Structure and Properties of Low-Isotacticity Polypropylene Elastomeric Fibers Prepared by Sheath-Core Bicomponent Spinning

Structure and properties of low-isotacticity polypropylene elastomeric fibers prepared by sheath-core bicomponent spinning: effect of localization of high-isotacticity component near the fiber surface

“…The tensile modulus decreased with the increase in the sheath layer composition and with the decrease of sheath IPP content. In a previous paper [23], it was found that there was a quantitative accordance between the variation of contraction ratio after spinning and the variation of tensile modulus of the as-spun fibers with the change of sheath layer composition. This was because the higher tensile modulus corresponded to the lower degree of elastic stretching in the spin-line.…”

“…By contrast, in our previous paper on the sheath-core bicomponent melt spinning of the blend of IPP and LPP with the constant IPP content of 10 wt% as the sheath and the pure LPP as the core [23], it was speculated for the mechanism of the formation of highly oriented α form crystals in the core that even though crystallization of the IPP component in the blend started to occur at higher temperatures, deformability of the blend could be maintained because the content of IPP was only 10 wt%, and accordingly orientation of the core component, LPP, could proceed in the spin-line. In this research, highly oriented α form crystals were formed in the core even when the IPP content in the blend was increased up to 40 wt%, suggesting that the deformability of the blend of IPP and LPP was maintained after starting the crystallization of the IPP component in the spin-line, even at such a high IPP content.…”

“…In the bicomponent melt spinning of the LPP and the blend of IPP and LPP, enhancement of the structure formation of the blend can be expected because of its higher crystallizability. Such an effect becomes more significant for the sheath or core component with lower composition [23].…”

“…Fiber samples were prepared at the take-up velocity of 2 km/min. In a previous paper, sheath IPP content was kept constant at 10 wt% while sheath layer composition was varied from 0% to 50% [23]. Accordingly, total IPP content was changed from 0 wt% to 5 wt%.…”

“…In a previous paper, we investigated the effects of sheath/core composition on the high-order structure and mechanical properties of elastomeric bicomponent fibers consisting of LPP as the core component and the blend of LPP and IPP as the sheath component, in that the sheath layer composition and the total IPP content were varied, while keeping the IPP content in the sheath layer constant at 10 wt% [23]. Through the analyses of the as-spun bicomponent fibers, it was found that the as-spun fibers exhibit a relatively large elastic recovery of higher than 85%, and that the crystallization of IPP was enhanced when the sheath layer composition was low, while the crystallization of LPP was suppressed with the increase in the sheath layer composition.…”