Combined Testing Methods

Chapter 4 Examples of combined testing methods for the evaluation of certain hazardous substances are described. In the case of substances whose methods of handling are restricted by law, every evaluation method stipulated in the law is mentioned in this book. 

The challenge of the twenty-first century will be to understand the capabilities and limitations of these methods. Combining information on new molecules obtained from structure-activity relationships with results on macromolecular alterations in Skintex that occur for undiluted molecules may provide more information on dermal toxic effects of particular chemical classes. Combining test methods can provide a... 

Special probe geometries and combinations of different types of magnetic field sensors make an important contribution to the further improvement of the eddy-current testing method and results in new applications. 

The assessment of the contribution of a product to the fire severity and the resulting hazard to people and property combines appropriate product flammabihty data, descriptions of the building and occupants, and computer software that includes the dynamics and chemistry of fires. This type of assessment offers benefits not available from stand-alone test methods quantitative appraisal of the incremental impact on fire safety of changes in a product appraisal of the use of a given material in a number of products and appraisal of the differing impacts of a product in different buildings and occupancies. One method, HAZARD I (11), has been used to determine that several commonly used fire-retardant—polymer systems reduced the overall fire hazard compared to similar nonfire retarded formulations (12). 

Another ASTM test method. Potential Gum (D873), combines the existent gum and the oxidation stabihty tests to measure potential gum. A sample of gasoline is subjected to the oxidation stabihty test for 960 min, filtered to remove particulates, and then subjected to an existent gum test. The potential gum is expressed as the total (unwashed) gum in this test. 

While the carbon dioxide/caiistic test method has become accepted, one should use the results with caution. The chemical reaction masks the effect of physical absorption, and the relative values in the table may not hold for other cases, especially distillation applications where much of the resistance to mass transfer is in the gas phase. Background on this combination of physical and chemical absorption may Be found earher in the present section, under Absorption with Chemical Reaction. ... 

The combination of conductive flooring 7/ia conductive footwear is the preferred method of grounding. Untreated concrete flooring with conductive footwear is usually adequate, but its conductivity should be measured (Fowler and Klein, Static Phenomena and Test Methods for Static Gontrolled Floors, EOS/ESD Symposium Proceedings, pp. 27-38, 1992). Where this method is impractical, personnel grounding devices are available. 

Combination electrical methods Tomashov and Mikhailovsky describe a method developed in the Soviet Union. This test is essentially a combination of resistivity measurement and polarisation rates on iron electrodes in soil in situ. The usefulness and value of this procedure has not as yet been determined by practical application by corrosion engineers. The development of this combination test does, however, represent an attempt to integrate some of the complex factors controlling corrosion rates in soil. Much more research on these factors and methods of measurement should in the future enable the corrosion engineer to evaluate soil properties with respect to application of corrosion-alleviating operations. 

These test methods and the number and complexity of the variables present is related to the level of sophistication of the test. The combination that can influence test data defines the test limitations. Variables are found not only in test methods, but also in other non-test-related areas affecting data generation. Examples include misinterpretation, misuse, or misapplication of the test or any of its integral parts (test setup, test procedure, reporting, etc.) contribute to their limitations (2 to 11, 64,208). 

The Underwriters Laboratories utilizes a combination of methods for environmental conditioning and adhesion testing to evalu-... 

Description of samples tested, specific test methods used, exposure medium notes, solubility parameters, and other important details are provided. Emphasis is on providing all relevant information so the most informed conclusions and decisions can be made by the user. Over 60,000 individual entries (specific tests) are covered in the database. Classes of materials covered include thermosets, thermosetting elastomers, thermoplastics, and thermoplastic elastomers. Approximately 700 different trade name and grade combinations representing over 130 families of materials are included. Over 3300 exposure environments are represented. 

Where the consequences of combining two or more materials under given conditions of temperature, confinement, etc., are unknown and cannot be predicted with certainty, testing may need to be performed to screen for potential incompatibilities. Two common test methods used for this purpose are differential scanning calorimetry and mixing cell calorimetry (described later in this section). 

Linear combination of atomic orbitals (LCAO) method, 16 736 Linear condensation, in silanol polycondensation, 22 557-558 Linear congruential generator (LCG), 26 1002-1003 Linear copolymers, 7 610t Linear density, 19 742 of fibers, 11 166, 182 Linear dielectrics, 11 91 Linear elastic fracture mechanics (LEFM), 1 509-510 16 184 20 350 Linear ethoxylates, 23 537 Linear ethylene copolymers, 20 179-180 Linear-flow reactor (LFR) polymerization process, 23 394, 395, 396 Linear free energy relationship (LFER) methods, 16 753, 754 Linear higher a-olefins, 20 429 Linear internal olefins (LIOs), 17 724 Linear ion traps, 15 662 Linear kinetics, 9 612 Linear low density polyethylene (LLDPE), 10 596 17 724-725 20 179-211 24 267, 268. See also LLDPE entries a-olefin content in, 20 185-186 analytical and test methods for,... 

The following hydrogen gas leakage surveys and test methods may be employed, as applicable, singly or in combination, in accordance with written procedures ... 

The number and type of test pieces exposed for each measurement point will depend on the property being measured. If measurement is non-destructive, e.g., loss of mass or colour, then the same specimens can be used throughout the test, being replaced in the oven after each measurement. If the measurement is destructive then one set of specimens must be prepared for each combination of duration and temperature. It is recommended to expose at least two reserve sets in case the threshold level has not been reached by the end of the last planned duration. Usually the number specified in the relevant test method standard is chosen but, again, the more the better. An example and some of the problems are described in Section 12.2. 

The uncertainty of a measurement is always a very important consideration but it is especially so with durability tests. In addition to the basic physical test methods, there are the complications of exposure conditions, tests spanning long times and the process of extrapolating results to make predictions. The combination of these factors will inevitably lead to large uncertainties that can very easily be of such a magnitude that any conclusions are meaningless. Terms used to describe precision include repeatability, which refers to within laboratory variation and reproducibility, which refers to variation between laboratories. 

The following are the major subjects of the book the various institutions, agencies, and programs involved in chemicals regulation (Chapter 2). The data for hazard assessment (Chapter 3) and the hazard assessment process, i.e., identihcation and characterization of the various toxicological effects and the associated test methods (Chapter 4). Standard setting for threshold effects (Chapter 5) and non-threshold effects (Chapter 6). Exposure assessment (Chapter 7) and risk characterization (Chapter 8). Regulatory standards set by various bodies (Chapter 9) and combined actions of chemicals in mixture (Chapter 10). 

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