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Block Copolymer Micelle Toughened Isotactic Polypropylene
Macromolecules ( IF 5.1 ) Pub Date : 2017-08-31 00:00:00 , DOI: 10.1021/acs.macromol.7b01656 Jun Xu 1 , Micah J. Howard 1 , Vikas Mittal 2 , Frank S. Bates 1
Macromolecules ( IF 5.1 ) Pub Date : 2017-08-31 00:00:00 , DOI: 10.1021/acs.macromol.7b01656 Jun Xu 1 , Micah J. Howard 1 , Vikas Mittal 2 , Frank S. Bates 1
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A series of compositionally symmetric poly(ethylene-alt-propylene)-b-poly(ethylene-ran-ethyl ethylene) (PEP–PEEE) diblock copolymers were synthesized by anionic polymerization of isoprene and butadiene followed by heterogeneous catalytic hydrogenation. These materials were melt blended with isotactic polypropylene (iPP) at concentrations between 1.25 and 20 wt %, and the resulting morphologies were investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Uniformly dispersed micelles with an average diameter of approximately 100 nm were obtained in blends with PEP-PEEE molecular weights of 100 and 240 kg/mol. Tensile tests showed a 25-fold increase in the strain at break at a concentration of just 2.5 wt % with no discernible loss in elastic modulus or tensile strength. Blends containing 5 and 10 wt % micelles displayed 5 and 12 times the Izod impact strength of the pure iPP, respectively. Conversely, blends prepared with PEP homopolymer formed larger particles (≈0.5 μm in diameter) accompanied by marginal improvement in the tensile and impact properties at the same concentrations. The toughening mechanisms were investigated using electron microscopy, which revealed cavitation-induced shear yielding and multiple crazing in the iPP/PEP–PEEE blends, and limited plastic deformation in the iPP/PEP blend. A published theory that accounts for this type of toughening has been employed to model the rubber modified solids when subjected to different stress states leading to predictive criteria for cavitation and shear yielding. These results establish the relationship between rubber particle size and toughness in rubber-modified iPP.
中文翻译：
嵌段共聚物胶束增韧的全同立构聚丙烯
一系列组成对称的聚（乙烯- ALT -丙烯） - b -聚（乙烯- RAN -乙基乙烯）（PEP-PEE ë）二嵌段共聚物是由异戊二烯和丁二烯的阴离子聚合来合成，随后均相催化氢化。将这些材料与等规聚丙烯（i PP）以1.25至20 wt％的浓度熔融共混，并使用透射电子显微镜（TEM）和扫描电子显微镜（SEM）研究所得的形貌。与PEP-PEE E共混获得平均直径约100 nm的均匀分散的胶束分子量分别为100和240 kg / mol。拉伸试验表明，在浓度仅为2.5 wt％的情况下，断裂应变增加了25倍，而弹性模量或拉伸强度没有明显降低。包含5和10 wt％胶束的共混物分别显示出纯i PP的艾佐德冲击强度的5和12倍。相反，用PEP均聚物制得的共混物形成较大的颗粒（直径约0.5μm），同时在相同浓度下拉伸和冲击性能略有改善。使用电子显微镜，其揭示空穴诱导剪切屈服和多个龟裂的增韧机制进行了研究我PP / PEP-PEE ë共混物，以及在有限的塑性变形我PP / PEP共混物。考虑到这种类型的增韧作用的已发表理论已被用来对橡胶改性的固体进行建模，使其经受不同的应力状态，从而得出气蚀和剪切屈服的预测标准。这些结果建立了橡胶改性的i PP中橡胶粒度与韧性之间的关系。
更新日期：2017-08-31
中文翻译：
嵌段共聚物胶束增韧的全同立构聚丙烯
一系列组成对称的聚（乙烯- ALT -丙烯） - b -聚（乙烯- RAN -乙基乙烯）（PEP-PEE ë）二嵌段共聚物是由异戊二烯和丁二烯的阴离子聚合来合成，随后均相催化氢化。将这些材料与等规聚丙烯（i PP）以1.25至20 wt％的浓度熔融共混，并使用透射电子显微镜（TEM）和扫描电子显微镜（SEM）研究所得的形貌。与PEP-PEE E共混获得平均直径约100 nm的均匀分散的胶束分子量分别为100和240 kg / mol。拉伸试验表明，在浓度仅为2.5 wt％的情况下，断裂应变增加了25倍，而弹性模量或拉伸强度没有明显降低。包含5和10 wt％胶束的共混物分别显示出纯i PP的艾佐德冲击强度的5和12倍。相反，用PEP均聚物制得的共混物形成较大的颗粒（直径约0.5μm），同时在相同浓度下拉伸和冲击性能略有改善。使用电子显微镜，其揭示空穴诱导剪切屈服和多个龟裂的增韧机制进行了研究我PP / PEP-PEE ë共混物，以及在有限的塑性变形我PP / PEP共混物。考虑到这种类型的增韧作用的已发表理论已被用来对橡胶改性的固体进行建模，使其经受不同的应力状态，从而得出气蚀和剪切屈服的预测标准。这些结果建立了橡胶改性的i PP中橡胶粒度与韧性之间的关系。
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