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Synthesis of polyurethane-imide (PU-imide) copolymers with different dianhydrides and their properties

✍ Scribed by Lin, Ming-Fung; Shu, Yao-Chi; Tsen, Wen-Chin; Chuang, Fu-Sheng


Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
281 KB
Volume
48
Category
Article
ISSN
0959-8103

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✦ Synopsis


This study reports the synthesis of polyurethane±imide (PU±imide) copolymers using 4,4'diphenylmethane diisocyanate (MDI) polytetramethylene glycols (PTMGs) and different aromatic dianhydrides. Differential scanning calorimetry (DSC) results indicate that PU±imide copolymers had two phase structures containing four transition temperatures (T gs , T ms , T gh and T mh ). However, only PU±imide copolymers were formed by soft PTMG(2000) segments possessing a T ms (melting point of soft segment). When different aromatic dianhydrides were introduced into the backbone chain of the polyurethane, although the T gs (glass transition temperature of the soft segment) of some of PU±imide copolymers did not change, the copolymers with long soft segments had low T gs values. The T gh (glass transition temperature of hard segment) values of PU±imide copolymers were higher than that of polyurethane (PU). In addition, the high hard segment content of PU±imide copolymer series also had an obvious T mh (melting point of hard segment). According to thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA), the PU±imide copolymers had at least two stages of degradation. Although the T di (initial temperature of degradation) depended on the hard segment content and the composition of hard segment, the different soft segment lengths did not obviously in¯uence the T di . However, PU±imide copolymers with a longer soft segment had a higher thermal stability in the degradation temperature range of middle weight loss (about T d 5%±50%). However, beyond T d 50% (50% weight loss at temperature of degradation), the temperature of degradation of PU±imide copolymers increased with increasing hard segment content. Mechanical properties revealed that the modulus and tensile strength of PU±imide copolymers surpassed those of PU. Wide angle X-ray diffraction patterns demonstrated that PU±imide copolymers are crystallizable.


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