Influence of the rubber crosslinking density of a core–shell structure modifier on the properties of toughened poly(methyl methacrylate)

Four kinds of core–shell structure acrylic impact modifiers (AIMs) with different rubber crosslinking densities were synthesized. The effects of the rubber crosslinking density of the AIMs on the crack initiation and propagation resistance and the mechanical properties of the AIM/poly(methyl methacrylate) (PMMA) blends were investigated, and we found that the maximum stress intensity factor, crack propagation energy, and Izod impact strength reached maximums when the appropriate rubber crosslinking density of AIM, 2.51 × 10²⁵ crosslinks/m³, was adopted. Transmission electron microscopy photographs of the AIM/PMMA blends showed that the AIMs dispersed uniformly in the PMMA matrix. Meanwhile, through the analysis of optical photos and scanning electron microscopy of the impact fracture surface, we found that the deformation mechanism of the AIM/PMMA blends was local matrix shear yielding initiated by rubber particle cavitation of the AIM. The rubber of the AIM, whose crosslinking density was 2.51 × 10²⁵ crosslinks/m³, was beneficial to the formation of intensive voids and initiated the local shear yielding of nearby modifiers of the PMMA matrix effectively in impact tests, which led to higher Izod impact strengths. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparison of some butadiene-based impact modifiers for polycarbonate

The relationship of blend morphology to deformation mechanisms and notched Izod impact strength was studied with three butadiene-based impact modifiers for polycarbonate (PC). The impact modifiers were a linear polybutadiene (PB), a styrene–butadiene–styrene block copolymer (SBS), and a structured latex particle having a PB core and methyl methacrylate/styrene shell (MBS). The particle-size distribution in the blends was determined from transmission electron micrographs (TEM). Fractographic analysis combined with TEM examination of thin sections from impacted specimens provided insight into the failure mechanisms. Good impact was achieved with PC/MBS blends when cavitation of the core–shell particles relieved triaxiality and enabled the matrix to fracture by the plane stress ductile tearing mode that is characteristic of thin PC. The best impact properties were obtained with PC/SBS blends when the modifier was dispersed as aggregates of small particles. Cavitation at the weak internal boundaries relieved triaxiality, but subsequent coalescence of cavitated particles during ductile drawing of the matrix created critical size voids and the resulting secondary cracks reduced the toughness of the blend. In general, PB did not significantly enhance the impact strength of PC. © 1994 John Wiley & Sons, Inc.     

Toughening of polyvinylchloride by methyl methacrylate–butadiene–styrene core–shell rubber particles: Influence of rubber particle size

An analysis was made on the effects of rubber particle size on the mechanical properties and deformation mechanisms of transparent polyvinyl chloride (PVC) blends containing core–shell methyl methacrylate–butadiene–styrene (MBS) impact modifiers. The critical interparticle distance was found not to be the criterion for the brittle‐ductile transition in the blends. In tensile tests, the blends with larger (100–280 nm) rubber particles exhibited intense stress‐whitening, while one blend with small (83 nm) rubber particles showed only slight stress‐whitening. These differences were due to an increase in resistance to cavitation with decreasing rubber particle size. Transmission electron microscopy studies on blends with a bimodal distribution of particle sizes showed that in the whitened zone of Izod specimens the larger rubber particles cavitated and expanded on yielding, while the smaller particles remained intact. However, Izod test results showed that small MBS rubber particles can toughen the PVC matrix very effectively, especially at low temperatures and at low rubber concentrations. The deformation mechanisms responsible for these effects were discussed. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Mechanical properties and deformation behaviors of acrylonitrile‐butadiene‐styrene under Izod impact test and uniaxial tension at various strain rates

Two polybutadiene‐graft‐acrylonitrile‐styrene copolymer (PBD‐g‐SAN) impact modifiers with different rubber particle size were synthesized by seeded emulsion polymerization. Acrylonitrile‐butadiene‐styrene (ABS) blends with a constant rubber concentration of 15 wt% were prepared by blending those impact modifiers and SAN resin. The major focus was the mechanical properties and deformation mechanisms of ABS blends under Izod impact test and uniaxial tension at various strain rates from 2.564 × 10^?4 S^?1 upto 1.282 × 10^?1 S^?1. By the combination of transmission electron microscope and scanning electron microscope, it was concluded that crazes and cavitation coexisted in ABS blends. The deformation mechanisms of ABS blend containing large rubber particles was rubber particles cavitation and shear yielding in the matrix including crazes, and they do not change with the strain rate. Different from ABS blend with large rubber particles, deformation mechanism of ABS with small rubber particles under tensile condition was only involved in shear yielding in the matrix and no crazes were formed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Co-continuous polycarbonate/ABS blends

Co-continuous PC/ABS (50/50) blends were studied with a variable polybutadiene (PB) content (0-40%) in ABS. Polycarbonate (PC), styrene-acrylonitrile (SAN) and PB were blended in two steps using a twin screw extruder. Rectangular bars were injection moulded and notched Izod impact tested at different temperatures and in single edge notch tensile tests at 1 m/s and different temperatures. Co-continuous PC/ABS gave a brittle-to-ductile transition temperature lower than expected based on notched Izod results for dispersed ABS in PC. The brittle-to-ductile transition temperature, in the co-continuous PC/ABS blends, decreased with increasing rubber content in SAN. The fracture energies showed an optimum at 15% PB in SAN while at the same time a delamination was seen on the ductile fracture surface, due to failure of the PC/SAN interface. Delamination disappeared when the rubber content in SAN or the temperature was increased. Specimens containing a welding were injection moulded to study the influence of rubber and AN content in the SAN on the interface. Weldline strength of the blends was very poor compared to PC, but improved with increasing rubber content in SAN.     

Fabrication of Super Tough Polycarbonate/Styrene-Etylene-Butylene-Styrene Grafted Maleic Anhydride (SEBS-g-MA) Blends: Morphological,Short Term Static Mechanical and Fracture Performance Interpretation

Impact behaviours, tensile properties and fracture performance of polycarbonate (PC)/styrene ethylene-butylene-styrene-grafted-maleic anhydride (SEBS-g-MA) copolymer blends at SEBS-g-MA volume fraction Φ_d = 0–0.39 are evaluated. In presence of rubber a significant augmentation in notched Izod impact strength was observed while tensile modulus and strength decreased. Morphological studies reveal good interaction between the PC and the rubber particles showing homogeneous dispersion of SEBS-g-MA in the polycarbonate matrix. Interparticle distance of the dispersed phase evaluated from the morphology studies by scanning electron microscopy (SEM) and the impact strength dependence on the concentration of the blending rubber were analysed. The essential work of fracture approach is applied to study fracture properties of the blends. With increasing SEBS-g-MA concentration nonessential or plastic work increased which explained the enhancement of impact strength of blends.     

Influence of ABS type on morphology and mechanical properties of PC/ABS blends

The morphology and the mechanical properties of polycarbonate (PC) blends with different acrylonitrile–butadiene–styrene (ABS) materials were investigated. PC/ABS blends based on a mass-made ABS with 16% rubber and large (0.5–1μm) rubber particles are compared to blends based on an emulsion-made ABS with 50% rubber and small, monodisperse (0.12 μm) rubber particles over the full range of blend compositions. The blends with the bulk ABS showed excellent impact strength for most compositions, and those containing 50 and 70% PC exhibited ductile to brittle transition temperatures below that of PC. The blends with the emulsion ABS showed excellent toughness in sharp notch Izod impact tests at room temperature and in standard notch Izod impact tests at low temperatures near the T_g of the rubber. By melt blending the various ABS materials with a styrene–acrylonitrile (SAN 25) copolymer, materials with lower rubber concentrations were obtained. These materials were used in blends with PC to make comparisons at constant rubber concentration of 5, 10, and 15%. The results of this investigation show that brittle ABS materials can produce tough PC–ABS blends. It is apparent that small rubber particles toughen PC–ABS blends at lower rubber concentrations and at lower temperatures than is possible with large rubber particles. However, additional work is needed to understand the nature of toughening in these PC–ABS blends with different rubber phase morphologies. It is of particular interest to understand the exceptional ductility of some of the blends at low temperatures. © 1994 John Wiley & Sons, Inc.     

ACR增韧PBT/PC合金的研究

研究了“核-壳”结构的ACR对PBT/PC(质量比80/20)合金的力学性能和耐热性的影响。结果表明:随着ACR用量增加,共混物的缺口冲击强度不断增大,而拉伸强度、弯曲强度、维卡耐热度降低。当ACR的加入量为5份时,缺口冲击强度提高1倍,当ACR的加入量为30份时,缺口冲击强度约为纯PBT/PC合金的5倍。从增韧效果来看,FM50略好于KM355。     

Super HIPS: improved high impact polystyrene with two sources of rubber particles

Significant improvements in impact strength were achieved in polystyrene blends that combined conventional HIPS particles in combination with particles produced by compositional quenching. A commercial HIPS was solvated and blended with additional polystyrene, rubber and diblock copolymer, and the mixture was flash devolatilized to give the end-product. Impact strengths of injection and compression molded samples and tensile properties are reported. It is known that the best impact modified polystyrene obtained by compositional quenching, here called aHIPS, has smaller and lower modulus rubber particles than conventional HIPS, and has more than twice the impact strength of conventional HIPS. The novel blends of HIPS and aHIPS reported here exhibit synergism, the impact strength of the blend being higher than expected as a linear average of the component properties. The rubber phase volume including occlusion was held at 23%. An interior optimum in rubber efficiency (i.e. Izod impact per unit weight of rubber) was observed when 75% of the phase volume was derived from HIPS while an interior minimum was observed when 25% of the phase volume was derived from HIPS. The elongation at break and tensile impact strength exhibited a form of negative synergism, indicating that conventional HIPS is superior in low speed tests and aHIPS is better in high speed tests such as Izod.     

光盘级聚碳酸酯(PC)的回收利用技术

实验采用PE-g-MAH、MBS增韧PC,结果表明,PE-g-MAH/PC共混物冲击强度为纯PC的5倍,但仍为脆性断裂。MBS质量含量达10%时,PC合金开始表现为韧性断裂;MBS质量含量达15%时,MBS/PC共混物冲击韧性可为PC的30倍,达到399 J/m。对共混物损伤机制的研究表明,MBS增韧PC共混物的增韧机理为橡胶粒子的空洞化引发基体的剪切屈服。增韧体系符合Wu提出的临界粒间距模型。采用酯交换-缩聚法对PC进行扩链,研究表明,在300℃、1.5mmHg真空度下充分反应后,PC的分子量由29324提高到53035,且分子量分布略变窄。经超临界处理,PC的水解产物为双酚A。     

马来酸酐接枝三元乙丙橡胶共聚物增容AES/PC共混物的研究

研究了马来酸酐接枝三元乙丙橡胶共聚物（EPDM-g-MAH）作为增容剂对丙烯腈三元乙丙橡胶苯乙烯共聚物/聚碳酸酯（AES/PC）（70/30）共混物结构和性能的影响。结果表明,EPDM-g-MAH作为反应型增容剂,能有效地减小低橡胶含量的AES/PC共混物中PC分散相的粒径,提高共混物的力学性能;当EPDM-g-MAH用量为3份时,橡胶含量为21 %的AES/PC共混物的缺口冲击强度提高近1倍,同时能保持较高的拉伸强度和热变形温度。     

Physical aging and thermal aging resistance of polycarbonate/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) blends

The effect of thermal annealing on the mechanical properties of polycarbonate (PC) was investigated by tensile testing, Izod impact testing, and differential scanning calorimetry (DSC). An endothermic peak appeared in the DSC curve by annealing at various temperatures below T_g. The peak area, as a measure of the degree of physical aging, increased with annealing time. The Izod impact strength decreased suddenly just before an endothermic peak became detectable. The results imply that at the very early stage of physical aging, a trigger for the ductile‐to‐brittle transition may be initiated. By blending hydrogenated styrene‐butadiene‐styrene block copolymer (SEBS), the embrittlement by annealing was prevented. That is, in the PC/SEBS blends, the physical aging of PC matrix proceeded in the same way as in neat PC; however, the Izod impact strength did not decrease. This thermal aging resistance seems to originate from the negative pressure effect of SEBS particles that provides dilational stress fields for PC matrix to enhance the local segment motions. POLYM. ENG. SCI., 52:1958–1963, 2012. © 2012 Society of Plastics Engineers     

Rubber-Toughened polymer blends of polycarbonate (PC) and poly (ethylene terephthalate (PET)

The intrinsically impact brittle nature of the PC/PET blends can be effectively toughened by incorporating butylacrylate core-shell rubber. The rubber-modified PC/PET blend possess both excellent low temperature impact properties and reduced notch sensitivity. The ductile-brittle transition temperature of the blend decreases with the increase of rubber content. The presence of rubber in the PC/PET blend does not relieve the strain rate induced yield stress increase. Two separate modes, localized shear yielding and mass hear yielding, work simultaneously in the rubber toughening mechanism. The plane-strain localized shear yielding dominates the toughening mechanism at lower temperature and results in brittle failure. At higher temperature, the planestress mass shear yielding dominates the toughening mechanism and results in ductile failure. The critical plastic zone volume can be used to interpret the observed phenomenon.     

ABS树脂中胶含量对PC/ABS合金性能及微观结构的影响

采用胶含量(质量分数,下同)为60％的丙烯腈-丁二烯-苯乙烯接枝共聚物(ABS)接枝粉料与苯乙烯-丙烯腈共聚物(SAN)以不同比例进行共混,制备了胶含量范围为10％～55％的ABS树脂.将胶含量不同的ABS树脂与聚碳酸酯(PC)以30/70、50/50、70/30的质量比利用熔融共混技术,制备了组成不同的PC/ABS共混物,考察了ABS树脂胶含量对不同组成的PC/ABS合金性能的影响.研究结果表明:随着ABS树脂中胶含量的增加,ABS树脂的冲击强度不断提高,屈服强度、模量及熔体流动速率逐渐降低.随着PC/ABS合金中ABS胶含量的增加,合金的冲击强度显著提高,ABS树脂中胶含量大于30％以后,合金的冲击强度变化不大,且3种组成的PC/ABS合金的冲击强度相差不大.合金的屈服强度、模量及熔体流动速率却随着ABS中胶含量的增加不断降低,其中组成为30/70的PC/ABS合金最低.利用扫描电镜观察了PC/ABS组成为70/30合金的微观结构,研究表明,ABS树脂形成连续相,PC为分散相,随ABS树脂胶含量的增加,合金的相形态变得更精细.     

Mechanical and thermal properties of high‐density polyethylene toughened with glass beads

Glass beads were used to improve the mechanical and thermal properties of high‐density polyethylene (HDPE). HDPE/glass‐bead blends were prepared in a Brabender‐like apparatus, and this was followed by press molding. Static tensile measurements showed that the modulus of the HDPE/glass‐bead blends increased considerably with increasing glass‐bead content, whereas the yield stress remained roughly unchanged at first and then decreased slowly with increasing glass‐bead content. Izod impact tests at room temperature revealed that the impact strength changed very slowly with increasing glass‐bead content up to a critical value; thereafter, it increased sharply with increasing glass‐bead content. That is, the Izod impact strength of the blends underwent a sharp transition with increasing glass‐bead content. It was calculated that the critical interparticle distance for the HDPE/glass‐bead blends at room temperature (25°C) was 2.5 μm. Scanning electron microscopy observations indicated that the high impact strength of the HDPE/glass‐bead blends resulted from the deformation of the HDPE matrix. Dynamic mechanical analyses and thermogravimetric measurements implied that the heat resistance and heat stability of the blends tended to increase considerably with increasing glass‐bead content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2102–2107, 2003     

Studies on Polycarbonate and Polydimethylsiloxane Rubber Blends

Polycarbonate (PC) and polydimethylsiloxane (PDMS) rubber blend were made by melt blending using a twin-screw extruder. The blends were characterized by mechanical testing, thermal studies, electrical properties and morphological studies. The notched lzod impact strength increased greatly when the rubber content was 20%. The morphology of PC/PDMS blends showed dispersed rubber particle in the PC matrix. The impact strength, which increased with PDMS rubber concentration, has been analyzed on the basis of the interphase adhesion and crazing mechanisms. Tensile and flexural modulus as well as strength decreased with increase in PDMS rubber content. Predictive models have been used to explain the tensile modulus and strength properties. Incorporation of PDMS decreases the glass transition temperature of PC and facilitates its processing. Scanning electron microscopy has been employed to study the phase structure.     

Thermal aging of impact-modified polycarbonate

Glassy polymers undergo relatively rapid physical aging just below their glass transition temperatures that can lead to embrittlement of normally tough materials like polycarbonate (PC). One approach for solving the embrittlement problem is to incorporate an impact modifier that can cause toughening when the matrix loses its inherent ductility due to physical aging. The effects of thermal aging below the glass transition temperature of polycarbonate on selected properties of blends of PC with various core-shell impact modifiers have been studied. Observed changes in mechanical properties are related to rubber content, free volume, fracture morphology, discoloration, enthalpy relaxation, glass transition temperature, intrinsic viscosity, and dynamic mechanical behavior. Blend mechanical properties are affected by chemical changes in the impact modifier that occur simultaneous with the physical aging of the PC matrix. The degradation mechanisms involved reduce the effectiveness of the modifier for toughening and also lead to a loss of molecular weight of the PC matrix. Blends containing 10% methacrylated butadiene-styrene (MBS) core-shell impact modifiers give the maximum extension of time to embrittlement at 135°C in air. More thermally stable modifiers are required for further extending the ductile mode of failure for physically aged PC blends.     

Interaction of polymerization conditions,structural variables,and mechanical properties of rubber-modified plastics produced from bulk polymerized styrene/poly(butadiene-co-styrene)

Rubber-modified polystyrenes were prepared by bulk polymerization with seven different butadiene–styrene copolymers of differing chemical microstructures. The products were structurally characterized through measurement of the swell ratio, percent insolubles, intrinsic viscosity of the soluble fraction, and transmission electron microscope photomicrographs. Increasing initiator concentration or raising polymerization temperature gives lower molecular weight, higher rubber crosslink density, and decreased grafting. Increasing rubber content generally leads to aggregation. Tensile stress–strain curves and Izod impact strengths were measured. High Izod impact strength and increased elongation to break are favored by increasing matrix molecular weight, rubber content, and extent of grafting.     

Mechanical properties of epoxy resin modified with polycarbonate and reactive polybutadiene

Epoxy resin Epidian 5 cured with triethylene tetramine was modified with hydroxyl‐terminated polybutadiene (PB) and polycarbonate (PC). Compositions with different amount of modifiers were obtained and tested for their impact strength, flexural strength, as well as resistance to crack propagation. The latter was assessed by evaluating the critical stress intensity factor under three‐point bending mode using single‐edge notched specimens. Scanning electron microscopy was used to analyze the fractured sample surfaces. The obtained results revealed that the mechanical properties of epoxy resin were improved due to the formation of heterogeneous phase with rubber particles, which arrest the propagation of cracks. Moreover, synergism effect was observed with the hybrid composition containing 10% PC and 2.5% of reactive PB. The impact strength was higher by ～ 15% than the sum of impact strength of compositions containing only one modifier. Another hybrid composition with 2.5% PB and 2.5% PC also exhibited synergism effect with the flexural strain at break, the energy at break under flexure, as well as the brittle fracture energy estimated from the critical stress intensity factor measurements. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

三元乙丙橡胶增韧PET/PC共混物的研究

采用三元乙丙橡胶（EPDM）及甲基丙烯酸环氧丙酯接枝三元乙丙橡（EPDM-g-GMA）作为PET/PC共混物的改性剂,并对共混体系的力学性能、相容性和断裂机理进行研究。力学性能测试结果表明EPDM-g-GMA质量分数为15%～20%时,共混体系实现了脆韧转变,当加到25%时冲击强度最高可达860 J/m,实现超韧;当PET/PC组成比为48/32时,PET/PC相容性最好,共混体系力学性能最佳。EPDM-g-GMA中环氧官能团与PET的端羧基、羟基发生反应使共混体系相容性提高。SEM结果显示共混物的增韧机理是基体的剪切屈服。