Abstract: In this paper, HSPET (high shrinkage polyethylene terephthalate), COPEET(copolyether-ester) and commercially available PTT (polytrimethylene terephthalate) or PET(polyethylene terephthalate) and PA6(polyamide 6) were used for manufacturing side-by-side bicomponent fibers, and the effects of forming process on the structure and properties of the fibers were studied. It then discussed the mechanisms for the formation of the elasticity of the fibers: the good compatibility of the two components is the necessary condition for forming three dimensional crimps; the big thermal shrinkage difference between the two components is originated from the different orientations and crystal structures of the two; draw-setting process is an important means for forming the above-mentioned structural differences;controlling "dumbbell" cross section structure of the bicomponent fiber is an important way for obtaining best elasticity; while suitable heat treatment conditions can give the optimum fiber elasticity.

Key words: side-by-side bicomponent fibers; structure control; properties; mechanism for the formation of elasticity