The polymers which disintegrate by themselves during a certain period of time by enzymatic hydrolysis and to some extent by oxidation, are known as biodegradable polymers. Example $\rightarrow$ Poly- $\beta$-hydroxy-butyrate-co- $\beta$-hydroxyvalerate (PHBV), which is used in orthopaedic devices and in controlled drug release, and poly (glycollic acid) poly (lactic acid) or commonly known as dextron, which is used for stitching of wounds after operation.