BIODEGRADABLE POLYMERS PART 2. POLYLACTIC AND POLYGLYCOLIC ACIDS – SYNTHESIS, PROPERTIES, MODIFICATION, AND APPLICATIONS

Recently, the production of biodegradable polymer materials based on naturally renewable raw materials has become widespread in polymer technology. This reduces carbon emissions because biological raw materials absorb CO2 from the air. It also reduces the accumulation of polymer waste in the environment because biodegradable polymers decompose faster than traditional fossil fuel-based plastics. This review analyzes literary sources from the past two decades regarding the production and use of biodegradable polymers, such as polylactic acid (PLA) and polyglycolic acid (PGA). These polymers are synthesized from the natural monomers lactic acid (LA) and glycolic acid (GA), which are obtained through the fermentation of starch or sugar. The paper describes the synthesis and characteristics of LA and GA monomers. Methods of LA polymerization are also considered. The paper shows that the physical, thermal, and mechanical properties of PLA depend on its molecular weight, molecular weight distribution, and the ratio of its optical isomers. The paper also presents the properties of PLA obtained from different isomers, as well as the physicochemical characteristics of PLA compared to synthetic polymers, such as polypropylene, polyethylene terephthalate, and polyamide. The paper also considers examples of copolymerization of the PLA monomer with GA, ε-caprolactone, dimethylsiloxane, and ethylene glycol using various catalysts. Additionally, the paper discusses methods of PLA modification, such as adding nanoparticles of zinc, copper, silver, titanium dioxide, silicon dioxide, and so on, or by plasticizing it with various chemical compounds. These methods improve the rheological, thermal, mechanical, antibacterial, and other properties of polymer materials based on PLA. The review also describes the synthesis of PGA and its properties. Specifically, it compares the gas and water vapor permeability of PGA with similar characteristics of polylactic acid (PLA) and other synthetic polymers, including polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, and polyamide. The review also describes the applications of PLA and PGA and the mechanisms by which these polymers decompose in nature. The review covers 56 scientific and technical publications in total. The analysis concludes that synthesizing biopolymers from natural monomers, such as lactic and glycolic acids, is economically and ecologically sound.