Testing coating powders

Solvent absorption measurement has been shown to be a sensitive and useful test method in the manufacture of epoxy powder coatings. A test method was defined and the effects of time and temperature of immersion described. It was shown that solvent absorption is a measure of raw material properties (EEW of the epoxy resin, and CTBN elastomer type and concentration), the homogeneity of the extrudate, as well as the state of cure. The information obtained from solvent absorption measurements has proven to be extremely important not only in quality control analysis but also in providing an insight into the structure function relationships in epoxy resin chemistry. 

DIN 55690 classifies and identifies coating powders according to the binder. Standards for testing coating powders in powder form are summarized in Table 3.9. Relevant European standards (CEN) have not yet been drafted. Quality aspects are described in detail in [3.50]. 

Table 3.9. Standards for testing coating powders in powder form...

A catalytic activity test of the MOjC-coated powder revealed that at 275°C, it had comparable activity to commercial bulk MOjC after 1 h on stream. At these conditions Ihe carbon monoxide conversion with the MAFBS-prepared... 

Methods for evaluating the performance of powder coatings are the same as those used for conventional coatings. Test methods for coating powders include particle size distribution, powder free flow, sintering, fluidization characteristics, and others. They have been reviewed in detail and reported in the literature (120,121). In addition, the American Society for Testing and Materials has issued a comprehensive standard that covers the most important test methods for the evaluation and characterization of powder coatings (122). 

ASTM D3451-01, Standard Guide for Testing Coating Powders and Powder Coatings, 2001. 

Easily available commercial polymers which show promising solubilities are polyvinyl chloride, polystyrene. Nylon 6T (polyterphthalamide), polyethyleneoxide and polyisoprene. Some low molecular weight casting resins were examined. The polymer resins Acyloid B72 and B66, polyester PE 20 were soluble in tetrahydrofuran and dimethylformamide but suitable films could be cast from THF. A coating powder was also tested (nylon 11) but was found to be insoluble in all solvents. Solvent mixtures (TFA/DMF, TFA/CHCl and others were tried. 

Nonferrous Metals-, Electrodeposition Coatings-, Metal Powders-, Surgical Implants, Part 7, 1972 Annual Book ofASTM Standards, American Society for Testing Materials, Philadelphia, Pa., 1972. 

In the United States, a number of physical tests are performed on siUcon carbide using standard AGA-approved methods, including particle size (sieve) analysis, bulk density, capillarity (wettabiUty), friabiUty, and sedimentation. Specifications for particle size depend on the use for example, coated abrasive requirements (134) are different from the requirements for general industrial abrasives. In Europe and Japan, requirements are again set by ISO and JSA, respectively. Standards for industrial grain are approximately the same as in the United States, but sizing standards are different for both coated abrasives and powders. 

The relative reactivity of thermosetting powders can be easily deterrnined by the gel time or stroke-cure test. A small amount of powder is placed on a hot plate, usually at 200°C, and the time until the coating composition gels, or no longer forms fibers, is deterrnined. Powders are characterized by relative gel times (cure rate) as shown in Figure 1. 

Paint—Tests for Formulated Products and Applied Coatings" and "Standard Recommended Practices for Testing Polymer Powders ia Powder Coatings," ASTM 3451, 1991 MnnualBook ofMSTM StandardsYo. 06.01, American Society for Testing and Materials, Philadelphia, Pa. 

For parenteral use, the antibiotic is packed in sterile vials as a powder (reconstituted before use) or suspension. For oral use it is prepared in any of the standard presentations, such as film-coated tablets. Searching tests are carried out on an appreciable number of random samples of the finished product to ensure that it satisfies the stringent quahty control requirements for potency, purity, freedom horn pyrogens and sterility. 

Direct and indirect competition formats, illustrated in Figure 1, are widely used for both qualitative and quantitative immunoassays. Direct competition immunoassays employ wells, tubes, beads, or membranes (supports) on to which antibodies have been coated and in which proteins such as bovine semm albumin, fish gelatin, or powdered milk have blocked nonspecific binding sites. Solutions containing analyte (test solution) and an analyte-enzyme conjugate are added, and the analyte and antibody are allowed to compete for the antibody binding sites. The system is washed, and enzyme substrates that are converted to a chromophore or fluorophore by the enzyme-tracer complex are added. Subsequent color or fluorescence development is inversely proportionate to the analyte concentration in the test solution. For this assay format, the proper orientation of the coated antibody is important, and anti-host IgG or protein A or protein G has been utilized to orient the antibody. Immunoassays developed for commercial purposes generally employ direct competition formats because of their simplicity and short assay times. The price for simplicity and short assay time is more complex development needed for a satisfactory incorporation of the label into the antibody or analyte without loss of sensitivity. 

Garlic supplements - powder tablets or capsules, steam-distilled oil, vegetable oil macerate extract, or extract aged in dilute alcohol - are widely available and are taken by millions. Since the active principle, allicin, is not present in garlic bulb, the supplements rely on the presence of precursor alliin and enzyme alliinase. In tests on 24 commercial brands of enteric-coated tablets, all except one gave low dissolution allicin release 83% of the brands released less than 15% of their potential allicin.78,79 Relevant factors were impaired enzyme activity caused by excipients and slow tablet disintegration. Caveat emptor ... 

Polyester polyols, 25 464 468 Polyester resin(s), 11 302 coating resins, 7 104-106 cyclopentadiene and dicyclopentadiene applications, 8 230 flammability of, 20 115-116 properties in powder coating, 7 43t standard test methods for, 20 11 It unreinforced, 10 187t weathering of, 20 116 Polyester resin-based powder coatings, organic titanium compounds in, 25 125 Polyester resin composites, 26 762-763 Polyester resin formulations ingredients of, 20 96t unsaturated, 15 511-512 Polyesters, 10 185-189, 497 12 655-656. See also Thermoplastic polyesters Unsaturated polyesters acid resistance of, 20 7-8 antioxidant applications, 3 121 aromatic ionic, 23 722 based on 1,4-cyclohexanedimethanol, 12 674-675... 

---