Inelastic response of copolyurethane elastomers with varying soft segment molecular weights and preparation procedure |
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Authors: | Cristina Prisacariu Elena Scortanu Bogdan Agapie Victor A Prisacariu Sergiu Coseri |
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Affiliation: | 1. Romanian Academy's Institute of Macromolecular Chemistry ‘Petru Poni’, , Iasi, 700487 Romania;2. Department of Engineering Science, University of Oxford, , Oxford, OX1 3PJ UK |
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Abstract: | A family of thermoplastic polyurethane elastomers (TPUs) based on the soft segment poly(oxytetramethylene) (PTMO2000 and PTMO1000) were synthesized by the one‐shot and prepolymer methods. Two hard segments were chosen, 4,4′‐methylenebis(phenyl isocyanate) (MDI) (non‐crystallizable) and 4,4′‐dibenzyl diisocyanate (DBDI) (crystallizable). Microphase separation and crystallinity were investigated using small‐angle X‐ray scattering and wide‐angle X‐ray scattering, and dynamic viscoelastic properties were also determined. An increased hard phase degree of crystallinity was primarily achieved by use of DBDI instead of MDI, regardless of the preparation procedure and soft segment molecular weight. An increase of the molecular weight leads to an increase in phase separation and to a decrease in hysteresis. For the DBDI based polymers, a lower soft segment molecular weight resulted in an increase in crystallinity. The DBDI series of TPUs obtained by the one‐shot and prepolymer methods showed higher hysteresis and residual elongations compared with the corresponding materials achieved with MDI. Although the materials varied widely in response to first loading, regardless of the preparation procedure, they displayed remarkable reproducibility and commonality in cyclic responses within the maximum strain envelope. The thermomechanical experiments revealed a better thermal behavior with increase of the soft segment molecular weight from PTMO1000 to PTMO2000.© 2013 Society of Chemical Industry |
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Keywords: | polyurethane polymerization method molecular weight structural studies tensile cycling |
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