A py-GC/MS technique for structural elucidation of rubber samples to investigate regional effects on bio-coagulated natural rubber

- Pyrolysis (at 550 °C) GC/MS analyses of five raw NR samples produced by different coagulation methods and from different regions (within 6 months).
- Up to the present, no report has been obtained on the use of py-GC/MS to investigate regional effects on molecular structures of bio-coagulated NR.
- Elucidation of similarities on the molecular structures of three raw NR samples coagulated by microbes or natural way and from different regions.
- Some differences were found on the ones of two raw NR samples coagulated by acetic acid or new technique, as compared with that of bio-coagulated NRs.
- A conclusion has been conducted that the coagulated processing, rather than the regions, is a main factor affecting the molecular structures of NR.

In this paper, the molecular structures of five kinds of original natural rubber (NR) samples produced by different coagulation methods and from different regions(within six months) were studied using a pyrolysis (at 550 °C) gas chromatography/mass spectrometry (py-GC/MS) technique. The result showed that the similar molecular structures of the major degradation products, monomers (2-methyl-1,3-butadiene and 1,3-pentadiene) along with dimers of a large number of 1-methyl-4-(1-methylethenyl)cyclohexenes (limonenes) and small amounts of tran limonenes, were all found in three original NR samples, SMR20 and STR20 made all by natural coagulation, and MC-SCR5 coagulated rapidly by microorganisms. Also, the relative productivity (57.48%-59.27%) of the monomers are similar. But the some differences of the molecular structures, the monomers which included 1,4-pentadiene, 3-methyl-1,2-butadiene and 2-pentyne along with more tran limonenes dimers were exhibited in two original NR samples, GSR-RSS3 coagulated by new technology and HN-SCR5 by acetic acid, their relative productivities (61.22% and 65%) have also more differences, as compared with that of the bio-coagulated natural rubbers. Conbine our previous and current works, a conclusion can be obtained that the rubber-productions of origin is not the main factor affecting the molecular structures of natural rubber, but the coagulation processing.