Other Poly alkylene terephthalate s

On paper at least, the simplest of the PAT is poly(methylene terephthalate)  

There is no such compound as methanediol, so the polymer cannot be made by the usual reaction between diacid and diol, and is instead synthesised from an alkali metal salt of terephthalic acid and dibromomethane. Trials with this polymer [83] showed that it rapidly thermally degraded at the melt processing temperature. It was suggested that this initially involved loss of formaldehyde and formation of anhydride structures, swiftly followed by crosslinking and rapid discoloration. 

A few studies have been made on the thermal degradation of poly(l,4-cyclohexylenedimethylene terephthalate) [84—86], although these have little to say concerning the likely breakdown mechanism. Assuming the same process is applied here as in straight-chain poly(alkylene terephthalate)s, the process might be deduced as follows [NB (CgHjo) denotes the 1,4-cyclohexyl moiety in the polymer backbone]  

an hydroxyl end may also undergo either of these two types of reaction  

It is thus anticipated that the small-molecule breakdown products will be l,4-bis(methylene)cyclohexane and 4-methylenecyclohex-anemethanol. Such by-products have been found in the pyrolysis of the copolymer poly(ethylene- o-l,4-cyclohexylenedimethylene terephthalate) [87]. 

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Photodegradation and Oxidation of Other Poly(alkylene terephthalate)s... 

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