Physical and Chemical Changes during Hydrothermal Ageing of Poly (ethylene terephthalate)

Hydrothermal ageing of poly(ethylene terephthalate)(PET)and the effect of water during the different stages of ageing process had been investigated macroscopically and microscopically.The hydrothermal ageing mechanism was discussed accordingly.The results showed that there were changes of two aspects:chemical changes owing to hydrolysis,and physical changes arising from re-crystallization and structure relaxation caused by water and temperature.These factors had effect on the properties throughout the whole ageing process,and different factors played the dominant role at the different stages.In the early stage of aging,re-crystallinization was the key factor and then hydrolysis was the predominant reaction.