Analysis of Elastomer Vulcanizate Composition by TG-DTG Techniques

Abstract

Abstract Two common problems and probable solutions in the TG-DTG analysis of unknown elastomer vulcanizates have been discussed. The first problem concerns the difficulty in quantitatively determining the oil and elastomer in compounds where their volatilization temperature ranges overlap. After a review of the published works in this area, isothermal TG (with or without vacuum) is recommended. The “High Resolution” TG also shows promise and should be explored further. The second problem concerns separate determination of the elastomer-carbon residue and added carbon black in the compound, since both often oxidize together. Subtraction of the predetermined elastomer-carbon residue from the total weight loss in oxygen, was suggested in the literature. However, the quantity of char found depends on the type of the elastomer, its concentration, and the curative composition, as well as the TG temperature profile. The problem is not, therefore, fully resolved. Experiments using a slow feed of lean oxygen gas and isothermal conditions were also suggested in the literature. Under this condition, oxidation of carbon black and char may occur at slightly different temperatures and overlapping is minimized. However, this could be achieved only for large- and mediumparticle-size blacks (soft blacks) which oxidize at higher temperatures and not for the smaller particle size blacks used mostly in tire treads. Further work using the slow feed of lean oxygen with a superimposed isothermal program and/or vacuum conditions is recommended.