Synthesis of sub‐micrometer core–shell rubber particles with 1,2‐azobisisobutyronitrile as initiator and deformation mechanisms of modified polystyrene under various conditions

BACKGROUND: Sub‐micrometer core‐shell polybutadiene‐graft‐polystyrene (PB‐g‐PS) copolymers with various ratios of polybutadiene (PB) core to polystyrene (PS) shell were synthesized by emulsion grafting polymerization with 1,2‐azobisisobutyronitrile (AIBN) as initiator. These graft copolymers were blended with PS to prepare PS/PB‐g‐PS with a rubber content of 20 wt%. The mechanical properties, morphologies of the core‐shell rubber particles and deformation mechanisms under various conditions were investigated. RESULTS: Infrared spectroscopic analysis confirmed that PS could be grafted onto the PB rubber particles. The experimental results showed that a specimen with a ‘cluster’ dispersion state of rubber particles in the PS matrix displayed better mechanical properties. Transmission electron micrographs suggested that crazing only occurred from rubber particles and extended in a bridge‐like manner to neighboring rubber particles parallel to the equatorial plane at a high speed for failure specimens, while the interaction between crazing and shear yielding stabilized the growing crazes at a low speed in tensile tests. CONCLUSION: AIBN can be used as an initiator in the graft polymerization of styrene onto PB. The dispersion of rubber particles in a ‘cluster’ state leads to better impact resistance. The deformation mechanism in impact tests was multi‐crazing, and crazing and shear yielding absorbed the energy in tensile experiments. Copyright © 2009 Society of Chemical Industry     

Photochemical aging and processability of life‐time‐controlled polystyrene/high‐impact polystyrene blends

This work investigated the influence of the addition of acetophenone and benzophenone (2.5 and 5%) on the photodegradability of polystyrene/high‐impact polystyrene blends (50/50 w/w) prepared by sheet extrusion, aiming to improve their decomposition during exposure to a natural environment. The modified materials were submitted to photodegradation under controlled conditions, and the extent of degradation was monitored by suitable characterization techniques, such as infrared and ultraviolet–visible spectroscopy, viscosimetry, and measurements of the mechanical properties. The processability of the modified blends was also studied by capillary and oscillatory rheometry. Evidence for the formation of hydroperoxides and carbonyl groups, the occurrence of chain scission, and the loss of mechanical properties was achieved, being greater for samples with benzophenone. It was also observed that for the same ketone level, benzophenone caused greater changes in the mechanical properties, and this was in agreement with the decrease in the molecular weight observed. Thus, the addition of this type of chemical compound could enhance the photodegradability of polystyrene/high‐impact polystyrene blends without a significant effect on their processability and mechanical performance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Blends of sulphonated polystyrene and polystyrene: Morphology and deformation modes

Blends of sulphonated polystyrene, neutralized with metal ions, have been prepared in various proportions with polystyrene homopolymer. Morphology, microstructure, and deformation modes of strained, cast thin films have been examined by transmission electron microscopy. Variables studied include blend composition and ion content. In blends of low ionomer concentration, the ionomer component phase-separates and takes the form of small dispersed particles. With the increase of ion content, the average particle size increases and, as crazes develop in the matrix, particles elongate and fibrillate. These ionic crosslinked particles adhere well to the matrix, share in carrying the applied stress and reinforce the matrix polymer. Implications of these results for mechanical performance of bulk samples are discussed.     

Stress‐relaxation behavior of natural rubber/polystyrene and natural rubber/polystyrene/natural rubber‐graft‐polystyrene blends

We studied the stress‐relaxation behavior of natural rubber (NR)/polystyrene (PS) blends in tension. The effects of strain level, composition, compatibilizer loading, and aging on the stress‐relaxation behavior were investigated in detail. The dispersed/matrix phase morphology always showed a two‐stage mechanism. On the other hand, the cocontinuos morphology showed a single‐stage mechanism. The addition of a compatibilizer (NR‐g‐PS) into 50/50 blends changed the blend morphology to a matrix/dispersed phase structure. As a result, a two‐step relaxation mechanism was found in the compatibilized blends. A three‐stage mechanism was observed at very high loadings of the compatibilizer (above the critical micelle concentration), where the compatibilizer formed micelles in the continuous phase. The aged samples showed a two‐stage relaxation mechanism. The rate of relaxation increased with strain levels. The aging produced interesting effects on the relaxation pattern. The rate of relaxation increased with temperature due to the degradation of the samples. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Flame‐retarded polystyrene with phosphorus‐ and nitrogen‐containing oligomer: Preparation and thermal properties

A phosphorus‐ and nitrogen‐containing compound (2‐dimethylamino ethyl phenyl hydroxyethyl acrylate phosphate) and its oligomer (poly(2‐dimethylamino ethyl phenyl hydroxyethyl acrylate phosphate), PDPHP) were synthesized and characterized. The polystyrene (PS) composites with various amounts of PDPHP were prepared by melt blending. The thermal stability of the PDPHP and PS composites was investigated by thermogravimetric analysis. The flame retardancy of the composites was evaluated using microscale combustion calorimeter and limiting oxygen index test. A Fourier transform infrared (FTIR) spectroscopy coupled with a thermogravimetric analyzer was also used to study the gas phase from the degradation of PS composites. The char residues of the PS composites containing 30 wt % PDPHP were analyzed by FTIR and scanning electron microscopy. The results suggest that the incorporation of PDPHP into PS can evidently enhance the char formation and improve the flame retardancy of virgin PS. The compact and coherent char formed during degradation was attributed to the enhancement of char quality and flame retardance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanisms of plastic deformation in biodegradable polylactide/poly(1,4‐cis‐isoprene) blends

Polylactide (PLA), a main representative of biodegradable and made from renewable resources polymers, is surprisingly brittle at ambient temperature. In this article it is investigated how to increase its toughness by a strategy called “rubber toughening” using poly(1,4‐cis‐isoprene), a major component of natural rubber, which is immiscible with PLA, could be well dispersed in PLA matrix and is biodegradable. Immiscible blends of PLA with poly(1,4‐cis‐isoprene) were prepared by melt blending and their properties were studied and optimized. Incorporation of as low as 5 wt % of rubber increased the strain at break of compression molded film during uniaxial drawing, and also improved its tensile impact strength by 80%. The complex mechanism of plastic deformation in the blends leading to improvement of ductility and toughness was revealed. The rubbery particles initiated crazing at the early stages of deformation, as evidenced by transmission and scanning electron microscopy and also by small angle X‐ray scattering. Crazing was immediately followed by cavitation inside rubber particles, which further promoted shear yielding of PLA. The sequence of those mechanisms was proven by microscopic investigation. All three elementary mechanisms acting in the sequence indicated are responsible for surprisingly efficient toughening of PLA by a major component of natural rubber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Compatibilization effects of styrenic/rubber block copolymers in polypropylene/polystyrene blends

Compatibilizing effects of styrene/rubber block copolymers poly(styrene‐b‐butadiene‐b‐styrene) (SBS), poly(styrene‐b‐ethylene‐co‐propylene) (SEP), and two types of poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS), which differ in their molecular weights on morphology and selected mechanical properties of immiscible polypropylene/polystyrene (PP/PS) 70/30 blend were investigated. Three different concentrations of styrene/rubber block copolymers were used (2.5, 5, and 10 wt %). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the phase morphology of blends. The SEM analysis revealed that the size of the dispersed particles decreases as the content of the compatibilizer increases. Reduction of the dispersed particles sizes of blends compatibilized with SEP, SBS, and low‐molecular weight SEBS agrees well with the theoretical predictions based on interaction energy densities determined by the binary interaction model of Paul and Barlow. The SEM analysis confirmed improved interfacial adhesion between matrix and dispersed phase. The TEM micrographs showed that SBS, SEP, and low‐molecular weight SEBS enveloped and joined pure PS particles into complex dispersed aggregates. Bimodal particle size distribution was observed in the case of SEP and low‐molecular weight SEBS addition. Notched impact strength (a_k), elongation at yield (ε_y), and Young's modulus (E) were measured as a function of weight percent of different types of styrene/rubber block copolymers. The a_k and ε_y were improved whereas E gradually decreased with increasing amount of the compatibilizer. The a_k was improved significantly by the addition of SEP. It was found that the compatibilizing efficiency of block copolymer used is strongly dependent on the chemical structure of rubber block, molecular weight of block copolymer molecule, and its concentration. The SEP diblock copolymer proved to be a superior compatibilizer over SBS and SEBS triblock copolymers. Low‐molecular weight SEBS appeared to be a more efficient compatibilizer in PP/PS blend than high‐molecular weight SEBS. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 291–307, 1999     

Structure and mechanical properties of uniaxially oriented films of syndiotactic polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends

The structure and mechanical properties of highly oriented films of a miscible blend of syndiotactic polystyrene and poly(2,6‐dimethylphenylene‐1,4‐oxide) (sPS/PPO) were studied in the composition range of sPS/PPO = 10/0 to 5/5. The oriented films were prepared by stretching the amorphous films of the blends. Wide‐angle X‐ray diffraction and polarized FTIR spectroscopy were used to analyze the amount of mesophase and molecular orientation. Drawing of the amorphous films of sPS and sPS/PPO blend induced a highly oriented mesophase. The mesophase content increases with increasing draw ratio and becomes nearly constant above a draw ratio of 3. Under the same draw ratio, the mesophase content decreases with increasing PPO content. The orientation function in the mesophase is as high as 0.95–0.99 irrespective of the composition and draw ratio. On the other hand, the orientation of molecular chains in the amorphous phase and mesophase increases with increasing draw ratio, and it decreases with increasing PPO content. The drawn films of pure sPS show high strength and high modulus in the drawing direction, but exhibit low strength in the direction perpendicular to the drawing. In the case of sPS/PPO = 7/3 blend, however, the ultimate strength in the perpendicular direction was dramatically improved compared with that of pure sPS and the ultimate strength in the parallel direction was similar to that for the oriented pure sPS. The improved mechanical properties in the sPS/PPO blends were discussed in relation to the structural characteristics of the sPS/PPO blend system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:2789–2797, 2004     

The characteristic properties of poly(methyl methacrylate)/polystyrene core‐shell composite polymer latex

In this study, the poly(methyl methacrylate/polystyrene (PMMA/PS) core‐shell composite latex was synthesized by the method of soapless seeded emulsion polymerization. The morphology of the PMMA/PS composite latex was core‐shell structure, with PMMA as the core and PS as the shell. The core‐shell morphology of the composite polymer latex was found to be thermally unstable. Under the effect of thermal annealing, the PS shell region first dispersed into the PMMA core region, and later separated out to the outside of the PMMA core region. This was explained on the basis of lowing interfacial tension between the PMMA and PS phases owing to the interpenetration layer. The interpenetration layer, which was located at the interface of the core and shell region, contained graft copolymer and entangled polymer chains. Both the graft copolymer and entangled polymer chains had the ability to lower the interfacial tension between the PMMA and PS phases. Also, the effect of thermal annealing on the morphology of commercial polymer/composite latex polymer blends was examined. The result showed that the core‐shell composite latex had the ability to enhance the compatibility of the components of polymer blends. The compatibilizing ability of the core‐shell composite latex was better than that of a random copolymer. Moreover, the effect of the amount of core‐shell composite latex on the morphology of the polymer blend was investigated. The polymer blends, which contained composite latex above 50% wt, showed the morphology of a double sea‐island structure. In addition, the composite latex was completely dissolved in solvent to destroy the core‐shell structure and release the entangled polymer chains, and then dried to form the entangled free composite polymer. The entangled free composite polymer had the ability to enhance the compatibility of the components of the polymer blend as usual. The weight ratio 3/7 commercial polymer/entangled free composite polymer blend showed the morphology of the phase inversion structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 312–321, 2003     

Dynamic mechanical and morphological behavior of blends of polystyrene and poly[acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene)‐g‐styrene] prepared by in situ polymerization of styrene

PS/AES blends were prepared by in situ polymerization of styrene in the presence of AES elastomer, a grafting copolymer of poly(styrene‐co‐acrylonitrile) – SAN and poly(ethylene‐co‐propylene‐co‐diene)–EPDM chains. These blends are immiscible and present complex phase behavior. Selective extraction of the blends' components showed that some fraction of the material is crosslinked and a grafting of PS onto AES is possible. The morphology of the noninjected blends consists of spherical PS domains covered by a thin layer of AES. After injection molding, the blends show morphology of disperse elastomeric phase morphology in a rigid matrix. Two factors could contribute to the change of morphology: (1) the stationary polymerization conditions did not allow the mixture to reach the equilibrium morphology; (2) the grafting degree between PS and AES was not high enough to ensure the morphological stability against changes during processing in the melting state. The drastic change of EPDM morphology from continuous to disperse phase has as consequence a decrease in the intensity of the loss modulus peaks corresponding to the EPDM glass transition. However, the storage modulus at temperatures between the glass transition of EPDM and PS/SAN phases does not change significantly. This effect was attributed to the presence of the SAN rigid chains in the AES. © 2009 Wiley Periodicals, Inc. Journal of Applied Polymer Science, 2009     

Influence of core–shell rubber particles synthesized with different initiation systems on the impact toughness of modified polystyrene

Core–shell poly(butadiene‐graft‐styrene) (PB‐g‐PS) rubber particles were synthesized with different initiation systems by emulsion grafting polymerization. These initiation systems included the redox initiators and an oil‐soluble initiator, 1,2‐azobisisobutyronitrile (AIBN). Then the PB‐g‐PS impact modifiers were blended with polystyrene (PS) to prepare the PS/PB‐g‐PS blends. In the condition of the same tensile yield strength on both samples, the Izod test showed that the notched impact strength of PS/PB‐g‐PS(AIBN) was 237.8 J/m, almost 7 times than that of the PS/PB‐g‐PS(redox) blend, 37.2 J/m. From transmission electron microscope (TEM) photographs, using the redox initiators, some microphase PS zones existed in the core of PB rubber particles, which is called “internal‐grafting.” This grafting way was inefficient on toughening. However, using AIBN as initiator, a great scale of PS subinclusion was seen within the PB particle core, and this microstructure increased the effective volume fraction of the rubber phase with a result of improving the toughness of modified polystyrene. The dynamic mechanical analysis (DMA) on both samples showed that the glass transition temperature (T_g) of rubber phase of PS/PB‐g‐PS(AIBN) was lower than that of PS/PB‐g‐PS(redox). As a result, the PB‐g‐PS(AIBN) had better toughening efficiency on modified polystyrene than the PB‐g‐PS(redox), which accorded with the Kerner approximate equation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 738–744, 2007     

Effect of rubber particle cavitation on the mechanical properties and deformation behavior of high‐impact polystyrene

Rubber particle cavitation has been the focus of many investigations because it dramatically affects the mechanical properties of polymeric blends. In this work, the effect of rubber particle cavitation on the mechanical behavior of high‐impact polystyrene was studied. The extent of cavitation in rubber particles was varied via different thermal contraction/expansion cycles in the range of −100 to 23°C. Tensile, creep, and Charpy impact tests were conducted to evaluate the effects of the degree of cavitation on the general mechanical properties. The notch‐tip damage zone and deformation micromechanisms were also investigated by a transmitted optical microscopy technique to reveal the effects of cavitation on toughness. The results of this investigation illustrate a close relationship between the degree of rubber particle cavitation and the mechanical performance of high‐impact polystyrene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1110–1117, 2007     

Magnetite‐coated polystyrene hybrid microspheres prepared by miniemulsion polymerization

Hybrid microspheres with a polystyrene core coated with magnetite nanoparticles were prepared by miniemulsion polymerization. Acrylic acid was used as a comonomer to promote the anchoring of the magnetite nanoparticles onto the polymeric surface. The addition of a hydrophobic agent prevents effectively the monomer from diffusing into the aqueous phase. Magnetite was treated with a silane coupling agent in order to introduce some interactions with the polymers. The morphology and the structure of the hybrid microspheres were characterized using X‐ray diffraction, infrared spectroscopy, transmission electron microscopy and thermogravimetric analysis. The results show that the morphology of the hybrid microspheres was influenced by the concentrations of acrylic acid, hydrophobic agent and surfactant, and that the degree of coating can be tuned by changing these parameters. The miniemulsion polymerization technique is adaptable to the synthesis of magnetite‐coated polymer particles, and the synthesis can be scaled up. Copyright © 2008 Society of Chemical Industry     

Preparation,morphology, and mechanical properties of elastomers based on α,ω‐dihydroxy‐polydimethylsiloxane/polystyrene blends

α,ω‐Dihydroxy‐polydimethylsiloxane/polystyrene (PDMS/PS) blends were prepared by the solution polymerization of styrene (St) in the presence of α,ω ‐dihydroxy‐polydimethylsiloxane (PDMS), using toluene as solvent and benzoyl peroxide (BPO) as initiator. The PDMS/PS blends obtained by this method are a series of stable, white gums, which were vulcanized to elastomers at room temperature with methyl‐triethoxysilicane (MTES). The use level of MTES was far more than the necessary amount used to end‐link hydroxy‐terminated chains of PDMS, with the excess being hydrolyzed to crosslinked networks, which were similar to SiO₂ and acted as filler. Investigations were carried out on the elastomeric materials by extraction measurement, swelling measurement, and scanning electron microscopy. The extraction data show that at each composition the amount of soluble fraction is less than expected and the difference between experimental and theoretical values becomes more and more significant as PS content increases. This is mainly due to the grafting of PS onto PDMS and the entanglement of PS in the interpenetrating polymer network (IPN), which consists of either directly linked PDMS chains or chains linked via PS grafts and is formed by free radical crosslinking of PDMS during the radical polymerization of St. PS grafted on PDMS is insoluble and PS entangled in the IPN is difficult to extract. Both render the soluble fraction to be less than expected. As the St content in preparing PDMS/PS blends increases, the probability of grafting PS onto PDMS also increases, which may subsequently produce a higher crosslinking level of PDMS networks that linked via PS grafts by radical crosslinking. As a result, not only the amount of insoluble PS increases but also PS entangled in the IPN is more difficult to extract. Scanning electron microscopy demonstrates that the elastomer system has a microphase‐separated structure and a certain amount of PS remains in the PDMS networks after extraction, which is in accordance with the extraction data. Moreover, the mechanical properties of the elastormeric materials have been studied in detail. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3542–3548, 2004     

Reinforced polystyrene via solvent‐exfoliated graphene

Solvent‐exfoliated graphene (SEG)‐reinforced polystyrene (PS) composites were prepared using a straightforward solution‐casting method. SEG sheets, obtained by sonication‐assisted solvent direct exfoliation from natural graphite, were well dispersed in the PS matrix as evidenced from scanning electron microscopy and transmission electron microscopy observations. Addition of 0.5 wt% SEG resulted in a 6% increase in tensile strength and a 77% improvement in Young's modulus over pure PS due to the effective load transfer between SEG and PS matrix. The Young's moduli of the PS/SEG composites were obtained from both tensile experiments and calculations using the well‐established Halpin–Tsai model. Results from dynamic mechanical analysis indicated that the storage modulus of the PS/SEG composites was significantly improved relative to neat PS. The glass transition temperatures of the composites were found to increase substantially upon addition of SEG, consistent with differential scanning calorimetry analysis. © 2017 Society of Chemical Industry     

Particle‐size‐dependent properties of sulfonated polystyrene nanoparticles

The influence of sulfonation reaction time, temperature and the parent polystyrene (PS) particle size on the degree of sulfonation (DS), ion exchange capacity (IEC), morphology and glass transition temperature (T_g) of sulfonated polystyrene (SPS) particles was investigated. A longer reaction time (ca 2 h) at 40 °C and a smaller particle size resulted in SPS particles with a high DS. It was found that a larger PS particle size did not readily yield SPS particles with a high DS even with a longer reaction time. Contrary to the popular belief in the literature that a higher DS ensures a high IEC, we observed that the proportionality of IEC to DS is primarily controlled by the SPS particle size. Larger IEC values were obtained for larger particles rather than smaller ones despite their similar DS, owing to the presence of strong interactions between ? SO₃H groups within the particles in the latter case which restricts the availability of free H⁺ for ion exchange. The SPS particles displayed a core‐shell morphology in which the outer shell appeared because of sulfonation on the PS. The DS value and the SPS particle size significantly influenced the shell thickness and thereby the morphology of the SPS particles. Copyright © 2012 Society of Chemical Industry     

Compatibilization of polypropylene/polystyrene blends with poly(styrene-b-butadiene-b-styrene) block copolymer

The compatibilizing effect of the triblock copolymer poly(styrene-b-butadiene-b-styrene) (SBS) on the morphology and mechanical properties of immiscible polypropylene/polystyrene (PP/PS) blends were studied. Blends with three different weight ratios of PP and PS were prepared and three different concentrations of SBS were used for investigations of its compatibilizing effects. Scanning electron microscopy (SEM) showed that SBS reduced the diameter of the PS-dispersed particles as well as improved the adhesion between the matrix and the dispersed phase. Transmission electron microscopy (TEM) revealed that in the PP matrix dispersed particles were complex “honeycomblike” aggregates of PS particles enveloped and joined together with the SBS compatibilizer. Wide-angle X-ray diffraction (WAXD) analysis showed that the degree of crystallinity of PP/PS/SBS slightly exceeded the values given by the addition rule. At the same time, addition of SBS to pure PP and to PP/PS blends changed the orientation parameters A₁₁₀ and C significantly, indicating an obvious SBS influence on the crystallization process in the PP matrix. SBS interactions with PP and PS influenced the mechanical properties of the compatibilized PP/PS/SBS blends. Addition of SBS decreased the yield stress and the Young's modulus and improved the elongation at yield as well as the notched impact strength in comparison to the binary PP/PS blends. Some theoretical models for the determination of the Young's modulus of binary PP/PS blends were used for comparison with the experimental results. The experimental line was closest to the series model line. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2625–2639, 1998     

Rice husk powder–filled polystyrene/styrene butadiene rubber blends

Natural fibers are rich in cellulose and they are a cheap, easily renewable source of fibers with the potential for polymer reinforcement. The presence of large amounts of hydroxyl groups makes natural fibers less attractive for reinforcement of polymeric materials. Composites made from polystyrene (PS)/styrene butadiene rubber (SBR) blend and treated rice husk powder (RHP) were prepared. The RHP was treated by esterification and acetylation. A similar series of composites was also prepared using maleic anhydride–polypropylene (MA–PP) as a coupling agent. The processing behavior, mechanical properties, effect of thermooxidative ageing, and surface morphology of untreated and chemically modified RHP were studied. There was a decrease in tensile strength (except MA–PP composites), elongation at break, and Young's modulus in chemically treated RHP composites. The postreaction process during thermooxidative ageing enhanced the tensile strength and Young's modulus of the esterified and MA–PP composites. Acetylation treatment was effective in reducing the percentage of water absorption in RHP/PS–SBR composites. In general chemically treated RHP/PS–SBR composites and MA–PP showed a better matrix phase and filler distribution. However, the degree of filler–matrix interaction was mainly responsible for the improvement of mechanical properties in the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3320–3332, 2004     

Preparation and characterization of high‐impact polystyrene using different types of polybutadiene

The mechanical, morphological, and rheological properties of polymer blends based on polystyrene (PS) and three different types of polybutadiene (PB) were studied. The polymer blends containing 20% of PB were processed in a Haake mixer at 180°C and 60 rpm for 6 min. The materials exhibited impact strength superior to that of the PS. An increase was observed in the impact strength of 138, 208, and 823%, when low‐cis polybutadiene (PB_l), high‐cis polybutadiene (PB_h), and styrene–butadiene block copolymer (PB_co), were respectively used. The materials presented dispersed morphology with polybutadiene domains, with sizes inferior to 1 μm, randomly distributed in the PS matrix. The viscous and storage moduli increased as the applied frequency increased. The flow activation energy, calculated by Arrhenius equation, varied from 34 to 71 kJ/mol. In the rheological experiments all polymer blends presented pseudoplastic behavior, showing decreasing viscosities as the shear rate increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Rheological,mechanical and morphological properties of thermoplastic vulcanizates based on high impact polystyrene and styrene‐butadiene rubber

Thermoplastic vulcanizates (TPVs) based on high impact polystyrene (HIPS)/styrene‐butadiene rubber (SBR) blends were prepared by dynamic vulcanization technique. The rheological, mechanical and morphological properties of the dynamically vulcanized blends were investigated systematically. As determined by capillary rheometer, the apparent viscosity of the blends decreases as the shear rate increases, indicating obvious pseudoplastic behavior. At low shear rate, the apparent viscosity of these blends is considerably higher than that of neat HIPS and decreases with the increase of HIPS concentration. The increase of HIPS content in the dynamically vulcanized blends contributes to the increase of tensile strength and hardness properties, while elongation at break and tensile set at break reach a maximum at 30 and 50 wt % of the HIPS content, respectively. The etched surfaces of the HIPS/SBR TPVs were investigated using field‐emission scanning electron microscopy, the morphological study reveals continuous HIPS phase and finely dispersed SBR elastomeric phase in the TPVs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010