Volume-14 (09/2006)

Methods for Wettability Determination on Hydrogel

The measurement of surface properties and wettability of hydrogels, such as soft contact lenses and a variety of sol-gels, can be very difficult. The difficulties stem from the ability to measure wetting on a wetted surface as well as the probability of drying, and thus the changing of surface properties, as an experiment proceeds. Methods for determining wettability on such samples are described below, using either an environmental chamber or a captive bubble arrangement for measuring contact angles with water.

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How plastics lose their hydrophobia

Wetting problems of plastics with aqueous systems are countered by selective surface pretreatment, such as ozonization; this has the effect of polarizing the surface and thus giving it a greater affinity for polar solutions and dispersions. The effectiveness of the treatment and the influence of its duration have been quantified for the two plastics POM and PBTP by using surface free energy determinations obtained with the DSA100 contact angle measuring system.

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