE blends indicated that the blends were miscible in the melt. In contrast, the rheological properties of LLDPE/UHMWPE showed that the miscibility of the blends was decided by the composition of LLDPE. The differential scanning calorimetry results and scanning electron microscopy photos of the LLDPE/UHMWPE blends were consistent with the rheological properties, whereas with regard to the thermal and morphological properties of LDPE/UHMWPE blends, the results reveal three endothermic peaks and phase separation, which indicated a liquid–solid phase separation in the LDPE/UHMWPE blends. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013