Mechanical properties of polystyrene/ethylene-propylene copolymer blends

Some mechanical properties of blends of polystyrene (PS) and ethylene-propylene-rubber (EP) were derived from stress-strain and impact measurements. The strength and impact properties are improved by adding EP-g-PS graftcopolymer, prepared by reacting PS with EP, to the blends. It is assumed that the EP-g-PS graftcopolymer acts as an adhesive at the interface between the thermoplast and the rubber phases. The addition of the graftcopolymer reduces the dimensions of the dispersed rubber particles. High values of impact strength at reasonable values of tensile moduli could be reached by replacing EP for a smaller or larger part by EP-g-PS copolymer. These kinds of EP-modified PS blends had much higher impact values than those of comparable PS blends containing low density polyethylene (1 dPE) and 1dPE-g-PS graftcopolymer or this graftcopolymer only. It seems attractive to ascribe these results to the non-crystallinity of the PE-g-PS as compared with the crystallinity of 1dPE in 1dPE and in 1dPE-g-PS. However some caution seems recommendable as EP-modified PS fractures with microshear whereas, the PE-modified PS shows crazing.     

Influence of triblock copolymer interfacial modifiers on fracture behavior of polystyrene/ethylene-propylene rubber blends

In a previous study, two triblock copolymers of styrene/ethylene-butylene/styrene (SEBS), of different molecular weights, were used to compatibilize a blend of 80 vol% polystyrene (PS) and 20% ethylene-propylene rubber (EPR). The emulsification curve, which relates the average minor phase particle diameter to the concentration of interfacial agent added, was used to quantify the effect of the interfacial agents on the blend morphology. Links between morphology, interface, and properties were established by combining the emulsification curve with a fracture mechanics approach. The aim of this work is to foster the understanding of the effects of these two triblock copolymers on the fracture behavior of the blend over various loading rates and temperatures. The focus is on the brittle-ductile transition in fracture behavior, which is a critical condition for the application of these materials. It has been found that adding an interfacial agent lowers the temperature at brittle-ductile transition. However, this effect is much more pronounced for the copolymer with a lower molecular weight. The time-temperature dependence of fracture performance of the blend is also affected by the interface and morphology. When loading rate increases, the shift of the temperature at brittle-ductile transition is less significant for the blend with an interfacial agent having a lower molecular weight. The effect of loading rate and temperature on the brittle-ductile transition in fracture performance of the blends is controlled by an energy activation process. Adding the interfacial agents results in a plasticizing effect of the polystyrene matrix and a reduction in the energy barrier controlling the fracture process. With the addition of interfacial agent, the yield stress slightly increases at low concentration, attains a maximum value, and then decreases. The increase in yield stress confirms the coupling role of the copolymer and is in agreement with the observed emulsification curves. The reduction of yield stress and increase in ultimate strain with the copolymer concentration demonstrate the plasticizing effect of the interfacial agent. The result of stress relaxation tests also confirms the above effects of the interfacial agent.     

Crystallization and morphology of reactor-made blends of isotactic polypropylene and ethylene-propylene rubber

The crystallization and morphology of reactor-made blends of isotactic polypropylene (PP) with a large content of ethylene-propylene rubber (EPR) (i.e., > 50%) were investigated. In the blends, PP was found to form spherulites during the crystallization process, with the growth rate constant under isothermal conditions. For crystallization temperatures in the range of 118–152°C, the birefringence of the spherulites varied from negative to positive by decreasing crystallization temperature, while homopolypropylene (homo-PP), the same as used in the blends as a matrix, showed negative spherulites in the whole temperature range investigated (118–152°C). Both the spherulite growth rate and the overall crystallization rate were slower for the blends than for homo-PP. The density of the crystallization nuclei was lower in the blends than in the homo-PP. It was concluded that a large amount of EPR content in the reactor-made blends of PP retards and hinders the crystallization of the matrix. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1007–1014, 1997     

Compatibility and tensile behavior of polypropylene/ethylene-propylene rubber blends

This study clarifies and quantifies factors which increase the ductility of a low-molecular-weight propylene homopolymer having an intrinsic viscosity of 0.89 dl/g. The tensile behavior of homopolymer/ethylene-propylene rubber (EPR) blends was studied from the viewpoint of the associated molecular structure of EPR and its compatibility with the homopolymer. When EPR is “dissolved” in a homopolymer, the glass transition temperature (T_g) of the amorphous phase of a homopolymer was found to shift to a lower temperature, with homopolymer/EPR compatibility being subsequently evaluated using this shift, i.e., Δt_g. Results show two conditions are required to improve the ductility of the low-molecular weight propylene homopolymer: ΔT_g must be ≥ 3°C and ≥ 30 wt% EPR must be blended with the homopolymer.     

The dynamics of montmorillonite clay dispersion and morphology development in immiscible ethylene-propylene rubber/polypropylene blends

The evolution of morphology during the melt compounding of polypropylene (PP), maleated ethylene-propylene rubber (EPR-g-MAn) and onium-ion exchanged montmorillonite clay (NR₄⁺-MM) is described. Irrespective of the ratio of components, clay partitions into the EPR-g-MAn phase exclusively, with significant amounts of mineral exfoliation occurring in the very early stages of compounding. These changes in filler distribution and dispersion are accompanied by reductions in the size of the dispersed PP phase, as the rate of droplet coalescence falls in response to an elevated EPR-g-MAn matrix viscosity. However, when NR₄⁺-MM is localized in a dispersed EPR-g-MAn phase, coalescence increases as a result of hindered particle break-up.     

The effect of reactive compatibilization of carboxylated polystyrene on morphology and toughness of polyamide-1010/polystyrene blends

The morphology and notched impact behaviour of polyamide-1010/polystyrene (PA1010/PS) (90/10) blends compatibilized by carboxylated polystyrene (CPS) have been studied. It is found that the addition of CPS has a beneficial effect upon the morphology of the resulting blends which leads to a finer dispersion of the PA1010 spherulites and of the PS particles in the PA1010 matrix. However, with increasing CPS content, the shape of the PS domains appears less regular, which may be due to the cracking of the PS spherical domains. Infrared analysis was performed to confirm the formation of PS–PA1010 graft copolymer during the blending process. The notched impact toughness of the compatibilized blends shows a maximum which is almost triple that of the binary blend at approximately 5 wt% of the CPS addition based on the amount of PS. © 1999 Society of Chemical Industry     

Morphology and properties of blends of polypropylene with ethylene-propylene rubber

Great attention has been paid to the toughening of isotactic polypropylene (PP) in recent years in order to make full use of this plastic. This paper presents the results of our study on the compatibility of PP with ethylene-propylene-diene rubber (EPT), polybutadiene rubber (PB) or styrene-butadiene rubber (SBR) through characterization of the blends' morphology, and on. the morphology and properties of binary blends of PP with EPT (EPT/PP) and ternary blends of PP, EPT, and polyethylene (PE) (EPT/PE/PP). Morphological structure of solution blends and the great improvement in low-temperature impact strength and other properties of the mechanical blends have shown the difference among EPT, PB, and SBR in compatibility with PP, the effectiveness of using EPT as PP's toughening agent, and the effect of EPT on EPT/PP blend as both toughening agent and compatibilizer. Addition of EPT to EPT/PP made interesting changes in morphology but no effect on properties was observed.     

Thermal study on binary blends of ethylene-propylene elastomers and acrylonitrile-butadiene rubber

Summary The thermal behavior of several formulations consisting of ethylene-propylene elastomers and acrylonitrile-butadiene rubber was investigated by differential scanning calorimetry. The sample compositions cover the whole concentration range of ((EPDM, EPR)/NBR = 100/0, 20/80, 40/60, 60/40, 80/20 and 0/100). The evaluation of molar enthalpies for studied polymer blends allowed to calculate molar capacities at various temperatures from 335 K up to 450 K. Due to the lack of additivity in the molar capacities of studied blends, the contributions of each component to the overall values of C_p are calculated. The dependency of component contributions on their concentrations follows a first order function, which explains the existence of a certain interaction between components.     

Determination of ethylene-propylene rubber in crosslinked blends with 1,4-polybutadiene

Crosslinked blends of ethylene-propylene rubber (EPR) and 1,4-polybutadiene (BR) were investigated by metathesis degradation of the BR component; the percentage of EPR was determined by weighing the polymeric residue. The metathesis reaction was carried out with an excess of 1-octene in the presence of the catalyst WCl₆/(CH₃)₄Sn. In crosslinking with dicumyl peroxide, the best results were obtained with 10 to 30 wt.-% of EPR and medium crosslinking degrees. Analysis of sulphur vulcanizates (received with the accelerator N-cyclohexyl-2-benzothiazyl sulphenamide) gave tolerable results only for low sulphur contents (1.5 wt.-%). Determination of EPR was also possible in non-crosslinked blends with BR.     

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     

Effects of reactive melt mixing on the morphology and thermal behavior of linear low-density polyethylene/rubber blends

Linear low-density polyethylene (LLDPE)/polybutadiene (PB) and LLDPE/poly(styrene-b-butadiene-b-styrene) (SBS) binary blends were prepared by simple melt mixing or by reactive blending in the presence of a free-radical initiator, and for comparison, pure LLDPE was treated under the same conditions with a comparable free-radical initiator concentration. The effect of the reactive melt mixing on the morphology of the blends was studied with transmission electron microscopy, and the corresponding particle size distributions were analyzed and compared to highlight the effects of the crosslinking and grafting phenomena. Thermal properties of the obtained materials were investigated with differential scanning calorimetry and dynamic mechanical thermal analysis (DMTA). In particular, the effect of the reactive mixing parameters on the amorphous phase mobility was investigated. The influence of the chemical modification on the crystallization behavior of LLDPE, neat and blended with PB and SBS, was also studied with dynamic and isothermal differential scanning calorimetry tests, and the isothermal thermograms were analyzed in light of the Avrami equation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

动态硫化通用聚苯乙烯/粉末丁苯橡胶共混物的性能

采用双螺杆动态硫化工艺,用粉末丁苯橡胶(PSBR)改性通用聚苯乙烯(GPS)制备GPS/PSBR共混物,考察了二者的质量比、软化剂用量、增强剂种类和加工工艺对共混物性能的影响,并对共混物的性能与高抗冲型聚苯乙烯(HIPS)进行了对比.结果表明,当GPS与PSBR的质量比为80∶20时,使用软化剂可提高共混物的加工流动性;纳米高岭土对共混物有较明显的增强作用;用动态硫化工艺制得共混物的性能与HIPS相当,其耐老化性能优于非动态硫化工艺制得的共混物.     

Compatibility of waste rubber powder/polystyrene blends by the addition of styrene grafted styrene butadiene rubber copolymer: effect on morphology and properties

Waste rubber powder/polystyrene (WRP/PS) blends with different weight ratio were prepared with styrene grafted styrene butadiene rubber copolymer (PS-g-SBR) as a compatibilizer. The graft copolymer of PS-g-SBR was synthesized by emulsion polymerization method and confirmed through Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC). The copolymer at different weight ratio was subsequently added into the blends. The effects of weight ratio of WRP/PS and compatibilizer loading on mechanical properties were investigated. PS/WRP blends in a weight ratio of 80/20 showed higher impact strength. Moreover, the impact strength of the blend materials increased with the addition of SBR-g-PS, however, decreased at a high loading of the copolymer. The morphology and thermal properties of WRP/PS blends were examined by DSC, scanning electron microscopy (SEM), thermogravimetry (TG). DSC indicated that compared with PS/WRP blend, the glass transition temperature (T _g) of PS matrix phase in PS/WRP/SBR-g-PS blend shifted to low temperature because of the formation of chemical crosslinks or boundary layer between PS and WRP, and the T _g of WRP phase of both the PS/WRP and PS/WRP/SBR-g-PS blends did not appear. SEM results showed that interfacial adhesion in the blends with the PS-g-SBR copolymer was improved. The morphology was a typical continuous–discontinuous structure. PS and WRP presented continuous phase and discontinuous phase, respectively, indicating the moderate interface adhesion between WRP and PS matrix. TG illustrated that the onset of degradation temperature in the PS/WRP/PS-g-SBR blend decreased slightly by contrast with PS/WRP blend and the degradation of PS/WRP blends with and without SBR-g-PS was completed about at the same values.     

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     

In situ reactive compatibilization of aramid/polystyrene blends using amine‐functionalized polystyrene

High molecular weight aramid chains (Ar) were synthesized from aromatic diamine and diacid chloride. Amine functionality was introduced to polystyrene (PS) in two steps i.e., nitration followed by reduction producing amino functional polystyrene (APS) which serves as a reactive compatibilizer, being reactive with the Ar end‐groups. APS was characterized by FTIR, NMR spectral data, and exploited in the preparation of Ar/APS blends, and the effect of reactive compatibilization on blend morphology and interfacial adhesion was explored. Two blend systems Ar/PS and Ar/APS were investigated over a range of PS or APS ratios. To assess the effect of amine units incorporated in PS, on the compatibility with Ar; morphology, thermal, and mechanical properties were probed. Incorporation of reactivity into the system has resulted in significant refinement of the blend morphology and augmentation of thermal stability. The in situ generation of APS‐g‐Ar copolymers during solution mixing of APS and Ar was evaluated using spectroscopic analysis. In addition to stabilizing the microstructure, in situ compatibilization was found to alter the mechanical properties of the Ar/APS interface. Ar/APS blend containing 10 wt% APS was found to demonstrate optimum mechanical reinforcement as complemented by the optimal thermal and morphological profiles of 10 wt% Ar/APS blend. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Investigation on particular morphology of immiscible polyamide 12/polystyrene blends

In this article, a particular phase morphology of immiscible polyamide 12/polystyrene (PA12/PS) blends prepared via in situ anionic ring-opening polymerization of Laurolactam (LL) in the presence of PS was investigated. SEM and FTIR were used to analyze the morphology of the blends. The results showed that PS is dispersed as small droplets in the continuous matrix of PA12 when PS content is less than 5 wt %. When the PS content is higher than 10 wt %, two particular phase morphologies appeared. First, dispersed PS-rich particles with the spherical inclusions of PA12 can be found when PS content is between 10 wt % and 15 wt %. Then, the phase inversion (the phase morphology of the PA12/PS blends changes from the PS dispersed/PA12 matrix to PA12 dispersed/PS matrix system) occurred when PS content is higher than 20 wt %, which is completely different from traditional polymer blends prepared by melt blending. The possible reason for the particular morphology development was illuminated through phase inversion mechanism. Furthermore, the stability of the phase morphologies of the PA12/PS blends was also investigated. SEM showed that the particular morphology is instability, and it will be changed upon annealing at 230°C for 30 min. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dielectric and mechanical properties of polystyrene/acrylonitrile–butadiene rubber blends

The dielectric and mechanical properties of polystyrene(PS)/acrylonitrile–butadiene rubber (NBR) blends were studied with the aim of improving the insulation properties of NBR. Compatibility investigations, performed with viscosity and dielectric methods and confirmed with the calculated heat of mixing, indicated that such blends were incompatible. To overcome the problem of phase separation between NBR and PS, we chose epoxidized soya bean oil to act as a compatibilizer and added 3% to the blends under investigation. This led to the conclusion that a sample containing 10% PS (either pure or scrap) possessed the most suitable electrical and mechanical properties. For this reason, the sample was chosen for studying the effect of the addition of three types of fillers (quartz, talc, and calcium carbonate) in increasing quantities (up to 80 phr) on the dielectric and mechanical properties. The variation of the dielectric properties with temperature (20–60°C) was also investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 540–552, 2002     

丁腈橡胶/乙丙橡胶并用胶性能的研究

研究丁腈橡胶(NBR)/三元乙丙橡胶(EPDM)并用比对力学性能、老化性能和耐油性能的影响以及增容剂对共混胶性能的影响.结果表明,在NBR/EPDM共混胶中随EPDM用量的增加,硫化胶的硬度、拉伸强度、撕裂强度和定伸应力呈现下降趋势、拉断伸长率及耐低温性能有所改善,降低了NBR的耐汽油性能,但提高了耐含乙醇汽油性能.随着增容剂CM用量的增加,硫化胶拉伸强度、撕裂强度、100％定伸应力及硬度都呈增大趋势,采用扫描电镜可以清晰的看到添加CM改性后NBR/EPDM共混胶相容性得到显著改善.     

Compatibilisation of heterogeneous acrylonitrile-butadiene rubber/polystyrene blends by the addition of styrene-acrylonitrile copolymer: effect on morphology and mechanical properties

Compatibility of polystyrene (PS) and acrylonitrile-butadiene rubber (NBR) blend is poor, hence technological compatibilisation was sought by the addition of styrene-acrylonitrile copolymer (SAN). The interfacial activity of SAN was studied as a function of compatibiliser concentration by following the morphology of three different blend series, viz. PS/NBR 30/70, 50/50 and 70/30. Incorporation of SAN into PS/NBR blends improved tensile, tear, hardness and impact properties. Addition of SAN beyond the saturation level (critical micelle concentration) adversely affected the ultimate properties. Attempts were made to understand the conformation of the compatibiliser at the interface. The protocol of mixing was varied, and, its effect on the mechanical properties was investigated. The experimental results were compared with the theoretical predictions of Noolandi and Hong.     

Ultrasonic properties and morphology of devulcanized rubber blends

The ultrasonic properties of two devulcanized rubber (DR) blends with a styrene‐butadiene‐styrene (SBS) copolymer compound (ACE) are investigated using a transmission method. The DR materials are obtained from commercial rubber crumbs (RC) by a proprietary devulcanization technique. Measurements on the acoustic attenuation and travel velocity are conducted on the samples with different sample thicknesses in the pulsed mode. Attenuation coefficients of the materials are obtained by changing the frequency of the ultrasound in the tuned tone‐burst mode. The two DR/ACE blends show marked differences in the attenuation and attenuation coefficient, although the ultrasonic velocities are similar. These differences arise from the variation of the remaining degree of crosslinking in the DR materials. The acoustic velocities in the three materials are similar. The morphologies of the DR/ACE blend samples, observed using scanning electron microscopy (SEM) with different staining agents, explain their similarities and differences. There are two crops of rubber particles: larger ones belong to the original rubber crumbs that survived devulcanization; the smaller ones are fragments of partially DR. These crosslinked particles contribute to the overall degree of crosslinking in the blends. The devulcanized fractions of the DR materials are dispersed in the ACE matrix. Scattering at the interface accounts for the differences in the acoustic attenuation of the samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012