Submitted to: Bio Environmental Polymer Society
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 2003
Publication Date: August 10, 2003
Citation: Shogren, R.L., Petrovic, Z., Liu, Z., Erhan, S.Z. 2003. Biodegradation behavior of some vegetable oil-based polymers. Bio Environmental Polymer Society. p. 37. Technical Abstract: Recently, Shogren (1) has described the preparation of polyesters from the reaction of epoxidized soybean oil with polycarboxylic acids and their use as coatings. Petrovic et al (2) have prepared rigid polyurethanes (PU) by reacting vegetable oil polyols with diisocyanates. Liu et al (3) have prepared epoxy resins from epoxidized soybean oil (ESO) and various polyamines. Little is known, however, about the biodegradability of such materials. Such knowledge would be useful whether the polymer was intended to degrade safely in the environment or be durable and have long term resistance to degradation. The potential biodegradability of the polymers mentioned above was assessed by mixing 1 g of sample with 50 g soil (50% moisture) and measuring the amount of CO2 released using a respirometer (Columbus Instruments, Columbus, OH) for 60-80 days at temperatures of 30-58 degrees C. Films of soybean oil and linseed oil which were oxidatively polymerized (Co catalyst) on a kraft paper support were 90-100% mineralized to CO2 after 70 days at 30 degrees C. Mineralization to CO2 of powdered ESO/adipic acid and ESO/citric acid polyesters were 35% and 7%, respectively, after 80 days at 30 degrees C. Mineralization of the available carbon in vegetable oil polyurethanes was less than 7.5% after 70 days at 30 degrees C and 25 days at 55 degrees C compared to 100% for soybean oil. Among the different PU's, the rate of degradation seemed to increase as the number of hydroxy groups per triglyceride polyol decreased. There was no signficant degradation of the polyamine/ESO resins after 100 days at 58 degrees C. These results are generally consistent with previous biodegradation studies on other types of functionalized polymers, i.e. polyamine/epoxy resins are slow to degrade while polyesters degrade more quickly due to the more readily hydrolysable ester bond. Polymers with a higher cross-link density or branched monomers also normally degrade more slowly due to motional restrictions and difficulty for enzymes to gain access. The more rapid degradation of oxidatively polymerized oils is probably due to the introduction of enzyme-accessible chain ends such as carboxylic acids as well as lower molecular weights and glass transition temperatures.