The rubber particle size dependence of crazing in polypropylene
The rubber particle size dependence of crazing in polypropylene
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DOI：
10.1002/pen.760251011
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发表时间：
1985-07
影响因子：
3.2
通讯作者：
B. Jang;D. Uhlmann;J. B. Sande
中科院分区：
文献类型：
--
作者：
B. Jang;D. Uhlmann;J. B. Sande
研究了丁苯共聚物（SBR）和三元乙丙橡胶（EPDM）共混改性聚丙烯的拉伸银纹和夏比冲击行为。通过改变橡胶相和PP基体之间的相对粘度，得到不同的橡胶粒径分布。透射电子显微镜和计算机辅助图像分析被用来提供粒度信息。一般而言，具有较小橡胶颗粒的PP共混物比具有较大颗粒的PP共混物更坚韧且更具延展性，这可能是因为前者在促进银纹和/或剪切屈服方面代表了橡胶相的更有效利用。发现平均粒径D ≥ 0.5 μm的样品表现出明显的银纹。在给定的样品中，在D < 0.5 μm的单个橡胶颗粒周围没有出现银纹。D越高，形成银纹的倾向越大。D ≤ 0.5 μm的试样表现为剪切屈服，很少有银纹出现，存在一个临界橡胶颗粒尺寸，这是由于在有限的径向距离内需要保持足够的应力集中，以允许银纹的萌生和生长，而这需要有限的体积。小颗粒，诱导较小的应力增强区，因此，在引发银纹是无效的。
The tensile crazing and Charpy impact behavior of polypropylene modified with styrene-butadiene copolymer (SBR) and ethylene-propylene-diene monomer (EPDM) was studied. Various rubber particle size distributions were obtained by varying the relative viscosities between rubbery phase and PP matrix. Transmission electron microscopy and computer-aided image analysis were used to provide particle size information. In general, PP blends with smaller rubber particles are tougher and more ductile than those with larger particles, probably because the former represents a more efficient use of rubbery phase in promoting crazing and/or shear yielding. Samples with average particle diameter D ≥ 0.5 μm were found to exhibit pronounced crazing. Within a given sample, no crazes appeared to develop around individual rubber particles with D < 0.5 μm. The higher the D, the greater the propensity to form crazes. The behavior of samples with D ≪ 0.5 μm appeared to be dominated by shear yielding; very few crazes could be found. That there exists a critical rubber particle size is explained by the requirement that sufficient stress concentration be maintained to a finite radial distance to permit the initiation and growth of a craze, which requires a finite volume. Small particles, inducing smaller stress-enhanced zones, are therefore not effective in initiating crazes.