Procedure for Determining Physical Properties of Films from GR-S Latices

Abstract

Abstract This article describes a new procedure for determining the physical properties of films from GR-S type of synthetic rubber latices. To obtain satisfactory films for testing, the latex solids should be above 30 per cent. A suitable formulation which will reach the optimum cure in from 30 to 60 minutes at 100° C is as follows: Polymer 100.0 Sulfur 2.0 Zinc oxide 3.0 Zinc mercaptobenzothiazole 1.5 Zinc dibutyldithiocarbamate 0.5 If zinc mercaptobenzothiazole is to be omitted, it is desirable to increase the dithiocarbamate to about 1.0 part. If the dithiocarbamate is not used, vulcanization should be carried out at higher temperatures, e.g., 120° C. These vulcanizing ingredients may be used as a composite dispersion by ball-milling the accelerator, sulfur and zinc oxide with 0.5 parts dispersing agent, such as Daxad-11, Vultramine, etc., to give a 45 to 50 per cent dispersion. It is recommended that freshly prepared pastes be used, since experience has shown that erratic results may be obtained when old pastes are used, particularly those containing zinc oxide. Additional stabilizers, such as soap, may be used with this compound if required in some cases. Films should be prepared promptly after the compound is made, for prevulcanization may occur in the final films and produce erratic results.