Browsing by Author "Tsonev T."

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    Shape memory polyurethanes based on recycled polyvinyl butyral II. mechanical and shape memory properties
    (2014-01-01) Tsonev T.; Nenkova S.; Herzog M.
    Shape memory polyurethanes (SMPUs) based on recycled polyvinyl butyral and 4,4'-diphenylmethane diisocyanate, hexane-1,6-diol, and polypropylene glycol of varying hard segment content were investigated. Their mechanical properties and shape memory effect in particular were examined defining the amorphous soft segment domain as a reversible phase, while the crystalline hard segment domain as a frozen phase. Effects of hard segment content (30-45 %) and maximum strain on the cyclic tensile and mechanical properties below (25°C) and above (70°C) material glass transition temperatures were studied. The properties reversibility observed on repeated deformation was improved by decrease of the deformation magnitude and the increase of the hard segment content.
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    Shape memory polyurethanes based on recycled polyvinyl butyral. I. Synthesis and morphology
    (2013-10-17) Tsonev T.; Herzog M.; Nenkova S.
    Shape memory polyurethanes (SMPUs) were synthesized by 4,4′- diphenylmethane diisocyanate (MDI), hexane-1,6-diol (HD), polypropylene glycol (PPG), and recycled polyvinyl butyral (PVB). Dynamic mechanical analysis, differential scanning calorimetry and Fourier transformation infrared attenuated total reflection spectroscopy was used to characterize the poly (vinylbutyral-urethanes). Micro-phase domain separation of hard and soft segments and phase inversion were investigated. Increasing the hard segment content, i.e., average hard segment molecular weight, leads to an increase in the degree of micro-phase separation, hard domain order and crystallinity. The crystalline hard segment structures combined with the elastic nature of soft segment matrix provide enough physical and chemical crosslinks to have shape memory effect. © 2013 Versita Warsaw and Springer-Verlag Wien.