Molecular mobility and structure of ultrasonically treated unfilled butadiene rubber

Abstract

We have used 1H NMR relaxation and pulsed‐gradient spin–echo diffusion, 13C NMR relaxation, and quantitative bulk measurements to characterize molecular mobility in unfilled butadiene rubber before and after an intense ultrasound treatment. In an effort to improve our understanding of the treatment process, we have performed the characterization at the molecular level. The 1H NMR T2 relaxation decay has been successfully described with a three‐component model, which shows the evolution of the proportions and intermolecular mobilities of the changing spectrum of the motional species. The intramolecular mobility of the carbon backbone and structure has been examined with 13C NMR, which shows significant isomerization resulting from the ultrasound treatment. The diffusion rates of the ultrasonically treated samples reflect the measured changes in the molecular weights of the sol fractions. This investigation is the first to characterize the details of the delicate balance of the crosslinking, backbone modification, chain scission, and network degradation as an ultrasound treatment progresses. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1875–1887, 2004

Molecular Mobility of Unfilled and Carbon-Black-Filled Isoprene Rubber: Proton NMR Transverse Relaxation and Diffusion

“…This observation was similar to the cases of BU 18 and BR, 19 but opposite to the observation in SBR, 13 where the glass transition temperature was found to exceed those of the respective virgin vulcanizates. The molecular weight of the sol increased with increasing ultrasound amplitude, suggesting that at larger amplitudes breaking of the rubber chains is more immediate and more severe and results in the creation of more macroradicals.…”

“…Input of copious energy in one of several forms (e. g., mechanical, thermal, electric, chemical, biological, irradiation) is necessary to break a significant fraction of these chemical crosslink bonds for reprocessing and recycling of the materials. 12 Non-spectroscopic solid-state NMR has been applied to study the molecular dynamics of, and diffusion in, various types of elastomers under ultrasound treatment, including SBR, 13,14 silicone rubber, 15,16 polyurethane rubber, 17 butyl rubber, 18 BR, 19 and NR. Among them, the high-power ultrasound process is one of the most promising methods; it is a relatively fast, can be conducted as a continuous rather than a batch process, and it involves no solvents or other chemicals.…”

The Role of Carbon Black on Devulcanization of Natural Rubber by Microwaves

“…This technique is widely mentioned by the literature to detect the status of devulcanization of elastomers 4,5,[14][15][16]24,31,32,39,41,[43][44][45][46][47][48][49][50][51][52] . In general, the content of soluble material (sol) increases with the increasing of devulcanization degree, due to the breaks of the cross-linkings and, consequently, the release of these molecules from the three-dimensional network of vulcanized rubber.…”

Evaluation of hydroxyl terminated polybutadiene‐isophorone diisocyanate gel formation during crosslinking process

“…In case of polymers, magnetization decay is known to be much more complex than that of simple molecules 22, 23. In various polymers such as polydimethylsiloxane rubber,24, 25 polybutadiene rubber,26 and butyl rubber,27 the global magnetization decay was composed of 2 or 3 relaxation times in order to fit correctly the CPMG data ( R 2 > 0.999).…”