Vacuum mixing

Ammonia is generated by the reaction of diphenylguanidine and magnesium oxide with ammonium perchlorate. The cure rate of polysulfide propellant formulations can be a function, of the amount of ammonia removed during the mix cycle. Frequently, a vacuum is placed on uncured propellant to remove entrapped air. Too long a vacuum mix cycle, with polysulfide propellants, can remove excess ammonia changing the reaction condition during cure. 

Mix Process. Usually all liquid components (except the diisocyanate), antioxidants, ballistic additives, bonding agents, and metallic fuel are blended together and transferred to the mixer, a jacketed stainless steel vessel with provisions for vacuum mixing. This mixer is not much different from those found in the bread-baking industry, from which, in fact, this one was derived. Depending on the type of propellant, the... 

Adjust flow rate such that the temperature rise of the suspension does not exceed 10°C. Collect the milled suspension in a stainless steel-jacketed tank with vacuum. Mix at 25° to 30°C under vacuum until a uniform suspension is achieved. 

Here the melt solidifies into an amorphous structure which is broken into small rod shaped pieces by mechanical agitation. The flavor pieces are recovered by centrifugation, dried under a vacuum, mixed with a free flowing agent and packaged for sale. The product of this process contains 8-20% flavor load and is exceptionally stable to deterioration by oxidation. 

Granulate the mixture I with solution II, dry at 60 °C with vacuum, mix with III and press with high compression force. 

Preparation of Hydrated Silicates. The hydrated silicate specimens used were all in the paste form—that is, mixtures of one of the calcium silicates with a limited amount of water to form a slurry, which sets and hardens as portland cement itself does. These pastes were prepared by the vacuum mixing procedure described by Powers, Copeland, Hayes, and Mann (23), adapted so that the temperature of the mix upon removal from the mixer was the temperature at which the specimen was to be hydrated. The 5° specimens were made by starting with an ice-water mixture the-50° specimens by starting with preheated water. A manostat was incorporated into the pumping system to prevent the pressure from dropping below the vapor pressure of water at the desired final temperature. This was especially important for the 50° mixes, to prevent excessive cooling. 

Preparation of clay-bonded sand by vacuum mixing and cooling... 

In Japan, a vacuum mixing and cooling plant has been in operation since 1993, with a prepared sand throughput of 100 m /h. 

Dunne, N., Xu, Y., Daly, C., Makem, J., Walker, G. Orr, J. (2006) Development of operator independent bone cement vacuum mixing system for joint replacement surgery. Plastics Rubber and Composites, 35, 317-323. 

Geiger, M. H., Keating, E. M., Ritter, M. A., Ginther, J. A., Faris, P. M. Meding, J. B. (2001) The clinical significance of vacuum mixing bone cement. Clinical Orthopaedics and Related Research, 258-266. 

Lidgren, L., Bodelind, B. MoUer, J. (1987) Bone-Cement Improved by Vacuum Mixing and Chilling. Acta Orthopaedica Scandinavica, 58, 27-32. 

Rocha et al. [112] demonstrated that the parent polymer of the series, po-ly(glycolic acid) n=l, is immiscible with PCL. They blended poly(glycolic acid) with PCL-767 and PCL-787 (Table 1) by freeze drying mixed solutions under vacuum, mixing the polymers in a Haake rheometer at 235 °C and then compression moulding. Two TgS were observed by DMA, unshifted from those of the homopolymers drastic phase separation was reported for 50 50 blends. 

Table 4. Fracture toughness of hand and vacuum mixed bone cement under different steriliza tion conditions. Values are reported as mean (standard deviation). n indicates number of sam pies in each group [106]...

Vacuum mixing is defined as such mixing in a closed system under an internal pressure which is significantly lower than atmospheric pressure. 

Because of all the listed benefits it offers, vacuum mixing is mostly used for the mixing of adhesives at the adhesive suppher. 

Limit possibie air bubbles by vacuum mixing or using freshiy boiied water and carefuiiy cast and compact sampies. 

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