Effect of physical and chemical crosslinking structure on fatigue behavior of styrene butadiene elastomer

The fatigue behavior of two styrene butadiene rubbers, thermoplastic elastomer (SBS) with physical crosslinking structure and vulcanized styrene butadiene rubber (SBR) with chemical crosslinking structure, was investigated. The fatigue lives of SBS and SBR were greatly affected by the fatigue frequency, amplitude, and temperature. The fatigue lives of both SBS and SBR decreased with the increasing fatigue frequency and amplitude. However, the effect of fatigue temperature on the fatigue life of SBS was different from that of SBR. With the increasing fatigue temperature, the fatigue life of SBS first decreased and then increased, however, the fatigue life of SBR showed continuous decreasing trend. The tensile strength of SBS first increased and then decreased with the increase of fatigue time, but the tensile strength of SBR was not significantly influenced by the fatigue time. The fatigue amplitude had greater effect on the tensile strength of SBS than that of SBR. The permanent deformation of both SBS and SBR increased with temperature; however, the parameter for the former rubber was higher than that of the latter. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40917.     

Thermal and mechanical properties of microcellular thermoplastic SBS/PS/SBR blend: effect of crosslinking

This study investigates the effect of peroxide crosslinking on the structure and mechanical properties for SBS/PS/SBR foams composed of polystyrene (PS), poly(styrene-b-butadiene) diblock copolymer (SBR-1502), and poly(styrene-b-butadiene-b-styrene) triblock copolymer (SBS). The cell size and its distribution of SBS/PS/SBR foams were investigated by SEM images, showing the smaller and denser of hollow cells for the SBS/PS/SBR foam containing the higher concentration of DCP (dicumyl peroxide). As expected, the density of the SBS/PS/SBR foams increases with increasing the content of DCP. The high density of polymeric foams exhibits the high mechanical properties such as hardness, shrinkage, tensile strength, tear strength, elongation at break, and compression set.     

Mechanical properties and morphology of polypropylene composites. Talc-filled,elastomer-modified polypropylene

The balance of impact strength and rigidity of polypropylene can be significantly improved by physical blending of the polypropylene with a talc filler and a variety of elastomer types. Unsaturated elastomers were found to be effective impact strength improvers in 70/15/15 percent PP/elastomer/talc composites, whereas saturated elastomers gave rise to a high stiffness of such compounds. This is attributed primarily to different tendencies of the elastomers to coat the filler surface. Studies on a wider range of compositions, using a butadienestyrene-butadiene (SBS) block copolymer and a ethylene-propylene-diene (EPDM) terpolymer as representatives of the two elastomer classes, indicated that at high stiffness levels (flexural modulus > 1.6 GN/m²), the composites with SBS show the best balance of properties, whereas at higher impact levels EPDM leads to a higher rigidity and impact strength. On the basis of morphological studies such differences can be explained qualitatively, in spite of the complex structure of these composites.     

Blends of i‐PP and SBS. I. Influence of the in situ compatibilization on the morphology

This article concerns the in situ compatibilization of immiscible isotactic polypropylene/butadiene‐styrene‐butadiene triblock copolymer blends (i‐PP/SBS) by means of a reactive mixture. For this purpose, maleated PP (PP‐MAH) and SBS (SBS‐MAH) were used as functionalized polymers and 4,4′‐diaminediphenylmethane was used as a coupling agent between maleated polymers, resulting in a graft copolymer. Binary blends i‐PP/SBS, nonreactive ternary blends i‐PP/PP‐MAH/SBS, and reactive ternary blends i‐PP/PP‐MAH/SBS‐MAH with varying diamine and anhydride molar ratios were prepared. Torque measurements suggest a graft copolymerization during the melt blending for ternary reactive blends, but the extension of the grafting does not vary with the diamine and anhydride molar ratio, but with the elastomer concentration. The morphology of the blends was investigated by scanning electron microscopy. The morphology of binary and ternary nonreactive blends is similar, exhibiting elastomer domains disperse in the i‐PP matrix, whose sizes increase with elastomer concentration. On the other hand, the elastomer domain size in the ternary reactive blends is practically independent of the blends composition and of the diamine and anhydride molar ratio. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 847–855, 2002     

Stress Relaxation in Peel Adhesion

The peeling of an adhesive joint consisting of an SBS copolymer and two Mylar film substrates proceeds by cohesive rubber rupture, and the strength increases with test rate. Stress relaxation during peeling is shown to account for this behavior and relaxation data after peeling is used to predict the rate dependence of the peel force.     

Toughening of recycled polystyrene used for TV backset

The recycled polystyrene (rPS) was toughened with ethylene‐octylene copolymer thermoplastic elastomer (POE) and high‐density polyethylene (HDPE) with various melt flow index (MFI), compatibilized by styrene‐butadiene‐styrene copolymer (SBS) to enhance the toughness of rPS for use as TV backset. The rPS/POE binary blends exhibited an increased impact strength with 5–10 wt % POE content followed by a decrease with the POE content up to 20 wt %, which could be due to poor compatibility between POE and rPS. For rPS/POE/SBS ternary blends with 20 wt % of POE content, the impact strength increased dramatically and a sharp brittle‐ductile transition was observed as the SBS content was around 3–5 wt %. Rheological study indicated a possible formation of network structure by adding of SBS, which could be a new mechanism for rPS toughening. In rPS/POE/HDPE/SBS (70/20/5/5) quaternary blends, a fibril‐like structure was observed as the molecular weight of HDPE was higher (with lower MFI). The presence of HDPE fibers in the blends could not enhance the network structure, but could stop the crack propagation during fracture process, resulting in a further increase of the toughness. The prepared quaternary blend showed an impact strength of 9.3 kJ/m² and a tensile strength of 25 MPa, which can be well used for TV backset to substitute HIPS because this system is economical and environmental friendly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Interfacial adhesion evaluation in (low‐density polyethylene)/elastomer blends

Low‐density polyethylene (LDPE) with different elastomers at a ratio of 50/50 wt% blends was prepared by using a co‐rotating twin‐screw extruder. Three kinds of elastomers were used: ground tire rubber (GTR), partially crosslinked butyl rubber (Kalar^®), and styrene‐butadiene‐rubber block copolymer (SBS; Kraton^®). For better characterization of interaction between polyethylene and elastomer, influence of the type of elastomer on the properties of compositions LDPE/elastomer was determined. In the studies, two types of partially crosslinked butyl rubber (differing over filler content and Mooney viscosity) and two types of SBS (differing over structure: linear/branched) were used. The influence of kind and type of elastomer on static mechanical properties (tensile strength, elongation at break, hardness), dynamic mechanical properties, thermal properties, and morphology of obtained compositions were characterized. LDPE/linear SBS copolymer blend had the best mechanical properties, as a result of better compatibility in comparison with other investigated blends. The reason for improved compatibility was an increase of mobility of chain segments in the amorphous phase of polyethylene associated with their partial plasticization by flexible polybutadiene blocks present in SBS copolymer. J. VINYL ADDIT. TECHNOL., 22:492–500, 2016. © 2015 Society of Plastics Engineers     

SBS and SEBS block copolymers as impact modifiers for polypropylene compounds

Blends of polypropylene (PP) and thermoplastic elastomers (TPE), namely SBS (styrene‐butadiene‐styrene) and SEBS (styrene‐ethylene/1‐butene‐styrene) block copolymers, were prepared to evaluate the effectiveness of the TPE type as an impact modifier for PP and influence of the concentration of elastomer on the polymer properties. Polypropylene homopolymer (PP‐H) and ethylene–propylene random copolymer (PP‐R) were evaluated as the PP matrix. Results showed that TPEs had a nucleating effect that caused the PP crystallization temperature to increase, with SBS being more effective than SEBS. Microstructure characterization tests showed that in most cases PP/SEBS blends showed the smallest rubber droplets regardless of the matrix used. It was seen that SEBS is a more effective toughening agent for PP than SBS. At 0°C the Izod impact strength of the PP‐H/SEBS 30% b/w blend was twofold higher than the SBS strength, with the PP‐R/SEBS 30% b/w blend showing no break. A similar behavior on tensile properties and flexural modulus were observed in both PP/TPE blends. Yield stress and tensile strength decreased and elongation at break increased by expanding the dispersed elastomeric phase in the PP matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 254–263, 2005     

Adhesion of RFL-coated aramid fibres to elastomers: The role of elastomer–latex compatibility

The performance of fibre-reinforced composites is strongly dependent on the nature and the strength of the fibre–matrix interface. Good interfacial bonding is required to ensure load transfer from matrix to reinforcing fibres. For rubber-reinforced composites, resorcinol formaldehyde latex (RFL) is known as a fibre surface coating which is able to provide good adhesion between rubber and fibres. In the present study, aramid fibres are investigated, because of their significantly higher modulus and strength, compared to other commercial fibres. Their adhesion after being coated with RFL, in compounds based on natural rubber (NR) and in NR blended with a small amount of styrene butadiene rubber (SBR) is investigated. It is shown that though having very similar tensile properties, the latter compound has much better adhesion to RFL which is also less sensitive to RFL ageing, compared to the pure NR compound. It is argued that an interphase region is formed between RFL and the elastomer, which is stronger for the compound containing SBR due to its enhanced compatibility with the latex part of the RFL.     

Reactive blending of polyamides with epoxidized elastomers

Melt blending of aliphatic polyamides (PA6, PA66, PA12) with epoxidized and nonepoxidized elastomers (SBS, BS, PB) was investigated. IR and rheological studies have shown that epoxidized elastomers can simultaneously react both with polyamides and within their own phases during melt blending. Relative intensity of both processes is the main factor, which determines structure and properties of blends. SEM observations indicated that use of epoxidized elastomers improves blend homogeneity and decreases mean size of dispersed elastomer phase in comparison with nonepoxidized elastomers. Mechanical properties of epoxidized elastomers based blends are generally better with respect to similar blends with nonepoxidized elastomers. They depend on blend composition and type of polyamide and elastomer. Elastomer addition decreases tensile strength of all systems but in some cases, a considerable rise of impact strength was measured. Epoxidized SBS block copolymer was found to be the most effective modifier, especially with respect to PA6 and PA12. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

顺丁烯二酸钾基(苯乙烯-丁二烯-苯乙烯)嵌段共聚物离聚体的力学性能及其应用

用环氧化(苯乙烯-丁二烯-苯乙烯)嵌段共聚物(SBS)开环反应合成了含顺丁烯二酸钾基的SBS离聚体,考察了离子基团不同含量对含顺丁烯二酸钾基的SBS离聚体力学性能的影响,研究了离聚体/聚丙烯(PP)共混物的力学性能和耐溶剂性能,以及离聚体对氯醇橡胶(CHR)/SBS共混物的增容效果。结果表明,该离聚体呈现热塑性弹性体行为;随着离子基团含量的增加,离聚体的拉伸强度及扯断伸长率增大,但当离子基团含量超过1.69mmol/g时,离聚体的力学性能又有所下降,离子基团最佳含量为1.23~1.69mmol/g;该离聚体与PP共混,在拉伸强度方面呈现协同效应;离聚体作为增容剂提高了SBS与CHR的相容性,当离聚体质量分数为3%时,力学性能达到最佳,共混物的耐溶剂性能也得到了改善。     

Grafting starch xanthate with vinyl monomers and hydrogen peroxide in foam rubber production

Starch xanthate with degrees of substitution (D.S.) ranging from 0.12 to 0.56 reacted with vinyl monomers (acrolein, acrylamide, acrylic acid, acrylonitrile, methyl acrylate, or styrene) and hydrogen peroxide to form aqueous gels of starch–polyvinyl monomer graft copolymer. The same reactions conducted in a rubber latex medium resulted in a self-acidifying, self-heating, and self-foaming coagulation to give a foam rubber. Such products were formed from several synthetic latices (NBR, SBR, polyisoprene, and polychloroprene types) and natural rubber latex; noted for each were the effects of the D.S., of monomer and peroxide concentrations, and of starch:elastomer ratios. The dried foams were evaluated by standard strength tests. Foam rubber of acceptable extensibility and enhanced tensile strength (up to 110 psi) was obtained with 0.12–0.15 D.S. xanthate and with proper balance of vinyl monomer, peroxide, and starch:elastomer ratio. Resilience was fair to good, but compression set was rather poor compared to most foam rubbers of general use.     

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.     

增黏树脂与弹性体SBS的相容性以及与热熔压敏胶性能的关系

热熔压敏胶(HMPSA)是一类不含溶剂的胶粘剂,在工业应用中占据很大的比重。工业上常用的增黏树脂有松香树脂、萜烯树脂和石油树脂三种。增黏树脂与热塑性弹性体SBS(苯乙烯/丁二烯/苯乙烯嵌段共聚物)的相容性存在一定的差异性,从工业角度重点研究和比较了增黏树脂的结构差异与性能之间的关系,并对其一般规律进行了探索。研究结果表明,当增黏树脂的软化点为100～110℃时,相应的HMPSA可获得较低的熔融黏度和较高的剥离强度,其初粘力为1～2cm;当增黏树脂的软化点为100℃时,剥离强度依次为含萜烯树脂HMPSA>含松香树脂HMPSA>含石油树脂HMPSA;当W(增黏树脂)= 210%时(相对于弹性体SBS而言),含石油树脂HMPSA的综合性能劣于含松香树脂(或含萜烯树脂)的HMPSA;当W(增黏树脂)≥210%时,HMPSA的熔融黏度低于10000mPa·s,但持粘力增强(即意味着内聚力增强)。     

Segmental mobility in the vicinity of Tg in PS/SBR blends: Nanodomain size prediction of the dispersed phase

The blends of polystyrene (PS) and styrene‐butadiene rubber (SBR) are melt‐blended at different ratios to form physical thermoplastic elastomers. This polymeric blend is expected to behave more or less similar to chemically synthesized block copolymers such as styrene‐butadiene block copolymers (SBS). In this study, mechanical and the thermomechanical properties of this blend are investigated and compared to those of SBS copolymer. As far as morphology is considered, the blend shows a two‐phase morphology with an interface, which shows very weak interactions. According to the observed morphology and the domain size of dispersed phase the blends are of good integrity. The mechanical properties of the blends confirm the integrity of the blend and effective interface stress transfer. The tensile and Izod impact properties of the blends shows improvements upon increase in SBR content of the blend. As SBR content augments the elongation at break increases, whereas tensile dissipated energy and impact resistance go through a maximum. Therefore, blend with SBR‐content in 60–75% range can be considered as preferred one. In a wide range of concentration a phase inversion was observed and T_g‐depression was detected also for the SBR phase. This T_g‐depression was correlated to the changes in dynamics of segments (segmental mobility) near the surfaces. Using the proposed relationships between T_g‐depression and the thickness of the thin films, it was tried to calculate domain size of SBR inclusions in PS matrix. A rough correlation between SBR domain sizes in SEM images and calculated thicknesses using T_g‐depression in thin films was found. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Physicochemical characterization of the filler–matrix interface in elastomer‐encapsulated fly ash/polyester particulate composites

An attempt was made to improve the toughness of fly ash (FA)/general‐purpose unsaturated polyester resin (GPR) composites. Elastomer [styrene–butadiene rubber (SBR) or acrylic copolymer (AC)]‐encapsulated fillers (FA or CaCO₃) were made through the coagulation of the emulsified elastomer containing the filler with constant stirring. The elastomer‐encapsulated fillers were added to GPR at concentrations as high as 15 wt % to make FA/SBR or AC/GPR composites. The mechanical properties (i.e., the tensile strength, tensile modulus, tensile elongation, flexural strength, flexural modulus, impact strength, and hardness) of FA/GPR, FA/SBR/GPR, and FA/AC/GPR composites were studied. The tensile‐fractured surfaces of all the composites were studied with scanning electron microscopy. The thermal stability was studied with thermogravimetric analysis. An analysis of the results indicate that this modification technique is rather easy and more economical than the chemical modification of filler surfaces with functional silane coupling agents. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 171–184, 2005     

两亲性聚氧乙烯接枝(苯乙烯-丁二烯-苯乙烯)三嵌段共聚物

通过环氧化(苯乙烯-丁二烯-苯乙烯)三嵌段共聚物(SBS)与端羧基甲氧基聚乙二醇的开环反应,合成了带聚氧乙烯支链的两亲性SBS接枝物,通过红外光谱及核磁共振氢谱进行了表征,并确定了该两亲性聚合物具有良好的乳化性质及相转移催化性质.     

A novel type of shape memory polymer blend and the shape memory mechanism

A novel styrene-butadiene-styrene tri-block copolymer (SBS) and poly(?-caprolactone) (PCL) blend were introduced for its shape memory properties. Compared to the reported shape memory polymers (SMPs), this novel elastomer and switch polymer blend not only simplified the fabrication process but also offer a controllable approach for the study of mechanisms and the optimization of shape memory performances. Microstructures of this blend were characterized by differential scanning calorimetry (DSC), AFM microscope observation and tensile test. DSC results demonstrated the immiscibility between SBS and PCL. AFM images and stress-strain plot further confirmed the two-phase morphology within the blend. It was found that the SBS and PCL continuous phases contributed to the shape recovery and shape fixing performances, respectively. A detailed shape memory mechanism for this type of SMP system was then concluded and an optimized SMP system with both good recovery and fixing performances was designed from this mechanism.     

基于响应面法的高黏度复合改性沥青中丁苯橡胶/苯乙烯-丁二烯-苯乙烯嵌段共聚物/胶粉的最优掺量

采用响应面（Box-Behnken）法,以丁苯橡胶（SBR）、苯乙烯-丁二烯-苯乙烯嵌段共聚物（SBS）和胶粉各自的掺量作为影响因素,以沥青的三大技术指标、60℃动力黏度及170℃布氏黏度为评价指标建立各自的响应面模型,探讨三种添加剂掺量对沥青技术指标的影响规律,并优选出高黏度复合改性沥青中SBR、SBS和胶粉的最佳掺量。结果表明,分别以质量分数5%、5%和15%的SBS、SBR和胶粉复合而成的高黏度复合改性沥青性能最好,其针入度为4.63 mm,延度为364 mm,软化点为86.5℃,60℃动力黏度为78 158 Pa·s,170℃布氏黏度为2.72 Pa·s,各项指标均高于标准要求。     

SBSBS的合成及其性能研究

以齐聚二烯烃基二锂为引发剂，四氢呋喃为催化剂，在环己烷中采用三步加料法合成了对称五嵌段丁苯共聚物ＳＢＳＢＳ。实验结果表明，在相同Ｍｎ，Ｓ／Ｂ值时，ＳＢＳＢＳ具有与ＳＢＳ类似的海岛形态，呈典型的热塑性弹性体性质，其拉伸强度、３００％定伸应力、扯断伸长率与ＳＢＳ相当，永久变形优于ＳＢＳ，并存在ＴｇＰＳ和ＴｇＰＢ两个峰。