Block copolymer of polyurethanes with poly(m-phenylene isophthalamide)

In this study,we modified two kinds of conventional polyurethane (PU) by the low molecular weight diamine-terminated wholly-rigid aromatic polyamide poly(m-phenylene isophthalamide) (PmIA) (Nomex). Two molecular weights (1000 and 2000) of poly(tetramethylene glycol) (PTMG) with 4,4-diphenylene methane diisocyanate (MDI) and with three different ratios of low molecular weight diamine-terminated PmIA prepolymer with different molecular weight of 346, 584, 823 were synthesized to form six PmIA-PU block copolymers. Various block copolymers were also obtained by different ratios of wholly-rigid PmIA prepolymers. Inherent viscosity results indicated that the block copolymers are more viscous than conventional polyurethanes, suggesting that the block copolymers had sufficiently high molecular weights. Moreover, results obtained from differential scanning calorimetry (DSC) and dynamic mechanical properties analysis (DMA) demonstrated that the block copolymers not only exhibited a glass transition temperature (T_g) under 0 °C, but also had a higher storage modulus (E) than those of the conventional PU. Opitical microscopy (OM), phase contrast microscopy (PCM), and transmission electron microscopy (TEM) analyses confirmed that all of the block copolymers had a dispersed phase structure. The mechanical properties, tensile strength and 300% modulus of the block copolymers were found to be better than those of conventional PU.