Abstract
Several methods were explored for characterizing sized yams and size films in order to establish relationships that might be useful in predicting weaving performance. A variety of natural and synthetic sizes were applied to cotton and to polyester/cotton spun yams in a laboratory sizing apparatus. Although yam tensile tests indicate that sizing generally increases yam strength and decreases yarn extensibility, these tests were inadequate for differentiating among sizing agents. Important differences among the various sizes and levels of size add-on could, however, be detected by measuring rupture lifetimes of the treated yarns using the TRI cyclic tensile abrader, which imposes simultaneous tensile, bending, and abrasive stresses.
Two factors appear critical to size performance: the size must form a tough but flexible film to protect the yam from flexing and rubbing actions, and there must be good adhesion between size and yam. The flexibility requirement was established by correlating the tensile behavior of films prepared from the various size polymers with rupture lifetimes of the sized yams. The degree of adhesion was evaluated by measuring the wettability of the size films, using an adaptation of the Wilhelmy wetting force method, and matching the resulting contact angle hysteresis patterns.
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