CHAPTER 7: Production of Low-cost Polyesters by Microwaving Heating of Carboxylic Acids and Polyol Blends

Numerous issues such as price uncertainty, manufacturing costs, environmental disposal, and geo-political issues affect the petroleum-based polymer industry. As an alternative, interest in the development of bio-degradable non-petroleum-based polymers has risen steadily since the 1980s. However, the price of traditionally used non-petroleum-based polymers (e.g., poly(lactic acid) is high and not competitive with petroleum-based polymers (e.g., polyethylene terephthalate). Therefore, the development of even lower cost non-petroleum-based polymers is needed. One possibility is to prepare co-polyesters using polyfunctional acids and alcohols such as citric acid and glycerol, respectively. Normally, citric acid and glycerol are considered to be plasticizers and are employed as additives to increase the fluidity of other materials (e.g., plastics, concrete, wallboards and clay). Heating to achieve citric acid-glycerol co-polyester polymerization is necessary, followed by a curing process to achieve final solidification. Of interest in this chapter is the use of microwave heating, which offers a useful tool to rapidly prepare samples to examine the mechanical properties of these polyesters.