Characterization of the Reversion Process in Accelerated Sulfur Curing of Natural Rubber

Chen, C. H.; Koenig, Jack L.; Shelton, J. Reid; Collins, E. A.

doi:10.5254/1.3535831

Cited by 51 publications

(39 citation statements)

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“…The model SBR was composed of 26 butadienes (cis-1,4-polybutadiene) and 4 styrenes that were located between (butadiene) 5 to meet 23 wt % styrene content of emulsion SBR. The model SBR had the sequence of B 5 -S-B 5 -S-B 5 -S-B 5 -S-B 6 , where B and S indicate butadiene and styrene units, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Stress relaxation, tensile strength, and resilience increase in proportion to the content of di-and polysulfides, whereas fatigue and thermal aging resistance decrease. 1 Sulfide linkages, especially polysulfides, are dissociated by heating 5,6 and this brings about decrease of the crosslink density. Curatives, especially sulfur, in rubber vulcanizates make new crosslinks 7 and this result in increase of the crosslink density.…”

Section: Introductionmentioning

confidence: 99%

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Influence of rubber composition on change of crosslink density of rubber vulcanizates with EV cure system by thermal aging

Choi

2000

J. Appl. Polym. Sci.

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ABSTRACT:Variation of the crosslink density of a rubber vulcanizate depending on the rubber composition after the thermal aging was studied with single rubber, biblend, and triblend vulcanizates of natural rubber (NR), butadiene rubber (BR), and styrenebutadiene rubber (SBR). The efficient vulcanization (EV) system was employed to minimize the influence of free sulfur in the vulcanizate on the change of the crosslink density. Thermal aging was performed at 40, 60, and 80°C for 20 days with 5-day intervals. The crosslink densities of the vulcanizates after the thermal aging increase. For the single rubber vulcanizates, variation of the crosslink density by the thermal aging has the order: SBR Ͼ BR Ͼ NR. For the biblend vulcanizates, variations of the crosslink densities of the NR/SBR and SBR/BR blends are larger than that of NR/BR blend. Variation of the crosslink density of the vulcanizate increases by increasing the SBR content in the vulcanizate. Variation of the crosslink density of the rubber vulcanizate depending on the rubber composition was explained by miscibility of the blends, combination reaction of the pendent groups, and mobility of the pendent group.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of rubber composition on change of crosslink density of rubber vulcanizates with EV cure system by thermal aging

Choi

2000

J. Appl. Polym. Sci.

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“…The reversion process is thermally initiated and primarily associated with overcure or high temperature service conditions. Reversion involves reactions that lead to the desulfuration of polysulfidic linkages and main-chain modification (cis-to-trans isomerization) which results in weaker network structures (Mori, 2003;Chen et al, 1981). As desulfuration progresses, the distribution shifts from polysulfidic to mono-and di- sulfidic crosslinks and eventually crosslink density is also lost.…”

Section: Rheological Characteristicsmentioning

confidence: 99%

Influence of Crosslinking Method on the Properties of Natural Rubber Mixtures

Stelescu¹,

Manaila²,

Crăciun³

et al. 2016

The International Conference on Advanced Materials and Systems

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The most important stage in the rubber processing technology is vulcanization / crosslinking, which confers mechanical and thermal stability to rubbers. During crosslinking, rubber molecules with chain configuration are linked by chemical bridges / bonds, and the rubber mass turns from its plastic mass into an elastic one. This is normally done by sulphur and accelerator for general purpose rubbers. The chemistry of vulcanization is complex and the resulting crosslinks may be mono-, di-, tri-or higher poly-sulphides, with a proportion which is among others largely determined by the vulcanization system, the cure time and the temperature. These compounds and their reaction products could be responsible for cytotoxicity and allergycausing compounds, such as nitrosamines and nitrosatable materials. For these reasons, the aim was to eliminate or reduce toxic ingredients in elaborating and developing crosslinking technologies for natural rubber mixtures, so that the resulting materials may be used in the pharmaceutical or food industry, as well as in manufacturing other rubber goods (toys, various components for footwear, rubber plates, seals and hoses for various purposes, etc.). This paper presents a study on the influence of the vulcanization method on the characteristics of a natural rubber blend. The tested methods have been: (1) with sulphur and vulcanization accelerators, (2) with benzoyl peroxide in the presence of a polyfunctional monomer. Modification of characteristics was analysed depending on the crosslinking method.

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“…11,12 Crosslink type and degree of crosslink density of a rubber vulcanizate determine the physical properties such as modulus, hardness, resilience, elongation at break, heat build-up, and so forth. 13 Sulfide linkages, especially polysulfides, are dissociated by heating 14,15 and this brings about decrease of the crosslink density. Curatives, especially sulfur, in rubber vulcanizates make new crosslinks 16 and this results in increase of the crosslink density.…”

Section: ⅰ Introductionmentioning

confidence: 99%

Thermal Aging Behaviors of Weather Resistant Rubber Composites of EPDM, IIR, and BIIR

Choi

Kim²

2012

Elastomers and Composites

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ABSTRACT：EPDM, IIR, and BIIR composites were thermally aged and the crosslink density changes were investigated. Crosslink densities of the EPDM composite increased with increasing the aging time and temperature, whereas those of IIR and BIIR composites for long-term aging at high temperatures tended to decrease. Activation energies for the crosslink density changes of the EPDM composite were higher than those of the BIIR one. The experimental results were explained with the number of allylic hydrogens, activation of the zinc complex, the steric hindrance effect, and oxidation of rubber chain. Ⅰ. IntroductionR group rubbers such as natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), and acrylonitrilebutadiene rubber (NBR) have unsaturated hydrocarbon (C=C double bond) backbones. Due to the C=C double bond backbones, they have lots of allylic hydrogens which participate in sulfur crosslinking reaction. 1 Hence, degrees of crosslink density changes of the R group rubber composites by themal aging are relatively high, and their physical and chemical properties are also changed. 2-10 Of R group rubbers, isobutene-isoprene rubber (butyl rubber, IIR) has relatively good thermal resistance properties since it has only isoprene content with less than 3 wt%. 11,12 Crosslink type and degree of crosslink density of a rubber vulcanizate determine the physical properties such as modulus, hardness, resilience, elongation at break, heat build-up, and so forth. 13 Sulfide linkages, especially polysulfides, are dissociated by heating 14,15 and this brings about decrease of the crosslink density. Curatives, especially sulfur, in rubber vulcanizates make new crosslinks 16 and this results in increase of the crosslink density. Crosslink density of a rubber vulcanizate is changed by thermal aging. 4,[17][18][19][20] In general, when sulfur-cured rubber vulcanizates are thermally aged, the crosslink densities increase and the degree also increases as the aging temperature and time increase. [21][22][23] Crosslink density change by thermal aging is also one of reasons about permanent deformation of a rubber vulcanizate. [21][22][23] Brown and coworkers reported physical property changes of rubber composites after natural aging for 40 years and compared with the accelerated heat aging results. 24,25 Relative deviations for the physical property changes of naturally aged rubber vulcanizates were very big but the results were valuable. The big deviation of the physical property may be due to the difference in the initial states of the samples. A number of samples are needed to measure physical properties and to perform thermal aging for a long time. Sample size should be small to minimize the experimental errors, but relatively large sample size for measurement of the physical properties should

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Characterization of the Reversion Process in Accelerated Sulfur Curing of Natural Rubber

Cited by 51 publications

References 0 publications

Influence of rubber composition on change of crosslink density of rubber vulcanizates with EV cure system by thermal aging

Influence of rubber composition on change of crosslink density of rubber vulcanizates with EV cure system by thermal aging

Influence of Crosslinking Method on the Properties of Natural Rubber Mixtures

Thermal Aging Behaviors of Weather Resistant Rubber Composites of EPDM, IIR, and BIIR

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