Charge separation associated with contact charging between polymers

Magezi, Daudi Subi (1980) Charge separation associated with contact charging between polymers. University of Southampton, Doctoral Thesis.

Abstract

Experimental investigations have been carried out on the polarity and magnitude of the charge transferred after multiple contacts between 1W different pairs of commercial polymers. Equilibrium contact angles between the 10 different polymer samples and a selection of pure organic liquids were determined. The surface energy value of a given polyner sample was obtained from a graphical plot of the cosine of the equilibrium contact angle versus the surface tension of the liquid and applying the Zisman relationship. The polymer samples were arranged in order of decreasing surface energy values. It was observed that the middle order neighbouring polymers were very close in surface energy values. A contact charging series was arranged such that a given polymer making multiple contacts with another polymer above it in the series charged negative. It charged positive after making multiple contacts with another polymer below it in the series. A few pairs did not obey this rule, including those whose members had been cut from the same polymer. Causes of the inconsistency were contributed to, inter alia, the relative humidity of the experimental conditions, the observed closeness in the surface energy values and a second order effect. An interesting relationship was observed between the arrangement of the polymer, surface energy values, and the contact charging series. This meant that the polarity of the charge transferred between 2 dissimilar commercial polymers after successive multiple contacts could be determined by a consideration of the surface energy values. The hi & pr surface energy polymer tended to charge positive with respect to the lower surface energy polymer. The magnitude of the charge transferred seemed not to depend on the position of a polymer in the series. It varied a great deal. It was also observed that provided experiments are performed with reasonable amount of care and following reasonable surface-cleaning, the hitherto widely believed need to perform experiments in vacuum was not essential. Attempts were made to correlate some of the authors' results with results published by manufacturers as the true nature of a polymer surface depends on the manufacturer's specification of colour, grade, finish, additives used, etc. it became evident that in situ measurements had to be done on all samples before generalisations can be made on the correlation.

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