Permeation through polymer latex films

Chainey, M., 1984. Permeation through polymer latex films. PhD, Nottingham Trent University.

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The permeation characteristics of films formed from polymer latices have been studied. Three areas of work were involved, namely preparation of polymer latices, preparation of films from these latices and determination of the film permeabilities.

A wide range of polymer latices were produced by surfactant-free emulsion polymerisation, which is known to produce a monodisperse product of controllable particle size. The kinetics of the styrene reaction were determined and compared with the predictions of several published theories.

Film forming core-shell latices were prepared by a novel 'shot-growth' technique, in which the core particles are polymerised in situ. This technique was found to produce a monodisperse product at a lower number density of core particles than required by conventional seeded growth techniques.

A freshly prepared latex contains impurities such as unreacted monomer and reaction biproducts. The traditional methods of purification, namely dialysis and ion-exchange are inefficient in the removal of some of these impurities, and can lead to further contamination. The microfiltration technique devised during this study proved to be rapid and efficient in removing contaminants.

Several techniques for preparing thin films from polymer solutions or latex dispersions reported in the literature were evaluated. After extensive trials all were rejected, as the minimum thickness of film which it was possible to cast was at least an order of magnitude larger than that required. A flash casting technique was devised and successfully employed to prepare a wide variety of thin films. Polymer films prepared by this method were characterised by scanning electron microscopy.

The gas permeabilities of homopolymer films cast from solution and latex dispersions were measured. The permeabilities of solvent cast films remained constant for the period of several months over which they were examined. The permeability coefficients of most latex films started off at a value considerably higher than that of the corresponding solvent cast film and then dropped at a rate dependent on the polymer concerned. This reduction is attributed to ageing processes occurring within the film after casting. Latex film permeability coefficients are always higher than those of solvent cast films, and this suggests that latex films never become completely homogeneous.

The permeabilities of heterogeneous films cast from blends of two homopolymer latices and from core-shell latices also diminish after casting. The rate and extent of this reduction decreases with increasing content of hard, undeformable dispersed phase.

Item Type: Thesis
Creators: Chainey, M.
Date: 1984
ISBN: 9781369325713
Divisions: Schools > School of Science and Technology
Record created by: Laura Ward
Date Added: 08 Jul 2021 08:44
Last Modified: 22 May 2024 14:13

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