Effect of initiator concentration

Flgure 4 The effect of initiator concentration on the variation of monomer conversion by the polymerization time in the emulsion polymerization of styrene. Styrene-water = 1/3 SDS = 15.4 mM reaction volume = 300 ml stirring rate = 250 rpm temperature = 70°C. 

Lu et al. [86] also studied the effect of initiator concentration on the dispersion polymerization of styrene in ethanol medium by using ACPA as the initiator. They observed that there was a period at the extended monomer conversion in which the polymerization rate was independent of the initiator concentration, although it was dependent on the initiator concentration at the initial stage of polymerization. We also had a similar observation, which was obtained by changing the AIBN concentration in the dispersion polymerization of styrene conducted in isopropanol-water medium. Lu et al. [86] proposed that the polymerization rate beyond 50% conversion could be explained by the usual heterogenous polymer kinetics described by the following equation ... 

Figure 2 Effect of initiator concentrator on total conversion percent and grafting efficiency. LR 30 1, reaction time 1 h, reaction temperature 27°C, monomer concentration 1 mL/g pulp, and acid concentration 1% — = total conversion (%) 0—0 = grafting efficiency (%).

Fig. 25. The effect of initiator concentration on molecular weight and conversion of PaMeSt prepared using the HSi(CH3)2CH2CH29JCH2Cl/Me3Al initiating system (See Table 8 for reaction conditions)...

As shown by the data in Fig. 31, the chain transfer constant of this initiator, Q = 1.0. In this context it is of interest to remember that the effect of initiator concentration on the molecular weight of HSi-PaMeSt was negligible, probably because of unfavorable thermodynamics (Sect. III.B.3.b.iv.). In contrast, with isobutylene chain transfer from the propagating carbenium ion to initiator is thermodynamically favorable (see Sect. IH.B.4.b.i.). Thus it is not surprising to find a large Q. The chain transfer mechanism has been illustrated in Scheme 5. 

In this paper we present a meaningful analysis of the operation of a batch polymerization reactor in its final stages (i.e. high conversion levels) where MWD broadening is relatively unimportant. The ultimate objective is to minimize the residual monomer concentration as fast as possible, using the time-optimal problem formulation. Isothermal as well as nonisothermal policies are derived based on a mathematical model that also takes depropagation into account. The effect of initiator concentration, initiator half-life and activation energy on optimum temperature and time is studied. 

Figure 1 shows the effect of initiator concentration on optimum temperature and optimum time. It is noticed that increasing the initiator concentration hardly affects the optimum temperatures. However, optimum time decreases considerably from 297 minutes (lo = 0.03 mol/L) to 99 minutes (Iq = 0.15mol/L). As is well known, and shown in Figure 2, equilibrium monomer concentration (M, ) increases with temperature. If temperature is increased further, the monomer concentration can not be reduced to the desired final level because of high values. The initiator concentration should be chosoi taking into account the cost of the initiator and the savings due to reduced time of reaction. An initiator concentration Io=0.10 mol/L that resulted in t,=128 minutes was chosen for further simulation studies. 

In this paper we formulated and solved the time optimal problem for a batch reactor in its final stage for isothermal and nonisothermal policies. The effect of initiator concentration, initiator half-life and activation energy on optimum temperature and optimum time was studied. It was shown that the optimum isothermal policy was influenced by two factors the equilibrium monomer concentration, and the dead end polymerization caused by the depletion of the initiator. When values determine optimum temperature, a faster initiator or higher initiator concentration should be used to reduce reaction time. 

Fig.4. Effect of initial concentration of ethylene on decomposition rate...

The Effect of Initiator Concentration on the Rate of Polymerization. BME, 2,2-dimethoxy-2-phenyl acetophenone, 2-hydroxy-2,2-dimethyl acetophenone and Darocur-3331 (its structure is not known) were chosen for further evaluation on the effect of initiator concentration on the rate of polymerization. They were chosen because they are the among the most active or the least active initiator in polymerizing HEMA. 

The algorithms developed in this chapter can model any situation, e.g. they can serve to demonstrate the effects of initial concentrations and rate constants in kinetics and of total concentration and equilibrium constants in equilibrium situations. Very importantly, these algorithms further form the core of non-linear least-squares fitting programs for the determination of rate or equilibrium constants, introduced and developed in Chapter 3, Model-Based Analyses. 

Fig. 28.5 Effect of initial concentration of Particle size < 300 xm, amount adsorbent = 0.2 g, pH = 8, temperature = 30 C, stirring time = 4 h...

The initiator concentrations required for cationic polymerizations are smaller than those for radical polymerizations frequently 10 to 10" mol of initiator per mol monomer is sufficient to achieve a high rate of reaction. The effect of initiator concentration on the rate and average degree of polymerization depends on the monomer and a variety of other factors and does not follow a consistent pattern. 

Effect of Initiator Concentration of the Propagation Rate of Butadiene and Isoprene in Hexane... 

Hirvonen et al. (1995) evaluated the feasibility of the UV/H202 process for the removal of trichloroethylene (TCE) and erythromycin (perchloroethylene [PCE]) in contaminated groundwater. The formation of chloroacetic acids (CAs) was used as an indication of partial degradation. The dominant byproduct, dichloroacetic acid (DCA), accounted for the major part of the total yield of CAs. The observed concentrations of trichloroacetic acid (TCA) and DCA were relatively low compared with the total amount of TCE and PCE degraded. The effect of initial concentrations of the parent compounds, hydrogen peroxide, and bicarbonate on the yield of by-product was inves-... 

Figure 8. Effect of initiator concentration on particle formation when monomer concentration is very low (S0 = 6.25 g/L H20, 50°C)...

Fig. 4. Effect of initial concentration on fluoride uptake particle size, 0.150-0.300 mm sorbent dose, 2g/L agitation speed, 300 rpm and solution temperature, 295.1 K.

Fig. 9. Effect of initial concentration on fluoride removal from water. BDST model simulation is represented by continuous line. Bed height = 3 cm, flow rate- 9.8mL/min particle size = 0.150-0.355 mm and pH = 6.2-6.4.

Table II. Effect of Initiator Concentration on Percent Grafting and Molecular Weight...

Figure 10. Effect of initiator concentration on the graft copolymerization of methyl methacrylate onto cellulose nitrate initiated by a, benzoyl peroxide and b, azobisisobutyronitrile. Key O, grafting efficiency 9, percent grafting.

Effect of Initial Concentration and Column Length on the Critical Flow Rate, Lc... 

Fig. 6. Effect of initial concentration on breakdown time and critical flow rate.

Effect of Initial Concentration, Flow Rate, and Column Length on k... 

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