Polymer Degradation Essay

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There are many types of polymer degradation mechanisms: thermal, mechanical, photochemical, radiation chemical, biological and chemical degradation (Schnabel, 1981). According to ASTM definition, “degradable plastics are the plastics that are designed to undergo a significant change in its chemical structure under specific environmental conditions, resulting in a loss of some properties that may vary as measured by standard methods appropriate to the plastic and the application in a period of time that determines its classification”. This definition can be applied to many polymer degradation types including photodegradation, thermooxidation, hydrolysis and biodegradation. Autooxidation is the cause of thermooxidative degradation of organic materials without light. In natural photodegradation, sunlight reduces the molecular weight of the polymers by photooxidation and direct bond cleavage (Hand Book of Polymer Degradation, 2000). Another mode of degradation is hygrothermal degradation. Substantial loss of weight and mechanical properties of a material due to the effects of moisture and temperature is called hygrothermal degradation (Balakrishnan, Hassan, Imran, & Wahit, 2011). For instance, aged PLA/jute fiber composites in hygrothermal environment showed 15% decrease in tensile strength after 24 h…show more content…
The elongations-to-break of aged PHB and PHBV at 15°C decreased by 64% and 72%, respectively, after 168 days (Srubar et al., 2012). Ultimate strengths decreased by 28% and 8.9% for PHB and PHBV, respectively. During the aging process, the amorphous regions of PHB and PHBV underwent glassy aging in the rigid amorphous fraction, resulting a significant embrittlement. Over the testing period, PHB and PHBV samples had a maximum increase in modulus of 166% and 178%, and crystallinity of approximately 41% and 58%, respectively (Srubar et al.,
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