目的 探究微纤网络和相容剂对聚丙烯（PP）微注塑成形制品“皮-芯”结构和力学性能的影响规律。方法 基于“熔融共混-高速热拉伸”原位成纤技术,以聚对苯二甲酸乙二醇酯（PET）为成纤相、聚丙烯接枝马来酸酐（PP-g-MAH）为界面相容剂,制备PP微纤增强复合材料;采用微注塑成型工艺制备具有典型“皮-芯”结构的微制品。借助扫描电镜、偏振红外光谱和纳米压痕等手段,系统表征微制品内部PET微纤形态、分子链取向及局部力学性能,分析相容剂与微纤网络的协同作用对制品宏观和微观力学性能的影响。结果 PP-g-MAH的添加显著减小了PET分散相的相畴尺寸,当相容剂含量为1~2质量份时,在PP基体中形成直径约400 nm、分布均匀的PET微纤网络。该微纤结构与相容剂的协同作用使微注塑制品芯层厚度占比显著提高,并大幅增强PP分子链的取向程度,使皮层与芯层的取向差异趋于均匀化,芯层的硬度和弹性模量甚至可超越皮层。与未添加相容剂的PP/PET共混物相比,相容化微纤增强复合材料的微注塑制品屈服强度、杨氏模量和拉伸断裂能分别提高33.5%、306.3%和110.8%。结论 原位微纤网络结构与界面相容的协同效应可有效解决PP微注塑制品芯层取向程度低、模量不足等问题,为高性能PP微注塑制品的强韧化改性提供了一条新的工艺路径。
Abstract
The work aims to investigate the effects of microfibrillar networks and compatibilizers on the “skin- core” structure and mechanical properties of polypropylene (PP) micro-injection molded products. PP/PET microfibrillar composites were prepared via an in situ fibrillation technology combining “melt blending and high-speed hot stretching”, with polyethylene terephthalate (PET) as the fibrillated phase and maleic anhydride-grafted polypropylene (PP-g-MAH) as the interfacial compatibilizer. Subsequently, micro-injection molding was employed to fabricate products with typical “skin-core” structures. The morphology of PET microfibers, molecular chain orientation, and local mechanical properties within the micro-injection molded products were systematically characterized by scanning electron microscopy, polarized infrared spectroscopy, and nanoindentation. The synergistic effects of the compatibilizer and the microfibrillar networkon the macroscopic and microscopic mechanical properties of the products were investigated. The results demonstrated that the addition of PP-g-MAH significantly reduced the domain size of the PET dispersed phase. When the compatibilizer content was 1-2 parts by weight, a uniformly distributed PET microfibrillar network with an average diameter of approximately 400 nm was successfully constructed within the PP matrix. The synergistic effect of the microfibrillar structure and compatibilizer significantly increased the core-layer thickness fraction and enhanced the orientation degree of PP molecular chains, thereby reducing the orientation difference between the skin and core layers. Furthermore, the hardness and elastic modulus of the core layer could exceed those of the skin layer. Compared with the non-compatibilized PP/PET blend, the compatibilized microfibrillar composites exhibited increases of 33.5%, 306.3%, and 110.8% in yield strength, Young’s modulus, and tensile fracture energy, respectively. In conclusion, the combined effects of the in situ microfibrillar network and interfacial compatibilization enhance molecular orientation and modulus in the core layer of PP microinjection-molded products, providing a new processing strategy for the strengthening and toughening of high-performance PP micro-injection molded products.
关键词
聚丙烯 /
原位成纤 /
增容剂 /
微注塑 /
皮-芯结构 /
力学性能
Key words
polypropylene /
in situ fibrillation /
compatibilizer /
micro-injection /
“skin-core” structure /
mechanical properties
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基金
国家自然科学基金（52575462,U1909219）
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