By David Reed, UT EditorAkron, Ohio-Thermoplastic polyurethane (TPU) composites with much improved tensile strength and negligible changes in tensile modulus have been synthesized, according to an online report from Asim Pattanayak,and Sadhan Jana, from the Department of Polymer Engineering, University of Akron.Published 4 Oct. 2005 by Wiley InterScience (www.interscience. wiley.com), the report says the composites contained intercalated, tethered layered silicate particles and were made by mixing low molecular weight prepolymers containing isocyanate groups with reactive layered silicate clay, followed by catalysed chain extension with butanediol. The molar ratio of -NCO and -OH functional groups in the composite was varied between 1.0 and 1.2, the report says. Composites with -NCO to -OH molar ratio 1.1 provided the best improvement in mechanical properties-the composite with 5 %w clay gave a 60-% increase in tensile strength and a 50-% increase in strain at break, while the tensile modulus increased only by 15 % over unfilled TPU.An appreciable proportion of the -NCO groups was consumed in reaction with moisture present in the clay and some in quaternary ammonium ion-catalysed dimerisation and trimerisation, the researchers report in Polym. Eng. Sci., 45: 1532-1539, 2005, published by the Society of Plastics Engineers.Current address for Asim Pattanayak is GE Global Research, Bangalore, India, and any correspondence should be directed to: S.C. Jana, Email: email@example.com”
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