علوم محیطی (Sep 2018)
Study of photodegradation, biodegradability, water absorption, and mechanical properties of biodegradable plastics for using in packaging industries
Abstract
Introduction: Plastic wastes are becoming a major problem all around the world. Degradation of synthetic polymers takes a long time, and so they remain in the environment for many years. Plastic packagings are one of the main sources of solid wastes. Using biodegradable plastic may be a solution to this problem. Mixing synthetic polymers with biopolymers is one way to produce biodegradable plastics. Another way to degraded plastic materials is photodegradation. Photodegradable plastics could be used in packaging industries because a huge amount of packaging plastics are being thrown away in nature. Material and methods: In this research, photodegradable and biodegradable compounds of starch and linear low-density polyethylene were prepared. Samples with different levels of starch (i.e., 3.7, 7.4, 10, 15, and 20 %wt) with a constant amount of 5% PE-g-MA were prepared. PE-g-MA used as coupling agent. The mechanical properties of polymer sample were done by santam instrument. Water absorpton of starch base polymer were evaluated. Soil burial tests shown the biodegradability of samples in the nature. starch-based polymer was exposed to mold growth to simulate biotic degradation. Photodegradability of samples were measured by exposure them to sunlight for 3 months. In order to determine bacterial degradability, samples were exposed to aspergilus niger for 84 days. Results and discussion: The tensile strength and Young’s modulus were decreased by the increase in starch content of the samples. The results of water absorption of the samples showed that when the starch percentage was higher, the water absorption was significantly increased. After being buried in soil for 11 months, the weight of the blends was decreased by increasing the starch level, which is an indication of biodegradation. The weight loss after removal of starch was probably caused by soil microorganisms. If the amount of starch is low, the compound would be affected by the low-density polymer matrix and unavailable to soil microorganisms. The more the samples remained in the soil, the more consumption of polymer chain by microorganism happened. Mold growth on polymeric samples confirmed the biodegradability of LLDPE/starch sheets. Mould biodegradation depends on microorganisms and their metabolism. Conclusion: According to the results, the blends are biodegradable and photodegradable and so are applicable in packaging industries. Soil burial is a simple simulation of the landfill. These blends are suitable for packaging goods.
