Powdered Lead Stabilizers

Chemical Type Tribasic Lead Sulfate/Coated 

Chemical Type Modified Basic Lead Sulfate 

Chemical Type Basic Lead Carbonate/Coated 

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Halstab Powdered Lead Stabilizers (Continued) Halthal EP ... 

Because of the stringent U.S. requirements on handling lead-based powders, these stabilizers are only found in flexible electrical wire insulation in the United States because no other stabilizers have been developed which have the low conductivity afforded by these materials. 

When not used in applications that justify semibulk handling, lead-in-air requirements are usually met through the use of dispersions, such as prills, extruded strands, or pressed tablets. With direct use of lead stabilizer powder, addition is customarily scheduled with the resin, for which the stabilizer has affinity. The dispersed forms include additives to prevent agglomeration, which often in soft compounds detract... 

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. 

Electrical Coatings (Bus Bars and Cable Trays) These tend to be similar to the wire insulation coatings associated with them that is, they use higher phthalate and trimellitate plasticizers, and lead stabilizers. In fact, the addition of 2-3 phr dispersion resin to the standard PVC insulation compound used with the coated article will usually generate the powder coating formulation. 

Dibasic Lead Sulfate. Dibasic lead sulfate [12036-76-9] 2PbOPbSO, is a white powder, mol wt 749.70, mp 961°C. The dibasic compound can be prepared by fusion of the two components. It has been sold as a PVC stabilizer in Japan and is sold in Europe in combination with dibasic lead phosphite. 

In addition to the additives used in a formulation to help stabilize the protein to freezing, the residual moisture content of the lyophilized powder needs to be considered. Not only is moisture capable of affecting the physicochemical stability of the protein itself, equally important is the ability of moisture to affect the Tg of the formulation. Water acts as a plasticizer and depresses the Tg of amorphous solids [124,137,138]. During primary drying, as water is gradually removed from the product, the Tg increases accordingly. The duration and temperature of the secondary drying step of the lyophilization process determines how much moisture remains bound to the powder. Usually lower residual moisture in the finished biopharmaceutical product leads to enhanced stability. Typically, moisture content in lyophilized formulations should not exceed 2% [139]. The optimal moisture level for maximum stability of a particular product must be demonstrated on a case-by-case basis. 

Ni-YSZ cermet anodes satisfy most of the basic requirements for SOFC anodes. The effective conductivity of a Ni-YSZ cermet anode increases with the Ni to YSZ volume ratio, relative density, and decreasing the particle size ratio of NiO to YSZ. While coarse YSZ powders may result in poor mechanical strength and low stability, coarse NiO powders may lead to poor effective conductivity. The effective conductivity increases with the temperature at which the NiO is reduced to Ni metal in a reducing atmosphere. Further, very low reduction temperatures (e.g., below 400°C) may result in not only low electrical conductivity, but also poor mechanical strength. 

These are the changes that are observed in a pigment powder as it is processed or heated in the application medium. Modifications in the sizes of the crystallites of a polycyclic pigment which is treated in its application medium under varying conditions [108] maybe derived from X-ray crystallographic data. Table 5 reflects a clear correlation between crystallinity and thermal stability increased crystallinity leads to improved heat fastness. 

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