Development of Highly Crystalline Polyurethanes from Hydroxy Terminated Polyesters
Keywords:
Diisocyanate, DSC, Polyurethanes, TGA, THPAbstract
The present work describes two series of crystalline polyester based polyurethanes pent synthesized from 4, 4' diphenyl methane diisocyanate, chain extender 1,4 patanediol and low molecular weight polyesters, one with and another without the cross-linker, trimethylol propane (THP). The soft segment of the polyurethanes were composed of PEG based polyesters, which introduces waxy character to the polymers, but disphenyl methane disocyanate good crystalline to the polyurethanes. It was observed that incorporation of certain percentage of cross linker reduces the crystallinty of the system. The polyester ware prepared using both aliphatic acids such as maleic acid and phthalic anhydride. The synthesized polyurethanes were examined by thermo gravimetric analysis, which showed that the polyurethanes molergo thermal degradation at lower temperatures in oxygen atmosphere compared to that of the inert nitrogen atmosphere. The degradation pattern shows the fact that in oxygen atmosphere the degradation step is expanded one where as in the inert atmosphere the degradation step is rather stepper. The samples were also investigated by DSC, which reveals the melting temperature of the samples. The XRD curves also support the crystalline nature of the polyurethanes.
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