Because of critical shortages of commercial plasticizers used with polyvinyl chloride type electrical insula¬tion, it has become necessary occasionally for manufacturers to substitute new and sometimes not thoroughly tested materials, to plasticize these resins. The present acceptance test used by the Navy on synthetic resin insulation will not always show differences in the types of plasticizers used. Conse¬quently, a manufacturer might submit one kind of plasticizer in the insulation put up for the extensive type or brand approval tests and then later, because of a shortage of material, substitute another plasticizer. This substitution might not be detected in the short acceptance test.nThe purpose of this work is to give a relatively short method that can be used in acceptance tests and that is sufficiently sensitive to show differences between re¬lated types of plasticizers but at the same time is free-from interference by inconsequential impurities.nThe method developed involves the extraction of a small quantity of the plasticizer from the resin and then a determination of the electrical properties of this plasticizer at high radio frequencies as a function of temperature. ^ach plasticizer so far observed has given a reproducible curve different from that of any other. Since it is possible, however, that carves of some materials may lie close to, -those of others, refractive index measurements are found valuable as supplemental information.nA number of chemical procedures of analysis have been investigated. They are useful for conformation pur¬poses on many types of plasticizers and necessary when studying new materials
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