The fillers in rubber compounds are inorganic materials other then sulphur and carbon black that have been added to it. A fairly accurate determination of percentage of fillers in rubber compounds which do not contain materials which will decompose at ashing temperature can be made by heating a known weight of the compound under test inside a muffle furnace to a temperature of 550 ± 25°C for a period of 90 minutes and finding the percentage by weight of the residual ash. The ash so obtained can be further utilized for chemical analysis for determination of inorganic sulphur in absence of antimony, halogens, or antimony sulphide.
This method is applicable for most rubber formulations except those that contain fillers that decompose on heating to the ashing temperature. Also, if the compound under test contains carbonates which decompose on heating to the ashing temperature or clays and silicates which will loose water at this temperature, the filler percentage determined by this method will not be accurate and may not fully represent the original percentage of inorganic fillers present in the
ASTM D 297 1981
Standard Test Methods for Rubber Products Chemical Analysis
Range of force measurement
Opacity Tester with digital galvanometer
Internal Co-efficient Friction Tester
Vicat Softening Point Tester (upto 120º C)