Thermal Degradation of Copolymers of Vinyl Acetate and Vinyl Chloride

McLaren, Ian F (1967) Thermal Degradation of Copolymers of Vinyl Acetate and Vinyl Chloride. PhD thesis, University of Glasgow.

Abstract

Thermal degradation of polymeric materials may take place in two general ways. The first way is by splitting off monomer units or several monomer units joined together. The second, and that found in the breakdown of poly (vinyl acetate) and poly (vinyl chloride), is loss of side groups to leave conjugated polyene sequences. In the first chapter of this thesis, the previous work done on the degradation of poly (vinyl acetate), poly (vinyl chloride) and copolymers of vinyl acetate and vinyl chloride is discussed in terms of the possible mechanisms. The polymers used in the work described in this thesis were prepared by standard methods and the copolymerisation of vinyl acetate sad vinyl chloride was studied before polymers, for degradation, were prepared. The ratios of vinyl acetate to vinyl chloride in the copolymers were determined by nuclear magnetic resonance spectroscopy The degradation of the polymers was studied firstly in the solid phase and later in solution. The degradations in solution were initially performed in ethyl benzoate and later in tri-toluyl phosphate. The reason for this is that the kinetics of the degradations in ethyl benzoate are dependant almost entirely upon the retention of the acetic acid produced in the degradation. This seems to cause a very marked acceleration of the degradation. The degradations in tritoluyl phosphate solution showed the same relative stabilities of the copolymers as was found in the solid phase. Further investigations in this medium were carried out with the object of investigating the discolouration of the copolymers and the energy of activation of degradation The rate of discolouration was found to be minimum at 10% VA and 10% VC and at a maximum at 50% to 75% VC. The energies of activation have a general tendency to increase from PVC to PVA with a slight drop around 50% VC. The effects of the reaction product and oxygen on the rate of degradation are demonstrated. The results found are discussed and a mechanism for degradation is postulated* This involves mainly an activation of VA groups by adjacent VC units and then allylic activation by the double bond so formed. The cross linking reaction is postulated to be a polyene condensation reaction. The controversy of the radical versus non-radical argument for the degradation of PVC is not resolved but it is concluded that the true mechanism of degradation of PVC is probably a mixture of each, the predominance depending upon the conditions. Finally, possibilities, for future work are presented and the possible outcome discussed.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Polymer chemistry, Organic chemistry, Physical chemistry, Thermodynamics
• Date of Award: 1967
• Depositing User: Enlighten Team
• Unique ID: glathesis:1967-78444
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 28 Feb 2020 12:09
• Last Modified: 28 Feb 2020 12:09
• URI: https://theses.gla.ac.uk/id/eprint/78444