Blending water-soluble aliphatic-aromatic copolyester in starch for enhancing the adhesion of sizing paste to polyester fibers

In this paper, an attempt has been made to ameliorate the adhesion of starch to polyester fibers for warp sizing. The amelioration was achieved by blending newly developed water-soluble aliphatic-aromatic copolyester (WSACP) in starch because the copolymer had been proved to possess better biodegradability than pure aromatic polyester. The attempt was focused on the determination of the molar ratio of aliphatic units incorporated into WSACP, the amount of WSACP blended, and the analysis of experimental observations from viewpoints of adhesion theory. The adhesion was evaluated in terms of tensile strength and work-to-break by using a slightly sized polyester roving method. It was observed that the adhesion depended markedly not only on the molar ratio of aliphatic units to aromatic ones but also on the amount of WSACP blended in starch. With the increase in the ratio, the adhesion did not show much sensitivity to the adhesion until the ratio equaled 30:70. This means that incorporating a certain amount of aliphatic units into water-soluble polyester does not greatly influence the adhesion. However, the adhesion decreased significantly when the ratio exceeded 30:70. Hence, it can be concluded that the molar ratio of aliphatic units to aromatic ones should be 30:70 in consideration of biodegradability and adhesion. In addition, the adhesion increased as the amount of WSACP blended in starch increased initially. However, excessively increasing the WSACP content reduced the adhesion. The strongest adhesion was observed at a 10% (w/w) WSACP content.