Effect of halloysite nanotube on microstructure, rheological and mechanical properties of dynamically vulcanized PA6/NBR thermoplastic vulcanizates

ABSTRACT

Dynamically vulcanized thermoplastic vulcanizate (TPV) nanocomposites based on polyamide-6 (PA6) and acrylonitrile butadiene rubber (NBR) reinforced by halloysite nanotubes (HNT) were prepared via a direct melt mixing process. The effects of HNT on the physical, mechanical, and rheological properties of nanocomposites were investigated. The prepared PA6/NBR/HNT nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning colorimeter (DSC), dynamic mechanical thermal analysis (DMTA), and rheological measurements. The morphology study of prepared nanocomposites shows that the introduction of HNT into the PA6 phase causes a decrease in the size of NBR droplets. The mechanical measurements revealed that Young’s modulus of TPV nanocomposites increased with the HNT loading up to 54%. DMTA results show that the introduction of 10 wt% of HNT into the PA6/NBR TPV leads to a 30% increase in storage modulus. The rheological measurements revealed that the storage modulus of nanocomposites has an increase of more than 200% in the presence of 7 wt% of HNT loading. Analytical stiffness modeling of Young’s modulus of the TPV nanocomposites was investigated using Hui–Shia and Wu models. Both models have some deviations from experimental results and been modified to predict Young’s modulus of the nanocomposites containing HNT with more precisions. The viscosity behavior of TPV nanocomposites was studied using a Carruea–Yasuda model and showed that the yield stress of nanocomposites increases with higher HNT loadings, indicating the formation of a nanotube network along with NBR phase network.

KEYWORDS:

• Dynamic vulcanization
• halloysite nanotube
• morphology
• nanocomposites
• thermoplastic vulcanizate