High Speed Stirring

If a mechanical degradation of a solution of two polymers is carried out by high speed stirring, the formation of a block copolymer is not probable as the scission of polymer molecules at low concentration is not caused mainly by intermolecular interaction, such as by collision of molecules and through entanglements, but by displacements due to hydrodynamic forces in velocity gradients. Nakamo and Minoura (98) did obtain reaction by stirring a benzene solution of polyethylene oxide and poly(methyl methacrylate). 

If mechanical degradation of a polymer solution by high speed stirring is carried out with a vinyl monomer in an inert atmosphere the monomer will be polymerized by the free macroradical. Goto and Fujiwara, for example, studied poly(vinyl acetate vinyl acetate) agitated in an Homomixer at 30000 rpm in a nitrogen atmosphere at 65° C (99). They found that the polymerization rate, Vp, is proportional to the square root of the initial concentration of poly(vinyl acetate)  

By the above results and by the general rate equations for initiation, propagation, and termination, Minoura concluded that the polymerization rate is proportional to the monomer concentration (M) and to the square root of the dif- 

The radical reaction mechanism was confirmed by polymerizing a mixture of styrene and methyl methacrylate. The ratio of the monomers in the copolymer (1.15) was nearly equal to the value (1.05) calculated from the reactivity ratio for radical copolymerization and differed considerably from the value of 10.5 for the cationic copolymerization and from the value 0.15 for anionic copolymerization (78). 

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Procedure. Add Nopco 1444B to hot water with high speed stirring. Add Naugawhite slowly, allowiag a few minutes between additions. After all the Naugawhite has been stirred ia, continue stirring for 15 min. 

The preparation of the reagents, on the other hand, is somewhat involved and requires high-speed stirring (5). Given below, therefore, is an alternate method of preparation of phenyl(trichloromethyl)mercury that requires only conventional stirring (9). The use of this compound to prepare 7,7-dichloronorcarane is also given. 

A suspension of 69.0 grams of 2-trifluoromethylphenothiazine in 1 liter of toluene with 10.9 grams of sodium amide is heated at reflux with high speed stirring for 15 minutes. 

A 1-1. three-necked flask equipped with a reflux condenser, an inlet for dry nitrogen, and a mechanical stirrer is flushed with dry nitrogen. It is then charged with 340 g. (4.00 moles) of piperidine (Note 1), 4.4 g. (0.19 g. atom) of sodium, and 5.0 g. (5.1 ml., 0.063 mole) of pyridine (Note 2). While a slow stream of nitrogen continues to pass through the flask, the solution is heated under reflux with high-speed stirring for approximately 10 minutes. 

FIG. 1 Schematic drawing of the high-speed stirring (HSS) apparatus. An organic phase separated from the dispersed system by the teflon phase separator is continuously circulated through the photodiode array detector. 

Br-PADAP showed a significant adsorption at the interface of heptane-water under high-speed stirring conditions (5000 rpm). At the toluene-water interface, the... 

FIG. 6 Measurements of the interfacial adsorptivity and the extraction rate from the absorbance changes of the organic phase by means of the high-speed stirring method, (a) Heptane-water system... 

Nakano, A. and Minoura, Y., Degradation of aqueous poly(acrylic acid) and its sodium salt solutions by high-speed stirring, /. Appl. Polym. Sci., 22, 2207, 1978. 

The following procedure is carried out in a ventilated hood. Finely powdered dry sodium cyanide (29.4 g., 0.60 mol) and 180 ml. of dimethylformamide (DMF) are placed into a 1-1., three-necked, standard-taper round-bottomed flask equipped with a reflux condenser, dropping funnel, and Hirshberg stirrer connected to a high-speed stirring motor. External cooling is provided by a cold-water or ice-water bath. Carbon disulfide... 

The kaolin was from BDH Ltd. and was dispersed by high-speed stirring at around neutral pH. The resulting suspension was allowed to stand overnight and the sedimented material was rejected. The remaining suspension contained particles up to about 2 ym in size. Final suspensions for the flocculation experiments were made up in 10 3m NaCl, to control the ionic strength. 

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)... 

Determine the effective stirring velocity at low, medium, and high speed stirring and compare it to the manufacturer specification. 

The high speed stirring minimizes undesired bimolecular reactions. 

High speed stirring has be claimed by Nozaki for giving block copolymers from polymer-monomer mixtures (775). Among the polymers which have been subjected to such a degradation are addition polymers (polyvinyl chloride, polystyrene, polyacrylamide) as well as cellulose derivatives, phenol-formaldehyde linear condensation products and polyethylene terephthalate. 

Aerating liquids, semiliquids, and powders, usually caused by excessive high-speed stirring... 

Mechanical stabilities were determined at 35 C and 55% total solids content by means of a Klaxon high-speed-stirring mechanical stability test apparatus. The tests were carried out according to the procedure specified in either BS 1672 Part 2 1954 or... 

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