7. Time-Temperature Dependent Creep and Recovery Behaviour of MWCNTs-Polypropylene Nanocomposites

Time-dependent viscoelastic materials are characterized by their creep, recovery and stress relaxation behaviour under different thermo-mechanical conditions. Thermoplastic polymers are lightweight and fatigue resistant, among which polypropylene (PP) is widely used. Its high isotacticity provides excellent physical and mechanical properties. In the present study, multi-walled carbon nanotubes-polypropylene nanocomposites (MWCNTs/PP) were developed by solvent casting method using isotactic PP with MWCNT-COOH (surface functionalized). Surface morphology was observed using scanning electron microscopy to check for a uniform distribution of CNT into PP matrix. Time-temperature controlled short and long-term creep and recovery tests were conducted in creep mode using DMA. The effects of loading time and temperature on creep and recovery behaviour of nanocomposites with CNT loading were studied with respect to structural behaviour and thermal stability using SEM and TGA. It was found that MWCNT-PP nanocomposites show a decrease in creep compliance and creep and recovery strains at 20 °C, and an increase in creep compliance at 50 °C due to the relative motion of entangled polymeric chain and MWCNT.