10.1 Introduction

Biodegradable polymeric materials are dominated by polymers which contain hetero-atoms in their main chains. Chemical bonds such as ether-bonds, amide-bonds or ester-bonds are susceptible for hydrolytic attack and can lead to a primary reduction in molar mass of the polymers which is necessary to generate low molecular weight and water soluble intermediates able to penetrate biological membranes. The cleavage of the polymer chains can be catalysed by enzymes but also may take place without the action of the biological catalysts. The latter mechanism is predominantly observed when such polymers are degraded in human or animal bodies (medical applications) and also in this case the expression biodegradation usually is used.

In the history of biodegradable plastics, polyesters played a dominant part just from the beginning of the development. One of the first products developed as biodegradable plastics from the beginning of the 1970s was based on a polyester belonging to the group of poly(hydroxyalkanoates) and is called polyhydroxybutyrate (PHB). PHB and a number of other aliphatic polyesters and copolyesters are produced and intracellularly accumulated by a number of microorganisms [1]. A copolyester of PHB and poly(hydroxy valerate) was commercially produced by fermentation and was available on the market under the trade name BIOPOL (Metabolix) for many years. However, the production of this polyester was recently stopped, probably due to the high price level of the product and also some problems in material properties.

Beside the natural polyesters a number of synthetic aliphatic polyesters have also been shown...