About the activation energies of the main and secondary relaxations in cured styrene butadiene rubber

Ada Ghilarducci; Horacio Salva; Angel J. Marzocca

doi:10.1002/app.30332

About the activation energies of the main and secondary relaxations in cured styrene butadiene rubber

Journal of Applied Polymer Science ◽

10.1002/app.30332 ◽

2009 ◽

Vol 113 (4) ◽

pp. 2361-2367 ◽

Cited By ~ 9

Author(s):

Ada Ghilarducci ◽

Horacio Salva ◽

Angel J. Marzocca

Keyword(s):

Activation Energies ◽

Styrene Butadiene Rubber ◽

Butadiene Rubber ◽

Secondary Relaxations ◽

Styrene Butadiene

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Chemical Stress-Relaxation and Other Studies on Styrene-Butadiene Rubber

Rubber Chemistry and Technology ◽

10.5254/1.3540498 ◽

1974 ◽

Vol 47 (5) ◽

pp. 1265-1274 ◽

Cited By ~ 2

Author(s):

S. H. Kalfayan ◽

R. Rakutis ◽

R. H. Silver

Keyword(s):

Stress Relaxation ◽

Elevated Temperatures ◽

Activation Energies ◽

Hydroxyl Group ◽

Styrene Butadiene Rubber ◽

Chemical Stress ◽

Butadiene Rubber ◽

Relaxation Rates ◽

Relaxation Measurements ◽

Styrene Butadiene

Abstract The aging of styrene—butadiene rubber (SBR) was studied by three methods: stress relaxation, infrared spectroscopy, and swelling measurements, with the purpose of supplying information pertinent to understanding the basic mechanism of its aging. Stress-relaxation measurements in air and nitrogen at elevated temperatures indicated that atmospheric oxygen is the principal cause of chemical stress relaxation of SBR, rather than heat. Intermittent stress-relaxation measurements showed scission and crosslinking occurring simultaneously during network breakdown, and it was concluded that random scission in the backbone is indicated to take place in preference to scission in the crosslinks. Activation energies obtained from relaxation rates at several temperatures was 28 ± 0.5 kcal, comparable to literature values of 30 ± 2 kcals. The rates of carbonyl and hydroxyl group formation in SBR in air at various temperatures were determined by ir spectroscopy, both induction and maximum rates, νm, being measured. Activation energies calculated from these rates showed lower values compared to those obtained from stress-relaxation measurements. This may be due to the possibility that the processes being measured are not the same in each case. The three peaks appearing in the carbonyl region were ascribed to carboxyl, ketone, or aldehyde, and perester. The presence of these groups was confirmed by microanalytical methods. The absorption centered at 3450 cm−1 was attributed to hydrogen-bonded OH groups, i.e., alcohols and hydroperoxides. Positive chemical tests were obtained for hydroperoxide. The number of new network chains formed, νe, obtained from swelling measurements agreed well with those obtained from stress-relaxation measurements. It was found that the rate of the number of new network chains formed increased rapidly during the latter states of oxidation.

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