Fiber reinforced rubber modified polypropylene

Reinforcement can improve the modulus, heat distortion temperature and thermal expansion coefficient of rubber modified polypropylene. These improvements canbe obtained with a minimum sacrifice in resin ductility and impact toughness. Our studies have shown that reinforcement with small discontinuous fibers can provide a material with a good balance of stiffness and impact strength. The combination of small potassium titanate fiber reinforcement, polypropylene homopolymer and an impact modifier can produce a material with a tensile modulus of 470,000 psi, a notched Izod impact strength of 4.6 ft-lb/in. and a Gardner imact strength of 320 in-lb. Glass fiber reinforcement produces similar improvements in stiffness and retains Izod impact strength but drastically reduces Gardner impact strength. Polypropylene resin viscosity has a profound effect on composite impact strength. Transmission electron microscopy showed that a correlation exists between EPDM rubber particle size and impact strength: as rubber particle size is reduced, impact strength is increased. A 5 melt flow rate polypropylene was found to have the viscosity required to adequately shear and disperse the impact modifier. The paper describes an approach to broadening the utility of polypropylene homopolymers. The properties and flow of these materials compare very favorably with medium impact ABS.     

Toughening of nylon 6 with core-shell impact modifiers: Effect of matrix molecular weight

Rubber particle size is an important issue in toughening of engineering thermoplastics. Use of core-shell impact modifiers offers the advantage of a predetermined particle size; however, these particles must be appropriately dispersed in the matrix polymer to be effective for toughening. Recent work has shown that core-shell modifiers having a poly(methyl methacrylate) (PMMA) shell can be dispersed in nylon 6 with the aid of certain styrene/maleic anhydride (SMA) copolymers. These materials are miscible with PMMA and can also react with polyamides during melt processing. Enhanced interaction between the rubber and matrix phases as a result of the formation of in situ graft copolymers at the interface was suggested to contribute to the improved dispersion. However, rheological issues also influence the dispersion of core-shell modifier particles in the matrix. This article examines the influence of the matrix melt viscosity on the dispersion of the core-shell particles in the nylon 6 matrix and the resulting mechanical properties of the blends using four nylon 6 materials of different molecular weights. © 1996 John Wiley & Sons, Inc.     

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.     

管道防腐用环氧化SBS热熔胶的研制

利用有机过氧化物对SBS(苯乙烯-丁二烯-苯乙烯三嵌段共聚物)进行环氧化改性,得到ESBS(环氧化SBS);然后以此为基体树脂,辅以适宜种类及用量的增黏树脂、增塑剂和抗氧化剂等,制备出一种油气管道防腐用ESBS基热熔胶。结果表明:制备ESBS基热熔胶的最佳配方(以质量分数计)为47%ESBS、47%增黏树脂、1%抗氧剂和5%增塑剂;经环氧化改性后,ESBS基热熔胶对极性材料的粘接强度明显提高,其剥离强度和(钢/钢)剪切强度均满足使用要求。     

新型核-壳改性剂N-AIM对PMMA性能的影响

通过乳液聚合方法制备了不同橡胶粒径和橡胶相组成比的新型核-壳丙烯酸酯类抗冲改性剂（N-AIM）,将其与聚甲基丙烯酸甲酯（PMMA）进行熔融共混,得到了PMMA/N-AIM共混物。对PMMA/N-AIM共混物的形态结构、冲击性能和光学性能分别进行了考察。通过透射电镜（TEM）分析表明,橡胶粒径为100 nm时改性剂在基体中发生聚集,大于100 nm时均可均匀分散在基体中;冲击测试结果表明,随着N-AIM橡胶粒径的增加,共混物的冲击强度先增大后减小;光学测试表明橡胶组成比影响共混物的光学性能。     

Effects of particle size and rubber content on fracture toughness in rubber-modified epoxies

The effects of particle size of core-shell rubber on the fracture toughness of rubber-modified epoxies were investigated. Various sizes of core-shell rubber particles, from 0.16 to 1.2 μm in diameter, were synthesized by seeded emulsion polymerization. Particle size effects were clearly seen for lower crosslinked diglycidyl ether of bisphenol A (DGEBA)/piperidine resin. Fracture toughness increased as the particle size of core-shell rubber decreased from 1.2 to 0.4 μm. On the other hand, fracture toughness was constant in this range of particle sizes for higher crosslinked DGEBA/diaminodiphenylmethane (DDM) resin. Cavitation in the rubbery core and shear deformation in the matrix are the toughening mechanisms for DGEBA/piperidine resin, whereas cavitation is the only mechanism for DGEBA/DDM resin. Toughening effectiveness decreased with <0.2 μm core-shell rubber particles since they are difficult to cavitate. The effects of core-shell rubber content on fracture toughness of rubber-modified epoxies were also examined. The optimum rubber content for maximum toughness of rubber-modified epoxies decreased with decreased particle size of core-shell rubber in shear deformable DGEBA/piperidine resin. But the fracture toughness of rubber-modified DGEBA/DDM resins increased as the rubber content increased.     

Synergic Effect of Acrylate Liquid Rubber and Bisphenol A on Toughness of Epoxy Resins

The synergic effect of acrylate liquid rubber with pendant epoxy group and bisphenol A on the toughness of epoxy resins was presented in this paper. The addition of bisphenol A enhances the impact strength and elongation at break of epoxy resin and actually increases the ductibility of epoxy resin matrix. Much higher toughness efficiency can be achieved for the ALR modified epoxy resins by the incorporation of bisphenol A at the same time. The synergic promotion effect of acrylate liquid rubber and bisphenol A on the toughness efficiency of epoxy resins is attributed to the two-phase morphology and high ductibility of matrix, and the resultant large stress white zones and high shear yielding during the fracture process.     

ABS树脂冲击强度测试的影响因素

对比了4个牌号ABS树脂ASTM标准和国标悬臂梁冲击强度,剖析了ABS树脂橡胶相组成对测试结果的影响,并运用moldflow软件模拟冲击样件注塑成型过程,分析引起冲击强度测试结果差异的原因.结果表明,通过降低冲击测试样条注塑成型注塑速度减小样件表面剪切应力的方法,能够提高冲击强度测试结果,较高的橡胶含量可以减弱注塑速度...     

小粒橡胶粒子对SAN树脂的增韧作用

采用PB-g－SAN和SBR－g－SAN两种弹性体粒子分别与SAN树脂熔融共混,制得了一系列ABS树脂,研究了ABS树脂的形态结构和力学性能,结果发现,PB和SBR橡胶粒子均匀地分散在SAN基体中,其径分别为0.28μm和0.05μm左右。力学性能结果表明,在SAN树脂中随着PB-g－SAN含量的增加,ABS的冲击强度不断提高,而SBR小橡胶粒子不能增韧SAN树脂,但当SAN树脂中含有15％的PB-g－SAN共聚物时,随着SBR－g－SAN含量的增加,ABS树脂的冲击强度不断提高,SBR－g－SAN这种小橡胶粒子又表现出良好的增韧作用。     

Study on morphological,rheological, and mechanical properties of PP/SEBS‐MA/SGF hybrid composites

Hybrid composite samples composed of polypropylene as matrix, 20% short glass fibers (SGF) as reinforcement and varying amount of maleic anhydride (MA) grafted SEBS as compatibilizer and impact modifier were prepared by melt mixing in a modular twin screw extruder. The SEM examination performed on cryogenically fractured surfaces of hybrid samples showed a three‐phase type morphology in which SGF and rubber phase finely distributed in the PP matrix. SEM results also revealed that in the hybrid samples containing SEBS‐MA, the surface of the SGF are coated with a thin layer of SEBS‐MA, indicating a strong adhesion between SGF and matrix materials. The results of rheological studies showed nearly equal viscosity for compatible and incompatible hybrid samples. Tensile yield strength enhanced with increasing rubber content up to 10% above which it decreased and highest impact strength enhancement was obtained for sample containing 20% rubber. The impact strength of composites was found to be increased with increasing the SGF content. In final, it was shown that a good balance between stiffness and toughness could be achieved by adjusting the SGF and rubber content in this ternary system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2704–2710, 2007     

Improving the crack resistance of bulk molding compounds and sheet molding compounds

Fiber-reinforced plastics exhibit two types of mechanical failure: gross fracture and microcracking. Gross fracture involves both matrix and fiber failures. Principal resistance to crack propagation derives from partial decoupling of fibers and then stressing, remove finite volumes of them to fracture. Classical concepts of fracture mechanics can be applied to such composites, though modifications of methodology to treat anisotropy and other special effects are required. Microcracking occurs principally in the matrix phase and usually accompanies cyclic fatigue, drop impact, bending, or rapid cooling from molding temperatures. It lowers composite stiffness, environmental resistance and may reduce strength. Matrix resins require high fracture toughness to minimize or eliminate microcracking. This paper discusses cracking in bulk molding compounds and sheet molding compounds, complex materials containing high percentages of glass fibers and calcium carbonate filler. Microcracking can be greatly reduced by tire addition of small amounts of a rubber to the polyester matrix. Various tests such as impact, bending, acoustic emission and crack propagation demonstrate the improved toughness properties which result. No sacrifice of original strength characteristics occurs, and markedly improved resistance to damage has been noted with rubber modified epoxy and polyester matrix resins.     

Effects of reactive compatibilizer on the core-shell structured modifiers toughening of poly(trimethylene terephthalate)

Poly(trimethylene terephthalate)/polybutadiene grafted polymetyl methacrylate (PB-g-PMMA, MB) blends were prepared by melt processing with varying weight ratios (0-5 wt%) of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin as a reactive compatibilizer. DMA result showed PTT was partially miscible with MB particles in the presence of the compatibilizer. Fourier transform infrared (FTIR) and rheological measurements further identified the reactions between PTT and DGEBA epoxy resin. Scanning electron microscopy (SEM) displayed that the core-shell structured modifiers exhibit a smaller dispersed domain size with the addition of DGEBA epoxy resin. Mechanical tests showed the impact and tensile properties of PTT blends are improved by the introduction of DGEBA epoxy resin to the blends. SEM and TEM results showed shear yielding of PTT matrix and cavitation of rubber particles were the major toughening mechanisms.     

Modification of epoxy resins for improvement of adhesion: a critical review

Modification of epoxy resins for improvement of adhesion has been the subject of intense research throughout the world. Unlike for thermoplastics, physical blending is not successful for improvement of bond strength and impact strength of epoxy resins. The bond strength of an epoxy resin can be improved only by chemical modification with a suitable flexible modifier. Such chemical modification may either plasticize the epoxy matrix or lead to a two-phase microstructure. Both methods of chemical modifications are discussed critically in the present review.     

聚氯乙烯增韧改性剂的合成及共混改性研究

采用传统的乳液接枝聚合方法合成了以交联聚丙烯酸酯弹性体为核，聚氯乙烯（PVC）直接为壳层的新型聚氯乙烯复合改性剂，用于通用聚氯乙烯的增韧改性。通过粒径分析仪、透射电镜、动态力学分析等手段对复合粒子及其共混改性PVC材料进行了表征与测试。结果表明复合粒子具有核壳结构，粒径分布较窄；动态力学分析显示；改性剂的加入有效地改善了改性剂与PVC基体问的相容性；当改性剂加入量为6％（核壳质量比为50／50）时，改性PVC材料的缺口冲击强度为纯PVC的5倍。     

Synthesis of acid anhydride-modified flexible epoxy resins and enhancement of impact resistance in the epoxy composites

Epoxy resins are key materials used in various applications, including coatings, adhesives, and composites. Tougheners, such as nanoparticles, soft polymers, elastomeric polyurethanes, and core/shell particles, have been widely applied to compensate for the brittleness of the epoxy matrix and to enhance the impact resistance. Modifying epoxy resin by reacting it with a flexible component is one of the representative methods to overcome the weakness of cured epoxy polymers upon impact. For introducing flexible parts, we synthesized three types of epoxy-modified resins by reacting acid anhydride with glycidol, followed by reaction with bisphenol [F, S, or J] glycidyl ether to produce flexible modified epoxy resins. Mechanical tests, such as flexural strength and impact resistance tests, were performed by adding various amounts of the synthesized resin to the epoxy composites. The results of these tests suggest that the modified resins were effective in improving the toughness of the epoxy matrix.     

Toughening of AT-Resins with a Polyphenylquinoxaline

Acetylene terminated (AT) resins are addition-curable thermoset materials which do not generate volatiles during cure and therefore can be fabricated into void-free structures. They retain good thermal and mechanical properties even after exposure to high humidity environments. Their use as composite matrix resins and adhesives has shown promise. These resins, however, are brittle. Molecular structure modifications and blending with thermoplastic modifiers have been used to improve their toughness. In this work, improvement in toughness has been sought through the use of a polyphenylquinoxaline (PPQ) modifier. The blended systems showed improvements in toughness, thermooxidative stability, and lap shear strength over the original AT-resins.     

橡胶粒子尺寸对ABS树脂性能的影响

通过乳液聚合制备了橡胶粒子尺寸为64～420 nm的丙烯腈-丁二烯-苯乙烯(ABS)共聚物.然后将其与SAN-T树脂熔融共混制备橡胶质量分数为15%的ABS树脂.研究了橡胶粒子尺寸对ABS树脂力学性能影响和材料内部形态结构.结果表明:随着橡胶粒子尺寸的增加ABS树脂的冲击韧性提高.当橡胶粒子尺寸在320 nm时,拉伸强度达到最大,ABS树脂的综合性能达到最好.粒子尺寸在64～110 nm时,橡胶粒子在基体内部发生团聚,材料发生脆性断裂.当橡胶粒子尺寸在216～420 nm时,材料主要以韧性断裂为主,发生脆韧转变.具有双峰分布ABS-110nm/ABS-275 nm共混物大、小橡胶粒子间发生明显的协同作用.     

Synthesis and properties of nano carboxylic acrylonitrile butadiene rubber latex toughened phenolic resin

Nano carboxylic acrylonitrile butadiene rubber latex‐toughened‐phenolic resins (XNBRL‐PF) were prepared by in situ polymerization in this work. The influence of nano XNBRL on the microstructure and physical properties of modified PF resin was investigated. Impact test testified that the impact strength of XNBRL‐PF was remarkably improved compared to pure PF and as the content of XNBRL increased to 10 wt %, the impact strength of the XNBRL‐PF kept increasing. Scanning electron microscope analysis of the fracture surface of the XNBRL‐PF indicated that the XNBRL were uniformly dispersed in the PF matrix, with diameters ranging from 200 to 400 nm. The results of Fourier transform infrared spectroscopy proved that chemical reaction occurred between XNBRL and PF matrix, which can greatly improve the interface interaction between rubber particles and PF matrix. Thermogravimetric analysis test showed that the incorporation of XNBRL can improve the thermostability of PF at low temperatures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Toughening of epoxy resins by hydroxy‐terminated,silicon‐modified polyurethane oligomers

Epoxy resins are among the most versatile engineering structural materials. A wide variety of epoxy resins are commercially available, but most are brittle. Several approaches have been used to improve the toughness of epoxy resins, including the addition of fillers, rubber particles, thermoplastics, and their hybrids, as well as interpenetrating polymer networks (IPNs) of acrylic, polyurethane, and flexibilizers such as polyols. This last approach has not received much attention; none of them have been able to suitably increase resin toughness with out sacrificing tensile properties. Therefore, in an attempt to fill this gap, we experimented with newly synthesized hydroxy‐terminated silicon‐modified polyurethane (SiMPU) oligomers as toughening agents for epoxy resins. SiMPU oligomers were synthesized from dimethyl dichlorosilane, poly(ethylene glycol) (weight‐average molecular weight ～ 200), and toluene 2,4‐diisocyanate and characterized with IR, ¹H‐NMR and ¹³C‐NMR, and gel permeation chromatography. The synthesized SiMPU oligomers, with different concentrations, formed IPNs within the epoxy resins (diglycidyl ether of bisphenol A). The resultant IPN products were cured with diaminodiphenyl sulfone, diaminodiphenyl ether, and a Ciba–Geigy hardener under various curing conditions. Various mechanical properties, including the lap‐shear, peel, and impact strength, were evaluated. The results showed that 15 phr SiMPU led to better impact strength of epoxy resins than the others without the deterioration of the tensile properties. The impact strength increased continuously and reached a maximum value (five times greater than that of the virgin resin) at a critical modifier concentration (20 phr). The critical stress intensity factor reached 3.0 MPa m^1/2 (it was only 0.95 MPa m^1/2 for the virgin resin). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1497–1506, 2003     

Impact strength and morphology in poly(vinyl chloride) window profiles –relationship with gelation level

Abstract

The impact strength resistance of extruded PVC window profiles is a result of the combined effects of the interaction of their intrinsic material properties and processing/fabrication variables. Intrinsic variables include all the components of the formulation, such as the type and level of impact modifier and filler. As such, an appropriate level of toughness can be achieved by selecting the type and amount of rubber particles present in the matrix. However, the impact properties of poly(vinyl chloride) (PVC) profiles are also drastically affected by the thermal and shear history of the PVC matrix. The effect of processing on mechanical properties is explored by altering the temperature profile set on the extruder, and by varying the shear heating phenomena using different lubrication balances. The gelation level of any PVC formulation tends to increase with the level of work on the material, i.e. with increased melt temperature and shear history. The study reported in the present paper is intended to quantify the degree of fusion of the primary crystallites as a function of the melt temperature, and show the dependence of the toughness of the extruded profiles on the resulting free volume. Free volume in PVC extruded profiles depends on the degree of the gelation of the matrix and also on the cooling rate of the melt. As extrusion output increases, cooling of the melt is so fast that polymer chains have much less time to recover and reach a state of minimum entropy. Upon physical aging, the free volume tends to decrease. The reduction in free volume changes the non-equilibrium state of the glass phase, thus reducing the toughness of the material, and causing embrittlement under certain test conditions.

Finally, the effect of filler level and type of impact modifier (two intrin sic variables) on the impact strength of extruded profiles with various levels of free volume are presented.