聚合物材料脆韧转变判据及影响因素分析

综述了聚合物共混增韧机理包括弹性体增韧、刚性粒子增韧、弹性体与刚性粒子协同增韧等研究进展；着重介绍了临界基体层厚度、损伤竞争准数、分子链参数、临界界面黏结条件、临界特征长度等几种源于单一粒子填充的脆韧转变判据，并分析其在复合粒子填充改性聚合物中的适用性。此外，还结合增韧机理和脆韧转变判据讨论了基体性能、分散相状态及相间界面黏结强度等因素对复合体系韧性的影响，提出寻找合适的复合分散相、适当调整复合粒子的结构比例、改善相间界面黏结以及设计最佳断裂路径仍将是今后努力的方向。     

硬质无机粒子填充聚丙烯基复合材料的增韧机理及其定量判据

综述了硬质无机粒子(RIP)填充聚丙烯(PP)复合材料的増韧机理及其定量判据。大量的研究表明,最典型的增韧机理有逾渗模型理论、银纹化微观增韧机理和柔性界面层理论。在定量分析RIP填充PP复合材料的增强机理方面,主要阐述了两种判据:基体层厚度判据和界面黏结强度判据;并利用所述判据分析了相关文献的数据,得出了如下结论:当RIP平均粒径d临界粒径dc,体积分数Φf临界体积分数Φf C,或平均基体层厚度L临界基体层厚度Lc;界面相互作用参数B值在[1,2.6]之间时,RIP增强填充PP复合材料的韧性的机会较大。     

动态硫化增韧Co-PP/EVA共混物研究

研究了动态硫化和简单共混增韧共聚级聚丙烯(Co-PP)/乙烯-醋酸乙烯酯共聚物(EVA)共混物的力学性能、流动性能、形态结构和脆韧转变。结果表明:动态硫化共混物力学性能尤其是冲击强度明显优于简单共混物的,流动性则差于简单共混物的,动态硫化共混物中EVA颗粒尺寸小于简单共混物的;采用Wu氏增韧理论对2种共混物的脆韧转变进行了分析,动态硫化共混物的临界基体层厚度约为0.55μm,简单共混物的临界基体层厚度约0.60μm。     

动态硫化增韧聚丙烯／三元乙丙橡胶共混物的研究

研究了动态硫化和简单共混增韧聚丙烯（PP）／三元乙丙橡胶（EPDM）共混物的力学性能、形态结构、流动性能和脆韧转变。结果表明：动态硫化的增韧效率要比简单共混的增韧效率高；随着EPDM用量的增加，共混物的力学性能均随之发生变化，流动性明显降低；简单共混物的橡胶颗粒尺寸随EPDM含量的增加呈增大趋势，而动态硫化可以降低橡胶颗粒的尺寸；动态硫化物的临界基体层厚度大约为0.3μm，简单共混物的临界基体层厚度大约为0．2μm，并且动态硫化和简单共混物均在各自的临界基体层厚度处发生脆韧转变，验证了wu氏增韧理论。     

MBS对聚碳酸酯的增韧作用及其增韧机理的探讨

研究了甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物（MBS）对光盘级聚碳酸酯的增韧作用。结果表明，MBS对PC增韧效果显著，且MBS分散性越好，根据逾渗理论，达到脆一韧转变时所需的MBS含量越少。求得达到脆-韧转变时的临界粒间距为50nm。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MBS粒子的空洞化引发基体的剪切屈服。     

无机刚性粒子增韧增强PP研究进展

综述了近些年来无机刚性粒子增韧聚丙烯（PP）的结构设计、刚性粒子粒径及其分布、改性剂种类及用量对增韧增强效果的影响以及无机刚性粒子增韧PP的机理。大量的研究表明，在刚性粒子增韧PP中，弹性体包覆刚性粒子的壳一核结构设计具有优异的增韧效果。在定量分析PP增韧机理方面，介绍了脆韧转变分析中界面黏结判据和粒间距判据，以及有限元方法在此领域的应用，刚性粒子增韧机理主要为界面脱黏到空洞／银纹化损伤和空洞／剪切屈服损伤的转变。此外还介绍了目前刚性粒子与橡胶混杂增韧PP的研究进展。     

核—壳共聚物对光盘级聚碳酸酯的增韧研究

研究了甲基丙烯酸甲酯－丁二烯－苯乙烯共聚物（MBS）对光盘级聚碳酸酯的增韧作用，结果表明，MBS对PC增韧效果显著，且MBS分散性越好，达到晚一韧转变时所需的MBS含量越少，求得达到脆－韧转变时的临界粒间距为50nm，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MBS粒子的空洞化引发基体的剪切屈服。     

PP/HDPE/SBS三元共混物的研究——基体韧性和弹性体分散相对PP三元共混物脆—韧转变的影响

研究了固定PP/HDPE/SBS三元共混物配比,采用不同共混工艺条件下的脆-韧转变规律。研究表明:PP三元共混物的冲击强度与SBS分散相粒径有密切关系。当SBS分散相粒间距T等于临界值T_c时,PP三元共混物将发生脆-韧转变。研究还表明基体韧性与T_c有密切关系,当基体韧性增高时,T_c值将增大。     

PP／POE／纳米CaCO3复合材料力学性能研究

研究了PP/POE／纳米CaCO3复合材料的力学性能、脆-韧转变规律及其与纳米CaCO3含量、分散相POE粒径的关系。结果表明：含4份CaCO3的PP/POE／纳米CaCO3复合体系，达到脆-韧转变所需的弹性体POE量最少。纳米CaCO3的添加还可以提高复合材料的弯曲模量，在增韧的同时提高材料的刚性。研究发现PP／POE／纳米CaCO3三元体系的基体层厚度与脆-韧转变的关系符合逾渗定理。     

固态挤出1.聚合物固态可挤性

介绍聚合物在静水压下的脆韧转变以及结晶性聚合物的αｃ松驰现象，阐明固态挤出的理论基础，并给出了一些聚合物固态挤出的温度选择范围。     

Polyethylene toughened by caco3 particles—percolation model of brittle-ductile transition in hdpe/caco3 blends

The percolation model is used to interpret the brittle-ductile transition of HDPE/CaCO₃ blends. The percolation threshold (θ_sc) for HDPE/CaCO₃ blends is found to be 0.52, which is equal to π/6. The critical exponent (g) is found to be 0.83 for HDPE/CaCO₃ blends. The toughening efficiency of blends which have monodisperse, highly asymmetrical particles, strong interphase adhesion and high matrix toughness is greater. The brittle-ductile transition in polymer blends seems to be a universal percolation phenomenon.     

Brittle-ductile transition of particle toughened polymers: influence of the matrix properties

It was theoretically pointed out that the product of the yield stress and yield strain of matrix polymer that determined the brittle-ductile transition (BDT) of particle toughened polymers. For given particle and test condition, the higher the product of the yield stress and the yield strain of the matrix polymer, the smaller the critical interparticle distance (ID_c) of the blends was. This was why the ID_c (0.15 μm) of the polypropylene (PP)/rubber blends was smaller than that (0.30 μm) of the nylon 66/rubber blends, and the ID_c of the nylon 66/rubber blends was smaller than that (0.60 μm) of the high density polyethylene (HDPE)/rubber blends.     

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.     

ABS高胶粉增韧PA6的结构与性能研究

采用熔融共混法制备了苯乙烯-马来酸酐共聚物（SMA）增容的PA6/ABS共混物,用透射电子显微镜对PA6/ABS共混物结构进行了表征,研究了增容剂含量对PA6/ABS共混体系结构、性能以及脆-韧转变温度的影响。结果表明,随着SMA含量的增加,PA6/ABS共混体系的橡胶相粒径先逐渐减小,后趋于平缓;橡胶颗粒的多分散系数逐渐增加;基体层厚度不断减小;PA6/ABS共混体系的拉伸强度逐渐增加;PA6/ABS共混体系的脆-韧转变温度先减小,后上升。     

Polyethylene toughened by CaCO3 particle: Brittle-ductile transition of CaCO3-toughened HDPE

The dependencies of the notched Izod impact toughness of HDPE / CaCO₃ blends on CaCO₃ particle concentration and particle size are analyzed. It was found that the notched Izod impact strength (S) of HDPE / CaCO₃ blends depends discontinuously on CaCO₃ particle concentration. A brittle-ductile transition occurs when the CaCO₃ volume fraction (V_f) increases to a critical value (Vη_f). Furthermore, a brittle-ductile transition master curve can be constructed by taking the matrix ligament thickness (L) into account as a parameter instead of V_f. The results show that the critical matrix ligament thickness (L_c) is a single parameter for the transition and L_c = 5.2μm for HDPE / CaCO₃ blends. The impact strength, however, varies considerably with CaCO₃ particle size, which shows that CaCO₃ particle size is another dominating parametor for the toughness of HDPE / CaCO₃ blends. © 1993 John Wiley & Sons, Inc.     

The effect of rolling orientation on the brittle-ductile transition in polycarbonate fracture

The effect of orientation on the brittle-ductile transition in rolled polycarbonate was examined. It has been believed that the brittle-ductile transition is governed by the residual stress at low reduction and the orientation at high reduction. But, our experimental results revealed that the brittle-ductile transition is caused by neither the residual stress nor orientation. It is proposed that the brittle-ductile transition may be ascribed to the morphological change which is produced during plastic deformation on rolling.     

Control of intrinsic brittleness and toughness of polymers and blends by chemical structure: A review

The intrinsic brittle-ductile (craze-yield) behavior of polymers and blends are controlled by two chain parameters: entanglement density v_e and characteristic ratio C_x. These chain parameters can be predicted from chemical structure. Therefore, the intrinsic brittle-ductile behavior of polymers and blends can be controlled by chemical structure using group additivity. The chemical composition and chain structure which can give the ultimate toughness in polymers and blends are discussed.     

两类PE-HD/E-TMB共混物的脆韧转变及断面形态

用自制增韧母料(E-TMB)分别与2200J型高密度聚乙烯(PE-HD)(HE1)和2911型PE-HD(HE2)热机械共混制得HE1/E-TMB和HE2/E-TMB共混物,用力学性能测试法和扫描电子显微镜研究了两类共混物的脆韧转变和断面形态。结果表明,HE1/E-TMB共混物比HE2/E-TMB共混物在弹性体含量较低的情况下发生脆韧转变,二者的脆韧转变区分别是共混物弹性体质量分数的3%～10%和10%～14%;弹性体质量分数为8%时,HE1/E-TMB共混物的冲击断面为韧性断裂,HE2/E-TMB共混物的冲击断面为脆性断裂,二者属于不同的断裂机理。     

纳米莫来石填充PP/EPDM共混物的脆韧转变

制备了含纳米莫来石的三元乙丙橡胶(EPDM)和马来酸酐接枝三元乙丙橡胶(EPDM-g-MAH)母料,研究了纳米莫来石对聚丙烯(PP)/EPDM和PP/EPDM-g-MAH共混物脆韧转变的影响。结果表明:纳米莫来石的加入使PP/EPDM和PP/EPDM-g-MAH共混物的脆韧转变提前,尤其在纳米莫来石用KH-550改性后,PP/EPDM共混物发生脆韧转变时EPDM的含量由15%降至10%;在橡胶相含量相同时,加入纳米莫来石后共混物的弹性模量和拉伸强度略有下降,而断裂伸长率显著下降。