Effect of MWCNT functionalization on thermal and electrical properties of PHBV/MWCNT nanocomposites

Pristine multiwalled carbon nanotubes (P-MWCNTs) were functionalized with carboxylic groups (MWCNT-COOH) through oxidation reactions and then reduced to produce hydroxyl groups (MWCNT-OH). Pristine and functionalized MWCNTs were used to produce poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposites with 0.5 wt% of MWCNTs. MWCNT functionalization was verified by visual stability in water, infrared and Raman spectroscopy, and zeta potential measurements. Pristine and functionalized MWCNTs acted as the nucleating agent in a PHBV matrix, as verified by differential scanning calorimetry (DSC). However, the dispersion of filler into the matrix, thermal stability, and direct current (DC) conductivity were affected by MWCNT functionalization. Scanning electron microscopy (SEM) showed that filler dispersion into the PHBV matrix was improved with MWCNT functionalization. The surface roughness was reduced with the addition and functionalization of MWCNT. The thermal stability of PHBV/MWCNT-COOH, PHBV/P-MWCNT, and PHBV/MWCNT-OH nanocomposites were 20, 30, and 30 °C higher than neat PHBV, respectively, as verified by thermogravimetry analysis (TGA). Addition of pristine and functionalized MWCNTs provided electrical conductivity in nanocomposite, which was higher for PHBV/P-MWCNTs (1.2 × 10−5S cm−1).