Gelation and hardening mechanisms in a model polyester resin and related systems

Grieveson, Brian M (1957) Gelation and hardening mechanisms in a model polyester resin and related systems. PhD thesis, University of Glasgow.

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Widespread industrial use of unsaturated polyester "contact" resins has led to speculation concerning the mechanism of their hardening reaction, Model compounds for the commercial polyesters were therefore prepared, and their hardening reaction with methyl methacrylate was studied using an original combined viscometer-dilatometer. Investigations into the effect of variations in the amount and type of free radical initiator showed that the gelation of the model system occurred through a conventional addition copolymerisation between the two types of unsaturation present, and also provided confirmation for the proposed kinetic scheme for the pre-gelation reaction mechanism. Preliminary investigations were made into the change in the reaction rate curve in the region of the gel point when passing from a linear to a related polyfunctional (non-linear) polymerisation, and a theoretical explanation is given for the sharpening of the gradual rate increase into a definite kink occurring at the gel point. Infrared examination of the model polyesters prepared from maleic anhydride showed that almost complete isomerisation of the unsaturated linkage from the cis to the trans form took place during the polycondensation reaction. The final stages in the curing of a polyester resin, which are of direct technical interest because of their effect on the high temperature properties of laminating resins, were studied using a ball rebound relaxation technique which produced mechanical "spectra" of the polymer. Second order transition phenomena were shown to give rise to strong absorption peaks, the positions of which were used to follow curing reactions. An "isoelastic rate principle" is proposed for the final decay of the curing rate based on the supposition that curing mechanisms in this phase of the reaction are diffusion controlled relaxation processes. The applicability of the principle to resin systems in general was successfully illustrated by experiments on a base-catalysed epoxide system and an acid-catalysed urea-formaldehyde polycondensation as well as on the vinyl copolymerisation of the model polyester. Observations were made on the relationship between the final state of cure reached in the model polyester system and its original composition. Incidental measurements involved in the evaluation of the ball rebound relaxation technique led to the detection of unusual characteristics in the melting behaviour of linear polyethylenes and isotactic polypropylenes.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: M Gordon
Keywords: Polymer chemistry, Plastics
Date of Award: 1957
Depositing User: Enlighten Team
Unique ID: glathesis:1957-72523
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06

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