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  • 1
    Electronic Resource
    Electronic Resource
    Effect of crosslinking density on the physical properties of interpenetrating polymer networks of polyurethane and 2-hydroxyethyl methacrylate-teminated polyurethane (1998)
    Springer
    Journal of polymer research 5 (1998), S. 153-162 
    Details
    ISSN: 1572-8935
    Keywords: IPNs ; Polyurethane ; Crosslinking density ; Phase separation ; Blood compatibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Interpenetrating polymer networks (IPNs) of 2-hydroxyethyl methacrylate-terminated polyurethane (HPU) and polyurethane (PU) with different crosslinking densities of the PU network were prepared by simultaneous solution polymerization. Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) show that compatibility of component polymers in IPN formation depends on the crosslinking density of the PU network. Physical properties such as density and water absorption rely on the subtle balance between the degree of phase separation and the crosslinking density of the PU network. In spite of the occurrence of phase separation, the tensile moduli and tensile strength of the IPNs increase with the crosslinking density of the PU network. Morphological observation by scanning electron microscopy revealed different fracture surfaces between the compatible and incompatible IPNs. Surface characteristics of the IPNs, indicated as hydrogen bonding index and hard-to-soft segment ratio, are altered considerably by varying surface morphologies. Improved blood compatibility of IPN membranes is due to the variation of the hydrophilic and hydrophobic domain distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10965-006-0051-x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Blends of poly(p-oxybenzoate-co-p-phenylene isophthalate) and polycarbonate: Miscibility and free volume behaviors (1999)
    Springer
    Journal of polymer research 6 (1999), S. 211-218 
    Details
    ISSN: 1572-8935
    Keywords: Thermotropic liquid crystalline polymer ; Blend ; Miscibility ; Positron ; Free volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Blends of a thermotropic liquid crystalline polymer [poly(p-oxybenzoate-co-p-phenylene isophthalate)] (HIQ45) and a polycarbonate (PC) are studied with regard to their miscibility and free volume behavior. The glass transition temperatures (Tgs) of the blends are found to be uncharacteristically higher than those of the pure components, even increasing with the addition of the low-Tg component, HIQ45. Based on the non-appearance of the Tg of HIQ45 in the tanδ spectra of the blends and the observed homogeneous morphology of the blend, mixtures of HIQ45 and PC are concluded to be a miscible blend system. The free volume properties determined by positron annihilation lifetime spectroscopy show that close packing does not occur in these miscible blends as indicated by positive deviations in size and number concentration of free volume cavities from average values as a function of blend composition. The increase in free volume is attributed to the loss of liquid crystalline alignment of HIQ45 and disturbed packing of PC molecules due to intimate miscibility between different molecules. The free volume fraction index of the blend correlates well with measured blend density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10965-006-0090-3
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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