Stirring speed, effect

Figure 1 Effect of stirring speed on the rate of hydrogenation of DMIT over AHC-2. 5000 TON each reaction, ee s = 95-97%. Reactions run at 50° and 50 psig.

For surfaces covered with a monolayer (e.g., a protein), the value of /c2 is reduced by as much as 80% the effect of a compressed protein monolayer at different stirring speeds can be expressed (46) by ... 

Fig. 30a-d. Polymerization of methyl methacrylate by high speed stirring of polyethylene oxide solution, a) effect of monomer concentration on polymerization rate (PEO 4 g/100 ml, stirring speed 30000 rpm. b) effect of monomer (MMA) concentration on intrinsic viscosity of reaction mixture (PEO 4 g/100 ml, stirring speed 30000 rpm, solvent benzene, c) effect of PEO concentration on polymerization rate, d) effect of PEO concentration on intrinsic viscosity of reaction mixture (Stirring speed 30000 rpm)... 

Fig. 5. Effect of solvent and % CL on kobsd. Stirring speed is 600-650 rpm, and other experimental conditions are the same as in Fig. 3. (Reprinted with permission from Ref. 73). Copyright 1981 American Chemical Society)...

The effect holds for the stirring speed. At low rpm, the rate is proportional to stirring speed. At a certain value of the rpm, no further increase in rate is observed. 

Aliquots were removed from the flask periodically and were assayed for the released 5-FU at 265 nm using a Beckman DU-7 spectrophotometer. These hydrolysis studies were run for several weeks. The reproducibility of each technique was determined by rerunning the same sample at a different time. Host of these reproducibility studies were run using EHCF monomer because the release rates were faster than with the copolymers and because this EHCF monomer did not show zero-order release kinetics. The copolymer hydrolysis rates were determined at least two times and these results showed excellent agreement with each other. No detailed studies were made on any effect the stirring speed might have on the observed release rates, but the results obtained at either 300 or 600 RPH appeared to be the... 

Drug release may be affected by a number of process parameters such as drug loading, polymer molecular weight, polymer composition, initial concentration of the polymer in the organic phase of the emulsion, amount of emulsifier, stirring speed, vacuum pressure, solvent evaporation time and temperature. These parameters were kept constant and only the amount of NaOH was varied. Therefore, changes in the in vitro release curves should reflect only the effect of NaOH in various concentrations. ... 

The parameter estimation is made in a stirred Lewis-type cell (Fig. 10.11) where, in the plateau region, chemical reaction prevails. With increasing stirring speed the initial mass transfer rates will increase as diffusional effects are diminished and a plateau is reached where mass transfer is independent of diffusion, as discussed elsewhere [31, 46]. A further increase in stirrer speed will disrupt the planar interface, leaving the operating area for determining the kinetics parameters. 

Figure 3. Effect of stirring speed on mass transfer resistance, k. Key , solid...

Batch, semi-batch and continuous emulsion polymerizations are usually carried out in stirred tank reactors, where agitation by a stirrer is necessary. The type of stirrer chosen and its stirring speed can often affect the rate of polymerization, the number of polymer particles and their size distribution (PSD), and the molecular weight of the polymer produced. However, the effect of stirring on emulsion polymerization has never been the main research parameter in research programs [241]. This is probably due to the conflicting results obtained so far by various researchers. 

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