Essential work of fracture and failure mechanisms in dynamically vulcanized thermoplastic elastomer nanocomposites based on PA6/NBR/XNBR-grafted HNTs

A detailed fracture toughness analysis of dynamically vulcanized thermoplastic elastomer nanocomposites based on polyamide-6 (PA6) and nitrile butadiene rubber (NBR) reinforced by various concentrations of carboxylated nitrile butadiene rubber (XNBR)-grafted halloysite nanotubes (HNTs) was monitored through using essential work of fracture (EWF) procedure assisted by microstructure observations. The effect of various rubber phase and nanotube loadings on the morphology and fracture toughness of prepared multiphase polymer systems were investigated. The results of EWF analysis suggested that the dominant fracture mechanism in dynamically vulcanized PA6/NBR thermoplastic elastomers containing various rubber phase loadings was the dilatation shear bands resulted from repeated rubber particle debonding which enhances the shear yielding of PA6 matrix. Whereas, the incorporation of XNBR-grafted HNTs into the dynamically vulcanized PA6/NBR thermoplastic elastomers reduced the essential work of fracture followed by enhancement of non-essential work of fracture. However, the aggregation of nanotubes causes to form active sites for crack initiation. The results suggested that the XNBR-grafted HNTs can act as inhibitor sites for crack propagation when individually dispersed in the PA6/NBR multiphase systems.