TG-DTG-TIC plot of non-vulcanized Natural Rubber (NR), 3.36 mg, N2, continuous injection of the evolved gases at 1-min intervals. A constant high temperature is maintained in the GC column to allow the gas mixture to pass quickly and separate into its main components. (measurement with TG-GC-MS)
At the onset of the NR decomposition (32 min., 346.3°C), the primary volatile products are isoprene C5H8 (peak 1 in TIC chromatogram) and 1-methyl-4-(1-methylethenyl)-cyclohexene C10H16 (peak 2).
This continuous GC-MS mode shows the gas evolution as a function of temperature and time and allows for the selection of individual mass numbers (m/z) for continuous plotting as a function of temperature (single ion monitoring, SIM).
The second stage of the NR decomposition (onset at 38 min., 406.2°C) is characterized by the evolution of products in addition to isoprene and substituted cyclohexene (as shown above). These can be identified as 5,5-dimethyl-1,3-cyclopentadiene (C7H10, 94 m/z), 1-methylene-2-vinylcyclopentane (C8H12, 108 m/z) and beta-humulene (C15H24, 204 m/z).