The effect of morphology of ternary-phase polypropylene/glass bead/ethylene-propylene rubber composites on the toughness and brittle-ductile transition
The effect of morphology of ternary-phase polypropylene/glass bead/ethylene-propylene rubber composites on the toughness and brittle-ductile transition
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DOI：
10.1002/app.10756
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发表时间：
2002-08
影响因子：
3
通讯作者：
I. Dubnikova;S. M. Berezina;A. Antonov
中科院分区：
文献类型：
--
作者：
I. Dubnikova;S. M. Berezina;A. Antonov
研究了刚性填料含量为5- 40vol%（EPR/GB = 0.33）的三元聚丙烯（PP）/玻璃微珠（GB）/乙丙橡胶（EPR）复合材料的形态结构与冲击韧性的关系。结果表明，共混物的相形态主要有以下三种：（1）分散相和较弱的GB-PP粘附力;（2）分散相和较高的GB-PP粘附力;（3）GB颗粒被弹性体壳包覆。马来酸酐化PP或EPR分别用于制备第二和第三类复合材料。二元复合材料与刚性或橡胶相制备模型系统。复合材料的杨氏模量值包含GB封装的软夹层保持接近纯PP模量，并位于相应的边界与相分离分布的三元体系和橡胶改性PP。缺口冲击强度通过Izod和三点弯曲试验测量。具有弱粘附和高粘附相分离分布的体系表现出准脆性断裂。弹性体对GB颗粒的包覆显著提高了材料的韧性。核-壳夹杂分数的增加导致在试样本体内强烈的基体屈服和类似于橡胶增韧PP的脆韧转变。基于对载荷-时间曲线的分析，提出了脆性-韧性转变的判据，即裂纹萌生阶段临界塑性变形的累积。在夹杂物-基体边界处的局部失效微过程的开始应力被发现在能量耗散机制中起主导作用。与GB脱粘的应力相比，在弹性体壳-PP界面处开始局部基质屈服的应力的降低是在具有封装GB的系统中的起始阶段的密集能量吸收的主要来源。通过用弹性体壳包覆刚性颗粒可以获得最佳的刚度-韧性平衡。© 2002 Wiley Periodicals，Inc.应用聚合物科学杂志85：1911-1928，2002
Correlation between the morphology and the impact toughness was studied for ternary-phase polypropylene (PP)/glass bead (GB)/ethylene-propylene rubber (EPR) composites containing 5–40 vol % of rigid filler at a fixed volume fraction ratio EPR/GB equal to 0.33. The three following types of phase morphology were obtained: (1) separate dispersion of phases and weak GB–PP adhesion; (2) separate dispersion of phases and high GB–PP adhesion; and (3) encapsulation of GB particles by elastomer shell. Maleated PP or EPR was used for the preparation of second and third types of composites, respectively. Binary composites with either rigid or rubbery phases were prepared as model systems. Young's modulus values of composites containing GB encapsulated by a soft interlayer stay close to neat PP modulus and are located in the bounds corresponding to ternary systems with phase-separate distribution and rubber-modified PP. Notched impact strength was measured by Izod and three-point bending tests. Systems with the phase-separate distribution both with weak and with high adhesion exhibit quasi-brittle fracture. The encapsulation of GB particles by elastomer results in significant improvement of the toughness. An increase in core-shell inclusion fraction leads to intense matrix yielding within a specimen bulk and brittle–ductile transition similar to the rubber-toughened PP. A criterion of brittle–ductile transition was proposed on the basis of load-time curve analysis, which is an accumulation of critical plastic deformation on a crack initiation stage. The stress of start of local failure microprocesses at the inclusion–matrix boundary was found to play the dominating role in energy-dissipating mechanisms. The lowering of the stress at which a local matrix yielding starts at elastomer shell–PP interface compared to the stress of GB debonding is a main source of intensive energy adsorption at the initiation stage in the system with encapsulated GB. The optimal stiffness–toughness balance can be obtained by coating the rigid particles with an elastomer shell. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1911–1928, 2002