Effect of functionalized CNTs and liquid crystalline polymer on thermo-oxidative stability of polyethylene-based hybrid composites

Abstract

Hybrid composites based on polyethylene (PE) filled with thermotropic liquid crystalline polymer (LCP) and pristine or hydroxyl- or carboxylic-functionalized CNTs were prepared using melt extrusion process. Thermo-oxidative decomposition under dynamic and isothermal conditions was investigated using thermogravimetric analysis (TG). From TG profiles and activation energy analysis, the highest thermo-oxidative stability revealed from both dynamic and isothermal investigations was clearly observed for the PE-based hybrid composite filled with LCP and small amount of carboxylic-functionalized CNT. The melt rheological investigation showed that the effect of LCP and CNTs loading on viscoelastic characteristics of the composites was clearly pronounced at low frequency and the viscous part was found as a dominant factor. Complex viscosity, storage and loss moduli of the hybrid composite containing carboxylic-functionalized CNT showed the highest values compared among all samples examined. The morphological results observed using scanning electron microscopy and transmission electron microscopy indicated the improved dispersion of both LCP and carboxylic-functionalized CNT fillers. The obtained results indicated the importance of LCP-assisted dispersion of carboxylic-functionalized CNT through interface interaction, resulting in the remarkable improvement in thermo-oxidative stability of the composite