Electric resistivity of hydroscopic copoly(ester‐ether)s containing zwitterionic units and their utilization for antistatic modification of polyester fiber

Block copoly(ester‐ether)s containing different ionic units, i.e., sulfobetaine (S‐betaine), carbobetaine (C‐betaine), and ammonium tosylate, were prepared and evaluated as antistatic modifiers of PET fiber. The ionic units were readily derived from N,N‐bis(2‐hydroxyethyl)methylamine and co‐condensed randomly with the polyester and poly(oxyethylene) (PEO) units. For the copolymers containing S‐betaine units, a thick filament was melt‐spun to evaluate their apparent electric resistivity. Depending on the unit compositions (25–75 wt.‐% of PEO and 1–2 mol‐% of S‐betaine), resistivities ranging from 10 8 to 10 10 Ω cm ‐1 were obtained. Then, the three copolymer‐type modifiers were blended with poly(ethylene terephthalate) (PET) by the ordinary blend‐spinning technique. The blend PET fibers obtained showed not only good mechanical properties, but also improved antistatic properties. Particularly, the fiber blended with the copolymer containing S‐betaine units had the shortest half‐life time of leakage of static charge, although the surface area resistivity, being in the order of 10 13 Ω cm ‐2 , was similar to that of the fibers blended with the copolymers containing C‐betaine and ammonium tosylate units. These blend PET fibers were found to retain good antistatic properties even after dyeing and repeated washings, because both the hydrophilic and ionic groups are immobilized with the polyester chains.