Poly contact angle with various liquids

The effect of ultraviolet irradiation in air on the wettability of thin films of amorphous polymers has been studied. With poly(vinyl chloride), poly(methyl methacrylate), poly(n-butyl methacrylate), poly (ethylene terephthalate), and polystyrene the changes in contact angles for various liquids with irradiation time are a function of the nature of the polymer. A detailed study of polystyrene by this technique and attenuated total reflectance spectra, both of which are sensitive to changes in the surface layers, indicates that the contact angle method is one of the most sensitive tools for the study of polymer photooxidation in its early stages. The method is useful in following specific processes and in indicating solvents to be used in the separation and isolation of photooxidation products. 

The effect of UV radiation in air on the wettability of thin films of polyvinyl chloride (Fig. 10.106) poly(methyl methacrylate), poly(n-butyl methacrylate), poly(ethylene terephthalate) and polystyrene (Fig. 10.107) show that the changes in contact angle for various liquids with irradiation time are a function of the nature of the polymer [667]. 

Figure 2. Contact angle changes with various liquids on a film of poly (methyl methacrylate) irradiated in air...

Fig. 10.106. Contact angle 0) changes with various liquids on a film of poly(vinyl chloride) irradiated in air [667]. (Reprinted with permission from [667]. Copyright (1968) American Chemical Society.)...

This report is concerned with contact angle hysteresis and with a closely related quantity referred to as "critical line force (CLF)." More particularly, it is concerned with the relationship between contact angle hysteresis and the magnitude of the contact angle itself. Two sets of liquid-solid-vapor systems have been investigated to provide the experimental data. One set consists of Teflon [poly(tetrafluoroethylene), Du Pont] and a series of liquids forming various contact angles at the Teflon-air interface. The second set consists of polyethylene and a similar series of liquids. In neither case was the ratio of air to test liquid vapor at the boundary line controlled, but it can be assumed that the ambient vapor phase operative in all the systems was close to an equilibrium mixture. 

Poly(vinylidene Chloride) Copolymer. Contact angles observed on poly(vinylidene chloride) copolymer surfaces prepared by solvent evaporation are given in Table IV, along with the values obtained on highly polished surfaces of compressed disks of the additive-free powdered polymer. Values of 9 exhibited by the various liquids on each type of... 

Instead of determining the interfacial tension of a solid polymer with respect to a low-molar-mass liquid and then calculating the value of 7 v for the solid polymer from the surface tension, 7/v, of this liquid and the measureable contact angle d, the interfacial tensions of the molten polymer with respect to this liquid can be measured at various temperatures and the calculated ysi values can be extrapolated back to a temperature at which the polymer is solid. The method is not above suspicion, since the extrapolation may have to be carried out over a considerable temperature range and the surface structures of the molten and solid polymer are not necessarily identical. Such influences are apparent, for example, in the contact angles of molten polymers on solid polymers the contact angle of molten poly(butyl methacrylate) on solid poly(vinyl acetate) is equal to zero, but the contact angle of molten poly(vinyl acetate) on poly(butyl methacrylate) is 42°. 

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