Rubber accelerators, determination

Accelerators. During sulfur vulcanization of rubber, accelerators serve to control time to onset of vulcanization, rate of vulcanization, and number and type of sulfur cross-links that form. These factors in turn play a significant role in determining the performance properties of the vulcanizate. 

ISO 2440 1997 Flexible and rigid cellular polymeric materials - Accelerated ageing tests ISO 6914 2004 Rubber, vulcanized - Determination of ageing characteristics by measurement of stress at a given elongation... 

FDA approved 1998 for die following materials to be used in contact with food adhesive preservatives, 21CFR175.105 a rubber accelerator (up to 1.5% of weight of rubber), 21CFR177.2600 in the synthesis of slimicides for use in paper/paper-board, 21CFR176.300 an adjuvant in die manufacture of foamed plastics, 21CFR178.3010. Listed in 40CFR136.1 and USEPA Method 640 The Determination of Mercaptobenzothiazole in Municipal and Industrial Wastewaters. 

It has been known for a number of years that FD-MS is an effective analytical method for direct analysis of many rubber and plastic additives. Major components and impurities in commercial additives can be assessed quickly, and the FD-MS data can be used to help determine what (if any) additional analytical characterization is needed. Lattimer and Welch showed that FD-MS gives excellent molecular ion spectra for a number of polymer additives, including rubber accelerators (diWocarbamates, guanidines, benzothiazyl, and thiuram derivatives) antioxidants (hindered phenols, aromatic amines) p-phenylenediamine-based antiozonants, processing oils, and phthalate plasticizers. Zhu and Su characterized alkylphenol ethoxylate surfactants by FD-MS. Jackson et al. analyzed some plastic additives (hindered phenol antioxidants and a benzotriazole UV stabilizer) by FD-MS. ... 

In the transition zone, EHL is still important, but as more water is removed, EHL at the microscale (MEHL) becomes more important, and when the water layer is reduced to molecular levels, another mechanism, BL takes over. Since BL is the main mechanism by which friction is generated in the overall skidding process, any material properties which increase the proportion of BL in the transition zone relative to EHL, i.e., accelerate the transition from EHL to BL, will have an impact on overall skid performance. As discussed above, modulus is an important factor in determining the rate of water removal in EHL. Eor MEHL, it is the modulus on the microscale at the worn surface of the tread that is critical. There is evidence that after a certain amount of normal wear, a significant part of the surface of silica-filled compounds is bare silica, whereas in black-filled compounds, the surface is fully covered by rubber.The difference in modulus between rubber and silica is very large, so even if only part of the worn surface is bare silica, it would make a significant impact on the... 

Deformulation of vulcanised rubbers and rubber compounds at Dunlop (1988) is given in Scheme 2.3. Schnecko and Angerer [72] have reviewed the effectiveness of NMR, MS, TG and DSC for the analysis of rubber and rubber compounds containing curing agents, fillers, accelerators and other additives. PyGC has been widely used for the analysis of elastomers, e.g. in the determination of the vulcanisation mode (peroxide or sulfur) of natural rubbers. 

For the purpose of polymer/additive analysis most applications refer to vulcanisate analysis. Weber [370] has determined various vulcanisation accelerators (Vulkazit Thiuram/Pextra N/Merkapto/AZ/DM) in rubbers using PC. Similarly, Zijp [371] has described application of PC for identification of various vulcanisation accelerator classes (guanidines, dithiocarbaminates, thiuramsulfides, mercapto-substituted heterocyclic compounds, thioureas, etc.). The same author has also... 

Phenolic antioxidants in rubber extracts were determined indirectly photometrically after reaction with Fe(III) salts which form a red Fe(II)-dipyridyl compound. The method was applicable to Vulkanox BKF and Vulkanox KB [52]. Similarly, aromatic amines (Vulkanox PBN, 4020, DDA, 4010 NA) were determined photometrically after coupling with Echtrotsalz GG (4-nitrobenzdiazonium fluoroborate). For qualitative analysis of vulcanisation accelerators in extracts of rubbers and elastomers colour reactions with dithio-carbamates (for Vulkacit P, ZP, L, LDA, LDB, WL), thiuram derivatives (for Vulkacit I), zinc 2-mercaptobenzthiazol (for Vulkacit ZM, DM, F, AZ, CZ, MOZ, DZ) and hexamethylene tetramine (for Vulkacit H30), were mentioned as well as PC and TLC analyses (according to DIN 53622) followed by IR identification [52]. 8-Hydroquinoline extraction of interference ions and alizarin-La3+ complexation were utilised for the spectrophotometric determination of fluorine in silica used as an antistatic agent in PE [74], Also Polygard (trisnonylphenylphosphite) in styrene-butadienes has been determined by colorimetric methods [75,76], Most procedures are fairly dated for more detailed descriptions see references [25,42,44],... 

Ostromow [328] has described the use of conductometry for the analysis of extracts from elastomers and rubbers, such as the determination of various vulcanisation accelerations dithiocarbamates, thiurams (tetramethylthiuramdisulfide, tetramethylthiurammono-sulfide), 2-mercaptobenzothiazole, diphenylguanidine... 

Determination of the level of total sulfur in a rubber can give information on the type of cure system used, for example, elemental sulfur plus accelerator or sulfur donor system, etc. The ISO 6528-1 1992 method — Rubber — Determination of total sulfur content — Part 1 Oxygen combustion flask method is often employed. The principle of the method is oxidation by ignition in an atmosphere of oxygen in the presence of hydrogen peroxide, conversion of sulfur to sulfuric acid and determination of the sulfate by titration with barium perchlorate. The method is... 

The authors describe experiments on six NR compounds commonly used for latex gloves to determine the potential hazards of skin contact with reference to curing compounds and accelerators, including mercaptobenzthiazole and zinc dialkyldithiocarbamates. Simulation methods and the influence of a common hand disinfectant were investigated. In the case of tetramethylthiuram disulphide, it was discovered that decomposition products could be formed on the skin which are not present in the original rubber. 6 refs. Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. Accession no.849747... 

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