Synthesis, Morphology And Properties Of Polyurethane-Imides

Polyurethanes (PU) are becoming more and more important as engineering materials due to their many excellent properties such as high abrasion resistance, chemical resistance, and high flexibility. However, it's well known that conventional polyurethanes exhibit poor thermal stability which limits their more applications in many fields.An effective way to improve the thermal and mechanical properties of polyurethanes is chemical modification by introducing heteroaromatic groups into polyurethane backbones. The sea-island morphology caused by the incorporation of hard segment (chain-extender and imide chain) and soft segment (polyethylene glycol) provided the excellent synthesized properties of polyurethane-imides (PUI). In this work, a novel chain-extender owning three functional groups was prepared. In addition, different types of chain-extender introduced to PU chain were studied. Furthermore, the properties of dielectric constant and water resistance were studies by introducing Si-O bond into either PUI chain or PUI side chain. Finally, amine-terminated oligoimide and anhydride-terminated oligoimide were synthesized to prepare PUI. The effect of Imide content on properties of PUI was studied.The structures of PUI were confirmed through Fourier transform infrared spectra (FTIR). The existence of micro-phase separation morphology was confirmed though the results of Differential Scanning Calorimetry (DSC) analysis. Compared to conventional linear PU, the PUI exhibited higher tensile modulus but lower break elongation because of the huge cohesion energy of polar groups and interaction of H bonds. The results of Thermogravimetric analysis (TGA) and DTG disclosed that PUI owned higher degrading temperature and better thermal stabilities. PUI owning chain-extender AEAPS exhibited lower dielectric constant and higher contact angle than PUI containing DSiD, which meant better water resistance. Also, PUI synthesized from anhydride-terminated oligoimide exhibited better thermal stabilities than PUI synthesized from amine-terminated oligoimide, which showed more thermal degrading temperatures with the increase of imide content.