Mechanically robust, superelastic and lightweight composite foam enabled by hydrogen bond cross-linking

The structure collapse and significant plastic deformation of lightweight polymeric foams under various external mechanical loads has become an increasing challenge for practical applications. Herein, we report an efficient approach for fabricating the lightweight and highly porous ethylene vinyl acetate copolymer (EVA)-based composite foams with structural robustness and mechanical resilience by introducing flexible carboxylated EVA (EVA-COOH). The cells micromorphology of composite foams can be flexibly controlled by tuning the EVA-COOH concentration during the plasticizing process. Owing to the hydrogen bond cross-linking induced by EVA-COOH, the resulting lightweight composite foams (EVA-18/EVA-COOH) with low density (∼0.168 g/cm3) exhibit higher mechanical robustness including ultimate strength (∼1.66 MPa), tear strength (∼6.48 KN/m) and compressive stress at 50 % compressive strain (∼0.26 MPa) compared to that of traditional foams (such as EVA-18 composite foams). Strikingly, the elastic network provided by EVA-COOH also endows the composite foams with low hysteresis cycle performance at 50 % strain, stable elastic storage capacity at 20 % strain and high elasticity (rebound=∼44.2 %). It is envisaged that the mechanically robust, superelastic and lightweight composite foams offer a basic platform for utilizing EVA-based materials in various emerging applications, ranging from sensors to tissue engineering scaffold.