Conditioning procedures of test specimen

Conditioning procedures of test specimens and products are important in order to obtain reliable, comparable, and repeatable data within the same or different testing laboratories. Procedures are described in various specifications or standards such as having a standard laboratory atmosphere [50 2% relative humidity, 73.4 1.8°F (23 1°C)] with adequate air circulation around all specimens. The reason for this type or other conditioning is due to the fact the temperature and moisture content of plastics can affect different properties. 

The ASTM test describes in detail the apparatus for measuring compressive properties, preparation of test specimens, conditioning, and procedures. The standard test specimen is recommended to be in the form of a right cylinder or prism whose length... 

This practice covers specific procedures and test conditions for fluorescent UV exposure of plastics, including the preparation of test specimens and the evaluation of test results. The procedures are intended to induce property changes in the plastics... 

The objective of durability testing is to be able to predict the performance of an actual bonded structure on exposure to normal service conditions, based on the observed behavior of test specimens in accelerated laboratory procedures. Except in a few special cases, this is not possible at present. A number of methods, based on reaction rate theory and statistical approaches, show some progress, but, in general, satisfactory predictive methods have yet to be developed. This is important for the future use of structural adhesives, since the ability to predict performance will increase confidence in the use of structural adhesives as a viable joining method. 

Effectiveness of these EP oils can be evaluated by a number of laboratory test units such as those shown in Figure 4. While the American Society for Testing and Materials (ASTM) procedures describe a number of standard test procedures (10), the operating conditions and test specimen materials should be chosen to simulate as nearly as possible those in an appHcation. 

Laboratory tests used in the development of inhibitors can be of various types and are often associated with a particular laboratory. Thus, in one case simple test specimens, either alone or as bimetallic couples, are immersed in inhibited solutions in a relatively simple apparatus, as illustrated in Fig. 19.34. Sometimes the test may involve heat transfer, and a simple test arrangement is shown in Fig. 19.35. Tests of these types have been described in the literatureHowever, national standards also exist for this type of test approach. BSl and ASTM documents describe laboratory test procedures and in some cases provide recommended pass or fail criteria (BS 5117 Part 2 Section 2.2 1985 BS 6580 1985 ASTM 01384 1987). Laboratory testing may involve a recirculating rig test in which the intention is to assess the performance of an inhibited coolant in the simulated flow conditions of an engine cooling system. Although test procedures have been developed (BS 5177 Part 2 Section 2.3 1985 ASTM 02570 1985), problems of reproducibility and repeatability exist, and it is difficult to quote numerical pass or fail criteria. 

As reviewed it is important that test specimens or products be properly prepared based on available specifications and/or standards that provide controlled conditioning procedures when conducting weathering as well as all other tests. The following is one example. There are other conditions set forth to provide for testing at higher or lower levels of temperature and humidity. 

MIL-STD-304 is a commonly used accelerated-exposure technique to determine the effect of weathering and high humidity on adhesive specimens.66 In this procedure, bonded panels are exposed to alternating cold (-54°C) and heat and humidity (71°C, 95 percent RH) for 30 days. The effect of MIL-STD-304 conditioning on the joint strength of common structural adhesives is presented in Table 15.20. However, only relative comparisons can be made with this type of test it is not possible to extrapolate the results to actual service life. 

Blends were produced in a small Banbury mixer. About 3 lb of dry-blended material was added to the Banbury. After the flux point, blends were run for two more minutes and dumped. Conditions were speed No. 2, 30 psi on the ram, and a dump temperature of 310°F. Test specimens were molded on a 3-oz Van Dorn injection-molding machine front, middle, and rear zones were 500, 485, and 470°F, respectively. The mold temperature was 160°F the molding cycle was typical for ABS. Test methods were ASTM Standard Procedures. 

D. Specimen List type of specimens that can be used and recommended volume and minimum volume. Indicate conditions that render the specimen unacceptable, such as hemolysis or lipemia. List patient preparation procedures. Provide instruction for specimen handling before testing. 

Leather is a natural product and is subject to extensive variability. The physical and chemical properties vary considerably depending on the location from which the leather test sample is taken. The standard test method from the American Society for Testing and Materials (ASTM D2813, 1997) ensures random sampling of finished leather and fabricated leather items for physical and chemical tests. Test specimens should be cut from only one side of the backbone with their long dimension perpendicular to the backbone line. Test specimens should be taken from different parts of the shoulder, belly and tail of the leather. The number of specimens taken depends on the reliability of the test results, the deviation and the error of the testing procedures and should be recorded on the test report. Physical tests of leather and leather products, unless otherwise specified, should be performed under the standard atmospheric conditions of 50 4% relative humidity at 23 1 °C. 

In addition to testing methods and product specifications, ASTM Committee D-20 on Plastics has also prepared definitions of terms and recommended practices for molding test specimens and constructing testing equipment, conditioning and weathering procedures, and related standards. These are published in the ASTM books of standards (4-7). There is also a federal standard for laboratory atmospheric conditions for testing (34). 

The procedure specifies a testing machine, loading noses and supports (see Fig. 7.4), micrometers for measuring the width and depth of the test specimen, and conditioning of the test specimens. At least five specimens for each sample should be tested according to the procedure. It should be pointed that according to AC 174, flexural testing of minimum 15 specimens is recommended. 

The ASTM methods recommend test specimens of 12 by 12 or 6 by 6 in. in size. After conditioning as described in the procedure, the specimen shall be weighed and the width, length, and thickness measured. The specimen shall be submerged horizontally or vertically under 1 in. of distilled water at 20°C (68°F). After 24 h of submersion (Method B) the specimen shall be suspended for 10 min to drain, then remaining water wiped off, the specimen weighed, and the thickness measured. The procedure notes that specimens placed in water vertically will absorb considerably more water then those placed horizontally. 

Test values serve to rank materials according to ignition susceptibility under the actual use conditions. The procedure notes that specimens containing high levels of inorganic fillers are difficult to evaluate also, that the same material tested in different forms may give different results. 

A specimen may be in the form of pellets, powder, sheet, film, plastic cellular, or composite materials, with a specimen weight of 3.0 0.2 g. The ASTM procedure describes in detail cutting or folding sheet or film materials and conditioning test specimens. 

Two separate (and not necessarily related) readouts of the test are (a) flame spread along the surface of the specimen as a distance traveled by the boundary of a zone of flame over time and (b) smoke developed as a change in optical density (as a progress curve of light absorption percent) between the light source and the photoelectric cell mounted in the vent pipe. These data are used to calculate the respective FSI and SDI as described in the ASTM test procedure. The indexes are calculated as relative values to those of select grade oak (FSI arbitrarily set as 100) and inorganic reinforced cement board (FSI set as 0) surfaces under the specified conditions. 

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