THE MECHANICAL PROPERTIES OF POLYETHER-COPOLYESTER ELASTOMERS

Abstract

Polyether-copolyester block copolymer (T/i_??_Ph-E1540), in which the aromatic homopolyester (T) usually serves as the hard segment (the crystallizable parts of chains) were replaced by the aromatic copolyester (T/i_??_Ph), were synthesized.In this case, since the replacement of the hard segment depressed the rates of the growth of their crystallites and caused their crystallinity to decrease, the lowering of the fiber-strength was presupposed. It was suggested that this lowering would be compensated by increasing of the quantity of the hard segment.The purpose of this work was to investigate how the above mentioned replacement by the copolyester hard segment and compensation by the increment of the hard segment ratio affected the mechanical properties of block copolymers.The results obtained were as follows:1) As for the melt-spun fibers (T/i_??_Ph-E1540 [50/50]), since the ratio of i_??_Ph increased, their tensile strength and Young's modulus tended to become lower and elasticity greater.2) The melt-spun fibers whose i_??_Ph ratio ranging from 15.0 to 17.5 wt% exhibited the mechanical properties superior to those of T-E1540 [40/60].3) For the X-ray diagrams of the drawn and heat-treated fibers, the apparent degree of crystallinity of the hard segment in T/i_??_Ph (82.5/17.5)-E1540 [50/50] was nearly equal to that of T-E1540 [40/60] when their strengths of the interference spots on the equator of the diagram were compared with one another. The particle sizes of crystallites of the former, calculated from the breadth in radians of the diffraction interference at points of half-maximum intensity, were smaller than those of the latter.4) Further, on the particle sizes, the results observed under the polarizing microscope had the same tendencies as those described in (3), and the uniform dispersion of crystallites of T/i_??_Ph (82.5/17.5)-E1540 [50/50] within the soft segment matrix was also recognized.