Poly (Lactic Acid) Generated for Advanced Materials

Poly (Lactic Acid) Generated for Advanced Materials

Pranut Potiyaraj (Chulalongkorn University, Thailand)
Copyright: © 2017 |Pages: 22
DOI: 10.4018/978-1-5225-1971-3.ch005
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Abstract

The consumption of plastic products from petrochemical feedstock has increased sharply resulting in plastic waste problems while raw materials from fossil fuels tend to decrease rapidly. Researchers and the plastic industry have since proposed a sustainable solution through the development of bioplastics. Ideally, bioplastics which are synthesized from renewable bioresources normally render biodegradability in appropriate conditions. Polyester, one of the most diversely used synthetic polymers today, is an ideal choice for biodegradable polymers due to the relative ease of breaking ester linkages. Poly(lactic acid) or polylactide or PLA which is a thermoplastic polyester with many advantageous properties, for instance, environmentally friendly, biocompatibility, processability, and high chemical resistance is now available in the plastic market as a promising bioplastics. However, the cost of PLA is still much higher than that of general commodity plastics. In order to make PLA commercially competitive, advanced and innovative applications should thus be explored. In this chapter, technological background of PLA production as well as its economic situation is firstly reviewed. Then, the enhancement of PLA properties to suit advanced applications is illustrated. Some polymers used for blending with PLA along with some fillers utilized for the production of PLA composites are described. The chapter concludes with the degradation mechanism of PLA and the standard test methods.
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Background

A New Promising Bioplastics

PLA is a biodegradable thermoplastic aliphatic polyester synthesis from lactic acid which is derived from renewable biomass resources, such as corn starch, tapioca roots, or sugarcane. Its repeating unit is shown in Figure 1. Lactic acid has two optical isomers, i.e. L-lactic acid and D-lactic acid. A mixture of the two isomers is called DL-lactic acid. The polymerization of optically pure L- and D-lactic acids gives isotactic homopolymers of PLLA and PDLA, respectively. PLLA and PDLA are crystalline polymers with a melting temperature () around 180°C. The polymerization of DL-lactic acid leads to the formation of poly(DL-lactic acid) of which the degree of crystallinity is controlled by the ratio of D to L enantiomers used.

Figure 1.

Repeating unit of PLA

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