ABSTRACT The performance of fiber‐reinforced rubber composites is highly dependent on the interfacial adhesion between the fiber and the rubber matrix. Conventional resorcinol‐formaldehyde‐latex (RFL) dipping systems, although effective, pose significant health and environmental risks due to the toxicity of resorcinol and formaldehyde. In this study, a formaldehyde‐free and resorcinol‐free blocked waterborne polyurethane/latex (WPU/L) dipping system was developed. Key synthesis parameters, including blocking agent ratio, DMBA content, initial R ‐value, final R ‐value, and WPU/L mass ratio, were systematically optimized to improve emulsion stability, thermomechanical properties of the adhesive film, and interfacial bonding performance. Under the optimal conditions (5% DMBA, initial R ‐value of 2.7, final R ‐value of 1.2, and WPU/L mass ratio of 17/100), the treated polyester fiber/rubber composites exhibited a peel force of 5.47 N/strand and an H‐pullout force of 61 N, substantially outperforming untreated fibers (~1 N/strand) while retaining > 98% of fiber tensile strength. XPS and SEM analyses revealed that the enhanced adhesion originates from increased polarity, hydrogen bonding, and co‐vulcanization at the interface. This work presents a candidate reduced‐toxicity dipping system to replace conventional RFL and establishes a structure‐performance framework for designing sustainable interfaces in polymer composites. Direct comparative validation with RFL under identical conditions remains an important direction for future work.
Yang et al. (Fri,) studied this question.