Research on the Hydrophilic Modification Mechanism and Application of Polypropylene Fibers Based on Silane Coupling Agents and Acrylic Resin Composite Systems

Polypropylene (PP) fiber plays a significant role in civil engineering, textile engineering, and filtration/separation due to its excellent mechanical properties, chemical resistance, and low cost. However, its molecular chain, composed entirely of carbon and hydrogen, lacks polar functional groups, resulting in very low surface energy and poor hydrophilicity. This inherent defect severely limits its application effectiveness in scenarios requiring good interfacial adhesion or hydrophilic/moisture-absorbing properties. For instance, in concrete, the weak interfacial bond between the fiber and the cement matrix leads to low stress transfer efficiency; in textiles, its poor moisture-wicking property significantly affects wearing comfort.

This study aims to develop and systematically investigate a composite crosslinking agent, with silane coupling agent and waterborne acrylic resin as core components, for efficient and durable hydrophilic surface modification of PP fibers. The paper begins with an in-depth literature review, analyzing the surface characteristics and modification needs of PP fibers, and systematically summarizing the principles and limitations of existing hydrophilic modification techniques. Based on this, an innovative synergistic modification mechanism of "Silane Coupling Agent Bridging - Acrylic Resin Film Formation" is proposed: The hydrolyzed silanol groups of the silane coupling agent (e.g., KH-550) anchor onto the PP fiber surface, while the organic functional group (e.g., amino group) at the other end reacts chemically with the carboxyl groups on the molecular chains of the waterborne acrylic resin. Subsequently, through the resin's own crosslinking and curing, a robust, continuous, and hydrophilic group-rich three-dimensional network coating is constructed on the fiber surface.

Based on this mechanism, this paper designs a complete and feasible experimental research plan. The scheme details the entire process from the preparation of the composite crosslinking agent, the pre-treatment of PP fibers and the dip-dry modification process, to systematic characterization and performance evaluation. Characterization methods include Fourier Transform Infrared Spectroscopy (FTIR) for analyzing changes in surface chemical structure, Scanning Electron Microscopy (SEM) for observing surface morphology evolution, contact angle measurement and water absorption tests for quantifying the improvement in hydrophilic performance, and cement mortar flexural strength tests to verify the practical enhancement effect of the modified fibers in composite materials.

Through in-depth discussion and analysis of the anticipated results, this study theoretically demonstrates the feasibility and effectiveness of this composite crosslinking agent system. The expected results indicate that polar functional groups will be successfully introduced, and a dense coating will be formed on the surface of the modified PP fibers. The water contact angle can be significantly reduced to the hydrophilic range, and the water absorption rate will be greatly improved. Furthermore, the interfacial bonding with the cement matrix will be fundamentally improved, thereby significantly enhancing the flexural strength of cement mortar. This research not only provides a novel, environmentally friendly, and highly promising technical pathway for the hydrophilic modification of PP fibers but also offers theoretical reference for deeply understanding the construction mechanism of organic-inorganic hybrid coatings on fiber surfaces, holding significant theoretical and practical importance for promoting the development and application of high-performance PP fiber composites.