The effect of stearic acid on Mooney scorch time of epoxidized natural rubber (ENR 25
Effect of stearic acid concentration on the reversion behavior of epoxidized natural rubber
โ Scribed by B. T. Poh; Mohni B. Kasmuri
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 150 KB
- Volume
- 73
- Category
- Article
- ISSN
- 0021-8995
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โฆ Synopsis
The effect of stearic acid concentration on the reversion behavior of epoxidized natural rubber (ENR 25 and ENR 50) was carried out in the temperature range of 150 -180ยฐC and 0.5-14.5 phr of stearic acid loading. Three common accelerators; namely, zinc dimethyldithiocarbamate (ZDMC), tetramethylthiuram disulfide (TMTD), and N-morpholinylbenzothiazole-2-sulfenamide (MBS) and conventional sulfur vulcanization system was used throughout the study. A Monsanto oscillating-disk rheometer was used to determine the reversion behavior of the rubber. Results indicate that for all the accelerators used, reversion decreases with increasing stearic acid concentration. The rate of decrease is more gradual up to about 6.5 phr of stearic acid, after which a rapid drop of reversion is observed for both ENR 25 and ENR 50. This observation is attributed to the increasing amount of mono-and disulfidic crosslinks as a result of desulfuration of polysulfidic crosslinks. The higher the stearic acid loading, the greater is the retardation effect on vulcanization; that is, more time is available for desulfuration. Increasing temperature would increase the reversion of the rubber vulcanizate because of the increase in thermal energy to decompose more crosslinks, including mono-and ether crosslinks for temperature higher than 160ยฐC. ZDMC (an ultrafast accelerator) gives a higher reversion than MBS (a delay-action accelerator), because desulfuration occurs more slowly in the former system. The observed decrease in reversion as stearic acid concentration increases is technologically importance, because the aging property of the rubber vulcanizate is significantly improved.
๐ SIMILAR VOLUMES
Brabender-mixed blends of poly(acrylic acid) (PAA) and epoxidized natural rubber (ENR) were extruded through the capillary in a Monsanto processability tester, and the capillary pressure versus extrusion time plots were recorded. Constancy in capillary pressure with extrusion time was observed in th
The thermal degradation and thermooxidative degradation of epoxidized natural rubber (ENR) were studied by thermogravimetry (TG). In the thermal degradation of ENR, the initial temperature of weight loss T 0 ร 1.20B / 348, the temperature of maximum weight loss rate T p ร 1.07B / 392, and the final