Conductive polymer biocomposites based on poly(3-hydroxybutyrate) and poly(butylene adipate-co-terephthalate) with various graphene fillers for thermistor applications

The main objective of this research was to develop highly efficient conductive biopolymer composite films for pyroresistive and temperature sensors. Natural poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) was chosen as the base biopolymer material, and graphene nanomaterials of different structures, including raw and oxidized multi-walled carbon nanotubes and graphene nanoplatelets, were used as conductive fillers. The fabrication process involved a simple solvent casting procedure, where the conductive graphene fillers were incorporated into the biopolymer matrix without additional procedures. Due to the high crystallinity and poor film-forming ability of PHBV, a commercial poly(butylene adipate- co -terephthalate) (PBAT) was added as a modifier to improve the film quality. Through optimization, a PHBV/PBAT mass ratio of 50:50 was identified as the most promising composition to achieve composite films with desirable mechanical properties. The influence of graphene material structure and concentration on the crystallinity, thermal, mechanical, electrical, and piezoresistive properties of the composites was investigated. The results demonstrated that the PHBV/PBAT matrix filled with graphene materials has the potential to fully replace conventional structural composite materials, such as polypropylene, with biomaterials, making them suitable for a wide range of applications, including pyroresistive sensors.