Thermally expandable microspheres (TEMs) with different foaming temperatures were utilized to develop bimodal polypropylene (PP)/TEM composite foams through injection molding. The introduction of TEMs significantly enhanced the crystallization process of PP and optimized its viscoelastic behavior. As the TEM content increased, the foam density decreased. An optimal state where the cell structure remained intact was obtained at a 6.0 wt% TEM content and the composite foam exhibited the best comprehensive mechanical properties. Furthermore, with the introduction of a second type of high-temperature TEM as the co-blow agent, bimodal cells with size centralized at 12 μm and 57 μm were generated in the PP matrix. When the ratios of two TEMs were controlled at 3.0 wt% each, the PP/TEM 3 + 3 % foam with an equal amount of co-blowing agent achieved 7 %, 94 %, and 101 % improvement in tensile strength, toughness, and strain-at-break compared with the PP/TEM 6 % foam with sole DU300x TEM blowing agent, owing to the synergetic effects of stress dissipation and redirection within the bimodal cell structures and the transverse toughening of the rigid TEM microspheres. In addition, the composite foam exhibits a smooth surface appearance with a low surface roughness since the TEM shell could effectively prevent the burst of the microspheres during foaming. This work provides a simple and effective approach for manufacturing bimodal foams with high toughness and high-quality surfaces.

中文翻译：

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通过热膨胀微球注射成型制备的轻质、坚韧的聚合物泡沫，具有无缺陷的表面和双峰电池


利用具有不同发泡温度的热膨胀微球 （TEM） 通过注塑成型开发双峰聚丙烯 （PP）/TEM 复合泡沫。TEM 的引入显著增强了 PP 的结晶过程并优化了其粘弹性行为。随着 TEM 含量的增加，泡沫密度降低。在 6.0 wt% TEM 含量下获得泡孔结构保持完整的最佳状态，复合泡沫表现出最佳的综合力学性能。此外，随着第二种高温 TEM 作为共冲剂的引入，在 PP 基体中产生了尺寸集中在 12 μm 和 57 μm 的双峰单元。当两种 TEM 的比例控制在各 3.0 wt% 时，由于双峰电池结构内应力耗散和重定向的协同效应以及刚性 TEM 微球的横向增韧，与使用单独 DU300x TEM 发泡剂的 PP/TEM 6 % 泡沫相比，使用等量共发泡剂的 PP/TEM 3 + 3 % 泡沫在拉伸强度、韧性和断裂应变方面分别提高了 7 %、94 % 和 101 %。此外，复合泡沫表现出光滑的表面外观和较低的表面粗糙度，因为 TEM 外壳可以有效防止发泡过程中微球的爆裂。这项工作为制造具有高韧性和高质量表面的双峰泡沫提供了一种简单有效的方法。