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     

Near-surface morphology effect on tack behavior of poly(styrene-b-butadiene-b-styrene) triblock copolymer/rosin films

The correlation between near-surface morphology and tack behavior of poly(styrene-b-butadiene-b-styrene) triblock copolymer (SBS)/rosin ester films was investigated using probe tack tests, transmission electron microscopy and small-angle X-ray scattering. The SBS/rosin films with rosin composition between 10 and 20 wt% rosin, prepared by slow evaporation of toluene during solvent casting, exhibited uniform near-surface morphology of lamellae oriented parallel to the surface. However, due to the limited solubility of rosin in the PS domains, the rosin started to phase-separate from the PS domains at 15 wt%, and formed fully separated micron-sized domains above 20 wt% rosin. The probe tack force of the SBS/rosin films increased steadily when the near-surface domain orientation changed from perpendicular cylinder to parallel lamellae on addition of rosin. Specifically, for a given lamellar morphology and surface orientation, macrophase separation of rosin plays a critical role in determining the tack properties of SBS/rosin films.     

Compatibilization effects of block copolymers in high density polyethylene/syndiotactic polystyrene blends

Three triblock copolymers of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) of different molecular weights and one diblock copolymer of poly[styrene-b-(ethylene-co-butylene)] (SEB) were used to compatibilize high density polyethylene/syndiotactic polystyrene (HDPE/sPS, 80/20) blend. Morphology observation showed that phase size of the dispersed sPS particles was significantly reduced on addition of all the four copolymers and the interfacial adhesion between the two phases was dramatically enhanced. Tensile strength of the blends increased at lower copolymer content but decreased with increasing copolymer content. The elongation at break of the blends improved and sharply increased with increments of the copolymers. Drop in modulus of the blend was observed on addition of the rubbery copolymers. The mechanical performance of the modified blends is strikingly dependent not only on the interfacial activity of the copolymers but also on the mechanical properties of the copolymers, particularly at the high copolymer concentration. Addition of compatibilizers to HDPE/sPS blend resulted in a significant reduction in crystallinity of both HDPE and sPS. Measurements of Vicat softening temperature of the HDPE/sPS blends show that heat resistance of HDPE is greatly improved upon incorporation of 20 wt% sPS.     

Asymmetric morphology from an organic/organometallic block copolymer

Block copolymer self-assembly is a burgeoning subject in polymer and materials science driven by both fundamental and applied inspirations. Whereas the vast majority of block copolymer studies have focused on highly symmetric morphologies, here we report the first observation of an unusual asymmetric cylindrical phase in thick films of an organic/organometallic block copolymer, poly(styrene-block-ferrocenyldimethylsilane) (PS-b-PFS). Microscopy and X-ray scattering data establish the lack of symmetry in this structure and reveal an unusual 3-D network organization. Following selective removal of the PS matrix, the remaining nanoporous film has characteristics of potential value in separation applications such as substantial interconnection (mechanical strength), uniform pore size, and chemical and physical stability.     

Influences of dicumyl peroxide on morphology and mechanical properties of polypropylene/poly(styrene‐b‐butadiene‐b‐styrene) blends via vane‐extruder

Polypropylene (PP) and poly(styrene‐b‐butadiene‐b‐styrene) block copolymer (SBS) were melt‐blended in the presence of initiator system. Dicumyl peroxide (DCP)/Triallyl isocyanurate (TAIC) via self‐deigned VE, aiming at in situ reactive compatibilization of toughed PP/SBS blend. The reactivity, morphology and mechanical properties of PP/SBS/DCP/TAIC blends were studied. Online torque detection was conducted to monitor changes in viscosities of reactive compatibilized blends, which could give proof of the interfacial grafted reaction induced by DCP/TAIC system. The effect of reactive compatibilization on the dispersed particles sizes and interfacial adhesion was studied by scanning electron microscopy. Analysis on mechanical performance revealed the impact strength improved after treated by initiator system, moreover, the impact‐fractured surface observation showed, the failure mode changed from debonding mechanism of neat 50PP/50SBS blend to plastic deformation mechanism of blend containing 3.0 phr initiator system. With improved interfacial adhesion, compatibilized blends not only were toughened but also exhibited enhanced tensile strength and thermal stability. Dynamic mechanical analysis showed a reduction of between PP phase and the PB segments in SBS phase, indicating reactive compatibilization of the blend was achieved. In the final part, a brief discussion was given about the dominant effects from chain scission of PP matrix to intergrafting reactions of PP and SBS, under different content of DCP/TAIC initiator system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41543.     

Relationship among microstructure, linear viscoelastic behavior and mechanical properties of SBS triblock copolymer-compatibilized PP/SAN blend

Morphological, rheological and mechanical properties of the polypropylene (PP) and poly(styrene-co-acrylonitrile) (SAN) blend containing poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer (ranging from 0 to 20 wt%) were studied by scanning electron microscopy (SEM), small amplitude oscillatory shear analysis, and both tensile and impact tests, respectively. SEM observations showed that SBS reduced the diameter of the SAN dispersed particles as well as improved the adhesion between the matrix and the dispersed phase. Close examination of SEM micrographs further revealed that the dispersed phase domains were complex aggregates of SAN particles enveloped and joined together with the SBS compatibilizer in the PP matrix. The variation of the dynamic rheological parameters, including dynamic moduli (G′ and G″), complex viscosity ( $ \eta^{ * } $ ), loss factor (tan δ), together with Cole–Cole diagrams, with blend composition particularly at low frequency regions were determined to evaluate the interfacial activity of SBS copolymer. A specific viscoelastic phenomenon, i.e., “the second plateau”, appeared at low frequencies for PP/SAN blend containing 20 wt% of SBS and exhibited a certain dependence on the SBS amount and dispersion state in the matrix. This phenomenon was attributed to the formation of aggregate structure between SAN particles and SBS triblock copolymer. Finally, the results of uniaxial tensile and Charpy impact tests conducted on both unnotched and notched specimens indicated that in PP/SAN blend, SBS functions as both compatibilizer and toughening agent.     

Application of phase dispersion–crosslinking synergism on recycling commingled plastic wastes

A tetra‐component blend, consisting of low‐density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS), was studied as a model system of commingled plastic wastes (LDPE/PVC/PP/PS, mass ratio: 70/10/10/10). Effects of chlorinated polyethylene (CPE), ethylene–propylene–diene monomer (EPDM), styrene–butadiene–styrene (SBS), and their mixture (CPE/EPDM/SBS, mass ratio: 2/2/2) on the mechanical properties and morphology of the system were investigated. With addition of several elastomers and their mixture, the tensile strength of the blends decreased slightly, although both the elongation at break and the impact strength increased. Among these elastomers, EPDM exhibited the most significant impact modification effect for the tetra‐component blends. SBS and the mixture have a good phase‐dispersion effect for the tetra‐component blend. By adding a crosslinking agent [dicumyl peroxide (DCP)], the mechanical properties of the tetra‐component blends also increased. When either SBS or the mixture was added to the blend together with DCP, the probability that the crosslinking agent (DCP) would be at the interface improved because of the phase‐dispersion effect of SBS. Therefore, more co‐crosslinked products will form between LDPE and other components. Accordingly, remarkable improvement of the interfacial adhesion and hence the mechanical properties of the tetra‐component blends occurred. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2947–2952, 2001     

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     

Reinforcement of peroxide‐cured styrene–butadiene rubber vulcanizates by mathacrylic acid and magnesium oxide

Through the neutralization of magnesium oxide (MgO) and methacrylic acid (MAA), magnesium methacrylate [Mg(MAA)₂] was in situ prepared in styrene–butadiene rubber (SBR) and used to reinforce the SBR vulcanizates cured by dicumyl peroxide (DCP). The experimental results show that the mechanical properties, dynamic mechanical properties, optical properties, and crosslink structure of the Mg(MAA)₂‐reinforced SBR vulcanizates depend on the DCP content, Mg(MAA)₂ content, and the mole ratio of MgO/MAA. The formulation containing DCP 0.6–0.9 phr, Mg(MAA)₂ 30–40 phr, and MgO/MAA mole ratio 0.50–0.75 is recommended for good mechanical properties of the SBR vulcanizates. The tensile strength of the SBR vulcanizates is up to 31.4 MPa when the DCP content is 0.6 phr and the Mg(MAA)₂ content is 30 phr. The SBR vulcanizate have good aging resistance and limited retention of tensile strength at 100°C. The SBR vulcanizates are semitransparent, and have a good combination of high hardness, high tensile strength, and elongation at break. The T_g values of the SBR vulcanizates depend largely on the DCP content, but depend less on the Mg(MAA)₂ content and the MgO/MAA mole ratio. The contents of DCP, Mg(MAA)₂, and the MgO/MAA mole ratio have also great effects on the E′ values of the vulcanizates. The salt crosslink density is greatly affected by the Mg(MAA)₂ content and MgO/MAA mole ratio, but less affected by the DCP content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2667–2676, 2002     

Morphology and mechanical properties of styrene-butadiene-styrene/polystyrene semi-interpenetrating polymer networks and their blends

SBS/PS semi-interpenetrating polymer networks (semi-IPNS) were synthesized by swelling a linear styrene-butadiene-styrene (SBS) triblock copolymer (SBS, Kraton 1102) with styrene monomer plus benzoin as photoinitiator and divinylbenzene as cross-linking agent. Polyblends were prepared by solution casting of SBS and polystyrene (PS) in their ideal solvents. Measurements were made for viscoelastic properties and mechanical properties of phase-separated polymer alloy (including SBS copolymers Kraton 4122), semi-IPNs and polyblends of several SBS and PS, with the same total PS content (48% PS). The dynamic mechanical behaviour shows distinct transitions for each polymer, in agreement with electron microscopy results that SBS/PS polymer alloy forms two phases; however, the phase domains were finer in the semi-IPNs than in SBS triblock copolymer and in polyblends of the corresponding polymers. Stress-strain data show that semi-IPNs exhibit higher tensile strength and modulus than the other two corresponding polymer alloys. A master curve was plotted to illustrate the stress relaxation behaviour of samples at higher temperatures. Our results also reveal that semi-IPNs have much better high-temperature mechanical strength.     

Cure characteristics and mechanical properties of styrene-butadiene rubber/hydrogenated acrylonitrile-butadiene rubber/silica composites

Composites of styrene butadiene rubber (SBR), hydrogenated acrylonitrile–butadiene rubber (HNBR) and silica were prepared. Sulfur (S), dicumyl peroxide (DCP) and a combination of S and DCP (M) were used as curing agents, respectively. The morphology of the composites with different blend ratio was examined to correlate with observations on mechanical properties by scanning electron microscopy. The effects of blend ratio and curing systems on the curing characteristics and mechanical properties, such as stress–strain behavior, tensile strength, elongation at break and hardness of SBR/HNBR/Silica composites, were studied. Composites prepared by M curing systems showed comparatively better mechanical properties, wet traction and rolling resistance than S and D curing systems. The tensile strength, tear strength, and elongation at break were improved by adding HNBR for M curing systems. The wet traction of the vulcanizates containing HNBR was better than that of the vulcanizates without HNBR. A relatively uniform dispersion of silica was observed for SBR/HNBR/silica compositions compared with SBR/silica composites.     

LLDPE/POE共混物的交联行为研究

采用过氧化物交联研究了线性低密度聚乙烯(LLDPE)/乙烯-α-辛烯共聚物(POE)共混物。研究了工艺、配方对LLDPE/POE共混物凝胶含量的影响,以及凝胶含量与材料力学性能的关系。结果表明,LLDPE/POE共混物的凝胶含量随引发剂的用量、交联温度和交联时间的增加而增加,达到一定程度后不再增加。在170℃,30min的条件下DCP能充分分解引发交联反应,DCP用量为1.5%时,共混物的凝胶含量可以达到80%以上,再增加时凝胶含量不再增加。DCP的加入顺序对共混物的凝胶含量影响不大。共混物的凝胶含量对其动态力学行为有影响。共混物的凝胶含量对拉伸性能影响不大。     

Nanostructured silica-type hybrids from poly(styrene-b-ethylene oxide-b-caprolactone) copolymers

By employing a triblock copolymer, poly(styrene-b-ethylene oxide-b-caprolactone) copolymer, as a structure-directing agent, a series of silica-type hybrid materials were prepared via a sol-gel method of (3-glycidyloxypropyl) trimethoxy silane and aluminum sec-butoxide. Small angle X-ray scattering and transmission electron microscopy analyses demonstrated that ordered nanostructures, from lamellar to 2-dimensional hexagonal columnar with a disordered intermediate morphology, were exhibited as a function of the amount of loaded silica nanoparticles. Among the observed morphologies, the silica particles in the lamellar sample were localized at the PS/PEO interface, which could be elucidated by the dominant translational entropy of small silica particles.     

Effect of styrene–isoprene–styrene,styrene–butadiene–styrene,and styrene–butadiene–rubber on the mechanical,thermal, rheological,and morphological properties of polypropylene/polystyrene blends

The mechanical, thermal, rheological, and morphological properties of polypropylene (PP)/polystyrene (PS) blends compatibilized with styrene–isoprene–styrene (SIS), styrene–butadiene–styrene (SBS), and styrene–butadiene–rubber (SBR) were studied. The incompatible PP and PS phases were effectively dispersed by the addition of SIS, SBS, and SBR as compatibilizers. The PP/PS blends were mechanically evaluated in terms of the impact strength, ductility, and tensile yield stress to determine the influence of the compatibilizers on the performance properties of these materials. SIS‐ and SBS‐compatibilized blends showed significantly improved impact strength and ductility in comparison with SBR‐compatibilized blends over the entire range of compatibilizer concentrations. Differential scanning calorimetry indicated compatibility between the components upon the addition of SIS, SBS, and SBR by the appearance of shifts in the melt peak of PP toward the melting range of PS. The melt viscosity and storage modulus of the blends depended on the composition, type, and amount of compatibilizer. Scanning electron microscopy images confirmed the compatibility between the PP and PS components in the presence of SIS, SBS, and SBR by showing finer phase domains. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 266–277, 2003     

Relationship between the cell structure and mechanical properties of chemically crosslinked polyethylene foams

The main objective of this work was to study the effect of the controlling parameters on the morphology and mechanical properties of the peroxide crosslinked low‐density polyethylene foams. The relationship between the morphology and mechanical properties was also considered. Using different Dicumyl peroxide (DCP) and azodicrbonamide (ADCA) concentrations, various foams with different cell structures were prepared. Gel content and density of the foams were measured according to the standard methods. The morphology was examined using SEM technique. The mechanical properties of the foams were evaluated by means of compression and creep recovery tests. The results showed that the gel content and the density are mainly controlled by DCP and ADCA concentration, respectively. The results also showed that the cell size distribution is mainly controlled by DCP concentration. Increasing of DCP increased the gel content and decreased the cell size and cell size distribution. Foam density was mainly controlled by ADCA concentration, whereas the morphology was less affected with ADCA concentration. The foams with small cell size and narrow cell size distribution showed higher mechanical strength and lower plastic strain. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Optimum toughening via a bicontinuous blending: toughening of PPO with SEBS and SEBS-g-maleic anhydride

The poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was toughened by melt extrusion through its blending with a styrene-b-ethylene/butadiene-b-styrene triblock copolymer (SEBS), or with maleic anhydride (MA) grafted SEBS (SEBS-g-MA). Their morphology, mechanical properties, and rheology have been investigated. Transmission electron microscopy revealed that both kinds of blends had an island-sea structure at low concentrations of SEBS or SEBS-g-MA and a bicontinuous one at sufficiently high concentrations. However, the percolation threshold was higher for SEBS than for the SEBS-g-MA. The Izod impact strength of PPO could be significantly improved through its blending with SEBS-g-MA, particularly in a blend with 20 wt% of SEBS-g-MA at which it had a maximum value. The rheological experiments indicated that the incorporation of SEBS increased and that of SEBS-g-MA decreased the melt viscosity of the system.     

过氧化物交联改性PE-HD/EVA防水材料的研究

用过氧化二异丙苯（DCP）交联法改善高密度聚乙烯/乙烯醋酸乙烯共聚物（PE-HD/EVA）防水材料的尺寸稳定性,研究了交联剂用量对PE-HD/EVA片材热稳定性和力学性能的影响。采用傅里叶变换红外光谱仪、差示扫描量热仪、X射线衍射仪、索氏提取交联度测试法等对片材进行了分析,研究了片材力学性能的影响因素。结果表明,随着交联度的增大,片材的软化温度和结晶度逐渐降低,晶体结构基本不变,晶粒尺寸减小, 拉伸强度提高;当DCP用量为1.2 %（质量分数,下同）时,片材的拉伸强度达到了最大值,其断裂伸长率比未交联片材降低了77 %,尺寸稳定性得到明显改善;交联改性对于PE-HD/EVA解决防水材料尺寸稳定性差等问题具有一定的指导意义。     

Review Highlighting Physical Prospects of Styrenic Polymer and Styrenic Block Copolymer Reinforced with Carbon Nanotube

High-performance styrenic copolymers with carbon nanotube have invented technical relevance. Polystyrene is used to compensate different deficiencies of carbon nanotube within PS/carbon nanotube composite. Dispersion of carbon nanotube content is essential for enhanced mechanical and thermal performance of styrenic copolymer/carbon nanotube composite. Multiwalled carbon nanotube has been reinforced in styrene-butadiene rubber, nitrile butadiene rubber, hydrogenated nitrile butadiene rubber, poly(styrene-b-isoprene-b-styrene), acrylonitrile butadiene styrene, and other styrenic copolymers to enhance electrical, mechanical, and thermal properties. Viscoelastic and photoactuation study of polystyrene-grafted-multiwalled carbon nanotube has been performed. Different styrene-based copolymers show high resistivity toward high impact and are used in food packaging, electrical devices, medical appliance, construction materials, motor oils, sealants, and household purposes.     

PS/SBR-g-PS共混物的力学性能和形态结构

采用种子乳液聚合技术在丁苯胶乳上接枝聚合苯乙烯 ,合成了一系列丁苯橡胶接枝聚苯乙烯共聚物 (SBR-g-PS)。将其与聚苯乙烯 (PS)树脂共混后 ,考察了 SBR-g-PS的组成 (SBR/ PS)对共混物的力学性能和形态结构的影响。结果发现 ,当 SBR/ PS为 6 7/ 33-5 0 / 5 0时 ,PS/ SBR-g-PS共混物表现出良好的综合力学性能 ,在 SBR-g-PS中随着接枝 PS的增多 ,像胶粒子在基体中的分散状况获得改善 ,在大橡胶颗粒中含有大量的 PS次级粒子。在外负载的作用下 ,共混物中的大橡胶颗粒引发了大量的银纹 ,吸收了断裂应变能 ,从而提高了材料的冲击韧性。     

Short glass fiber reinforced radiation crosslinked shape memory SBS/LLDPE blends

The poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (SBS) and linear low density polyethylene(LLDPE) were blended and irradiated by γ‐rays to prepare shape memory polymer(SMP). Various amounts of short glass fiber (SGF) were filled into SMP to form a novel shape memory SGF/SBS/LLDPE composite. The effect of SGF on the shape memory SGF/SBS/LLDPE composite was studied in terms of mechanical, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and shape memory effects. It is found that the SGF act as reinforcing fillers and significantly augment the glassy and rubbery stated moduli, tensile strength and shape memory properties. When SGF content is <2.0 wt %, full recovery can be observed after only several minutes at different temperatures and shape recovery speed reduces as the SGF content increases. The shape recovery time decreases as the temperature of the shape memory test increases and the shape recovery rate decreases with increment of cycle times. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40691.