Development and Standardization of Tests for Evaluating Processibility of Rubber

Abstract

This paper reviews the important wartime developments in methods of standardization and tests, heretofore unpublished, relating to the evaluation of processing quality. The term processing quality or processibility is used in the rubber industry to describe any one or all of the inherent characteristics of a rubber which may affect its behavior during the manufacturing process. The nonuniformity of various rubbers and the changes in behavior which occur with slight changes in the method of treatment make the determination of this quality one of the major problems in the manufacture of rubber goods. In an effort to measure this quality by laboratory methods, investigators had developed a number of different types of apparatus, usually with the idea of measuring some property which could be expressed as a function of the viscosity or the elastic recovery. In accordance with Scott Blair (1)4 and others, the term viscosity as used in this paper is not limited to Newtonian systems. In 1942 the Technical Committee of the Rubber Reserve Co., primarily composed of technical representatives from the rubber industry, reviewed methods existing at that time and decided that some measure of the viscosity should be used for controlling the processing quality of GR-S and that the Mooney viscometer (then called the Mooney plastometer) should be the standard instrument for this purpose in Government Synthetic Rubber plants. When the production of GR-I began, it was adopted as the standard control instrument for this rubber also. The Williams plastometer had been used as the control instrument for neoprene production and consequently was used for GR-M. Since May 1, 1947, however, the Mooney viscometer has been specified for grading GR-M production.

Rubber Recovery from Freshly Harvested Guayule

“…Table V, of constituents and viscosities, further illustrates that mechanical treatment of the shrub prior to milling does not degrade the crude rubber. The viscosities are measured in two waysby the Mooney viscometer (13) and by the Ostwald-Cannon-Fenske viscosimeter. The latter values are expressed as molecular weights (4).…”