Directional freezing in natural rubber foams to construct reinforced networks

Abstract

AbstractPolymer foams have great potential for applications in bioengineering, insulation and energy transfer and have attracted considerable interest. Natural rubber foam (NRF) is a polymeric porous foam with good elastic and mechanical properties. However, the presence of an inherently porous structure leads to poor mechanical properties, limiting practical applications. To improve the mechanical properties of polymer foams and increase their application versatility, we report a simple freeze‐casting approach to construct cellulose nanofibrils (CNF) reinforcement networks in a targeted manner without additional chemical modifications in the prepared NRF. The reinforcing physical network composed of CNF remains homogeneous and well distributed in the NRF collective. Moreover, the NRF/CNF composite has excellent mechanical properties, reaching a strength of 170 kPa at 60% compressive strain and 920 kPa tensile strength at 0.4% CNF, which is 1.8 and 4 times that of NRF, respectively.