Measuring the Contact Angles of Liquid Droplets on Wool Fibers and Determining Surface Energy Components

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Abstract
Contact angles of various liquids on wool fibers are measured using the liquid droplet method. A computational technique greatly simplifies contact angle calculations. Sur face energy components of differently treated wool fibers are determined from the contact angle data using current theories of surface energy. Values for the surface energy of wool fibers calculated using the equation of state and the geometric-mean equations show a dependence on the kind of liquid used. Calculations based on the acid-base approach give more consistent results, but for wool fibers with high polar components, reliable results are obtained only with particular liquids. Untreated wool fibers are weak γ- monopoles. Wool fibers set in steam have a higher γ LW and γ+, with the γ - remaining unchanged. Chlorination changes wool fibers to bipolar solids with substantial increases in γ LW,γ+, and γ-.