MECHANICAL AND DIELECTRIC-PROPERTIES OF SEGMENTED POLYURETHANE ELASTOMERS CONTAINING CHEMICAL CROSS-LINKS IN THE HARD SEGMENT

Mechanical and dielectric properties of two series of segmented polyur ethanes having soft segment concentration of 50 and 70% and a varying degree of crosslinking through the hard segment were studied. The degr ee of crosslinking in each series was varied by varying the butane dio l/trimethylol propane ratio in the chain extender mixture. Tensile str ength, elongation at break decrease, but elastic recovery increases mo notonically with increasing crosslinking. The plateau modulus in the d ynamic mechanical test decreases and then increases with increasing TM P content. Crosslinking causes broadening of the soft segment glass tr ansition as seen by permittivity and loss factor measurements. It also affects high temperature behavior (above the glass transition of the hard segment); it lowers permittivity, loss factor, and ionic conducti vity. (C) 1998 John Wiley & Sons, Inc.