Analysis is carried out by raising the temperature gradually and plotting weight against temperature. After the data is obtained, curve smoothing and other operations may be done such as to find the exact points of inflection.
Sampling material is heated under nitrogen gas until about 500 °C to determine low volatile ingredi- ents like oil, waxes and the like (40 – 420 °C). Po lymers degrade between 420 and 500 °C. Above 500 °C synthetic air is added to oxidize carbon bla ck (500 – 650 °C). Calcium Carbonate is detected
above 650 °C degrading to Calcium Oxide (Limestone to Quicklime reaction). The remaining residue 1
is an indication for other inert fillers (china clay ; Titanium oxide etc.)
9.2. Extraction, IR-Spectroscopy, and more
Most rubber compounds may be modified within broad limits in order to alter certain properties or to ease processing of compound. Plasticizers, waxes, anti-ageing and UV-protection additives as well as curing agents are supplemented to the main ingredients of a rubber compound. One way to ana- lyze these substances is solvent extraction and sequential chemical and/or physical analysis of the extract. IR-spectroscopy is a fast and easy method to compare compounds with back-up samples from the past in order to determine any changes of constituents. Gas and liquid chromatography, mass spectroscopy as well as IR and UV spectrometers may be employed to analyze new and used rubber parts for changes during operation. Interpretation of all methods mentioned above requires thorough comprehension of the application, experience, and intuition.