PHOTO-CROSS-LINKING OF SOME UNSATURATED POLYETHER URETHANE

Different unsaturated polyether urethanes have been prepared either by the reaction of methacrylic epoxide copolymers having different metha crylate moiety, with phenylisocyanate or by the reaction of bisphenol (A) of epichlorohydren (Araladite) with methacrylic acid followed by t he addition of toluene diisocyanate. The composition of such unsaturat ed polyether urethane were determined quantitatively by H-1-NMR spectr oscopy. The ultrasonic pulse echo technique was used in the range of f requencies between 2 and 8 MHz and temperatures between 240 and 360 K to detect the secondary relaxation both in the presence of a photoinit iator before and after cross-linking by using ultraviolet irradiation. The apparent activation energies for such relaxation were calculated and interpreted according to the flexibility of these polymers. Differ ential thermal analysis (DTA) and (TG) thermograms as well as IR spect roscopy were also measured and confirmed the formation of cross-linked polyether urethane. (C) 1998 Elsevier Science S.A. All rights reserve d.