Melt rheology of nanometre‐calcium‐carbonate‐filled acrylonitrile–butadiene–styrene (ABS) copolymer composites during capillary extrusion

The melt flow properties during capillary extrusion of nanometre‐calcium‐carbonate‐filled acrylonitrile–butadiene–styrene (ABS) copolymer composites were measured by using a Rosand rheometer to identify the effects of the filler content and operation conditions on the rheological behaviour of the sample melts. The experiments were conducted under the following test conditions: temperature varied from 220 to 240 °C and shear rate ranged from 10 to 10⁴ s^?1. The filler volume fractions were 0, 10, 20, 30, 40 and 50%. The results showed that the shear flow did not strictly obey the power law under the test conditions, and that the entry pressure drop (ΔP_en) and the extension stress (σ_e) in entry flow increased nonlinearly, while the melt shear viscosity (η_s) and extension viscosity (η_e) decreased with increasing the wall shear stress (τ_w) at constant test temperature. The dependence of the melt shear viscosity on the test temperature was approximately consistent with the Arrhenius expression at fixed τ_w. When τ_w was constant, η_s and η_e increased while ΔP_en and σ_e decreased with the addition of the filler volume fraction. © 2002 Society of Chemical Industry     

Effect of polymer matrix on the rheology of hydroxyapatite‐filled polyethylene composites

The effect of matrix polymer and filler content on the rheological behavior of hydroxyapatite‐filled injection molding grade high‐density polyethylene (HDPE) has been studied. Studies of the flow curves revealed that the matrix and the composite exhibit three distinct regions in the flow curve, namely, a pseudoplastic region at low to moderate shear rates, a plateau and a second pseudoplastic region at high shear rates. The shear stress corresponding to the plateau (τ_c) is dependent on both the filler concentration and the melt temperature. Addition of HA in the HDPE matrix increases the value of τ_c and decreases compressibility of the melt. An increase in temperature also raises the value of τ_c. From the nature of flow curves it is concluded that the matrix polymer largely decides the rheology of the composite.     

Rheological behaviors of glass bead‐ and wollastonite‐filled polypropylene composites modified with thermoplastic elastomers

Steady‐ and oscillatory‐shear rheological behaviors of polypropylene/glass bead (PP/GB) and PP/wollastonite (PP/W) melts modified with thermoplastic elastomers, poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) copolymer (SEBS) and the corresponding block copolymer grafted with maleic anhydride (SEBS‐g‐MA), were examined by means of a parallel‐plate rheometer. With adding the elastomers (SEBS and SEBS‐g‐MA) and fillers (spherical GB and acicular W) to PP, viscosity especially at low shear rates and shear‐thinning flow behavior at high shear rates were pronounced as evidenced quantitatively by Carreau–Yasuda (CY) parameters, but Cox–Merz analogy became weakened. Besides, melt‐elasticity in terminal region and relaxation time (t_c) in crossing point increased, indicating an enhancement in quasi‐solid behavior of molten PP. Comparing with the elastomers, rheological behaviors of molten PP were more influenced with adding the rigid fillers, especially with W due to distinct acicular shape of W particles. SEBS‐g‐MA elastomer more affected rheological behaviors of the ternary composites than SEBS elastomer, implying that SEBS elastomer and the filler particles behaved individually (i.e., development of separate microstructure) in (PP/GB)/SEBS and (PP/W)/SEBS ternary composites, but core‐shell microstructure developed with strong interfacial adhesion by adding SEBS‐g‐MA elastomer, and the filler particles encapsulated with the thick SEBS‐g‐MA elastomer interlayer (i.e., core‐shell particles) acted like neither big elastomer particles nor like individual rigid particles in melt‐state. Moreover, effects of SEBS‐g‐MA elastomer reached a maximum on rheological behaviors of (PP/W)/SEBS‐g‐MA ternary composite, indicating a synergy between core‐shell microstructure and acicular W particles. Correlations between oscillatory‐shear flow properties and microstructures of the blends and composites were evaluated using Cole–Cole (CC), Han–Chuang (HC), and van Gurp–Palmen (vGP) plots. COMPOS., 2012. © 2012 Society of Plastics     

Effect of bark flour on melt rheological behavior of high density polyethylene

The melt rheological behavior of neem bark flour (BF) filled high density polyethylene (HDPE) has been studied at varying volume fraction (?_f) from 0 to 0.26 at 180, 190, and 200°C in the shear rate range from 100 to 5000 s^?1 using extruded pellets of the composites. The melt viscosity of HDPE increases with ?_f because the BF particles obstruct the flow of HDPE. With the incorporation of the coupling agent HDPE‐g‐MAH, the viscosity decreased compared to the corresponding compositions in the HDPE/BF systems due to a plasticizing/lubricating effect by HDPE‐g‐MAH. The composites obeyed power law behavior in the melt flow. The power law index decreases with increase in the filler content and increases with temperature for the corresponding systems while the consistency index showed the opposite trend. The activation energy for viscous flow exhibited inappreciable change with either ?_f or inclusion of the coupling agent, however, the pre‐exponential factor increased with filler concentration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of glass bead content and surface treatment on viscoelasticity of filled polypropylene/elastomer hybrid composites

The dynamic mechanical properties of A‐glass bead filled polypropylene (PP)/ethylene–propylene–diene monomers polymer (EPDM) ternary composites have been measured over a temperature range from −80 °C to 100 °C and at a fixed frequency of 1 Hz, using a dynamic mechanical analyser (DMA), to identify the effects of the filler content and its surface treatment with a silane coupling agent on the dynamic viscoelastic behaviour. The results show that the storage modulus (E′_c) and loss modulus (E ″_c) of these composites with 10% volume fraction of EPDM at 25 °C increase non‐linearly with increasing volume fraction of glass beads (ϕ_g). At the same test conditions, the E′_c value of the PP/EPDM filled with pretreated glass beads is higher than that of the uncoated glass bead filled PP/EPDM system, especially at higher ϕ_g, while the difference in E ″_c between both systems is very small. The mechanical damping for the former decreases with increasing ϕ_g, but the opposite is true for the latter. The glass transition temperature of these composites varies irregularly with ϕ_g. The dynamic complex viscosity increases nonlinearly with an increase of ϕ_g. In addition, the interfacial structure between the matrix and inclusions has been observed by means of a scanning electron microscope. © 1999 Society of Chemical Industry     

Crystallization behavior of glass bead‐filled low‐density polyethylene composites

The effects of the filler content and the filler size on the crystallization and melting behavior of glass bead‐filled low‐density polyethylene (LDPE) composites have been studied by means of a differential scanning calorimeter (DSC). It is found that the values of melting enthalpy (ΔH_c) and degree of crystallinity (x_c) of the composites increase nonlinearly with increasing the volume fraction of glass beads, ϕ_f, when ϕ_f is greater than 5%; the crystallization temperatures (T_c) and the melting temperatures (T_m) of the composites are slightly higher than those of the pure LDPE; the effects of glass bead size on x_c, T_c, and T_m are insignificant at lower filler content; but the x_c for the LDPE filled with smaller glass beads is obviously greater than that of the filled system with bigger ones at higher ϕ_f. It suggests that small particles are more beneficial to increase in crystallinity of the composites than big ones, especially at higher filler content. In addition, the influence of the filler surface pretreated with a silane coupling agent on the crystallization behavior are not too outstanding at lower inclusion concentration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 687–692, 1999     

Effect of filler content and surface treatment on the tensile properties of glass‐bead‐filled polypropylene composites

The tensile properties of polypropylene (PP) filled with two A‐glass beads with the same size, PP/3000 (glass bead surface pretreated with a silane coupling agent) and PP/3000U (no surface pretreatment), have been measured by using an Instron materials testing machine at room temperature, to identify the effects of the filler surface pretreatment and its content on the tensile properties of these composites. The results show that the Young's modulus E_c of the composites increases non‐linearly with increasing volume fraction of glass beads ϕ_f, while the tensile yield strength σ_yc and tensile stress at break σ_bc of the composites decrease with an increase of ϕ_f, in the ϕ_f range 0–30%. Furthermore, the values of E_c and σ_bc of the PP/3000 system are somewhat higher than those of the PP/3000U system under the same test conditions, but this is in contrast to the tensile strain at break ε_bc and tensile fracture energy E_bc, especially at higher ϕ_f values. Good agreement is shown between the measured tensile strength and the predicted value by using an equation proposed in previous work. In addition, ε_bc and E_bc reach maximum values at ϕ_f = 25% for both systems. This indicates that there is a brittle–ductile transition for the composites in tension. © 2000 Society of Chemical Industry     

Melt flow behavior in capillary extrusion of nanosized calcium carbonate‐filled poly(L‐lactic acid) biocomposites

Nanosized calcium carbonate (nano‐CaCO₃)‐filled poly‐L ‐lactide (PLLA) biocomposites were compounded by using a twin‐screw extruder. The melt flow behavior of the composites, including their entry pressure drop, melt shear flow curves, and melt shear viscosity were measured through a capillary rheometer operated at a temperature range of 170–200°C and shear rates of 50–10³ s^?1. The entry pressure drop showed a nonlinear increase with increasing shear stress and reached a minimum for the filler weight fraction of 2% owing to the “bearing effect” of the nanometer particles in the polymer matrix melt. The melt shear flow roughly followed the power law, while the effect of temperature on the melt shear viscosity was estimated by using the Arrhenius equation. Hence, adding a small amount of nano‐CaCO₃ into the PLLA could improve the melt flow behavior of the composite. POLYM. ENG. SCI., 52:1839–1844, 2012. © 2012 Society of Plastics Engineers     

Melt density and volume flow rate of polypropylene/Al(OH)3/Mg(OH)2 flame retardant composites

Polypropylene (PP) flame retardant composites filled with aluminum hydroxide (Al(OH)₃), magnesium hydroxide (Mg(OH)₂) as well as zinc borate (ZB) were prepared with a twin‐screw extruder. The melt volume flow rate (MVR) and density of the composites were measured by means of a melt flow rate instrument under experimental conditions with temperature of 180°C and load varying from 2.16 to 5 kg, to identify the effects of the particle size and content. The results showed that MVR of the composites decreased with an increase of the filler weigh fraction (?_f) when ?_f was more than 10 phr. The MVR decreased first and then increased with an increase of the filler diameter (d). The melt density (ρ_m) of the composites increased linearly with an increase of ?_f and decreased linearly with the increase of d. In addition, the ρ_m increased with an increase of load. Under the same experimental conditions, the MVR decreased slightly while the ρ_m increased somewhat with addition of ZB for the PP/Al(OH)₃/Mg(OH)₂ composite systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Melt shear viscosity of PP/Al(OH)3/Mg(OH)2 flame retardant composites at high extrusion rates

The melt apparent shear viscosity (η_a) of polypropylene (PP) composites filled with aluminum hydroxide [Al(OH)₃] and magnesium hydroxide [Mg(OH)₂] was measured by means of a capillary rheometer under experimental conditions of temperature ranging from 180 to 200°C and apparent shear rate varying from 10 to 2 × 10³ s⁻¹, to identify the effects of the filler particle content and size on the melt viscosity. The results showed that the melt shear flow of the composites obeyed the power law and presented pseudoplastic behavior. The dependence of η_a on temperature was consistent with the Arrhenius equation. The sensitivity of η_a for the composite melts to temperature was greater than that of the unfilled PP, and weakened with increasing apparent shear rate. The η_a increased linearly with an increase of the weigh fraction of the flame retardant, especially in the low apparent shear rate region. The η_a of the composites decreased slightly with an increase of particle size of flame retardant. Moreover, the variation for the η_a with particle size of flame retardant was much less than with apparent shear rate under these test conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Tensile and Impact Properties of Hollow Glass Bead‐Filled PVC Composites

The tensile and notched Izod impact properties of poly(vinyl chloride) (PVC) composites filled with hollow glass beads (HGB) were measured at room temperature by means of an Instron materials testing machine to investigate the effects of the filler content and size on these mechanical properties. The results showed that the tensile yield strength (σ_yc) decreased gently with increasing HGB volume fraction (ϕ _f), while the tensile break strength (σ_bc) of the composites was somewhat greater than that of the unfilled PVC within ϕ _f = 0–20%. In addition, the dependence of σ_bc on ϕ _f was not obvious. The effect of HGB size on both σ_yc and σ_bc was insignificant. When ϕ _f < 5%, the notched impact strength (σ_IC) of the composites decreased quickly with increasing ϕ _f, and then it decreased slightly with the increase of ϕ _f. Similarly, the influence of the filler size on the impact properties was insignificant. Furthermore, the σ_yc of the samples was estimated using a tensile equation proposed in a previous paper. A good agreement was shown between the calculations and the measured data.     

First normal stress difference in capillary extrusion flow of nanometer calcium carbonate‐filled PLLA biocomposites

The nanometer calcium carbonate (nano‐CaCO₃)‐filled poly‐L ‐lactide (PLLA) biocomposites were prepared using a twin‐screw extruder. The first normal stress difference of the composites were measured by means of a capillary rheometer under experimental conditions with temperatures ranging from 170 to 200°C and shear rates varying from 50 to 10³ s^?1. The first normal stress difference (N₁) increased roughly linearly with increasing shear stress (τ_w). The sensitivity of the N₁ to τ_w increased with an increase of the die length–‐diameter ratio, and the N₁ value varied slightly with the filler weight fraction (?_f) as test temperature was constant. When the shear stress was fixed, the N₁ reached a minimum value for ?_f = 1%. The values of the N₁ of the composite melts decreased roughly linearly with a rise of temperature when the shear rate was constant. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Glass-fiber-reinforced polypropylene/EPDM blend. I. Melt rheological properties

Melt rheological properties of the blend of isotactic polypropylene (PP) and ethylene propylene diene rubber (EPDM) at varying ratios and of the glass fiber (GF) filled PP and PP/EPDM blend by varying both GF loading and blending ratio of the polyblend matrix are studied. Rheological measurements at 220°C in shear rate range 10¹?10⁴s^?1 were made on a capillary rheometer. Scanning electron micrographs of the extrudates are presented to show the morphology and the alignment of the glass fibers with respect to the flow direction. Variations of pseudoplasticity index, melt viscosity, and melt elasticity with EPDM content in PP/EPDM blend, and with varying GF content at any given composition of the matrix in PP/EPDM/GF ternary system, in the studied range are presented and discussed. Resultes on melt viscosity and melt elasticity show (i) reduced effect of GF at high shear rates on these properties and (ii) upward deviation of melt viscosity versus shear rate curve at low shear rates. A change in flow behavior in presence of GF is observed around a critical shear rate 2 × 10³ s^?1 and is attributed to the difference of interaction of GF and the dispersed rubber droplets at high and low shear rates. Elastic recovery showed nonequilibrium behavior at low shear rates.     

Die–swell behavior of glass bead‐filled low‐density polyethylene composite melts at high extrusion rates

The extrudate swell behavior of glass bead‐filled low‐density polyethylene (LDPE) composite melts was investigated using a constant rate type of capillary rheometer at high extrusion rates and test temperatures varied from 140 to 170°C. The results show that the die swell ratio (B) of the melts increases nonlinearly with increasing apparent shear rates for the system filled with the surface of glass beads pretreated with a silane coupling agent, while the B for the system filled with uncoated particles remains almost constant when the true wall shear rate is greater than 2000 s⁻¹ at a constant temperature. The values of B for both the pure LDPE and the filled systems decreases linearly with an increase of the temperature and an increase of the die diameter at fixed shear rates, and the sensitivity of B on the die diameter and temperature for the former is higher than that of the latter. Furthermore, the effect of the filler content on B is insignificant, while the values of B decreases, obviously, with an increasing glass bead diameter (d) when d is smaller than 50 μm; then B varies slightly with d. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 419–424, 2000     

Dynamic rheology,mechanical performance,shrinkage, and morphology of chemically coupled talc‐filled polypropylene

The oscillatory shear rheological properties, mechanical performance, shrinkage, and morphology of polypropylene (PP)‐talc composites chemically coupled by maleic‐anhydride‐grafted polypropylene (MAPP) were studied. The samples were prepared in a co‐rotating L/D = 40, 25 mm twin‐screw extruder. Tensile tests carried out on injection‐molded samples showed a reinforcing effect of talc up to 20 wt% on PP. Upon using MAPP, the mechanical performance of PP‐30% talc showed a maximum of about 10% increase in tensile strength at 1.5 wt% of MAPP. A Newtonian plateau (η₀) at the terminal zone was observed for the complex viscosity curve of pure PP and PP‐talc composites plotted against frequency up to 30 wt%. Upon increasing the talc content to 40 and 50 wt%, the complex viscosity at very low shear rates sharply increased and showed yield behavior that might be due to the formation of a network of filler agglomerates in the melt. Analysis of viscosity behavior in the power‐law region revealed that the flow behavior index‐n‐decreased from 0.45 for 10 wt% of talc down to about 0.4 for 40 wt% of talc. Upon increasing the talc content to 50 wt%, n decreased to a value even lower than that of the neat PP resin. The frequency of the crossover point represents molecular mobility and relaxation‐time behavior. The crossover frequency of the composites was nearly constant up to 30 wt% of talc and decreased at higher filler loadings. The optimum amount of coupling agent could be correlated with the minimum point in crossover frequency and crossover modulus. The shrinkage behavior of the composites with and without MAPP resin was studied and correlated with the rheological properties. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Melt rheology of polypropylene reinforced with polyaniline‐coated short glass fibers

This research deals with the melt rheology of isotactic polypropylene (iPP) reinforced with short glass fibers (SGF) coated with electrically conductive polyaniline (PAn). Composites containing 10, 20, and 30 wt % PAn‐SGF were studied. Moreover, a composite of 30 wt % PAn‐SGF was also prepared with a blend of iPP and PP‐grafted‐maleic anhydride (iPP/PP‐gMA). The composites showed linear viscoelastic regime at small strain amplitudes. The onset of nonlinearity decreased as the concentration of filler increased. The time‐temperature superposition principle applied to all composites. The filler increased the shear moduli (G′, G″) and the complex viscosity η*. Steady‐state shear experiments showed yield stress for the composites with 20 and 30 wt % PAn‐SGF. Strikingly, the 10 wt % composite showed higher steady state viscosity than the 20 wt %. Rheo‐optics showed that shear induced disorder of microfibers at a concentration of 10 wt %. However, at 20 wt % concentration shear aligned the microfibers along the flow axis, this would explain the anomalous steady state viscosity values. The viscosity exhibited a shear thinning behavior at high shear rates for all composites. Creep experiments showed that the filler induced greater strain recovery in the composites and that the amount of strain recovery increased as the PAn‐SGF concentration increased. However, the enhancement of strain recovery (as well as shear viscosity) was more significant when using the iPP/PP‐gMA blend, suggesting greater adhesion between this matrix and the filler PAn‐SGF. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Rheological and isothermal crystallization characteristics of neat and calcium carbonate‐filled syndiotactic polypropylene

Steady‐state and oscillatory shear behavior of three neat syndiotactic polypropylene (s‐PP) resins and a s‐PP resin (s‐PP#8) filled with CaCO₃ particles of varying content, size, and type of surface modification were investigated. All of the neat s‐PP resins investigated exhibited the expected shear‐thinning behavior. Both the storage and loss moduli increased with decreasing temperature. The shift factors used to construct the master curves were fitted well with both the Arrhenius and the Williams–Landel–Ferry (WLF) equations. The inclusion of CaCO₃ particles of varying content, size, and type of surface modification, to a large extent, affected both the steady‐state and oscillatory shear behavior of s‐PP/CaCO₃ compounds, with the property values being found to increase with increasing content, decreasing size, and surface coating of the CaCO₃ particles. Lastly, the effects of melt‐annealing and crystallization temperatures on isothermal crystallization behavior of s‐PP#8 filled with CaCO₃ particles of varying content, size, and type of surface modification were also investigated. The half‐time of crystallization of neat s‐PP#8 exhibited a strong correlation with the choice of the melt‐annealing temperature (T_f) when T_f was less than about 160 °C, while it became independent of T_f when T_f was greater than about 160 °C. On the other hand, the half‐time of crystallization of s‐PP#8/CaCO₃ compounds did not vary much with the T_f. Generally, the observed half‐time of crystallization decreased with increasing CaCO₃ content and increased with increasing CaCO₃ particle size. Finally, coating the surface of CaCO₃ particles with either stearic acid or paraffin reduced the ability of the particles to effectively nucleate s‐PP#8. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4515–4525, 2006     

Effects of extrusion conditions on rheological behavior of acrylonitrile–butadiene–styrene terpolymer melt

The influence of temperatures and flow rates on the rheological behavior during extrusion of acrylonitrile–butadiene–styrene (ABS) terpolymer melt was investigated by using a Rosand capillary rheometer. It was found that the wall shear stress (τ_w) increased nonlinearly with increasing apparent shear rates and the slope of the curves changed suddenly at a shear rate of about 10³ s^?1, whereas the melt‐shear viscosity decreased quickly at a τ_w of about 200 kPa. When the temperature was fixed, the entry‐pressure drop and extensional stress increased nonlinearly with increasing τ_w, whereas it decreased with a rise of temperature at a constant level of τ_w. The relationship between the melt‐shear viscosity and temperature was consistent with an Arrhenius expression. The results showed that the effects of extrusion operation conditions on the rheological behavior of the ABS resin melt were significant and were attributable to the change of morphology of the rubber phase over a wide range of shear rates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 606–611, 2002     

Mechanical properties and morphology of glass bead–filled polypropylene composites

The effects of the filler content and size on the mechanical properties such as tensile modulus, E_c, yield strength, σ_yc, and impact strength, S_IC, of glass bead–filled polypropylene (PP) composites have been investigated employing an Instron materials tester and a Ceast impact tester at room temperature. With increasing concentration of glass beads, E_c and S_IC increase, but σ_yc decreases non–linearly, within a filler volume fraction range of 0%−20%; under the same test conditions, the values of E_C and σ_yc for PP with bigger beads are somewhat lower than those of PP with smaller ones; the maximum values of S_IC for the composites are about 1.4 times as high as the unfilled PP; the interface between the matrix and the beads is a weak bond. The results indicate that the stiffness and the toughness of the PP composites are effectively improved by addition of glass beads.     

Thermal and mechanical properties of a polypropylene nanocomposite

An experimental polypropylene (PP) nanocomposite, containing approximately 4 wt % of an organophilic montmorillonite clay, was prepared and characterized, and its properties were compared with those of talc‐filled (20–40 wt %) compositions. Weight reduction, with maintained or even improved flexural and tensile moduli, especially at temperatures up to 70°C, was a major driving force behind this work. By a comparison with the analytical data from a nylon 6 (PA‐6) nanocomposite, it was found that the PP nanocomposite contained well‐dispersed, intercalated clay particles; however, X‐ray diffraction, transmission electron microscopy, dynamic mechanical analysis, and permeability measurements confirmed that exfoliation of the clay in PP was largely absent. The increased glass‐transition temperature (T_g) of a PA‐6 nanocomposite, which possessed fully exfoliated particles, indicated the molecular character of the matrix–particle interaction, whereas the PP nanocomposite exhibited simple matrix–filler interactions with no increase in T_g. The PP nanocomposite exhibited a weight reduction of approximately 12% in comparison with the 20% talc‐filled PP, while maintaining comparable stiffness. Undoubtedly, considerable advantages may be available if a fully exfoliated PP nanocomposite is fabricated; however, with the materials available, a combination of talc, or alternative reinforcements, and nanocomposite filler particles may provide optimum performance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1639–1647, 2003