Structure and Properties of Low-Isotacticity Polypropylene Elastomeric Fibers Prepared by Sheath-Core Bicomponent Spinning: Effect of the Composition of Sheath Layer with Constant High-Isotacticity Polypropylene Content

摘要

Development of metallocene catalyst provided the technologies for producing new types of polyethylene (PE) and polypropylene (PP). Based on this technology, PPs with controlled low-isotacticity (LPP) has been developed and applied for the production of elastomeric fibers. However, difficulty arose in the spun-bonding process of non-woven fabrics consisting of the LPP fibers because of its low crystallizability. With the aim of improving the processablity, melt spinning of sheath-core type bicomponent fibers was performed in this research using the blend of LPP and ordinary high-isotacticity polypropylene (IPP) as the sheath component and pure LPP as the core component. The prepared as-spun fibers with IPP content of 10 wt% in the sheath showed elastomeric property with reasonably good elastic recovery of higher than 85 wt%. The elastic recovery showed slight reduction with the increase of sheath layer composition from 0 to 50 wt%, which corresponds to the increase of total IPP content from 0 to 5 wt%. Tensile modulus and tensile strength of the as-spun bicomponent fibers increased significantly with the increase of total IPP content. Structural analyses of as-spun fibers consisting of LPP and IPP revealed that the crystallization of IPP component was enhanced especially when the composition of sheath component was low while that of LPP was suppressed significantly with the increase of the total IPP content. These results suggested the high modulus of sheath component in the fibers with low sheath layer composition.