Polylactic acids (PLA) are not new polymers. However, recent developments in the capability to manufacture the monomer economically from renewable feedstocks have placed these materials at the forefront of the emerging biodegradable plastics industry. Increasing realisation of the intrinsic properties of these polymers, coupled with a knowledge of how such properties can be manipulated to achieve compatibility with thermoplastics processing, manufacturing, and end-use requirements has fuelled technological and commercial interest in PLA products. This paper discusses the various technologies being used to produce polylactic acids. In addition, attention is drawn to how monomer stereochemistry can be controlled to impart targeted utility in the final polymers. Specific applications are described to illustrate further the range of properties that can be developed by utilising both the basic monomer/polymer chemistries in combination with post-modification techniques. Finally, the biodegradation mechanism of polylactic acids will be discussed and contrasted with other biodegradable polymers. (C) 1998 Elsevier Science Limited. All rights reserved.
