Determination of Molecular Structures of Acetone Solutes from Natural Rubber by Pyrolysis Gas Chromatography Coupled to Mass Spectrometry

Abstract

As the non-isoprene components, acetone solutes (AS) from natural rubber (NR) are a crude mixture impacting the processing and mechanical properties of natural rubber significantly. Thus, illustrating the compositions and molecular structures of AS clearly is useful to grasp the inherent features of NR. Therefore, the compositions of AS from different NR (coded as WF, STR, SMR and MRSS) were investigated effectively via stepped pyrolysis gas chromatography coupled to mass spectrometry (PyGC–MS), as well as the assistance of thermogravimetric analysis (TGA). The results demonstrated that two degradation stages showed up in TGA curves for all AS samples. Principally the volatilization of higher aliphatic acids like linoleic acid and stearic acid determined by PyGC–MS induced the first degradation stage. Moreover, the decomposition of polyisoprene with low molecular weight chiefly caused the second degradation stage according to the results from PyGC–MS. Finally, the relative contents of fatty acids in AS can be arranged as AS-STR > AS-WF > AS-SMR > AS-MRSS based on the conclusions of GC–MS. The results are meaningful to the development of NR basic theory. Schematic of the preparation and analysis of AS