Submitted to: Polymers and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2011
Publication Date: 10/28/2011
Citation: Tisserat, B., Selling, G.W., Byars, J.A., Stuff, A.M. 2011. Instrumental physical analysis of microwaved glycerol citrate foams. Journal of Polymers and the Environment. 20:291-298.
Interpretive Summary: Global petroleum-based-plastics account for 3.7 trillion dollars annual sales with 80% of the output being polypropylene, polyethylene, polycarbonate, and polyvinyl chloride (costing around $0.80 to #1.80/lb). Bioplastics account for only 3% of the worldwide total of plastics manufactured. One of the major problems with currently available bioplastics is their cost (~$2.00 to $3.00/lb). Currently available bioplastics are 2 or 3 times the cost of petroleum-based plastics. Therefore, a great need for new low-cost bioplastics exists. Polyester glycerides (i.e., citric acid and glycerol blends) polymers offer a new bioplastics that is inexpensive (~$1.00/lb). This study investigated the production of glyceride polymers through microwave heating and thermal curing. Rapid means to analyze these polymers was achieved by utilizing the Texture Analyzer. The techniques employed in this paper should speed development of new glyceride polymers.
Technical Abstract: Solid polyester glyceride polymers generated by microwave cooking were further cured in a conventional oven at 100 oC for 0, 6, 24, 48, or 72 hr and their physical properties were tested. Curing polyester glycerides resulted in decreased moisture content (MC), altered color, increased hydrated polymer weight loss (HWL), and increased polymer oven weight loss (OWL). Polyester polymer samples were evaluated for firmness and springiness employing a Texture Analyzer (Model TA/TX2i). Oven curing increased polymer firmness and springiness. For example, firmness and springiness in 48 hr cured samples increased 202 and 143%, respectively, when compared to uncured controls. High correlations were found comparing OWL, MC, HWL, firmness, and springiness. Compression molded samples obtained from ground cured and non-cured polyester glycerides were evaluated for tensile strength, elongation and Young’s modulus using the Instron universal test machine (Model 4201). Curing promoted higher tensile strengths and elongation but did not affect Young’s modulus values. High correlations were found between springiness, firmness, tensile strength, and elongation. The Texture analyzer was shown to have merit in the preliminary evaluation of the polyester glycerides.