Electrical and thermal characterisation of polymers reinforced with carbon nanostructures

This study presents the synthesis, functionalisation, and comprehensive characterisation of electrically conductive poly (methyl methacrylate) (PMMA)-based nanocomposites reinforced with graphene, multi-walled carbon nanotubes (MWCNTs), and their hybrid combinations. Carbon nanostructures were synthesised via molten salt electrolysis in LiCl and NaOH systems under a reversing overpotential regime, enabling efficient exfoliation of graphite and formation of high-purity nanomaterials. To improve dispersion and interfacial compatibility with the polymer matrix, the nanofillers were functionalised by nitric acid treatment and X-ray irradiation. Nanocomposite thin films containing 15 wt.% filler were prepared by solution casting and characterised by transmission and scanning electron microscopy (TEM, SEM), Raman spectroscopy, and inductively coupled plasma optical emission spectrometry (ICP-OES). Electrical properties were evaluated using the four-point probe method, while thermal behaviour was investigated by thermogravimetric and differential thermal analyses (TG–DTG–DTA). The results demonstrate that MWCNT-containing and hybrid graphene–MWCNT nanocomposites exhibit a significant increase in electrical conductivity due to the formation of percolating conductive networks, whereas graphene-only systems remain highly resistive. Thermal analysis reveals a transition from single-step degradation in neat PMMA to multi-stage degradation in nanocomposites, accompanied by a shift of the maximum degradation temperature (T_max) and increased char residue. The observed enhancements are attributed to improved interfacial interactions, restricted polymer chain mobility, and barrier effects introduced by carbon nanostructures. These findings confirm the effectiveness of electrochemically synthesised carbon nanomaterials as multifunctional fillers in PMMA-based systems.