Reinforcement of Polyureaurethane Elastomers from Hydroxyl terminated Polybutadiene Liquid Rubber by Carbon Black

Abstract

Carbon black reinforcement of polyureaurethane elastomers from hydroxyl-terminated polybutadiene liquid rubber (HTPB), tolylene diisocyanate, and 3, 3'-dichloro-4, 4'-diaminodiphenylmethane was investigated. In the carbon black unloaded elastomers, it was found that chemical crosslink density vo was the important factor affecting tear energy r, in particular, tensile strength at break TB, and elongation at break aB and that vc should be smaller than 0.3 x molicm8 to obtain the large values of the properties described above. In order to keep v smaller than 0.3x 10-4 mol/cm3 HTPB was required to have a functionality nearly equal to 2.0 and to be purified to remove metal ion which caused crosslinks.
In the loaded elastomers, HCC(N) and SAF blacks having small diameters showed exellent reinforcing effect, but the effect depended on v, ; in the case of vo 0.3 x 10-4 mol/cms, increased 2, -, 7 times by loading 30 phr of HCC(N) or SAF black, though TB hardly increased, since TB for the corresponding unloaded elastomers had been large enough. On the other hand, in the case of vo 0.3 x 10-4 molicms, TB was improved to about the same level of TB for the, elastomers having vo smaller than 0.3 X 10-4 molicm8, r, however, being left unimproved. Also the reinforcing effect by carbon black was compared with that by silica. The carbon black gave better r and TB than silica, implying that the affinity of fillers and HTPB was the another important factor to be considered.