Separation and identification of various vulcanization agents and antioxidants in two types of rubber by chromatographic and spectrometric methods.
The aim of this study was to separate and identify by chromatographic and spectrometric methods, the various allergenic vulcanization agents and antioxidants used in the manufacture of industrial rubber. Specimens of elastomers were manufactured specially for this study. The specificity of the gas chromatographic method developed allows separation of all the manufacturing additives in the selected rubber types after one injection only, even though they belong to extremely varied chemical categories. The GLC method was coupled with mass spectrometry, which permitted identification of the peaks obtained and the study of the fragmentation of the 4 reference products under various conditions. Separation by TLC was performed in parallel on the same extracts, allowing rapid identification of the products tested for, and showed new spots after vulcanization.
Off-line TLC-IR (UATR) characterization of additives in EPDM rubber
Abstract Sulfur donor accelerators and vulcanization agents, such as peroxides, due to their chemical characteristics and good thermal stability properties in rubber formulations, are essential to provide solutions in different sectors, such as aerospace and automotive, since they reduce the polymer degradation process (reversal), which can influence the performance of the elastomeric material. In this way, the use of methodologies for the components knowledge of a formulation is imperative for the structure proper establishment/property relationship of the elastomeric artifacts. The development of methodology that can separate and characterize the rubber formulation components is a constant challenge, still allows gaps, and is usually done by conventional but not coupled instrumental techniques. In this scenario, this paper aimed to contribute to the use of the off-line coupling of thin-layer or thin-layer chromatography (TLC)/infrared spectroscopy (FT-IR), by universal attenuated total reflection (UATR) for N-cyclohexyl-2-benzothiazolesulfenamide (CBS), tetramethyl thiuram disulphide (TMTD) and dicumyl peroxide (DCP), in formulations of ethylene and propylene diene monomer (EPDM) rubber containing the plasticizer naphthenic oil. This plasticizer was characterized in formulations that presented higher content of this compound, but the eluting systems were not effective in separating DCP. However, better separation of CBS and TMTD was observed.
Antioxidant analysis incorporating a thin-layer chromatographic separation procedure
The method described consists of three distinct and separate steps. Initially, a thin-layer chromatographic technique, involving the use of mixed silica gel-aluminium oxide plates, is used to separate and identify the extracted antioxidants. This step is followed by confirmation of the suspected identity and determination of the antioxidant by using infrared and ultraviolet spectroscopy.This method is considered applicable, over a range of concentrations, to the analysis of both antioxidants and ultraviolet screening compounds possessing ultraviolet absorbing properties, in polyolefinic polymers such as polyethylene, polypropylene, poly(4-methylpentene), etc. It can be used to detect such additives down to a level of 200 µg g–1, and possibly even less, in a given polymer.In addition, the procedure has been successfully applied to the separation of isomeric antioxidants and to the identification of antioxidants present in lubricating oils.