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Correlation Between Physico-Mechanical and Free Volume Properties of Gaur-Gum Filled Polyurethane/Polymethyl Methacrylate Biodegradable Composites

This study reports characterization of polyurethane/polymethyl methacrylate (PU/PMMA, 50/50) Semi-Interpenetrating Polymer Network (SIPN) prepared by in-situ polymerization, and filled with different weight percent (wt%) of natural polymer, Gaur-Gum (GG). These are characterized for density, tensile strength and percentage elongation at break. Positron annihilation lifetime measurements have also been carried out to measure the free volume of these composites. The results show good correlation between free volume content of the composites with the mechanical properties. These natural polymer-filled composites were subjected to biodegradation using a specific microorganism, Aspergillus niger. The influence of A. niger on composites has also been studied. The results show that the weight loss of the specimens exposed to A. niger media increases with increase in gaur gum in the composite. Interestingly the weight loss of GG-filled composites seems to be more than the quantum of GG incorporated which is a clear indication that degradation of PU/PMMA system is responsible for the weight loss.