Study of the thermal properties of shape memory polyurethane nanofibrous nonwoven

Thermal properties of polymer are very important to the understanding of morphology and shape memory effect of shape memory polymers (SMPs). In this article, the thermal properties of shape memory polyurethane nanofibrous nonwoven are investigated systematically from the morphology of nanofibers, crystalline structure, isothermal crystallization behavior, and thermal-dependent strain recovery. The results indicate that the thermal properties of shape memory polyurethane nanofibrous nonwoven are influenced greatly by the electro-spinning and the recrystalline condition. The crystal melting temperature (T (m)) decreases as the crystallization temperature (T (c)) decreases, while the relative degree of crystallinity (X (c)) increases with the decrease of T (c) within the temperature range of 20 to -30 A degrees C. In particular, when the annealing temperature is higher than 150 A degrees C, the T (m) shifts to higher value and the X (c) decreases significantly with the increase of T (c). Finally, temperature-dependent strain recovery curves show that the shape memory polyurethane nanofiber tends to have a lower recovery temperature as compared with the SMPU bulk film due to their ultrafine diameter.