Effects of Temperature and Relative Humidity on Polylactic Acid Plastic Degradation |
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Authors: | Kai-Lai G Ho Anthony L Pometto III Paul N Hinz |
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Institution: | (1) Department of Food Science and Human Nutrition and Center for Crops Utilization Research, Iowa State University, Ames, Iowa, 50011;(2) Department of Food Science and Human Nutrition, Iowa State University, Ames, Iowa, 50011;(3) Department of Statistics, Iowa State University, Ames, Iowa, 50011 |
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Abstract: | Three high molecular weight (120,000 to 200,000 g mol–1) polylactic acid (PLA) plastic films from Chronopol (Ch-I) and Cargill Dow Polymers (GII and Ca-I) were analyzed for their degradation under various temperature and relative humidity (RH) conditions. Two sets of plastic films, each containing 11 samples, were randomly hung in a temperature/humidity-controlled chamber by means of plastic-coated paper clips. The tested conditions were 28, 40, and 55°C at 50 and 100% RH, respectively, and 55°C at 10% RH. The three tested PLA films started to lose their tensile properties when their weight-average molecular weight (M
w) was in the range of 50,000 to 75,000 g mol–1. The average degradation rate of Ch-I, GII, and Ca-I was 28,931, 27,361, and 63,025 M
w/week, respectively. Hence, GII had a faster degradation rate than Ch-I and Ca-I under all tested conditions. The degradation rate of PLA plastics was enhanced by the increase in temperature and relative humidity. This trend was observed in all three PLA plastics (Ca-I, GII, and Ch-I). Of the three tested films, Ch-I was the first to lose its mechanical properties, whereas Ca-I demonstrated the slowest loss, with mechanical properties under all tested conditions. |
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Keywords: | Polylactic acid temperature relative humidity degradation |
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