A kinetic study of the hardening reaction of a model unsaturated polyester resin

McMillan, Ian D (1957) A kinetic study of the hardening reaction of a model unsaturated polyester resin. PhD thesis, University of Glasgow.

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The hardening mechanism of polyester "contact" resins is investigated with reference to a model system, methyl methacrylate/polyethylene fumarate (MMA/PEP), These reagents are completely compatible without the addition of any complicating factors. The preparation and characterisation of the PEP resin are described. The gelling characteristics of this system are investigated using a new viscometer-dilatometer (visco-dilatometer) technique for following polymer reactions The gel time and rate of polymerisation are investigated over a range of monomer feed ratio (PEF/MMA), catalyst concentration, temperature and degree of polymerisation of the initial polyester. Experimental points for the dependence of the gel time on the feed ratio and initial chain length are compared with theoretical curves for the gel time derived from classical gelation theory The gel time is found constant regardless of the catalyst concentration because, on the classical gelation behaviour, an increase in polymerisation chain length cancels out the effect of the increase in rate on gelation. This constancy of the gel time confirms that the reaction is a simple copolymerisation, The effect of temperature on both the rate and gel time is in accordance with the classical gelation theory. The direct determination of the main kinetic parameters, namely the reactivity ratios of the two monomers (MMA and PEP) is accomplished roughly by a technique of extracting the cross-copolymer formed by solvent extraction of the gel. The "network" polymer obtained is analysed by a density technique microanalysis and microhydrogenation to evaluate the monomer reactivity ratios. These techniques allow the bracketing of the values of the values rM and rF within a range which lies close to the values demanded by the theoretical treatment of the gel point. The investigation is extended beyond the gel point where a sudden increase in the polymerisation rate is observed. This gel effect is explained by the assumption of a model where the initial reaction constants remain constant but changes in the effective radical concentrations due to diffusion control lead to a decrease in the termination reaction. This Troramsdorf effect at the ge1 point is only observed in systems where the primary polymerisation chain is sufficiently large. Con-plete rate curves for the system, obtained by a combined dilatometer density tube technique are presented, showing the transition to the third stage of the reaction when both the initiation and propagation steps become subject to diffusion control. The polymerisation stops at approximately the same degree of cure or mobility irrespective of the feed ratio A preliminary theory for the state of cure is put forward in terms of three parameters: the concentration of crosslinks, the concentration of residual methylmethocrylate, and the concentration of residual free polyethylene fumarate chains.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: P D Ritchie
Keywords: Polymer chemistry, Plastics
Date of Award: 1957
Depositing User: Enlighten Team
Unique ID: glathesis:1957-73557
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: http://theses.gla.ac.uk/id/eprint/73557

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