The effect of surface treatments on the properties of ultra-high molecular weight polyethylene fiber/unsaturated polyester resin composites

Polymer composites have become an indispensable material in many industries due to their advantages such as lightness, durability, and flexibility. These materials not only replace traditional materials such as metal, wood, and ceramics but also offer lower costs and environmentally friendly properties. The addition of reinforcing materials into polymers enhances mechanical strength, chemical resistance, and thermal stability, expanding their application areas. Fiber- or particle-based reinforcement materials are widely preferred to improve composite performance. Particularly, high-performance polymer composites hold a significant market share in demanding applications such as aerospace, automotive, healthcare, and construction. In this context, the use of ultra-high molecular weight polyethylene (UHMWPE) fibers in unsaturated polyester resin-reinforced composites presents a significant potential for improving mechanical and chemical properties. In this study, UHMWPE fibers were reinforced with unsaturated polyester resin to fabricate composite materials. Various surface modification techniques were applied to improve the weak interfacial adhesion properties of UHMWPE fibers. Both "wet" chemical and "dry" techniques were used to modify the UHMWPE fibers, which were then homogeneously integrated into the polyester matrix. The mechanical performance of the obtained composites was examined in detail. Applied surface modification processes enhanced fiber-matrix interfacial bonding, improving properties such as tensile strength, elastic modulus, impact resistance, and flexural strength. For instance, composites containing 15% unmodified fibers exhibited a 38% reduction in tensile strength due to insufficient fiber-matrix interaction. In contrast, composites with 15% fiber content subjected to 4-hour chromic acid surface modification showed a 29% increase in tensile strength. Corona treatment applied to 15% fiber-reinforced composites resulted in a 7.7% increase in tensile strength, although excessive treatment negatively affected it. The silane coating method increased the elastic modulus by 53% in composites with 5% fiber content. Composites containing 15% corona-treated fibers showed a 90% increase in elastic modulus, but a 21% decrease in elongation at break, indicating that surface modification reduced flexibility. At high fiber contents, inadequate homogeneous distribution and fiber agglomeration negatively affected tensile strength and flexibility. This study demonstrates that surface modification techniques play a crucial role in enhancing the surface properties of UHMWPE fibers and improving the mechanical strength of composites. By optimizing modification durations, fiber contents, and surface treatments, it is possible to produce composites with high elastic modulus, flexural strength, and tensile resistance. These cost-effective and applicable methods contribute to the production of high-strength, less brittle, and high-value-added materials for industrial applications. The study provides valuable insights into the development of high-performance polymer composites in the literature.