Structure-property studies of a novel amorphous polyamide/layered silicate nanocomposite

Abstract

A novel amorphous polyamide/montmorillonite nanocomposite based on poly(hexamethylene isophthalamide) was successfully prepared by melt intercalation. Wide angle X-ray diffraction and transmission electron microscopy showed that the organoclay containing quaternary amine surfactants with phenyl and hydroxyl groups was delaminated in the polymer matrix, resulting in well-exfoliated morphologies even at high montmorillonite content. Differential scanning calorimetry results indicated that clay platelets did not induce the formation of a crystalline phase in this amorphous polymer. Tensile tests demonstrated that the addition of nanoclay caused a dramatic increase in Young’s modulus (almost twofold) and yield strength of the nanocomposites compared to the homopolymer. The nanocomposites exhibited ductile behavior up to 5 weight percent (wt%) of nanoclay. The improvement in Young’s modulus is comparable with semi-crystalline aliphatic nylon 6 nanocomposites. Dynamic mechanical analysis was performed to investigate the nature of constrained region as the reinforcement mechanism. The modulus enhancement of the organoclay nanocomposites was found to be strongly correlated to the volume of the constrained region, as well as the nanoclay content. The type of polymer-nanofiller interaction strongly influences the amount and modulus of the constrained region, and both the latter contribute to the enhancement in storage modulus of the polymer nanocomposite.