Evaluation of surface modification impact on PP/MWCNT nanocomposites by rheological and mechanical characterization, assisted with morphological image processing

Abstract

PP/MWCNT nanocomposites were prepared using polypropylene and modified carbon nanotubes (CNTs) via melt‐extrusion process. Pure PP was compared with maleic anhydride grafted polypropylene, reinforced with 0.5, 1, and 1.5 wt% COOH‐modified nanotubes (PPgCNT) and polypropylene/unmodified CNT nanocomposite (PPCNT) in 1 wt% content. Morphological analysis was performed using FTIR and SEM along with MATLAB and easy fit software‐assisted image processing. Image processing of SEM monographs for well‐distributed CNTs showed a distribution factor (β) close to 0 while β in agglomerated samples was close to 1. Mechanical properties showed that tensile strength and tensile modulus of nanocomposites were higher than pure PP, in contrast the tensile elongation at break was lower. In addition, nanocomposites with modified nanotubes showed higher tensile strength, tensile modulus, and lower elongation at break compare with unmodified CNT/PP nanocomposites. Capillary rheometries resulted that at high strain rate [100–1500 (s−1)], melting behavior of the samples is similar to the viscoplastic fluids, and Herschel‐Bulkley model is the best approach for prediction of the fluid's rheological behaviors. Adding the modified and unmodified CNTs only changed the model's parameters. Oscillating rheometry studies concluded that at 1% strain, molten nanocomposites followed the viscoelastic behavior while in higher shear rates flow behavior is different. According to the oscillatory rheometry results, storage modulus, loss modulus, complex modulus, and complex viscosity of PPgCNTs were higher than PP and PPCNT. It is concluded that by reduction of β, nanocomposites become more viscoplastic (in high shear rates). Finally, statistical analysis confirmed the rheological and mechanical results. POLYM. COMPOS., 40:E501–E510, 2019. © 2018 Society of Plastics Engineers