NOVEL METHOD FOR THE PREPARATION OF POLY(URETHANE-IMIDE)S AND THEIR PROPERTIES

A polymer blend consisting of polyimide (PI) and polyurethane (PU) was prepared by means of a novel approach. PU prepolymer was prepared by the reaction of polyester polyol and 2,4-tolylenediisocyanate (2,4-TDI ) and then end-capped with phenol. Poly(amide acid) was prepared from pyromellitic dianhydride (PMDA) and oxydianiline (ODA). A series of ol igo( amide acid)s were also prepared by controlling the molar ratio of PMDA and ODA. The PU prepolymer and poly(amide acid) or oligo( amide acid) solution were blended at room temperature in various weight rati os. The cast films were obtained from the blend solution and treated a t various temperatures. With the increase of polyurethane component, t he films changed from plastic to brittle and then to elastic. The poly (urethane-imide) elastomers showed excellent mechanical properties and moderate thermal stability. The elongation of films with elasticity w as more than 300%. The elongation set after the breaking of films was small. From the dynamic mechanical analysis, all the samples showed a glass transition temperature (T-g) at ca. -15 degrees C, corresponding to T-g of the urethane component, suggesting that phase separation oc curred between the two polymer components, irrespective of polyimide c ontent. TGA and DSC studies indicated that the thermal degradation of poly( urethane-imide) was in the temperature range 250-270 degrees C. (C) 1997 John Wiley & Sons, Inc.