Polystyrenes wettability measurements

Once laid, the polystyrene films were further purified by exhaustive extraction with methanol or n-heptane the progress of extraction was followed by the ultraviolet spectra of the extracts. These preirradiation extractions showed considerable variation in purity among the three polystyrenes in spite of reprecipitation measures. The degree to which solvents can remain with a 20/ film is suggested by the need of seven days of continuous methanol or n-heptane extraction to remove all of the extractable benzene from a film laid from that solvent and dried in vacuum at 65°C. for 24 hours. For film laid from methylene chloride, an optically clean n-heptane extract was obtained from the AIBN-ini-tiated sample within a few hours, but up to 48 hours were required for the benzoyl peroxide-initiated samples. The extracted 20/ polystyrene films were essentially non-absorbing above 285 m/, no absorption attributable to material other than polystyrene could be observed, and only one peak (337 m/ ) was seen in the fluorescence spectrum in methylene chloride. Once the films were purified by extraction, the products and wettability changes resulting from irradiation were the same for all polystyrene samples and were independent of the solvent from which the films were laid. 

Compatibility of polymers implies a semi-quantitative measure can be used to predict whether two or more polymers are compatible. The use of one of the semi-quantitative approaches, solubility parameter, was demonstrated by Hughes and Britt (22). It was concluded (8) that one parameter was insufficient to predict the compatibility. In this paper, we now introduce critical surface tension which is determined from the surface properties of a polymer. Though both of these parameters have been related by Gardon (15), we are inclined to use the latter because we can further describe the wettability between two polymers. For instance, by the use of yc, we can predict equally well that compatibility between polystyrene and polybutadiene can be improved if butadiene is... 

Assuming that there exists an equilibrium contact angle < %I2 for polystyrene on the non-wettable patches, then there exists a maximum amount of polystyrene which can be deposited on these patches. A deposited drop has the shape of a spherical cap with a circular base of diameter 2a and a height H. The volume of such a cap is then V = n-H + fF)I6. For small values of 0 (we have measured values of 0 0.1), we can approximate the height H of the cap hy This... 

A wettability change on the surface of polystyrene with triphenylmethane leucohydroxide was measured after UV irradiation. The contact angle with water (cos 0) increased from 0.2 to 0.8. The change in wettability induced by irradiation is due to the enhanced hydrophilic nature of the film surface brought about by the ionic dissociation of the chromophores. 

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