Effects of multiwalled carbon nanotubes functionalization on the morphology and mechanical and thermal properties of carbon fiber/vinyl ester composites.

Multiwalled carbon nanotube (MWCNT)/carbon fiber (CF)/vinyl ester (VE) laminate composites have been fabricated in this study. Pristine MWCNTs were treated with acid solution, which formed numerous oxygen-containing functional groups onto their surface, resulting in COOH-MWCNTs. Thereafter, acrylic functional groups were grafted onto the COOH-MWCNTs to generate acryl-MWCNTs. Three types of MWCNTs (pristine MWCNTs, COOH-MWCNTs, and acryl-MWCNTs) were used to reinforce the CF/VE-based composites. The dispersion of MWCNTs in the VE matrix and the interfacial interaction between MWCNTs and the VE matrix were investigated. Thereafter, the individual reinforcement efficiencies of these MWCNTs are compared. The flexural strength of the MWCNT/CF/VE composite with 1.0 phr acryl-MWCNTs content is 29.8% greater than that of neat CF/VE composites, and the flexural modulus of the MWCNT/CF/VE composite is 9.9% higher than that of neat CF/VE composites. Compared with neat CF/VE composites, 1.0 phr acryl-MWCNT/CF/VE composites exhibit an approximately 19.9 °C increase in glass transition temperature (Tg). The coefficients of thermal expansion significantly decreased from 47.2 ppm/°C of the neat CF/VE composites to 35.6 ppm/°C of the acryl-MWCNTs/CF/VE composites with 1 phr acryl-MWCNT content. This study provides a method for developing acryl-MWCNT/CF/VE composites with good dispersion of MWCNTs in VE matrix and strong interfacial interaction between the MWCNTs and VE matrix for enhancing the stress transfer from VE matrix to CF reinforcement.