Dodecyl mercaptan

The thiol ( -dodecyl mercaptan) used ia this recipe played a prominent role ia the quaUty control of the product. Such thiols are known as chain-transfer agents and help control the molecular weight of the SBR by means of the foUowiag reaction where M = monomer, eg, butadiene or styrene R(M) = growing free-radical chain k = propagation-rate constant = transfer-rate constant and k = initiation-rate constant. 

Continuous polymerization in a staged series of reactors is a variation of this process (82). In one example, a mixture of chloroprene, 2,3-dichloro-l,3-butadiene, dodecyl mercaptan, and phenothiazine (15 ppm) is fed to the first of a cascade of 7 reactors together with a water solution containing disproportionated potassium abietate, potassium hydroxide, and formamidine sulfinic acid catalyst. Residence time in each reactor is 25 min at 45°C for a total conversion of 66%. Potassium ion is used in place of sodium to minimize coagulum formation. In other examples, it was judged best to feed catalyst to each reactor in the cascade (83). 

If tertiary chlorine atoms are indeed critical to heat resistance, then reactions that consume them should improve polymer stabiUty. This is indeed the case. Post-reaction of polychloroprene with dodecyl mercaptan (111), use of higher levels of ethylene thiourea for curing (112), and inclusion of reactive thiols such as mercaptobenzimidazole in cure systems (113) all improve heat resistance. This latter technique is especially effective in improving the heat resistance of mercaptan modified polychloroprene. 

Chemical Designations - Synonyms 1-Dodecanethiol Dodecyl mercaptan Chemical Formula CH3(CHi)i(,CHiSH. 

The molecular weight of the continuous phase is an important parameter that affects the mechanics and the melt flow of the end product. It can be controlled by the use of a suitable chain transfer agent (e.g., /er/-dodecyl mercaptan Ct = 4.0) or their combinations (e.g., primary mercaptans Or = 26.0 and dimeric a-methyl styrene Ct = 0.1) [132]. 

Dodecyl hexaoxyethylene glycol, 24 129 Dodecyl mercaptan chain transfer,... 

While the addition of dodecyl mercaptan to styrene causes a reduction in DP, the rate of polymerization is essentially unchanged. Explain. 

Kennedy and Stock reported the first use of Oxone for many common oxidation reactions such as formation of benzoic acid from toluene and of benzaldehyde, of ben-zophenone from diphenyhnethane, of frawi-cyclohexanediol Ifom cyclohexene, of acetone from 2-propanol, of hydroquinone from phenol, of e-caprolactone from cyclohexanone, of pyrocatechol from salicylaldehyde, of p-dinitrosobenzene from p-phenylenediamine, of phenylacetic acid from 2-phenethylamine, of dodecylsulfonic acid from dodecyl mercaptan, of diphenyl sulfone from diphenyl sulfide, of triphenylphosphine oxide from triphenylphosphine, of iodoxy benzene from iodobenzene, of benzyl chloride from toluene using NaCl and Oxone and bromination of 2-octene using KBr and Oxone . Thus, they... 

Cross-linking is a predominant process during irradiation of siloxane polymers. Chain scissions are negligible.204-207 The cross-link density increases linearly with dose up to 160 Mrad (1600 kGy).207 At 5.0 MGy (500 Mrad) the G(X) value is O.5.209 Free radical scavengers, such as -butyl and terf-dodecyl mercaptan and diethyl disulfide, are the most effective antirads.210-211 At concentration of 10%, two thirds of the cross-links were prevented from forming, however, the scission yield was increased. 

Formulas for emulsion polymerization also include buffers, free radical initiators, such as potassium persulfate (KiSiOs), chain transfer agents, such as dodecyl mercaptan (G sSTT). The system is agitated continuously at temperatures below 100°C until polymerization is essentially complete or is terminated by the addition of compounds such as dimethyl dithiocarbamate to prevent the formation of undesirable products such as cross-linked polymers. Stabilizers such as phenyl Beta-naphthylamine are added to latices of elastomers. 

Figure I. Rate of change in macromolecular population dN/ dw as a function of conversion in emulsion copolymerization of styrene and butadiene (styrene butadiene = 29 71 by tot) concentration of tert-dodecyl mercaptan (TDM) modifier in phm A — run 4, 0.10 O — run 6, 0.20 X — run 7, 0.23...

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