Testing methods dispersion test

Testing of phthalocyanines includes crystallization (qv), flocculation, and appHcation in paints, plastics (qv), and printing inks (1). The ASTM standard specifications include CuPc in dry powder form for various appHcations (153). The specifications cover color (qv), character or tint, oil absorption, reactions in identification tests, and dispersions and storage stabiUty. Quantitative deterrninations are possible with ceric sulfate (30) or sodium vanadate (154). Identification methods are given (155), including tests for different appHcations. 

Specifications and Standards Test Methods. Hydroxyethylcellulose is included in the Hst of materials that are in compHance with requirements of the U.S. EDA for use in adhesives and in resinous and polymeric coatings employed on the food-contact surfaces of metal, paper, or paperboard articles, and other substrates intended for use in food packaging as specified in CER 21. HEC made dispersible by cross-linking with glyoxal is cleared only as an adhesive and as a component of paper and paperboard in contact with food. It has not been cleared as a direct food additive. 

Testing. Various test methods are provided by ASTM (16). These iaclude pigment tests of importance such as chemical analysis, presence of oversize particles, oil absorption, particle size distribution, degree of dispersion, presence of soluble components, etc. Numerous tests are also given by ASTM for the properties of filled and unfilled polymers. These iaclude, for example, such properties as impact resistance, stiffness, viscosity, tear resistance, hardness, color, and electrical resistivity. 

Comparison of Models Only scattered and inconclusive results have been obtained by calculation of the relative performances of the different models as converiers. Both the RTD and the dispersion coefficient require tracer tests for their accurate determination, so neither method can be said to be easier to apply The exception is when one of the cited correlations of Peclet numbers in terms of other groups can be used, although they are rough. The tanks-in-series model, however, provides a mechanism that is readily visualized and is therefore popular. 

Many computer codes, both public and private, are available to model dense cloud dispersion. A detailed review of these codes, and how they perform relative to actual field test data, is available (Hanna, Chang, and Strimaitis, Atmospheric Environment, vol. 27A, no. 15, 1993, pp. 2265-2285). An interesting result of this review is that a simple nomograph method developed by Britter and McQuaid (1988) matches the available data as well as any of the computer codes. This method will be presented here. 

Scale-up techniques for using the results of pilot plant or bench scale test w ork to establish the equivalent process results for a commercial or large scale plant mixing system design require careful specialized considerations and usually are best handled by the mixer manufacturer s specialist. The methods to accomplish scale-up will vary considerably, depending on whether the actual operation is one of blending, chemical reaction tvith product concentrations, gas dispersions, heat transfer, solids suspensions, or others. 

A test to determine the biodegradation rate of the dispersant and the biodegradation rate of the dispersant-oil mixture has been proposed [1302]. The test method is intended to supplement the toxicity tests and the effectiveness tests, which evaluate the performance of oil spill dispersants. 

Comparison of Effectiveness Tests. Three laboratory methods were compared the revised standard dispersant effectiveness test used and required for regulation in the United States, the swirling flask test (developed by Environment Canada), and the IFP-dilution test (used in France and other European countries) [1693]. Six test oils and three dispersants were evaluated. It was concluded that the three tests gave similar precision results, but that the swirling flask test was fastest, cheapest, simplest, and required the least operator skill. 

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