Effect of vapor‐grown carbon nanofibers and in situ hydrolyzed silica on the mechanical and shape memory properties of water‐borne epoxy composites

Vapor‐grown carbon nanofiber (VGCNF)/water‐borne epoxy (WEP) and SiO₂/WEP composites were successfully synthesized via freeze drying and hot‐press molding. VGCNFs were mixed directly with a WEP emulsion, while SiO₂ was synthesized by in situ hydrolysis of TEOS solution (3‐triethoxysilylpropylamine (KH550): tetraethoxysilane (TEOS): absolute ethanol = 1:5:20, w/w/w) dispersed in the WEP emulsion. WEP composites were obtained from these mixtures by freeze drying and compressing under a pressure of 10 MPa at 120°C for 2 h. The morphology and mechanical properties of the WEP composites were investigated by transmission electron microscopy, scanning electron microscopy, dynamic mechanical analysis and tensile testing. The shape memory (SM) properties of the WEP composites were evaluated by fold‐deploy SM testing. The effects of filler content and recovery temperature on the SM properties were revealed through systematic variation. The results confirmed that VGCNF and in situ hydrolyzed SiO₂ were homogenously dispersed and incorporated into the WEP matrices. Thus, significant improvements in the mechanical and SM properties of the composites were achieved. POLYM. COMPOS., 36:1712–1720, 2015. © 2014 Society of Plastics Engineers