Linear viscoelastic behavior of compatibilized PMMA/PP blends

In this work, the morphology and linear viscoelastic behavior of PMMA/PP blends to which a graft copolymer PP‐g‐PMMA has been added was studied. The copolymer concentration varied from 1 to 10 wt % relative to the dispersed phase concentration. The rheological data were used to infer the interfacial tension between the blended components. It was observed that PP‐g‐PMMA was effective as a compatibilizer for PMMA/PP blends. For PP‐g‐PMMA concentration added below the critical concentration of interface saturation, two rheological behaviors were observed depending on the blend concentration: for 70/30 blend, the storage modulus, at low frequencies, increased as compared to the one of the unmodified blend; for 90/10 blend, it decreased. For 90/10 blend, the relaxation spectrum presented an interfacial relaxation time related to the presence of the compatibilizer (τ_β). For PP‐g‐PMMA concentrations added above the critical concentration of interface saturation, the storage modulus of all blends increased as compared with the one of the unmodified blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of composition on the linear viscoelastic behavior and morphology of PP/HDPE blends

In this paper the influence of temperature and composition on the dynamic behavior and morphology of polypropylene (PP)/high-density polyethylene (HDPE) blends were studied. The blend composition ranged from 5 to 30 wt% of dispersed phase (HDPE) and the temperatures ranged from 180 to 220 °C. The interfacial tension between PP and HDPE at temperatures of 180, 200 and 220 °C was obtained from fitting Palierne's emulsion model [1] to the experimental data of PP/HDPE blends with different compositions and from the weighted relaxation spectra of PP/HDPE blends with different compositions, following Gramespacher and Meissner [2] analysis. The interfacial tension between PP and HDPE as inferred from the rheological measurements was shown to depend on PP/HDPE blend composition. However, the results indicated that there is a range of PP/HDPE blend composition for which interfacial tension between PP and HDPE is constant. Considering these values, it was shown that interfacial tension between PP and HDPE decreases linearly with increasing temperature.     

Polypropylene‐dispersed domain as potential nucleating agent in PS and PMMA solid‐state foaming

The potential of using dispersive domains in a polymer blend as a bubble nucleating agent was investigated by exploiting its high dispersibility in a matrix polymer in the molten state and its immiscibility in the solid state. In this experiments, polypropylene (PP) was used as the nucleating agent in polystyrene (PS) and poly(methyl methacrylate) (PMMA) foams at the weight fraction of 10, 20, and 30 wt %. PP creates highly dispersed domains in PS and PMMA matrices during the extrusion processing. The high diffusivity of the physical foaming agent, i.e., CO₂ in PP, and the high interfacial tension of PP with PS and PMMA could be beneficial for providing preferential bubble nucleation sites. The experimental results of the pressure quench solid‐state foaming of PS/PP and PMMA/PP blends verified that the dispersed PP could successfully increase the cell density over 10⁶ cells/cm³ for PS/PP and 10⁷ cells/cm³ for PMMA/PP blend and reduce the cell size to 24 μm for PS/PP and 9 μm for PMMA/PP blends foams. The higher interfacial tension between PP and the matrix polymer created a unique cell morphology where dispersed PP particles were trapped inside cells in the foam. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Relaxation behavior of polymer blends with complex morphologies: Palierne emulsion model for uncompatibilized and compatibilized PP/PA6 blends

This paper deals with the dynamic rheological behavior of polypropylene/polyamide6 (PP/PA6) uncompatibilized blends and those compatibilized with a maleic anhydride grafted PP (PP/PP-g-MAH/PA6). The terminal relaxation times of the blends predicted by the Palierne emulsion model were compared with those obtained from experimental relaxation time spectra. The Palierne model succeeded well in describing PP/PA6 uncompatibilized blends with relatively low dispersed phase contents (10 wt%) and failed doing so for those of which the dispersed contents were high (30 wt%). It also failed for the compatibilized ones, irrespective of the dispersed phase content (10 or 30 wt%) and whether or not interface relaxation was taken into consideration. In the case of the uncompatibilized blend with high dispersed-phase content, interconnections among inclusions of the dispersed phase were responsible for the failure of the Palierne model. As for the compatiblized blends, in addition to particle interconnections, the existence of emulsion-in-emulsion (EE) structures was another factor responsible for the failure of Palierne model. A methodology was developed to use Palierne emulsion model upon taking into account the effects of the EE structure on the viscosity of the continuous phase and the effective volume fraction of the dispersed phase.     

Rheological properties of polystyrene and poly(methyl methacrylate) blends

Rheological properties of the polystyrene (PS) and poly(methyl methacrylate) (PMMA) blends were studied by Advanced Rheometric Expansion System (ARES). Storage modulus and loss modulus of the PS and PMMA blends were measured, and the interfacial tension of the PS and PMMA blends were obtained with various emulsion models by using the storage modulus and loss modulus of the blends. The value of interfacial tension estimated from the Palierne emulsion model was found to be 2.0 mN/m. Also, the interfacial tension between PS and PMMA was calculated by a theoretical model. The values of interfacial tension of the PS and PMMA blends obtained by the experiment and theoretical model were found to be in good agreement.     

Melt rheology and interfacial properties of binary and ternary blends of PS,EOC, and SEBS

This works systematically investigates the interfacial properties of the binary and the ternary blends based on polystyrene (PS), ethylene octene copolymer (EOC), and styrene–ethylene–butylene–styrene (SEBS) by analyzing the melt linear rheological behavior of the blends and neat components. Moreover, the relationship between rheology, phase morphology, and mechanical properties of PS/EOC ternary blends with various quantities of SEBS were studied. The surface shear modulus (β) and interfacial tension values obtained by Palierne model indicated that the EOC/SEBS blend has the best interfacial properties, while the lowest interaction was found for PS/EOC blend. Based on the Palierne model and Harkin's spreading coefficients a core–shell type morphology with EOC phase encapsulated by the SEBS shell dispersed in the PS matrix was determined for the ternary blends. Scanning electron microscopy results revealed that both fibrillar and droplet forms of dispersed phase could be developed during the blending of PS and EOC in presence of SEBS. The extent of fibrillar morphology and interfacial interactions in PS/EOC/SEBS ternary blends was dependent on the SEBS content. The improvement of the mechanical properties of PS/EOC blends in the presence of SEBS was evidenced by the tensile and impact resistance experiments. The tensile strength reinforcement was more pronounced for the ternary blends with more fibrillar dispersed phase. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48791.     

Correlation of rheology and morphology and estimation of interfacial tension of immiscible COC/EVA blends

Rheology and morphology of cyclic olefin copolymer (COC) / ethylene vinyl acetate copolymer (EVA) immiscible blends with droplet and co-continuous morphologies were experimentally examined and theoretically analyzed using emulsion and micromechanical models. The blends showed an asymmetric phase diagram in which the EVA-rich blends had smaller dispersed size domains as compared to the COC-rich blends. This could be explained based on the higher melt elasticity and viscosity of COC as compared to EVA determined by the rheological investigations. The rheological tools were used to investigate the miscibility of the blends. From the melt viscosity data it is found that the COC/EVA blends show a positive deviation behavior at all compositions which is a hint for strong interaction between the COC and EVA. Analysis of Cole-Cole and Han diagrams revealed that COC/EVA blends, at high EVA contents, were more compatible than COC-rich blends. For the droplet morphology, Palierne model was more successful but, by increasing the dispersed phase content some deviation was observed. In the co-continuous region, the Coran model was in good correspondence with the experimental data as compared to the Veenstra’s model. The storage and loss modulus of EVA-rich blends had a better correspondence with the Palierne model than the COC-rich blends which further confirmed the morphological findings. Interfacial tension calculated for the COC/EVA blends using the Palierne model, were about 1.2 and 15 mN/m² for EVA-rich (10/90) and COC-rich blends (90/10), respectively. In both EVA-rich and COC-rich systems the interfacial tension increased with increasing the dispersed phase content.     

Morphology and rheology of immiscible polymer blends filled with silica nanoparticles

The effect of silica nanoparticles on the morphology and the rheological properties of an immiscible polymer blend (polypropylene/polystyrene, PP/PS 70/30) was investigated. Two types of pyrogenic nanosilica were used: a hydrophilic silica with a specific surface area of 200 m²/g and a hydrophobic silica having a specific surface area of 150 m²/g. First, a significant reduction in the PS droplet volume radius, from 3.25 to nearly 1 μm for filled blends with 3 wt% silica, was observed. More interestingly, image analysis of the micrographs proved that the hydrophilic silica tends to confine in the PS phase whereas hydrophobic one was located in the PP phase and at the PP/PS interface (interphase thickness ≈ 100-200 nm). Furthermore, a migration of hydrophilic silica from PP phase toward PS domains was observed.An analysis of the rheological experimental data was based on the framework of the Palierne model, extended to filled immiscible blends. Due to the partition of silica particles in the two phases and its influence on the viscosity ratio, limited cases have been investigated. The rheological data obtained with the hydrophobic silica were more difficult to model since the existence of a thick interphase cannot be taken into account by the model. Finally, the hypothesis that hydrophilic silica is homogeneously dispersed in PS droplets and that hydrophobic silica is dispersed in PP matrix was much closer to the actual situation. It can be then concluded that stabilization mechanism of PP/PS blend by hydrophilic silica is the reduction in the interfacial tension whereas hydrophobic silica acts as a rigid layer preventing the coalescence of PS droplets.     

Effects of compatibilizer on the morphological,mechanical, and rheological properties of poly(methyl methacrylate)/poly(N‐methyl methacrylimide) blends

The effects of compatibilizer on the morphological, thermal, mechanical, and rheological properties of poly(methyl methacrylate) (PMMA)/poly(N‐methyl methacrylimide) (PMMI) (70/30) blends were investigated. The compatibilizer used in this study was styrene–acrylonitrile–glycidyl methacrylate (SAN‐GMA) copolymer. Morphological characterization of the PMMA/PMMI (70/30) blend with SAN‐GMA showed a decrease in PMMI droplet size with an increase in SAN‐GMA. The glass‐transition temperature of the PMMA‐rich phase became higher when SAN‐GMA was added up to 5 parts per hundred resin by weight (phr). The flexural and tensile strengths of the PMMA/PMMI (70/30) blend increased with the addition of SAN‐GMA up to 5 phr. The complex viscosity of the PMMA/PMMI (70/30) blends increased when SAN‐GMA was added up to 5 phr, which implies an increase in compatibility between the PMMA and PMMI components. From the weighted relaxation spectrum, which was obtained from the storage modulus and loss modulus, the interfacial tension of the PMMA/PMMI (70/30) blend was calculated using the Palierne emulsion model and the Choi‐Schowalter model. The results of the morphological, thermal, mechanical, and rheological studies and the values of the interfacial tension of the PMMA/PMMI (70/30) blends suggest that the optimum compatibilizer concentration of SAN‐GMA is 5 phr. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43856.     

Influence of composition and phase morphology on rheological properties of polypropylene/poly(ethylene‐co‐octene) blends

In this article, the phase morphology and rheological properties of polypropylene (PP)/poly(ethylene‐co‐octene) (POE) blends with a droplet‐matrix microstructure were studied by scanning electron microscopy and rheological experiments. The data were analyzed to yield the variations of rheological behavior with blend composition and insight into the microstructure of PP/POE blends. The Palierne's emulsion type model was used to extract information on rheological properties, and the interfacial tensions between the PP and POE were determined by fitting the experimental data with this model. The results indicated that the interfacial tensions were shown to depend on blend composition and temperature. Rheological properties of PP/POE blends were investigated in a systemic way with varying shear histories. The results showed that shear history had an important effect on the rheological properties of the blends due to the dispersed phase (POE) domains refined with increasing preshear rate and preshear time. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Rheology and morphology of polytrimethylene terephthalate/ethylene propylene diene monomer blends in the presence and absence of a reactive compatibilizer

The dynamic rheological behavior and phase morphology of Polytrimethylene terephthalate (PTT) and ethylene propylene diene monomer (EPDM) uncompatibilized blends and those compatibilized with maleic anhydride grafted EPM (EPM‐g‐MA) were investigated. Effects of blend ratio and reactive compatibilization on the morphology and rheological properties of compatibilized and uncompatibilized blends have been analyzed. The viscosity ratio between the polymers was found to be sensitive to frequency which gave an indirect idea about the unstable morphology. The complex viscosity and dynamic modulus increased with increase in compatibilizer addition up to critical micelle concentration. Palierne and Choi‐Schowalter models were used to calculate the interfacial tension between the polymers. The interfacial tension decreased with the addition of compatibilizer up to CMC. It was also found that the minimum value of interfacial tension was found at CMC beyond that a levelling off is observed. The rheological properties of both compatibilized and uncompatibilized blends are found to be closely related to their phase morphology. POLYM. ENG. SCI., 50:1945–1955, 2010. © 2010 Society of Plastics Engineers     

Preparation of polypropylene and polystyrene with NCO and NH2 functional groups and their applications in polypropylene/polystyrene blends

Isocyanate‐ and amine‐functionalized polypropylene (PP) and polystyrene (PS) were prepared through grafting and copolymerization method. These compounds are used as precursors for PP‐graft‐PS (PP‐g‐PS) copolymers and reacted at the matrix interface of PP/PS blends. Functionalized polymer structures were characterized by ¹H NMR and FTIR spectroscopy. The effects of the synthesized compatibilizer on the rheological and morphological behavior of PP/PS blends were investigated systematically. Results showed that the functional polymer was successfully synthesized, and the additional two different compatibilizer systems dramatically decreased the size of the dispersed phase domains in PP/PS blends. Compared with the uncompatibilized blends, compatibilized blends exhibited a slightly higher crystallization temperature because the melting points of the blend components were not evidently affected by the addition of compatibilizer, as revealed by differential scanning calorimetry. The compatibilizer effect on the PP/PS blends was reflected through rheological property and dynamic mechanical analysis. POLYM. ENG. SCI., 55:614–623, 2015. © 2014 Society of Plastics Engineers     

Characterization of phase morphology of polymer melts (PP/PE blends) via rheology

The viscoelastic behavior of high impact polypropylene (PP) melts, a multiphase system with an isotactic PP matrix and inclusions consisting of mainly amorphous ethylene–propylene copolymer (EP), is strongly influenced by the size of small inclusions. The dynamic moduli of such two‐phase systems (reactor products) are well described by Palierne's emulsion model. For this analysis the reactor product is separated into matrix and dispersed phase via the different solubility in xylene. This analysis also provides information on the ratio interfacial tension to particle size of the dispersed phase. With morphology data (particle size) of the solidified heterophasic samples (Transmission Electron Microscopy), we estimate the interfacial tension between PP and EP copolymer via the emulsion model of Palierne and from the relaxation time spectra according to Gramespacher and Meissner. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

PS/PMMA共混体系的挤出流变行为

利用单螺杆挤出机,配备特殊设计的狭缝模头,在不改变螺杆转速的情况下获得流经口模的不同流量,研究了聚苯乙烯(PS)/聚甲基丙烯酸甲酯(PMMA)共混体系的挤出流变行为。结果表明,PS/PMMA共混物熔体的流变行为和其组分熔体的流变行为类似,都表现出假塑性流体的流动行为;在所研究的组成范围内,共混物熔体的非牛顿指数低于任一组分熔体。随着共混物黏度比的减小,其熔体的非牛顿指数呈下降的趋势;共混物熔体的黏度对加和性法则皆表现为负偏差,表明在界面处具有弱的相互作用。     

The effects of PC‐PMMA block copolymer on the compatibility and interfacial properties of PC/SAN blends

Block copolymers of polycarbonate (PC) and polymethylmethacrylate (PMMA), PCb‐PMMA, were examined as compatibilizers for blends of PC with styrene‐co‐acrylonitrile (SAN) copolymer. PC‐b‐PMMA was added to blends of PC with SAN containing various amounts of AN. The average diameter of the dispersed particles was measured with an image analyzer, and the interfacial properties of the blends were analyzed with an imbedded fiber retraction (IFR) test and an asymmetric double cantilever beam fracture test. The average particle size and interfacial tension of the PC/SAN blends reached a minimum value when the SAN copolymer contained about 24 wt% AN. A maximum in the adhesion energy was also observed at the same AN content. Interfacial tension and particle size were further reduced by adding PC‐b‐PMMA to the PC/SAN blends. Fracture toughness of the blends was also improved by enhancing the interfacial adhesion by the addition of PC‐b‐PMMA. The addition of PC‐b‐PMMA copolymer was more effective at improving the interfacial properties of PC/SAN blends than was varying the AN content of the SAN copolymers. The interfacial properties of the PC/SAN blends were optimized by adding a block copolymer and using an SAN copolymer that had minimum interaction energy with PC.     

An Investigation on Compatibilization Threshold in the Interface of Polypropylene/Polylactic Acid Blends Using Rheological Studies

This paper reports on the dynamic rheological behavior of polypropylene/(polylactic acid) (PP/PLA) uncompatibilized blends and those compatibilized with a terpolymer of ethylene, butylacrylate, and glycidylmethacrylate (PTW). The PP‐rich (75/25) and PLA‐rich (25/75) systems with 0, 2.5, 5, and 7.5 wt% of PTW were examined. We show how the decrease in the domain size of dispersed droplets and the homogeneity of the systems strongly depend on the composition. Morphological studies revealed 100% reduction in the size of PLA domains in the compatibilized PP‐rich system containing 5 wt% of PTW. Such rigorous domain size reduction was not observed for the PLA‐rich system. The complex moduli of the blends predicted by the Palierne emulsion model were compared with those obtained from the experimentally estimated complex moduli. We found two different behaviors for the 75/25 and 25/75 blend systems. Although the predictions for the 75/25 blend showed some deviations from the experimental data at low‐frequency region and fitted well at high‐frequency region, the 25/75 blends exhibited an opposite behavior. Furthermore, we found that the compatibilization had no significant effect on the predicted complex moduli of the both systems. J. VINYL ADDIT. TECHNOL., 22:19–28, 2016. © 2014 Society of Plastics Engineers     

Structure evolution in polymer blending using microfabricated samples

The transient rheological behavior and morphology evolution of polymethyl methacrylate (PMMA)/polystyrene (PS) binary polymer blends with well-defined initial structure were measured in simple shear flow under isothermal conditions. The size and distribution of the dispersed phase and the composition of the blends were designed and fabricated by Computer Numerical Controlling (CNC) machining, photolithography, and micro-embossing. Compatibilizer can easily be placed at the interface of the two components during sample preparation. The effects of initial dispersed domain size, blend composition, and interfacial tension on rheological behavior and morphology evolution were investigated. It was found that the transient shear stress and first normal stress difference are very sensitive to these parameters. The transient rheological responses up to the breakup point are compared with those predicted by both Doi-Ohta and Vinckier-Moldenaers-Mewis models.     

Immiscible polymer blends stabilized with nano-silica particles: Rheology and effective interfacial tension

The effect of inorganic silica nanoparticles on the morphology and viscoelastic properties of polypropylene/poly(ethylene-co-vinyl acetate) (PP/EVA) immiscible blends has been investigated. Different EVA with different molar masses were used in this study. Virgin and filled blends were prepared by using a twin-screw mini-extruder. Microscopy studies revealed a significant change in morphology of PP/EVA blend in the presence of silica nanoparticles. Also, the images proved the migration of silica nanoparticles toward EVA phase, and to the interface.The quantitative analysis of the rheological experimental data was based on the framework of the Palierne model, extended to filled immiscible blends. Based on this model, a method of determination of the interfacial tension from rheological measurement has been addressed with an improved accuracy. Even if silica mainly plays a thermodynamic role in the stabilization mechanism by decreasing the effective interfacial tension, the influence of particular rheological conditions and the structure of the phases must be taken into account for a complete understanding of the final morphology of such systems.     

Evolution of shell formation process in PP/PMMA/PS ternary blends: correlation between the melt rheology and phase morphology

Correlation between the melt rheology and phase morphology of PP/PMMA/PS ternary blends during the shell formation process were studied in detail. In this PP-matrix ternary system, theoretical predictions in agreement with the direct SEM observations demonstrated the core-shell morphology with PMMA and PS phases as core and shell phases, respectively. Morphological observations revealed that the complete shell formation takes place at about 12 and 9 wt% of PS minor phase in ternary blends composed of low and high viscosity PMMAs, respectively. In terms of rheological properties, this was corresponding to the maximum value on the storage modulus versus PS content (shell thickness) curves. Encapsulation of high viscosity PMMA core particles at lower PS contents was related to the bigger particles and low interfacial area in this system compared to the system with low viscosity PMMA core particles. At high PS contents, single and multi-core structures were observed for composite droplets of ternary blends containing low and high viscosity PMMAs, respectively. The single core morphology of low viscosity PMMA particles was related to the coalescence of core particles after the coalescence of the corresponding shells, while high viscosity PMMA cores are less likely to coalescence, leading to creation of multi-core morphology in latter system.