Reprocessable Cross-Linked EVA/Silica Nanocomposites with Superior Mechanical Properties via One-Step and Scalable Reactive Blending

Organic/inorganic nanocomposites uniquely combine the dual advantages of inorganic nanomaterials and organic polymers. However, poor compatibility between inorganic nanoparticles and polymer matrices always arises as a huge obstacle to be addressed while designing and preparing high performance organic/inorganic nanocomposites. In situ surface grafting of ethylene–vinyl acetate copolymer (EVA) onto nanosilica and partial cross-linking of EVA via dynamic Si–O–C bonds with nanosilica as the core were simultaneously achieved via the transesterification reactions between the inherent Si–OH groups on the surface of nanosilica and the ester groups in EVA. The reactions were conducted thorough a one-step, simple and scalable reactive blending approach. The cross-linking reaction of EVA was evidenced by torque curves, FT-IR spectra and gel fraction testing. Uniform dispersion of silica particles in EVA matrix was observed for resulting EVA/silica nanocomposites due to surface modification of silica. Consequently, tremendous enhancement in mechanical properties of resultant EVA/silica nanocomposites were detected. Compared to the original EVA, the tensile strengths and tensile modulus of the EVA/silica nanocomposites increased by 72.5% and 37.8%, respectively, while the elongation at breaks of the EVA/silica nanocomposites remained as high as that of the original EVA. Additionally, the dynamic nature of Si–O–C cross-linkages enabled partially cross-linked EVA/silica nanocomposites to demonstrate exceptional reprocess ability and recyclability. This was evidenced by the sustained mechanical properties of the EVA/silica nanocomposites, which were still maintained even after undergoing three rounds of reprocessing.