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3.9. Dielectric breakdown voltage (applicable only to Grade A tubing)—The tubing shall have a minimum dielectric breakdown voltage as specified in table 4 when tested in accordance with 4.9.
TABLE 4. Minimum dielectric breakdown voltage for Grade A, PTFE tubing Dielectric breakdown, minimum
Nominal wall thickness
3.10. Low temperature flexibility-The tubing shall remain flexible and free from cracks when tested in accordance with 4.10.
3.11. Minimum proof pressure (applicable only to Grade B tubing)—The tubing shall have a minimum proof pressure as specified in table 5 when tested in accordance with 4.11.
TABLE 5. Minimum proof pressure for Grade B, PTFE tubing
3.12. Color stability-The tubing shall exhibit no significant change in color after heat-aging for 5 hours at 200 ± 2 °C (392 4°F). This can be determined after completion of the heating cycle described in 4.10. The color of the tubing shall be as agreed upon by purchaser and seller.
4. INSPECTION AND TEST PROCEDURES
4.1. General-The inspection and test procedures contained in this section are to be used to determine the conformance of products to the requirements of this Voluntary Product Standard. Each producer or distributor who represents his products as conforming to this Standard may utilize statistically based sampling plans which are appropriate for each particular manufacturing process but shall keep such essential records as are necessary to document with a high degree of assurance his claim that all of the requirements of this Standard have been met. Additional sampling and testing of the product, as may be agreed upon between purchaser and seller, is not precluded by this section.
4.2. Test conditions-The test specimens shall be conditioned and tested in accordance with procedure A of ASTM D 618-61, Standard Methods of Conditioning Plastics and Electrical Insulating Materials for Testing.2
See footnote 1, page 2.
4.3. Dimensions and tolerances
4.3.1. Inside diameter-The inside diameter shall be determined in accordance with ASTM D 1675-65, Standard Methods of Testing Electrical Grade Polytetrafluoroethylene Tubing.3
4.3.2. Wall thickness-The wall thickness shall be determined in accordance with the procedures described in ASTM D 1675-65, except that no individual measurement shall exceed the tolerances specified in tables 1 and 2.
4.4. Melting point-The melting point shall be determined in accordance with section 14 of ASTM D 1457-69, using a shaving from the tubing rather than a molded disk.
4.5. Specific gravity-The specific gravity shall be determined in accordance with method A of ASTM D 792-66, Standard Methods of Test for Specific Gravity and Density of Plastics by Displacement.s
4.6. Tensile strength and elongation-The tensile strength and elongation shall be determined as specified in 4.6.1, 4.6.2, 4.6.3, and 4.6.4 on five longitudinal specimens and on five transverse specimens using a testing speed of 2 inches per minute. The test results for the longitudinal and the transverse specimens shall be averaged separately. Specimens which break in the jaws of the tensile tester shall be discarded, and new tests shall be made.
4.6.1. Tubing having an inside diameter of 0.625 inch and overThe tensile strength and elongation shall be determined in both the longitudinal and transverse directions in accordance with ASTM D 1457-69.
4.6.2. Tubing having an inside diameter less than 0.625 inch to 0.200 inch, inclusive-The tensile strength and elongation shall be determined in the longitudinal direction in accordance with ASTM D 1457-69, and in the transverse direction in accordance with ASTM D 412-68, Standard Method of Tension Testing of Vulcanized Rubber. Transverse specimens shall be ring specimens cut from tubing using the technique provided for heavy-walled tubing greater than 0.060 inch in thickness in paragraph 4.4.1 of ASTM D 412-68.
4.6.3. Tubing having an inside diameter less than 0.200 inch to 0.090 inch, inclusive-The tensile strength and elongation shall be determined in both the longitudinal and transverse directions in accordance with ASTM D 412-68. For longitudinal specimens, the tubing shall be slit parallel to the axis and flattened out, prior to punching out specimens. Specimen shape shall be in the form of a dumbbell as shown in figure 1. Transverse specimens, 1/4 inch long, shall be prepared in accordance with paragraph 4.4.1 of ASTM D 412-68.
3 See footnote 1, page 2.
FIGURE 1. Tensile specimen for tubing of 0.200 inch to 0.090 inch inclusive.
4.6.4. Tubing having an inside diameter less than 0.090 inchSpecimens shall be tested as filaments. Nonslip type loop knots shall be made in each end of the specimen so that there are 18% inches between the knots of the loops (see figure 2). The loops shall be placed over the drum of a standard wire specimen holder in the tensile machine and pulled in this position.
FIGURE 2. Tensile specimen for tubing less than 0.090 inch.
4.7. Weight loss-The loss in weight shall be determined in accordance with ASTM D 1675-65, except that the minimum weight of the test specimens shall be 50 grams, and the specimens shall be heated in a forced-draft oven for 3 hours at 300 ± 5°C (572 +9°F).
4.8. Dimensional stability-Cut a 10-inch specimen of tubing and determine the inner diameter and maximum and minimum wall thicknesses in accordance with 4.3.1. and 4.3.2. Place the specimen
on a steel mandrel having a diameter from 3 to 10 percent less than the inside diameter of the specimen. Mark and number a point at each end of the specimen on a line parallel to the axis of the tubing. Mark three more points at each end of the tubing at 90° intervals from the original points, and measure the linear distance between each set of parallel points using a steel rule or vernier calipers accurate to 0.01 inch. Remove the mandrel and place the specimen on a perforated tray, in an unrestrained position, in an oven for 3 hours at 2605 °C (500±9 °F). Remove the tray and allow the specimen to cool to 23 ± 1 °C (73.4 ± 1.8 °F). Slip the specimen onto the mandrel and take a new set of measurements. Determine the percent change in the distance between each of the four sets of points. Determine the inner diameter and maximum and minimum wall thicknesses at each end in accordance with 4.3.1 and 4.3.2. The percent change of any dimension shall not exceed that specified in table 3.
4.9. Dielectric breakdown voltage-The dielectric breakdown voltage shall be determined in accordance with ASTM D 1675-55.
4.10. Low temperature flexibility-Three specimens, each 12 inches long, shall be placed in a circulating-air oven at 200 ± 2 °C (3924 °F) for 5 hours, cooled to room temperature, and then conditioned at minus 55 ± 2 °C (-674 °F) for 4 hours. A fixed mandrel, selected in accordance with table 6, shall be conditioned at the same temperature. After completion of the conditioning period and while still maintained at the conditioning temperature, the specimens shall be rapidly wrapped about the mandrel for not less than two complete wraps. The speed of wrapping shall be approximately 2 seconds per 360° wrap.
4.11. Minimum proof pressure-A 5-foot-long test specimen shall be clamped off at one end and attached at the other end to a pressurizing device capable of maintaining air pressure to within plus or minus 1 psig of the minimum proof pressure specified in table 5 for the duration of the test. Immerse the entire specimen in water, adjust the air to the specified pressure, and maintain this pressure for at least 2 minutes. The presence of any bubbles emanating from the specimen shall constitute failure.
In order that purchasers may identify products conforming to all requirements of this Voluntary Product Standard, producers and distributors may include a statement of compliance in conjunction with their name and address on product labels, invoices,