CRYSTALLINE TRANSFORMATIONS AND MECHANICAL PROPERTIES OF POLYOLEFIN FIBERS

Abstract

Mechanical properties of fibers and films of isotactic polybutene-1 and its copolymers were studied in relation to the crystalline transformation of the Form II to Form I.No difference in the tensile strengths of fibers and films was recognized for the both crystalline forms, but there is a remarkable difference in the tensile elongation. Polybutene-1 fiber of the Form II shows much more drawability than that of the Form I. It is known that molecular and crystalline orientations in polybutene-1 fiber are more affected by drafting in melt-spinning than by drawing after spinning on account of accelerated transition due to drafting of the Form II to Form I.An interesting feature of the copolymers of butene-1 with 3-methyl-1-butene or 4-methyl-1-pentene is an ability to cocrystallize in type of the Form II of polybutene-1. Though it is known that the Form II of butene-1 homopolymer is less stable at room temperature than the Form I, it was found that the Form II of those copolymers is stablized owing to incorporation of those comonomer units into the crystal lattice of the Form II. Therefore, it is expected to improve the adverse properties such as the difficulty of drawing after spinning and the devitrification caused by crystal transition of polybutene-1 without lowering of its melting point, tensile strength and flexibility.