Powders, applications/preparation

Coating plastics, metals, etc. steps generally involve surface preparation, preheating substrate, powder applications, and post-heating. 

Although most pharmaceutical colorants in use today are of synthetic origin, a few are obtained from natural mineral and plant sources. For example, red ferric oxide is mixed in small proportions with zinc oxide powder to prepare calamine, giving the latter its characteristic pink color, which is intended to match the skin tone upon application. 

In the field of metallic powder applications, a method of plasma spray coating suitable for biomedical materials has been developed using titanium and calcium phosphate composite powder. By means of the mechanical shock process, the appropriate composite powder was prepared, and plasma sprayed on Ti substrate under a low-pressure argon atmosphere. A porous Ti coating layer was obtained in which the surface and the inside of the pores were covered thinly with hydroxyapatite. This surface coating is expected to show excellent bone ingrowth and fixation with bone (21). 

Pancreatin Obtained from porcine or bovine (ox) pancreatic tissue. White to tan, water-soluble powder. Major active principles (1) a-amylase, (2)protease, and (3) lipase. Typical applications preparation of precooked cereals, infant foods, protein hydrolysates. 

Pepsin Obtained from the glandular layer of hog stomach. White to light-tan, water-soluble powder amber paste or clear amber to brown aqueous liquids. Major active principle pepsin. Typical applications preparation of fish meal and other protein hydrolysates clotting of milk in manufacture of cheese (in combination with rennet). 

Carbohydrase (Bacillus stearothermophilus) Produced as an off-white to tan powder or a light-yellow to dark-brown liquid by controlled fermentation using Bacillus stearothermophilus. Soluble in water but practically insoluble in alcohol, in ether, and in chloroform. Major active principle a-amylase. Typical applications preparation of starch syrups, alcohol, beer, dextrose, and bakery products. 

Tolnaftate is a synthetic antifungal agent with a narrow spectrum of activity which is limited to dermatophytes (Epidermophyton, Microsporum and Trichophyton spp.). It could be used to treat mild localized dermatophytic infection. For topical application to dogs, tolnaftate is formulated as a 1% cream containing both polyethylene glycol and propylene glycol. The powder aerosol preparation is less likely to be effective for treatment, but could be applied to prevent spread of the infection. 

Technical tungsten powder grades prepared by hydrogen reduction are commercially available in average grain sizes from 0.1 pm (lOOnm) up to 100 pm. The whole palette of grain sizes find their application in cemented carbides. The main portion of tungsten powder produced (80%) is directed into that production. 

The pesticides are produced as application preparations marketed in the form which facilitates the application on the area treated in the dose necessary. For spraying the treated area, they are in the form of liquid emul-sifiable or powdered suspended concentrates. In this way, certain amounts of solvents and filling agents are also transported into the environment. These are particularly different mineral oils, tensides and in small aerosol products also freons. In some countries experiments are also aimed at the possibility of using certain antibiotics as pesticides. 

An interesting new approach appears the usage of supercritical fluids for the preparation of SLN aqueous dispersions or SLN dry powders. The preparation method described by Chattopadhyay et al. is basically a solvent evaporation process based on an o/w emulsion with the lipid and drug dissolved in an organic, water-immiscible solvent (chloroform). The organic solvent is then removed by the application of supercritical... 

Barabassy and Turza (4), using the same set of samples, studied the influence of the lyophilization process on spectral response, by taking reflectance spectra of the mixed powders as prepared and after reconstitution and lyophilization. The SEC increased by more than three times after lyophilization, also showing a calibration range double that before lyophilization, most likely because of residual water in the freeze-dried products. In protein determination the SEC increased from 1.89% to 2.772% after lyophilization, and for fat the SEC increased from 0.128% to 0.166%. The authors concluded that the accuracy obtained was acceptable for industrial practice. The use of NIR spectroscopy in milk powder evaluation could be extended also to applications for classification purposes. 

The properties described above qualify quinophthalone pigments for applications including high quality industrial finishes, coloring of plastics and metal deco inks. Commercial products are supplied as powders, pigment preparations and liquid dispersions. 

Powders from Colloidal Sol-Based Compotdtions. A common example of the synthesis of a single oxide from a colloidal precursor, following a well-known method (Yoldas, 1975), involves hydrolysis of aluminum secondary butoxide by addition of excess water, formation of boehmite, AlOOH and peptization of boehmite by an add to obtain a colloidal sol. Oh et al. (1996), to dte an application, prepared such colloidal sols and also seeded a part ofsuch a sol with 15 wt% ofa-alumina(<0.12/im). Up to 350°C, both the solid products were amorphous. However, seeding caused early (950°C) crystallization of the a-phase, while the unseeded conqiosition led to a late crystallization (1150°C) of the same phase. 

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