Two common problems in the TG-DTG analysis of unknown elastomer vulcanizates and probable solutions are discussed. The first problem concerns the difficulty in quantitatively determining the oil and elastomer in the compound in cases where their volatilization temperature range overlaps. After a review of the published works which studied this problem, isothermal TG (with or without vacuum) along with the use of "High Resolution" TG equipment is recommended.
The second problem concerns separate determination of carbon residue from the elastomers and added carbon black in the compound, which very often oxidizes together. Subtraction of the carbon residue formed by the elastomers, determined by previous analyses, from the total weight loss in oxygen, was suggested in the literature. However, the quantity of char depends on type of the elastomer, as well as its concentration, curative type and amount and rate of heating. The problem is not, therefore, fully resolved. Experiments under slow feed of lean oxygen gas and isothermal temperature 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 medium particle size blacks (soft blacks) which oxidize at higher temperatures and not for the smaller particle size blacks, (used mostly in tire treads). Further work under slow feed of lean oxygen with a superimposed isothermal program and/or vacuum is recommended. The capability of the recently announced "High Resolution Thermogravimetric Analyzer" should also be explored.
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