Pyrolysis gas chromatography/mass spectrometry identification of poly(butadiene-acrylonitrile) rubbers

Pyrolysis (py) coupled with gas chromatographic (GC) separation and mass spectrometric (MS) detection is routinely used to identify intractable polymers including cross-linked rubbers. For some rubbers, such as natural rubber, the major thermal degradation pathways and degradation products are known. The presence of the characteristic degradation products in the pyrolysate is sufficient to positively identify the rubber. Unambiguous identification of other rubbers is more difficult. For instance copolymer rubbers such as poly(butadiene-acrylonitrile) release degradation products from the butadiene rich areas, acrylonitrile rich areas, and areas in the rubber where butadiene and acrylonitrile are adjoined. Degradation products such as ethenylcyclohexene (the dimer of butadiene) and acrylonitrile are characteristic of poly(butadiene-acrylonitrile) rubbers but not unique to them. In this paper a pyrolysis gas chromatographic/mass spectrometric (py-GC/MS) method for the identification of poly(butadiene-acrylonitrile) rubbers is described. The method is based on the identification of compounds in the pyrolysate that can be attributed to areas of the copolymer rubber where acrylonitrile and butadiene molecules are adjoined. As these are unique to the pyrolytic degradation of poly(butadiene-acrylonitrile) copolymer rubbers they allow positive identification of these rubbers.