Wax in a rubber article migrates to the surface and plays the role of an antidegradant by formation of an impervious barrier on the surface. Wax solubility of a rubber article is important for understanding migration behaviors and film formation of wax as well as for determining the proper content of wax in a rubber compound. Wax solubilities of natural rubber composites reinforced with carbon black were measured using wax solution in toluene. A variation of the wax solubility with the carbon black content was investigated. Raw wax solubility decreased with the increase of carbon black content. Solvent swell-corrected wax solubility also decreased with the carbon black content. The raw wax solubilities were corrected with the rubber fractions, total bound rubber contents, and tightly bound rubber contents as well as the solvent swelling ratio to investigate the influencing parameters on wax solubility. It was found that the unbound and loosely bound rubber fractions as well as the solvent swelling enhanced the wax solubility while the tightly bound rubber fraction reduced it. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: E342-E347, 2012

A mixture of a UV absorber (Tinuvin 234 or Tinuvin 329) and a UV stabilizer (Tinuvin 770) was analyzed using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) without any matrix. Fragmentation patterns of the UV absorbers and stabilizer were also investigated. The mass spectra showed the [M+H](+) ions and some fragment ions. Tinuvin 234, Tinuvin 329, and Tinuvin 770 generated three (m/z 119, 370, 432), one (m/z 252), and two (m/z 124 and 140) fragment ions, respectively. These fragment ions can be used to identify the chemical structures of the UV absorbers and stabilizer. Since the UV absorber performed a role as the matrix, the ion abundance of the UV stabilizer was enhanced by mixing with the UV absorber. When organic materials extracted from polypropylene (PP) containing the UV absorber and stabilizer were directly analyzed using MALDI-MS without any matrix, the protonated molecule of the UV stabilizer was detected in abundance but the product ions of the UV absorber were not observed. When 2,5-dihydroxybenzoic acid was used as a matrix, the protonated molecule of the UV absorber was observed.

No abstract

This study examined the recovery behavior from the circular deformation of a thermally aged CR/NR composite. A linear sample of a rubber vulcanizate was made into circular form by fixing both ends of the sample with a pin and aging it thermally in air and distilled water. The recovery increased with the time after removal from circular deformation. The recovery decreased with increasing aging temperature and time. Recovery of the sample aged in air was smaller for long measurement times than that of the sample aged in distilled water. The difference in the recovery behavior of the samples aged in air and distilled water can be explained by changes in the crosslinking density and the annealing effect of the aging medium. The instantaneous recovery was obtained by extrapolating the linear recovery variations. They also showed a good linear relationship with the aging time.The recovery behavior at ambient temperature could be predicted using the experimental results of the accelerated thermal aging. In terms of the instantaneous time, it was predicted that the service lifetime of the sample aged in air at ambient temperature would be much longer than the sample aged in water.

No abstract