STUDY ON THE SYNTHESIS OF HIGH ELONGATION POLYURETHANE

In this paper, polyurethane (PU) was synthesized in the following step s: first, polytetramethaneoxy glycol (PTMG) prepolymerizes with 4,4'-d iphenylmethane diisocyanate (MDI) at a molar ratio of 1:2; then, the p repolymer continuously reacts with 1,4-butanediol (ED) or hexanedimine (HD) to extend the polymer chain. A series of PU samples could be syn thesized by reducing the amount of chain extender. The change in exten sibility of PU with the amount of chain extender was investigated. The results indicate that the extensibility of PU could be improved great ly with a reduction of the amount of chain extender. This could be asc ribed to the fact that excessive -NCO groups can react with the hydrog en atoms in -NHCOO-, and form branch chains. When the molecular weight of PTMG is 1684, with ED as the chain extender, the ultimate elongati on of PU was 2280%; when HD was the chain extender, the ultimate elong ation of PU was 1809%. The submicroscopic structure of the samples was found to be amorphous by the method of small angle laser light scatte ring, and these samples could dissolve in dimethyl formamide (DMF). Th e influence of DMF on the polymerization was also investigated. (C) 19 97 Elsevier Science Ltd.