Synergistic influence of multi-walled carbon nanotubes and graphene nanoparticles on the structural, thermal and mechanical characteristics of poly (3-hydroxybutyrate) films

Abstract

Poly (3-hydroxybutyrate) (PHB) is a linear, semi-crystalline biopolymer that belongs to polyhydroxyalkanoates family. It is completely bio-based, biocompatible, and biodegradable in nature. However, due to its low melt processing window, PHB becomes unstable during high-temperature processing. Carbon-based materials such as graphene (Gr) and multi-walled carbon nanotubes (MWCNT) suffer from restacking /agglomeration problems when loaded into polymer matrix. Recent studies revealed that MWCNT could bridge the gap between Gr flakes and loading them together can solve the agglomeration problem. In the present study, tip sonication-assisted solution casting method was used to fabricate PHB-based nanocomposites loaded with 0.3 wt% Gr, 0.3 wt% MWCNT, and their combination (0.3 wt% Gr and 0.3 wt% MWCNT). The prepared films were characterized using Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and Field emission transmission electron microscope (FETEM). Furthermore, structural, mechanical and optical properties were measured. FTIR analysis evidenced that the nature of the interaction between PHB matrix and nanofillers was physical. In comparison with neat PHB, significant improvement in UV and visible light barrier was observed for PHB/0.3Gr/0.3MWCNT films. TGA revealed that reinforcement of dual nanofillers viz. 0.3 wt% Gr and 0.3 wt% MWCNT significantly improved thermal degradation temperature (over 8 ℃ compared to PHB) than single nanofiller-loaded films. Likewise, the tensile strength of PHB-based films increased from 19±1.32 to 29±4.53 MPa, and crystallinity increased from 38.15 to 47.34 % with dual nanofiller loading. Therefore, it can be concluded that the inclusion of two carbonaceous nanofillers had a positive synergistic effect on the thermal, mechanical and optical properties of PHB.