Effect of temperature and filler volume fraction on the creep and recovery behaviour of MWCNT–COOH–reinforced polypropylene films

Abstract

Nonlinear viscoelastic behaviour of –COOH functionalized multi-walled carbon nanotubes reinforced polypropylene nanocomposites is examined up to 2% MWCNT concentration. Isochronal creep and strain recovery experiments are conducted in dynamic mechanical analyser with oscillatory inputs. Creep stress level of 5 MPa is selected and successive creep and recovery experiments are performed at $$-\,20\,^\circ $$ C, $$25\,^\circ $$ C and $$50\,^\circ $$ C to analyse the effect of temperature and MWCNT concentration on strain developed during creep loading and strain recovery stages. A well-known Schapery nonlinear viscoelastic solid model with Zapas–Crissman viscoplastic term is fitted to the experimental observations. Stress-dependent nonlinear model parameters are obtained under temperature and MWCNT loading. Viscoelastic and viscoplastic strains are predicted at the end of recovery period. High temperatures and low concentrations of MWCNT are observed to cause higher viscoplastic strain. Strengthening MWCNT up to 1% improves the thermomechanical behaviour and viscoelastic recovery and decreases the viscoplastic strain in nanocomposites. Temperature-dependent compliance behaviour of nanocomposites is investigated with Williams–Landel–Ferry model and Arrhenius model using time–temperature superposition principle.