Blending Polylactic acid with Natural Rubber and Chain Extenders as a Sustainable Packaging Solution
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Date
2022-05
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The Ohio State University
Abstract
Plastic waste and its health-related issues from petroleum-based plastics are becoming more evident as endocrine disrupting compounds such as phthalates and bisphenol A leach out of the material and into foods that are consumed. As of 2015 about 6300 million metric tons of plastic waste has been created. Conventional plastics are extremely stable and take hundreds of years in some cases to breakdown [26]. A potential, more sustainable alternative is polylactic acid (PLA). This bioplastic is a thermoplastic polyester derived from plant waste such as corn starch. Application and use of PLA is limited due to its low degradation temperature and difficulty processing into films. To overcome these issues, PLA can be blended with natural rubber and other additives. As such, we hypothesized that blending PLA (polylactic acid) with natural rubber (NR)and other additives would improve its stability and performance. Eleven blends were made with PLA, 10-20% NR, 0.5-1.5% chain extender, 2 parts per hundred peroxide and 4.2 parts per hundred coagent and melt blended at temperatures of 140-155 °C. Rheological and thermal analysis as well as water permeability testing were conducted to characterize the blends. 0.5% and 1% chain extender I decreased PLA onset degradation temperature (Ton) and peak degradation temperature (Tpk). Extensional Rheology of the blend PLA-NR-15%-P-C-II showed strain hardening behavior indicating possibility of film making. All blends with rubber showed decreases in their complex viscosity from dynamic and transient shear testing indicating an increase in ability to be processed commercially. All blends used in this study were found to have lower water vapor transmission rates than pristine PLA. Thus, blending PLA with NR and other additives improved processability and performance properties. The most promising blend (PLA-NR-15%-P-C-II) from this study is being considered for use in commercial applications.
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Keywords
sustainable, Polylactic acid, plastic, natural rubber, PLA