Degradation and Recyclability of Poly (Ethylene Terephthalate)

The physical and chemical properties of polymers depend on the nature, arrangement of chemical groups of their composition and the magnitude of intra or intermolecular forces i.e primary and secondary valence bonds present in the polymer. Degradation process occurs due to the influence of thermal, chemical, mechanical, radiative and biochemical factors occurring over a period of time resulting in deterioration of mechanical properties and colour of polymers. The degradation occurs due to changes accompanying with the main backbone or side groups of the polymer. Degradation is a chemical process which affects not only the chemical composition of the polymer but also the physical parameters such as colour of the polymer, chain conformation, molecular weight, molecular weight distribution, crystallinity, chain flexibility, cross-linking and branching. The nature of weak links and end groups in the polymers contribute to stability of polymers. The degradation process is initiated at the terminal units with subsequent depolymerization. For example paraformaldehyde with hydroxyl terminal starts to degrade at about 170°C whereas the same polymer with acetyl terminals decomposes at about 200°C [1]. Replacement of carbon main chain with hetero atoms like P, N, B increases the thermal stability e.g. PON polymers containing phosphorus, oxygen, nitrogen and silicon.