PECULIARITIES OF MELTING OF A LOW-MOLECULAR-MASS COMPONENT IN THE CROSS-LINKED RUBBER-LINEAR HYDROCARBON SYSTEM

Compositions based on various cross-linked rubbers containing octadeca ne were studied. It was established that at temperatures below the mel ting point octadecane occurs in the volume of cross-linked rubber in t wo phase states: (i) a crystalline state distributed in the volume of rubber matrix, and (ii) as a solution in rubber. At a definite ratio b etween dissolved and solid octadecane (1 : 6), which is independent of the types of rubber and vulcanizing agent and the degree of cross-lin king, thermograms of composition samples exhibit two melting peaks of the hydrocarbon. Octadecane dissolved in the polymer at a temperature of storage is redistributed between different structural regions of ru bber during migration of the main part of the hydrocarbon from the vol ume of polymer to its surface; this leads to an increase in the disper sity of the crystalline phase formed during abrupt cooling of the comp osition sample and to a decrease in the hydrocarbon melting point.