Physical Testing Methods 2 Viscosity

The quality of the ketchup that the American consumer uses on hamburgers and hotdogs is often judged by its resistance to flow. A ketchup that has a thick, flow-resistant consistency is generally considered to be of higher quality than one that flows readily from the bottle. However, this same consumer may become frustrated when the resistance to flow is so high that the ketchup does not flow in a timely manner from the bottle. The most desirable ketchup is thus the one that is judged to have a resistance to flow that is somewhere between the two extremes. 

The same might be said of ordinary house paint. Paint that has a low resistance to flow is runny and will likely not provide satisfactory coverage of a wall with just one coat. It is therefore judged to be of poorer quality than one that does provide good one-coat coverage. On the other hand, paint that is thick and gummy may also be judged to be of poorer quality because it may not be possible to apply it uniformly with either a brush or roller. 

There are dozens of other examples around the house for which we have similar quality standards in terms of their resistance to flow. Examples include other food products such as honey, pancake syrup, gravy, and ice cream toppings. Hygiene products include shampoo, hand lotion, and liquid soap. We might also cite pharmaceutical formulations, such as cough medicines, milk of magnesia, and liquid dietary supplements, as well as home and car care products such as caulks, glues, and motor oils. 

Just as a consumer may judge the quality of a product by its resistance to flow, so also quality assurance technicians in the chemical process industries may judge the quality of a fluid material or product by its resistance to flow. Examples include solutions of polymers (where a solution s resistance to flow is indicative of the quality of the undissolved polymer), asphalt formulations for roads and parking lots, lubricating oils, etc. 

Kirk Hunter of Texas State Technical College in Waco, Texas, authored Sections 15.4 and 15.6-15.10. 

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Standardized test methods for analyzing the chemical composition, viscosity, and physical properties of cellulose esters have been adopted by the ASTM and are described in substantial detail (110). 

The physical properties important for the projected use of hydraulic fluids are viscosity, density, foaming behavior, and fire resistance. There is no generally recognized test method for measuring flammability of hydraulic fluids, although various test methods maybe utilized (Moller 1989). 

The substitution of more benign solvents in many formulations will have global ramifications. For example, water-reducible coatings are products where the solvent system used to disperse and suspend solids is primarily water. The remainder of the solvent system may contain liquids that are classified as flammable or combustible liquids. Inherent limitations in these systems relate to product viscosity, accuracy in predicting overall fire hazard, abihty to assess physical changes of state when a product is tested, and test method rehabihty and ease of use (Scheffey and Tabar, 1996). 

It may also be necessary to test the incoming bulk materials in-house. These inspections usually consist of an evaluation of physical and chemical properties, such as color, viscosity, percentage of solids, weight per gallon, and moisture content. The tests should be those that can quickly and accurately detect deficiencies in the materials physical or chemical properties or differences from lot to lot. ASTM lists various test methods that are commonly used for acceptance of raw materials. Several of the more common test methods are described in Chap. 20. 

Rheology of SA Binders. Conventional test methods such as softening point, viscosity, penetration, Fraas break point, ductilities, etc. have been used to characterize the rheology of SA binders (11). The physical structure of SA binders is complex, and the sulfur-asphalt and sulfur-aggregate interaction make correlations to asphalt and to binder properties for aggregate rather difficult. 

Elemental Analysis and Physical Properties. Elemental analysis was accomplished by conventional microanalytical techniques in a commercial testing laboratory. Density, refractive index, average molecular weight (VPO), Conradson carbon residue, and ash content were determined by standard methods. Viscosity was determined by a cone-plate viscometer. Simulated distillation was accomplished using a y4" x 18" column of Anachrome Q, 3% Dexil 300, programmed from -30 to... 

A wide variety of tests is performed in TMA, which are adapted from physical tests that were used before the instrument became commonly available. These tests may also be modeled or mimicked in TMA, such as heat distortion (Fig. 9) and softening points. Methods to obtain the modulus, compressive viscosity, and penetrative viscosity have been developed. Many of these methods, such as ASTM D648 for example, will specify the stress the sample needs to be exposed to during the run. In D684, a sample is tested at 66 and 264 psi. Most TMAs on the market today have software available that allows them to generate stress—strain curves and to run creep—recovery experiments. Some are also capable of limited types of stress relaxation studies (for example a constant gauge length test " ). 

Analysis performed in the field is faster and more economical than analysis done in a laboratory. As analytical techniques are constantly improving and lighter and more portable equipment is being developed, more analytical work can be carried out directly in the field. Test methods are now available for measuring physical properties of oil such as viscosity, density, and even flash point in the field. Test kits have also been developed that can measure total petroleum hydrocarbons directly in the field. While these test kits are less accurate than laboratory methods, they are a rapid screening tool that minimizes laboratory analysis and may provide adequate data for making response decisions. 

ASTM D 1545-93. Standard test method for viscosity of transparent liquids by bubble time method. ASTM D 5201-97. Standard practice for calculating formulation physical constants of paints and coatings. ISO/FDIS 11890-1-99. Paints and varnishes - Determination of volatile organic compound content (VOC)... 

The objective in this study was to compare the long-term performance of these oils. To do this, changes in chemical and physical properties of the used oils were monitored using American Society of Testing Materials (ASTM) standard test methods [2]. Typically, used engine oil analyses include measurements of viscosity, acid and base numbers, water, glycol, soot, and metals content. In addition to the standard tests, fuel economy, deposit-forming tendencies, and friction and wear characteristics were determined on new and used oil samples in this study. 

Hundreds of test methods referring to polyolefin properties are actually employed. They consist of both physical (hardness, stiffness, tensile properties, solubility, viscosity, etc.) and chemical (acetone extractable, carbonyl content, etc.) tests, representing the objects of international, national, or industrial standards and specifications. Some of them, elaborated by ASTM Committee D-20, Subcommittee XII, Polyolefin Plastics, are indicated in Table 1. 

Because the quality and health aspects of foods cannot be measured by a single index, it necessarily follows that the subject of control methods in the canned food industry is very broad, and includes chemical, physical, organoleptic, and bacteriological tests, only the first of which is discussed here. The measurement of color, odor, optical clarity, texture, viscosity, and chemical composition has been used to evaluate canned foods, but in many cases the methods that are applicable to one product are either not applicable to another, or can be used only after considerable modification. 

Measurements of the common physical constants such as boiling point or refractive index are not sufficiently sensitive to determine the trace amounts of impurities in question. Besides the common spectroscopic methods, techniques like gas chromatography (GC), high-pressure liquid chromatography (HPLC), or thin-layer chromatography (TLC) are useful. The surest criterion for the absence of interfering foreign compounds lies in the polymerization itself the purification is repeated until test polymerizations on the course of the reaction under standard conditions are reproducible (conversion-time curve, viscosity number of the polymers). 

The key parameter for any drug product is its efficacy as demonstrated in controlled clinical trials. The time and expense associated with such trials make them unsuitable as routine quality control methods. Therefore, in vitro surrogate tests are often used to assure that product quality and performance are maintained over time and in the presence of change. A variety of physical and chemical tests commonly performed on semisolid products and their components (e.g., solubility, particle size and crystalline form of the active component, viscosity, and homogeneity of the product) have historically provided reasonable evidence of consistent performance. More recently, in vitro release testing has shown promise as a means to comprehensively assure consistent delivery of the active component(s) from semisolid products. 

Many of the tests described involve physical properties such as refractive index, viscosity or melting point of the fat, of the fatty acids or of the lead salts of the fatty acids. However, there were also many chemical tests such as Reichert, Polenske, iodine, saponification and acetyl values. These all gave information as to the composition of the fat, some information as to fatty acid composition, others as to other non-glyceride components of the fat. Thus the iodine value is a measure of unsaturated fatty acids in the fat, now obtainable in more detail from a fatty acid profile. Similarly the Reichert value is a measure of volatile fatty acids soluble in water. For most purposes this means butyric acid, and so the modem equivalent is the determination of butyric acid in the oil. The modem method for milk-fat analysis is thus carrying out the analysis in a similar way to the Reichert determination, but uses a technique that is less dependent on the exact conditions of the analysis and is thus less likely to be subject to operator error. The Reichert value could be useful, in theory, even if milk fat was not present. Lewkowitsch notes that some other oils do give high values. Porpoise jaw oil has a value almost twice that of milk fat, while some other oils also have significant values. It is unlikely that one would have come across much porpoise jaw oil even in 1904, and even less likely today. 

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