Mixed metal stabilizers powders

Stabilization systems for plastisols are discussed under specifie applications in Section 4.4. Powder mixed metal stabilizers or powder boosters are often added with filler, and may be, as a result, preferred with compounds of substantial filler loading. Liquid mixed metal or organotin stabilizers are typically added with (or to) the plasticizer. As discussed in Chapter 4, there is no longer any compelling... 

Although these mixed metal alkoxide complexes are a means of obtaining atomic mixing of the various metals, the stoichiometric ratio of metals may or may not be that desired for the ceramic powder. A different stoichiometric ratio, n, for the same two metals is not likely to be precipitated out just because the initial solution contains a different stoichiometric ratio. Also for many electronic ceramic compositions it is desirable to have many other metals incorporated at the ppm level into the ceramic powder as sintering aids, grain growth inhibitors, and crystal phase stabilizers. Adding these otiier metals is very difficult... 

In zinc-rich paints some early patents indicate the importance of a silica component. Colloidal silica was reacted with finely divided zinc to form a colloidal zinc silicate in which the excess zinc metal was suspended (654). A water-insoluble binder for zinc-containing coatings was produced by mixing alkali-stabilized colloidal silica with lithium hydroxide in suitable proportions (655). Evolution of gas from mixtures of colloidal silica with zinc powder is prevented by adding an indigoid compounds (656). Another formulation involves quaternary ammonium polysilicate solution milled with lead oxide as the binder for zinc (657). Some of the problems stem from the impurities in the zinc powder which promote reaction with the medium (658). Adhesion. of paints of this type of steel is improved by adding up to 2% of a styrene-acrylic resin dispersion (659). 

The electrolyte was used in the form of a stabilized zirconia tube 450 nun long, 12.7 mm o.d., 9 mm i.d., closed at one end. The electrodes, made by compacting the mixed metal and oxide powders in a cylindrical die, were pressed against the closed end of the zirconia tube. The cell was heated in an alumina work-tube in a vertical platinum alloy-wound resistance furnace. With the cell in the uniform temperature zone of the furnace the open end of the zirconia tube extended into the cold zone, and in initial experiments one electrode was placed inside and the other outside. The reason for using this configuration was to prevent interaction between the electrodes through the gas phase. 

To ensure that the experimental procedure adopted results in the highest-possible colloidal nanoparticle concentration, the sequence of precursor addition was reversed. A second scheme which involved mixing the metal salt powder with microemulsions already containing the stoichiometric amount of NaOH solution was tested. Both schemes succeeded in forming stabilized colloidal nanoparticles however, higher uptake was obtained when scheme 1, solubUizing the metal salt before adding NaOH, was employed. The lower uptake associated with scheme 2 was attributed to the formation of a mass transfer barrier of the metal oxide/hydroxide at the surface of the salt powder, which prevented further dissolution. 

Wire and Cable A major area of powder mixed metal use is in replacement of lead stabilizers in wire insulation and jackets. Jackets having minimal wet electrical requirements have the longest history of use. These were at first Ba/Zn powders (or liquids) but with improving technology, are now mosfly Ca/Zn/ zeolite or Ca/Zn/hydrotalcite blends. Standard test recipes are as follows ... 

Plasticized PVC compounds using mixed metal powder stabilizers are frequently based on calcium or barium stearate or laurate. In the presence of plasticizer, such stabilizers typically act as multifunctional lubricants. Liquid stabilizers often use analogous salts of liquid acids, such as those of octoic, oleic, or taU oil acids. These are similarly multifunctional, as are combinations with organotin stabilizers. In many cases, mixed metal stabifizers provide sufficient lubrication such that no further lubricants are needed. This must be considered in replacement of nonlubricating lead stabilizer systems. 

Tin-stabilized semirigid sheet is generally treated comparably to rigid compounds, with 0.3-0.5 phr of calcium stearate for internal lubrication, and 0.75-1.0 phr of a blend of paraffin wax and OPE wax for external lubrication. When stabilized instead with mixed metal powders, usually as a paste in epoxidized soybean oil, further lubricant addition is not often required. 

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