No abstract

Elastomers are commonly used as electrical insulators in marine acoustic devices. A previous paper discussed the very large decrease in electrical resistivity of a Neoprene GRT formulation when subjected to moderately high molding pressures. In the present paper, data will be presented showing similar dependencies on mold pressure for natural, polybutadiene, 39%-acrylonitrile NBR, and chlorobutyl elastomers and the absence of the effect for an EPDM, and a 27%-acrylonitrile NBR elastomer. These data are not easily explained. The previous paper also discussed that increasing the carbon-black loading caused the electrical resistivity to decrease at even lower molding pressures. Similar trends are presented here for the other elastomers whose electrical resistivities are dependent on molding pressure. Data will also be presented that show that the addition of poly-para-dinitrosobenzene (Poly DNB®) to a CR formulation will eliminate the mold pressure vs. electrical resistivity effect.