High-temperature pyrolysis simulation of acrylonitrile-butadiene model compound with experimental evidence

- Pyrolysis of acrylonitrile-butadiene based model system was investigated using ReaxFF molecular dynamics simulation.
- Acrylonitrile, 1,3-butadiene and small amount of 2-butene were identified as major pyrolysis products.
- The increased heating rate increased the initial degradation temperature and shortened the initiation time.
- The final heating temperature decreased the initial degradation.
- The mechanism and activation energy of degradation were in accord with the results from Py-GC-MS and TGA.

Molecular dynamic simulations (MD) were made for the first time on acrylonitrile-butadiene (NBR) model compounds to determine the thermal decomposition characteristics. The formation profile of various pyrolysis products with respect to time and temperature was examined. Acrylonitrile, 1,3-butadiene, and 2-butene were identified as major products at the initial stage of degradation of the copolymer. Other small molecular products including 4-vinylcyclohexene and cyclohex-3-enecarbonitrile were observed at high temperature. The formation mechanism of various pyrolysis products was explored with the help of the simulation method. The effect of increased monomer units on the thermal decomposition characteristics of the acrylonitrile-butadiene model compound was studied. The influence of heating rates and final heating temperatures on the formation of small major pyrolysis products was also analyzed. The initial decomposition temperature of the model compound increased with the rise in heating rate. The increase in both the heating rate and the final heating temperature reduces the initiation time for degradation. The pyrolysis products predicted from the atomistic simulation were in good agreement with the experimental results from pyrolysis gas chromatography-mass spectrometry (py-GC-MS). The ratio of the monomer units obtained during pyrolysis of the acrylonitrile-butadiene model compound in the simulation is also similar to the ratio obtained from py-GC-MS. The activation energy value for thermal decomposition of the acrylonitrile-butadiene copolymer obtained from the simulation was also consistent with the experimental findings from the thermogravimetric analysis (TGA).