Abstract
The crystallization and crystalline structure of syndiotactic-polypropylene (sPP) and syndiotactic-poly(1-butene) (sPB) blend containing 10 (Bl-10), 25 (Bl-25), 50 (Bl-50), 75 (Bl-75), and 90 (Bl-90) wt% of sPB, have been investigated by means of differential scanning calorimetry (DSC), FT-IR, and wide-angle X-ray diffraction (WAXD) analyses. The melt-crystallization behavior of the blend samples was studied by DSC on the cooling process at constant rates. Bl-50, Bl-75, and Bl-90 showed lower crystallization temperatures than the neat sPP. sPP in Bl-75 showed the lowest crystallization rate among the blend samples. Bl-90 showed a two-phase molten state, and sPP in Bl-90 crystallized via two-stepprocess. Time evolution of FT-IR spectroscopy at room temperature detected conformational transformation of the sPP polymer chain in the blend samples of Bl-50 and Bl-75. The absorption peaks intensity in the FT-IR spectra derived from the helical conformations in the crystalline phase decreased, and the planar zigzag conformations in the amorphous and mesophase phases decreased over the crystallization time. The time evolution of the WAXD profile of Bl-90 indicated that sPP in the blend accelerated the crystallization of sPB. The crystallized Bl-10, Bl-25, and Bl-50 samples showed diffraction peaks in WAXD profiles and melting endothermic peak in DSC profiles derived from only the sPP crystal. The crystallinity and melting temperature of sPP in the crystallized Bl-10, Bl-25, and Bl-50 samples were almost independent of the sPB content. Both the crystalline structure of sPP and sPB were detected in Bl-75 and Bl-90. Bl-75 showed the lowest crystallinity and melting temperature of sPP among the blend samples.
Highlights
Development of transition metal catalysts for olefin polymerizations has enabled us to synthesize highly syndiotactic poly(α-olefin)s with narrow molecular weight and composition distributions [1]
The crystallization process of such as polypropylene (sPP) in the blend samples was traced by the differential scanning calorimetry (DSC) measurement from 180 ̊C to 20 ̊C on the constant cooling rate of 3, 6, 12, or 24 ̊C/min
The crystallization and crystalline structure of the sPP-sPB blends were successively investigated with the wide-angle X-ray diffraction (WAXD), DSC, and FT-IR measurements
Summary
Development of transition metal catalysts for olefin polymerizations has enabled us to synthesize highly syndiotactic poly(α-olefin)s with narrow molecular weight and composition distributions [1]. The syndiotactic-poly (α-olefin)s, such as polypropylene (sPP), poly(1-butene) (sPB), poly(1-pentene), poly(1-hexene), poly(1-octene), poly(4-methyl-1-pentene), and poly(4-methyl-1-hexene), are of the polymers that can be obtained with Cssymmetrical syndio-selective metallocene catalysts [2] [3]. The syndiotactic-poly(propylene-co-olefin)s (olefin = ethylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene) were synthesized by a syndio-selective zirconocene catalyst, and the crystalline structure of the copolymers were studied [23] [27]. A (t2g2) conformation in the orthorhombic unit cell of both the sPP and sPB crystals should make possible existance of the 1-butene units in the sPP crystalline phase. This phenomenon is regarded as isomorphism [33]. We investigate the crystallization of sPP-sPB blend from melting, and study the effect of sPB content on the crystallization behavior and crystalline structure of the blend samples
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