EFFECT OF CROSSLINK DENSITY ON THE STRUCTURES AND PROPERTIES OF ALIPHATIC POLYURETHANE ELASTOMER

Abstract

A series of crosslinked aliphatic polyurethane (PU) elastomers with various crossslink densities were synthesized by the reaction of isophorone diisocyanate (IPDI) with polyether diol, trimethylolpropane TMP) and 1,4-butanediol (BDO) through one step method. The results showed that the crosslink density of PU elastomers exhibited a linear relationship to the content of TMP, while the content of hard segments of PU elastomers was fixed at 40 wt%. With the increase of the crosslink density of the PU elastomers, the glass transition temperature (T(g)) value of the hard segment domains in the PU dropped significantly from 32 degrees C to 21 degrees C, the T(g) value of the soft segment domains in the PU dropped slightly form -47 degrees C to -48 degrees C, and the degree of H-bonded urethane carbonyl in the PU decreased from 83% to 63%, which indicated that the micro-phase miscibility of the PU elastomers was enhanced. With the increase of the crosslink density of the PU elastomers, the TGA results showed that the onset decomposition and the maximum decomposition temperature of the PU elastomers increased from 285 degrees C to 319 degrees C and 325 degrees C to 349 degrees C respectively, which indicated that the thermal stability of the PU elastomers was also improved. The mechanical test indicated that the Young' s modulus, modulus at 100% extension and Shore A hardness of the PU elastomers significantly increased with the increase of the crosslink density of PU, while the elongation at break decreased.