The degradation of polymers and related model compounds

Sharpe, Hillary M (1962) The degradation of polymers and related model compounds. PhD thesis, University of Glasgow.

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This work describes the investigation of the physico-chemical aspects of the thermal degradation of PTC and related short-chain compounds (telomers). The latter, made with a chain transfer agent such ae bromotrichloromethane, consist of either one or two molecules of vinyl chloride joined to a molecule of bromotrichloromethane e.g. Cl3C-CH2-CHCl-CH2-CHClBr A system has been devised whereby the rates of degradation of these polymers and telomers can be followed empirically by titrating the quantity of acid evolved against standard alkali. The major processes occurring in the degradation of PTC are bromotrichloromethane and cross-linking, found to be first and second order processes respectively. Cross-linking is thought to be a random process of condensation between molecules, the rate at which it proceeds being dependent on such variables as polymer concentration and chain length. Dehydrochlorination is believed to commence at the chain ends, "sipper" down the chain and terminate at a cross-link. It is dependent on polymer concentration but not on chain length. Of the two processes, it is energetically easier for cross-linking to occur. There is no evidence to suggest that the degradation of the polymer is free radical in nature as is believed by some workers. In a parallel study on model compounds of PVC, the major factor influencing the pyrolysis was the reactivity of the -CCl3- group. Due to this reactivity no true comparison could be made between these compounds and the high polymer although breakdown rates for the telomers are of the same order as those for the cross-linking of PYGs indicating that intermolecular condensation is occurring between telomer molecules. The latter is thought to causes polymer formation. There is no reason to suppose that the decomposition of these compounds is free radical, although the breakdown may be partially ionic in character.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: W I Bengough
Keywords: Polymer chemistry
Date of Award: 1962
Depositing User: Enlighten Team
Unique ID: glathesis:1962-73317
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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