Epoxy and Basalt Fiber Synergistic Modification of Rigid Polyvinyl Chloride Foam with Enhanced Mechanical and Thermal Properties

To address the insufficient thermal stability and mechanical properties of rigid polyvinyl chloride (PVC) foam, this study employed supercritical CO 2 foaming combined with moisture-cross-linking processes to prepare PVC composite foams, which were modified through synergistic filling with epoxy resin (EP) and basalt fiber (BF). The effects of EP and BF on the properties of the composite foams and the associated synergistic enhancement mechanism were investigated. The results indicated that EP formed an interpenetrating three-dimensional cross-linked network with PVC molecular chains under the catalysis of triethanolamine, while the silanol groups on the BF surface formed Si–O–Si covalent bonds with the hydrolyzed silanol groups from the silane coupling agent, achieving strong interfacial bonding. At EP content of 3 phr and BF content of 0.5 phr, the foam exhibited optimal performance, with uniformly distributed cell sizes ranging from 20 to 45 μm. The compressive strength and tensile strength reached 1.62 and 6.32 MPa, respectively. The addition of basalt fibers at 0.5 phr enhanced the material stiffness by 26%, and at 1 phr, the impact strength was increased by 31.2%. The T g increased to 80 °C, the temperature at 50% weight loss reached 311.0 °C, and the char residue increased to 17.7%, indicating significantly enhanced thermal stability. The foam developed in this study achieved synergistic improvements in both mechanical properties and thermal stability, demonstrating significant application potential in the fields of building insulation and composite core materials.