50 research outputs found
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Novel poly(butylene terephthalate)/poly(vinyl butyral) blends prepared by in situ polymerization of cyclic poly(butylene terephthalate) oligomers
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Miscibility and phase behavior in blends of poly(vinyl butyral) and poly(methyl methacrylate)
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Miscibility and morphology of blends of poly(3-hydroxybutyrate) and poly(vinyl butyral)
The miscibility and morphology of blends of biodegradable poly(3-hydroxybutyrate) (PHB) and poly(vinyl butyral) (PVB) were studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). PHB is a semi-crystalline polymer while PVB can be regarded as a random copolymer containing vinyl butyral (VB) and vinyl alcohol (VA) units whose composition ratio can be systematically changed over a wide range. DSC measurements show two Tgs in the amorphous phase for all PVB and PHB blends, indicating phase immiscibility. However, partial miscibility was observed in 50/50 w/w blends containing PVBs with 25-36 wt% VA content, demonstrated by the inward shift of the Tgs of the two phases relative to those of the neat components. This shift exhibits a maximum value around 31 wt% of VA in PVB. The segmental interaction parameters XvA.HB, XvB,HB and Xv A.VB were determined and the copolymer composition dependence of the overall interaction parameter between PVB and PHB, x12, was then calculated. This parameter shows a minimum around 31 wt% VA content, consistent with the experimental data. The presence of a minimum can be interpreted in terms of a copolymer effect in which the unfavorable interaction between PVB and PHB is minimized at a certain copolymer compositions due to the repulsive intramacromolecular interaction between VA and VB units within the PVB chains. The composition manifesting minimum immiscibility was also consistent with the melting temperature (Tm) depression and a minimum in the fractional crystallinity of the PHB phase in the blends around this VA content. A co-continuous morphology was observed in the blends containing 25-33 wt% VA content PVBs, which might well result from more favorable interactions between the two component polymers at this copolymer composition
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End-group effect on chain conformation of poly(propylene glycol) and poly(ethylene glycol)
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SEGMENTED POLYURETHANE ELASTOMERS WITH LIQUID-CRYSTALLINE HARD SEGMENTS .2. INFRARED SPECTROSCOPIC STUDY
Segmented liquid crystalline polyurethanes (LCPUE) have been studied by infraredspectroscopy. The nematic liquid crystalline hard domains act as physical cross-links and can be orientedby the application of mechanical strain. The orientation function achievable in the hard segments resultsfrom the combination of mechanical strain and stress-softening. Furthermore, elastic deformation inducesthe rearrangement of some hard segments in the mesophase into a more ordered packing. Hightemperatureinfrared spectra have been correlated with thermal transitions of the LCPUE, and a liquidliquidmicrophase-separated morphology above the isotropization of the mesophase appears to exist
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SEGMENTED POLYURETHANE ELASTOMERS WITH LIQUID-CRYSTALLINE HARD SEGMENTS .3. INFRARED SPECTROSCOPIC STUDY
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FOURIER-TRANSFORM RAMAN-SPECTROSCOPIC STUDY OF A POLY(PROPYLENE OXIDE)-BASED MODEL NETWORK ELECTROLYTE
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APPLICATION OF A MOLECULAR SIMULATION TECHNIQUE FOR PREDICTION OF PHASE-SEPARATED STRUCTURES OF SEMIRIGID MODEL POLYURETHANES
Effects of catalyst and polymerization temperature on the in-situ polymerization of cyclic poly(butylene terephthalate) oligomers for composite applications
ABSTRACT: The in-situ polymerization at different polymerization temperatures, and the crystallization behavior of cyclic poly(butylene terephthalate) oligomers, using various process-suitable catalysts, are investigated in this paper. The choice of the catalyst has a large effect on the polymer conversion and the time required for polymerization, as studied by light transmittance measurements. The resulting polymer is characterized by GPC for molecular weight and polydispersity and by WAXD and DSC for crystal morphology. SALS is used for in-situ observation of the melt crystallization during polymerization. 1