Glass fiber reinforced polyamide-6 nanocomposites

Polyamide 6 nanocomposites (PA6/NC) are novel type of composite materials comprising extremely thin, "nanometer scale" dispersions of smectitic silicate platelets. We prepared such PA6/NC materials via a melt compounding technique using suitably organomodified montmorillonite or hectorite type clays. The high surface to volume ratio of such thin silicate dispersions in PA6/NC leads to a high reinforcement efficiency even at 2 to 5 wt% of clay, achieving high specific modulus, strength and heat distortion temperature under load (DTUL). In addition, the platelet orientation and their surface nucleation effects seem to promote a faster crystallization and higher crystallinity in PA-6/NC (particularly at the surface and in thin-wall injection moldings), as compared to the standard PA-6. Such morphological features in PA-6/NC also result in improved moisture resistance. Recognizing these benefits, we investigated the use of PA-6/NC as a matrix for making both short and long glass fiber (GF) reinforced composites. Significant improvements in modulus were achievable in both the dry and the moisture conditioned state for PA-6/NC compared to standard PA-6, at any given level of glass fiber reinforcement. In general a small amount (3-4 wt%) of the nanometer scale dispersed clay is capable of replacing up to 40 wt% of a standard mineral filler or 10-15 wt% of glass fiber in PA-6 composites to give equivalent stiffness at a lower density or a lower part weight advantage. In addition, improved moisture resistance, permeation barrier and fast crystallization/mold cycle time contribute to the usefulness of such composites.