Vegetable oil-based non-isocyanate polyurethane sizing agent: Constructing a “rigid-flexible” green interface for carbon fiber/epoxy composites

Abstract

Polyurethane sizing agents are widely applied in solving interface issues in carbon fiber composites. Influenced by the concept of sustainable development, the scientific community has been seeking a non-isocyanate green synthesis route for polyurethane to replace traditional petroleum-based polyurethane for decades. This article uses epoxidized soybean oil and CO₂ to prepare carbonated epoxidized soybean oil, and synthesizes a non-isocyanate polyurethane through five-membered cyclic carbonate aminolysis for the development of a green and efficient water-based non isocyanate polyurethane (BNIPU) sizing agent for constructing the “rigid-flexible” green interface of composites. The use of isocyanates in synthesis has been eliminated, achieving environmental friendliness and high efficiency. BNIPU sizing agent efficiently improves the interfacial properties of CF/EP composite materials. After evaluation, the IFSS and ILSS of the modified CF₂₀/EP composite reached 127.69 MPa and 96.22 MPa, respectively. Compared to the composite material without sizing, the improvement was 125.28% and 80.05%, respectively. This paper provides a new approach for a novel green synthesis route for polyurethane and suggests the possibility of partially replacing traditional polyurethane.