Studies on the Enzymatic Degradation Process of Epoxy-Polyurethane Compositions Obtained with Raw Materials of Natural Origin

Along with the development of technology and the increasing consumption of polymeric materials, which have become an integral part of man's everyday life, problems related to their disposal are arising. The presented research concentrates on the studies on the enzymatic degradation of selected epoxy-polyurethane materials filled with 2 or 5 wt.% of waste unmodified or chemically modified through mercerization wood flour. Composites, subjected to the degradation process, contained up to 60% of raw materials of natural origin. The enzymatic degradation was carried out for 28 days, in three environmental conditions, differing in the type of applied buffer, pH, process temperature, the amount, and the type of applied enzyme. In this study, the influence of two lipases was tested (specifically: lipase of microbiological origin-<i>Rhizopus Oryzae</i> Lipase, and one of animal origin-<i>Porcine Pancreas</i> Lipase). There were seven compositions tested, based on the polyaddition product of epoxidized soybean oil with bisphenol A, differing in the amount of filler and the type of modification to which wood flour was subjected before the application in the polymer composite. After enzymatic degradation, the greatest progress of biodegradation was observed at T = 30 °C, in a complex phosphate buffer with pH = 6.8, in the presence of the <i>Porcine Pancreas</i> enzyme. Under these conditions, a slightly smaller effect was also observed in the presence of the <i>Rhizopus Oryzae</i> enzyme. At the same time, the compositions containing mercerized wood flour turned out to be the most susceptible to biodegradation with the above-mentioned enzymes. After conducting the process in the full 4-week cycle numerous changes were noticed within the tested sample, such as (1) 7.0 %wt. of the overall weight loss of samples, (2) reducing the value of the static contact angle (e.g., from 116.7° before degradation to 27.2° at the end of the study), and (3) morphological appearance of the sample (sample's surface had suffered erosion noticed as smoothest roughnesses and numerous empty holes throughout its entire volume), concerning sample's condition before enzymatic degradation.