SEM and FT-IR investigation of bulk crystallized TPI and its epoxidized copolymers.
Item
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Title
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SEM and FT-IR investigation of bulk crystallized TPI and its epoxidized copolymers.
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Identifier
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AAI9405593
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identifier
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9405593
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Creator
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Vasanthan, Nadarajah.
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Contributor
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Adviser: Arthur E. Woodward
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Date
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1993
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Physical | Chemistry, Polymer
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Abstract
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Trans-1,4-polyisoprene structures in the alpha and the beta crystal forms with different morphologies were prepared by various crystallization methods such as direct method, annealing method, cast method and prenucleation method. The morphology of bulk crystallized unfractionated TPI and two fractions were studied using SEM for either the alpha or the beta crystal forms. The morphology generally studied was isothermal crystallization, carried to equilibrium, followed by cooling to room temperature. However some samples were studied at crystallization temperature. The morphology of bulk crystallized TPI, as observed using SEM, is a function of molecular weight, crystal form, crystallization temperature and post-crystallization cooling. The morphology is found to be lamellar and the organization depends on molecular weight, particularly for samples in the beta crystal form. For the alpha crystal form the size of the structures observed increases with increasing temperature. The melt crystallization of trans-1,4-polyisoprene was followed using FTIR spectroscopy. The spectral subtraction factor versus time was obtained at the crystallization temperature and after cooling to 25{dollar}\sp\circ{dollar}C for fractions and parent material. Crystallization of the beta crystal form was followed at 36 and 43{dollar}\sp\circ{dollar}C and the alpha form at 43 and 51{dollar}\sp\circ{dollar}C. Samples crystallized at 25{dollar}\sp\circ{dollar}C and annealed at 43{dollar}\sp\circ{dollar}C were also investigated. The effect of molecular weight on the crystalline/amorphous content depend on the crystal form/ morphology, the crystallization temperature and the thermal history. The amorphous fraction for prenucleated melt crystallized alpha form containing samples increased with molecular weight at the crystallization temperature and after cooling to 25{dollar}\sp\circ{dollar}C. Samples containing the beta crystal form showed a molecular weight dependence at crystallization temperature/annealing temperature that disappears upon cooling the sample to 25{dollar}\sp\circ{dollar}C. Bulk crystallization of solution epoxidized TPI also was investigated using SEM and FTIR spectroscopy. The effect of amount of epoxidation and crystallization temperature on final crystallinity, morphology and crystallization rate was investigated. The morphology is less dependent on the epoxidation amount, only showing a marked change at 9.8% epoxidation. The subtraction factor was plotted against the time for various solution epoxidized samples crystallized from the bulk. The rate of crystallization was observed from the slope of the plot. A decrease in rate occurs with increasing epoxi content or with increasing crystallization temperature. The crystallinity decreases linearly with increasing epoxi content at Tc = 25{dollar}\sp\circ{dollar}C and 36{dollar}\sp\circ{dollar}C and shows marked deviations from linearity at Tc = 36{dollar}\sp\circ{dollar}C. The differences in crystallinity between solution and melt crystallized samples are discussed.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
