Study of isothermal and non-isothermal elongational flow on new copolyamide based nanocomposites

The reinforcement of polyamides with nanometric layered silicates represents nowadays an innovative strategy to produce high performance plastics with enhanced structural and functional properties. Even if the presence of very low silicate content allows polymer nanocomposites to be produced with the conventional processing equipments, the difficulty in conveniently tuning materials and processing parameters to control the developed nanomorphology represents a great limit for the applications on industrial scale. The elongational flow is common in many plastic manufacturing processes such as fibre spinning, film blowing, extrusion coating, foaming, so that a better understand of its effects on degree of silicate exfoliation and orientation inside the polymer matrix represent a crucial point to optimize the final nanostructure, to set properly the processing conditions and to control the end properties of the product. The aim of this work is to investigate the effects of elongational flow on clay dispersion, exfoliation and orientation of polyamide based nanocomposites. Hybrids at different loadings of a commercial organoclay were produced by melt compounding using two polyamide matrices: a nylon 6 and a copolyamide with similar molecular weight. The elongational flow characterization was performed both in isothermal and non-isothermal conditions by using, respectively, elongational rheometer (SER) and fibre spinning technique. The rheological response of the different nanocomposites, correlated to TEM results, was used to probe the nanoscale arrangement developed within the uniaxial stretching and to explore the degree of silicate dispersion and orientation in function of initial nanomorphology and the different polymer-clay affinity due to the copolyamide structure