Abstract As a traditional general plastic, polypropylene (PP) has been widely used in daily life. Glass fibers are often used to further reinforce the properties of PP for its application in engineering area. However, there are still some drawbacks existing for glass fibers filled polypropylene composites, such as high filler content, easy fracture of glass fibers and damage to the machines during processing. Therefore, organic fibers are considered as an ideal candidate to replace glass fibers. In this work, short Kevlar fibers (KFs) modified by ball milling in phosphoric acid and surface hydrolyzation were introduced to PP matrix to improve the interfacial interaction and mechanical properties. It is found that KFs were exfoliated into several flaky microfibers and then broken into pieces during the ball milling process. With the aid of phosphoric acid, the KFs can be split further thereby increasing specific surface area greatly. Then the original and milled KFs were hydrolyzed by NaOH aqueous solution in order to introduce OH group on the surface of KFs. The dispersion and mechanical properties of PP reinforced with various KFs, including original, ball milled, and hydrolyzed, were investigated and compared. It was found that the combination of ball milling in phosphoric acid and surface hydrolyzation is the most effective way for enhancement of interfacial reaction and mechanical properties. Adding 10 wt. % of KFs could lead to an increase of tensile strength of PP from 30 MPa to 47 MPa, which only can be achieved by adding at least of 25 wt. % of glass fibers. The tensile test shows that hydrolyze of KFs surface are a more important factor to promote the interfacial interaction between fibers and matrix. Our work demonstrates that PP can be enhanced efficiently by the introduction of hydrolyzed and microfibrillated KFs. Although KFs are expensive compared with glass fiber at this moment, their high reinforcement efficiency and toughness could make them competitive as reinforcing filler for the preparation of advanced polymer composites with excellent mechanical and processing properties.

中文翻译：

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水解微纤化凯夫拉纤维增强聚丙烯复合材料的力学性能

摘要 聚丙烯（PP）作为一种传统的通用塑料，在日常生活中得到了广泛的应用。玻璃纤维通常用于进一步增强聚丙烯的性能，以使其在工程领域的应用。然而，玻璃纤维填充聚丙烯复合材料仍存在填料含量高、玻璃纤维易断裂、加工过程中易损坏机器等缺点。因此，有机纤维被认为是替代玻璃纤维的理想选择。在这项工作中，通过在磷酸中球磨和表面水解改性的短凯夫拉纤维 (KFs) 被引入到 PP 基体中，以改善界面相互作用和机械性能。研究发现，KFs 在球磨过程中被剥落成几个片状微纤维，然后破碎成碎片。在磷酸的帮助下，KFs 可以进一步分裂，从而大大增加比表面积。然后将原始和研磨的 KFs 用 NaOH 水溶液水解，以在 KFs 表面引入 OH 基团。研究和比较了用各种 KF 增强的 PP 的分散性和机械性能，包括原始的、球磨的和水解的。结果表明，磷酸中球磨和表面水解相结合是提高界面反应和力学性能的最有效途径。添加 10 重量。KFs 的百分比可以导致 PP 的拉伸强度从 30 MPa 增加到 47 MPa，这只能通过添加至少 25 wt.% 来实现。% 的玻璃纤维。拉伸试验表明，KFs 表面的水解是促进纤维与基体界面相互作用的更重要因素。我们的工作表明，可以通过引入水解和微纤化 KF 来有效增强 PP。尽管目前 KF 与玻璃纤维相比价格昂贵，但其高增强效率和韧性使其作为增强填料具有竞争力，可用于制备具有优异机械和加工性能的先进聚合物复合材料。