Thermal mechanical and dielectric properties of ethylene co vinyl acetate based composites

Abstract

The selection of a material for a specific application is carried out by analysing the performance under different mechanical, thermal and electrical conditions for any material. In this aspect polymer composites become a unique group whose properties can be tuned in accordance with the applications. The present research work carries out an extensive study on composites of ethylene-co-vinyl acetate (EVA) with modified chitosan as fillers keeping in mind the necessity of waste to energy goal. As an initial step towards the development of composites, modification of chitosan via graft polymerization is carried out. These modified chitosans namely, chitosan-g-PANi, chitosan-g-MMA, chitosan-g-HEMA and chitosan/phytic acid polyelectrolyte complex, were used as fillers in the polymer composites that were processed via melt-mixing. The processed polymer composites were characterized using infrared spectroscopy, mechanical and thermogravimetric analysis. The ones that comprised of chitosan-g-PANi were further explored for their dielectric properties. The thermal degradation kinetics and thermodynamic parameters were calculated for the developed materials. Non-isothermal model free methods viz, Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Starink, Tang, Friedman (FR) and Vyazovkin were employed for the calculation. The activation energy values obtained by the differential FR method shows an increase compared to the integral methods like FWO, KAS, Starink and Tang. This is due to the lack of assumptions and approximations employed during the calculations via FR method. The mechanical testing showed that the composites other than EVA/chitosan-g-PANi showed decrease in tensile strength with increase filler content. Samples with grafted PANi showed increased tensile strength with increase in filler concentration. The model-free kinetic methods pointed towards the endothermic nature of the degradation process progressed by the formation of activated complexes for all four systems. The study signifies the need for better understanding towards the degradation properties which will aid in developing methods in industrial scale recycling of similar materials. Further the developed materials can be investigated towards flame retardant and food packaging applications.