Structural Characterization of Ethylene-Propylene-Diene Rubbers by High-Resolution Pyrolysis Gas Chromatography

Abstract

Ethylene-propylene-diene rubbers (EPDMs) are now used for various purposes because of their excellent resistance to ozone, weather, and heat. Therefore, many kinds of EPDMs are provided as commercial polymers. Consequently, reliable methods for the structural characterization of EPDM have been needed in the fields of material development, process control, and quality assurance of the cured products. The iodine value method is generally used to determine the diene content in EPDMs. However, it is too time consuming to be a routine method. Until now, spectroscopic methods such as IR and NMR are generally used for the study of the composition and the sequence length distributions in EPDMs. Levine and Haines determined the content of ethylidenenorbornene (ENB) in ethylene-propylene-ethylidenenorbornene rubbers (ENB-EPDMs) by IR. Florence and Loustalot investigated ethylene-propylene-1.4-hexadiene rubbers by NMR. However, these spectroscopic methods often encountered the difficulties in the analysis of vulcanized rubbers since they were insoluble and usually contained many kinds of additives such as curing agents, plasticizers, stabilizers, and fillers. On the other hand, owing to the recent development of excellent pyrolyzers and highly efficient fused-silica capillary columns, pyrolysis-gas chromatography (PyGC) has become a powerful tool to give unique information about structures of high polymers. Furthermore, PyGC is advantageous to the practical analysis of insoluble polymeric materials such as vulcanized rubbers.

Quantitative ToF‐SIMS analysis of monomers, oxidation and trace elements in EPDM gels

“…However, there was a report of ENB detection using pyrolysis GC/MS. 24 In this pyrolysis GC/MS study, ENB was detected as a small increase in the C 7 H 8 C C C 7 H 10 C peaks, which were attributed to variations of the ENB five-membered ring. Based on this work, the relative intensities of the C 7 H 8 C and C 7 H 10 C peaks obtained in the ToF-SIMS spectra were examined as a function of ENB level in various EPDM standards.…”

A Study of the Sulphur Bridge Structure in EPDM Rubber Vulcanisates by Pyrolysis-Gas Chromatography

“…As shown in Figure 6, it was inferred [13] that the C 7 H 6 S components comprised a five-membered ring skeleton formed by scission of the S-S x bond at the bridge followed by cyclisation of the ethylidene methyl group with the sulphur in the cleaved S-S x bond and simultaneous detachment of the ENB residue in the intermediate from the main chain, so producing the condensed heterocyclic compounds 2,4-cyclopenta[2,3-b]thiophene C 7 H 6 S (I) and 2,5-cyclopenta[2,3-b]thiophene C 7 H 6 S (II).…”

“…Using FT-Raman and FT-IR spectra, Duystee [5] and Duin et al [6] have recently elucidated the structure of the bridges between sulphur and ENB as a model of crosslinked EPDM (Figure 1). Moreover, Verbruggen et al [7] have clarified the ENB terminal structure after thermal degradation at 265 °C by 13 C-NMR, as shown in Figure 2, providing useful information for structural analysis of the sulphur bridges in EPDM rubber vulcanisates.…”

“…In a previous investigation of vulcanisation mechanism [11], we identified methylthiophenes characteristic of For EPDM in particular, we have also reported on the feasibility of analysing the EP chain and quantifying the diene components in vulcanised EPDM by high resolution Py-GC with a hydrogen flame ionisation detector (FID) [12][13][14]. The present study used Py-GC with sulphurselective FPD in combination with a mass spectrometer (MS) to examine the sulphur-containing pyrolysis products that would be expected to form from the sulphur bridges in EPDM vulcanisates.…”

Characterization of pyrolysis products formed from styrene-1,2-unit heterosequence of styrene–butadiene copolymer

“…Pyrolysis-gas chromatography (pyrolysis-GC) and pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS) have been applied to characterize elastomers [5,[17][18][19][20][21][22][23][24][25][26][27]. Pyrolysis patterns of SBRs with differing microstructures were characterized by comparing the major pyrolysis products such as styrene, butadiene, and 4-vinylcyclohexene [19].…”