Effect of multi walled carbon nanotube on mechanical, thermal and rheological properties of polypropylene

In this study, multi-walled carbon nanotube (MWCNT) filled polypropylene (PP) nanocomposites prepared by melt processing methods by employing extruder and injection molding techniques were examined with various characterization methods and test procedures, in detail. Aim and novelty of the work were to merely investigate the effects of amount and dispersion of MWCNTs on mechanical, thermal and rheological properties of PP including no compatibilizer and thus chemical interaction and/or interfacial adhesion effect. The mechanical test results showed that the incorporation of MWCNTs increased the tensile strength (18.4%), flexural strength (35.2%) and modulus of elasticity (45%) while it decreased the impact strength (18%) and elongation at break (690%) values of PP/MWCNT nanocomposites. Thermal analysis data revealed that the MWCNT addition slightly increased the crystallization peak onset and peak maximum temperatures of PP under non-isothermal conditions. Frequency-dependent melt rheological behaviors of nanocomposites in linear viscoelastic regime pointed out that the storage modulus (G'), loss modulus (G''), complex viscosity (η*), and relaxation time of PP increased with the increasing amount of MWCNT. Non-linear rheological tests such as creep and stress relaxation also depicted that nanocomposites exhibited lower creep strain and relaxation rate than PP. Based on the thermal and mechanical test results, 0.3 wt% of MWCNT could be considered as the critical filler amount also called as “percolation threshold” for improving the solid-state physical properties of PP/MWCNT nanocomposites under the circumstances of no compatibilizer.