An efficient approach to manufacturing carbon nanosheets from lignite and their impact on the mechanical performance of semi-crystalline thermoplastic composites with comprehensive benchmarking

Abstract

Lignite-derived carbon nanosheets (CNS) offer a novel approach to producing carbon-based nanomaterials with unique advantages over other precursors. The primary mechanism successfully demonstrated the transformation of lignite into CNS by thermo-chemical treatment process through acid treatment (HNO3), catalyst impregnation (FeCl3), and carbonization (1000 °C, 5 min) steps resulting in the enrichment in the carbon content by maintaining the desired efficiency to be used as a filler in compounding process. Moreover, the produced CNS had superior characteristics in terms of carbon content reached 70 % and thermal stability even at 1000 °C compared to lignite. Subsequently, a comprehensive benchmarking study was conducted to achieve high compatibility and uniform dispersion between semi-crystalline thermoplastics such as HomoPP, CopoPP, PA6 and PA6,6 with CNS using a high-speed thermokinetic shear mixer. CNS exhibited enhanced compatibility with thermoplastics, leading to improved mechanical properties such as tensile and flexural modulus inpolymer composites. The benchmark studies revealed that a loading ratio of 0.5 wt% of CNS exhibited optimal reinforcement efficiency. Notably, PA6 matrix demonstrated the most significant improvement in yield strength, increasing by 12 %, while PA6,6 showed the highest increase in tensile modulus at 25 %. Similarly, PA6,6 exhibited the most notable improvement in flexural modulus with a substantial increase of 17 %. Conversely, HomoPP matrix displayed the highest improvement in flexural strength, increasing by 13 %. Furthermore, the incorporation of CNS into the polymer leads to an increase in the crystallization temperature from 182 °C to 194 °C for PA6-0.5 % CNS. These findings highlight the potential of CNS as versatile materials with promising polymer applications such as automotive and aviation.