The microstructure of a molded product considerably influences its macroscopic properties. In this study, the influence of molding process on microstructure, tensile property, and surface quality was explored on the glass fiber-reinforced polypropylene (GFRPP) parts molded by rapid heat cycle molding (RHCM) and conversion injection molding (CIM). Tensile strength and surface gloss were chosen to measure macroscopic properties of the molded parts. The microstructure including multilayer, fiber orientation, crystallinity, and fiber-matrix bonding strength were analyzed by simulations, scanning electron microscopy, wide-angle X-ray diffraction, and dynamic mechanical analysis. The relationship between the macroscopic properties and microstructure of the RHCM samples was also discussed. The results indicate that as the mold cavity surface temperature increases, the tensile strength increases firstly and decreases thereafter. The tensile strength of RHCM parts reached the maximum at the mold heating temperature of 60°C. It is also observed that the surface gloss of the sample increases as the mold cavity surface temperature rises, and the increase of surface gloss decreases distinctly with the mold heating temperature higher than 90°C.

中文翻译：

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快速热循环成型玻璃纤维增​​强聚丙烯零件的显微组织、拉伸性能和表面质量

成型产品的微观结构对其宏观性能有很大影响。本研究探讨了成型工艺对通过快速热循环成型 (RHCM) 和转化注塑成型 (CIM) 成型的玻璃纤维增​​强聚丙烯 (GFRPP) 零件的微观结构、拉伸性能和表面质量的影响。选择拉伸强度和表面光泽度来测量成型部件的宏观性能。通过模拟、扫描电子显微镜、广角 X 射线衍射和动态力学分析分析了包括多层、纤维取向、结晶度和纤维-基质结合强度在内的微观结构。还讨论了 RHCM 样品的宏观性能和微观结构之间的关系。结果表明，随着模具型腔表面温度的升高，抗拉强度先升高后降低。RHCM 制件的抗拉强度在模具加热温度 60°C 时达到最大值。还观察到样品的表面光泽度随着模具型腔表面温度的升高而增加，并且随着模具加热温度高于90℃，表面光泽度的增加量明显降低。