Styrene initiation, dibenzoyl peroxide

Propynol, Mercury(II) sulfate, Sulfuric acid, Water, 4479 Styrene, Air, Polymerising styrene, 2945 Styrene, Butyllithium, 2945 Styrene, Dibenzoyl peroxide, 2945 Styrene, Initiators, 2945 f Tetrafluoroethylene, 0628... 

Sebastian, D. H. et al., Polym. Eng. Sci., 1976, 16, 117-123 The conditions were determined for runaway/non-runaway polymerisation of styrene in an oil-heated batch reactor at 3 bar, using dibenzoyl peroxide as initiator at 3 concentrations. Results are presented diagrammatically. 

The rate of dispersion copolymerization of PEO-MA macromonomer and styrene was found to increase with increasing initiator concentration VA - water soluble, DBP (dibenzoyl peroxide) - oil soluble, [PEO-MA] =0.06 mol dnr3, [styrene] =2.13 mol dm-3, in ethanol/water, v/v4/l) [65,66] ... 

The parameters were determined in a batch reactor for thermal runaway polymerisation of styrene, initiated by azoisibutyronitrile, dibenzoyl peroxide or di-ferf-butyl peroxide. 

An other interesting example of copolymer is given by Georges et al. [52,59] who first demonstrated the living character of the polymerization of styrene initiated by dibenzoyl peroxide in the presence of Tempo or Proxyl (2,2,5,5-tetramethyl-l-pyrrolydinyloxy). Polystyrene with a narrow polydispersity (Mw/Mn = 1.2) is obtained and block copolymers with butadiene, isoprene, acrylate and methacrylate sequences are prepared ... 

Berger et al. [19] have studied polymerization of styrene initiated by dibenzoyl peroxide (DBP) with the carbonyl groups labelled by the isotope l4C. DBP can react in several ways [20, 21]... 

Butala et al. [43] applied optimization techniques to styrene polymerization initiated by BPO (dibenzoyl peroxide, 1 h half-life time, 91°C) and TBPB (tert-butyl perbenzoate, 1 h half-life time, 124°C). As mentioned before, the batch time can be minimized by using nonisothermal temperature profiles. Three independent runs with different optimization policies were performed. The detailed control policies are listed in Table 5.1. 

Fig. 10. Total number of panicles after styrene emulsion polymerizations as a concentration of free SD in the water phase before polymerization, initiators K,S20b (PPS) and dibenzoyl peroxide (BP). Other experimental conditions as in Fig. 9. Theoretical curves A-E calculated from the absorption isotherm, Eq. (107-108). Curves A-B, a = 4 g/dm . curves C-E, a = OA g/dm. (Reprinted by permission of J. Polym. Sci.)...

The free radical yield/for AIBN in styrene and various solvents at 50°C is /= 0.5. Because of induced decomposition,/varies strongly with solvent in the case of BPO. If, for steric reasons, the primary free radicals cannot recombine, then the free radical yield can, according to conditions, increase up to/= 1. Thus, the start reaction is rarely a simple function of added initiator concentration, since it depends on free radical yield and may also depend on induced decomposition. Because of this, faster initiator decomposition need not necessarily produce faster polymerization. For example, dibenzoyl peroxide decomposes a 1000 times faster in benzene than cyclohexyl hydroperoxide, but only polymerizes styrene five times as fast. 

The suspension polymerization of styrene is mostly carried out with dibenzoyl peroxide. Bulk polymerization is often no longer carried out purely thermally high-temperature initiators such as 1,2-dimethyl-1,2-diethyl-1,2-diphenyl ethane or vinyl silane triacetate, CH2=CH—Si(OOCCH3)3, are added. 

Practice shows that different monomers respond differently to the various classes of initiators (Table 16-15). Styrene, for example, is polymerized by free radicals produced by the decomposition of dibenzoyl peroxide, by cations formed from BF3 + H2O H [Bp30H] , by anions from UC4H9, or by Ziegler catalysts [e.g., TiCU plus A1(C2H5)3]. Vinyl esters, on the other hand, can only be polymerized free radically in the condensed (fluid) phase, formaldehyde only cationically and anionically, acetaldehyde only cationically, etc. 

Hill and coworkers [31] copolymerized acrylonitrile with methacrylic acid by a bulk process to very low conversions. The methacrylic acid was purified by passing it through a column packed with poly(styrene sulfonate) to remove the inhibitors. Acrylonitrile was passed through a column of neutral aluminum oxide. The initiator was dibenzoyl peroxide, which had been dissolved in chloroform and then precipitated with methanol. The polymerizations themselves were carried out, after thorough freeze-thaw... 

Recently, free-radical homopolymerizations and copolymerizations of styrene were performed in toluene and iV,N-dimethylformamide (DMF) as solvents in the presence of different initiators (i.e., tert-butyl perbenzoate (tBPB), dibenzoyl peroxide (DBPO), di-terf-peroxide (DtBP), dicumyl peroxide (DCP), and lauryl peroxide (LP) (Figure 7)). ... 

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