ARTC Craze Test

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TEST METHOD FOR

CRITICAL CRAZING STRESS OF PLASTIC MATERIALS WITH A GIVEN SOLVENT
(Test originally developed by the Aircraft Research Testing
Committee of the Aircraft Industries Association of America
for transparent plastic enclosure materials in May, 1952)

1. SCOPE:

1.1 This method of test Is used to determine the critical crazing stress of plastics with a given solvent, paint remover or thinner.

2. APPARATUS:

2.1 A cantilever jig to permit the stressing of specimens as illustrated In the attached photograph and constructed In accordance with the attached Sketches I and 11.'

2.2 A test specimen drilling jig constructed in accordance with the attached Sketch Ill.

2.3 A test specimen marking jig constructed In accordance with the attached Sketch Ill.

2.4 A portable specimen rack as illustrated In the attached Sketch IV.

2.5 A forced-circulation air oven and a constant temperature-constant humidity (73°F (23°C) and 50% R.H.) room for conditioning the test specimens and conducting the test.

2.6 A bench micrometer reading from 0 to 1.025" by 0.001" increments.

2.7 Suitable weight assemblies with weights, aluminum cups and shot.

2.8 A beam balance, capacity 0 to 21 pounds, by 0.01 pound divisions.

2.9 A quantity of 1/2" x I” pieces of number I Whatman Filter Paper.

2.10 A stop watch.

3. SOLVENTS.

3.1 Any or all of the following solvents.

3.1.1 Isopropanol meeting specification MIL-T-6094A.

3.1.2 Lacquer Thinner meeting specification MIL-T-6094A.

3.1.3 Toluene, Reagent grade.

3.1.4 Butyl Lactate Reagent grade.

3.1.5 Clear Keystone Grip-Flex 20-200 Spraying Lacquer, thinned to a 19 second Ford cup Viscosity

3.1.6 Any other solvent paint remover, thinner or material desired.

4. SPECIMENS:

4.1 Six standard I" x 7” x 0.250" or 0.125” crazing test specimens shall be used for each solvent. (The cantilever jig as illustrated was designed to test nominal 0.250" thick specimens and the geometry of the test Is effected when testing specimens of other thicknesses. It has been frequently used to evaluate 0.125" thick specimens, but should not be used to compare materials of various thicknesses.)

4.2 The specimen shall be freed of alI saw marks, chipped edges and other irregularities by shaping.

5.CONDITIONING:

5.1 Test specimens shall be preconditioned in accordance with one of the following procedures:

5.1.1 ASTM D618-61 Procedure B - 48 hours at 122°F (50°C) followed by cooling to room temperature in a desiccator over anhydrous calcium chloride or sulfate for at least 5 hours. Designate as condition I. (This is the method generally used by the Physics Laboratory.)

5.1.2 Two hours at the annealing temperature (Note I), fast cooled and followed by 7 days at 73°F (23°C) and 50 percent relative humidity. Designate as Condition II. - (This is the method generally used by the Altuglas Plastics Technology Center.

5.1.3 ARTC Method - 16 hours at 25°F (14°C) below their average deflection temperature under flexural load, cooled at a rate not exceeding 50°F (22°C) per hour, followed by 96 hours at 73 + 2°F (23 + 1°C) and 50 + 5 percent relative humidity. Designate as Condition III. (Conditioning by this procedure duplicates the test method outlined in the May 13, 1952 "Revised Tentative Requirements For Transparent Plastic Enclosure Materials" of the Aircraft Research and Testing Committee, of the Aircraft Industries Association of America, Inc.)

5.1.4 ASTM D618-61A - As received, no conditioning, samples should be held a minimum of 72 hours at 73°F(23°C) and 50 percent relative humidity before testing. Designate as Condition IV.

Note I. The following annealing temperatures are recommended: 248°F ( 120°C) for Plexiglas 55. 194°F (90°C) for Plexiglas G, Plexiglas K, and Plexiglas II sheets and Plexiglas V type molding powders, and Plexiglas 70 and Plexiglas DR. 176°F (80°C) for Plexiglas VM and 158°F (70°) for Plexiglas VS molding powders.

Note 2. Generally, conditions I and IV will yield lower values then II and III.

6. CALCULATION OF LOADS:

6.1 The specimen shall be placed In the marking jig and a pencil line shall be drawn up the sides of the specimen at 4" from the center of the 1-1/4" diameter hole.

6.2 The width and thickness of each specimen shall be measured to the nearest 0.001" at the pencil marks. These data along with the identification of the specimen shall be entered in the required records.

6.3 The load to be used with each specimen shall be calculated according to the following formula:

P =	SWT2
	6L

where, P = Load In pounds.
S = Maximum fiber stress in psi
L = Length of specimen from fulcrum to center of applied load in Inches.
W = Width of specimen in Inches.
T = Thickness of specimen In inches.

7. PROCEDURE:

7.1 The first specimen shall be tested at 2000 psi outer fiber stress. The specimen assembly shall be inserted In the crazing jig with the pencil marks in line with the center of the fulcrum.

7.2 The load shall be applied for ten minutes before the addition of solvent to the filter paper placed directly over the fulcrum. The filter paper shall be moved periodically during the five minute observation period and the actual time to craze shall be recorded. After five minutes of solvent applications the test shall be terminated.

7.3 If the specimen Is crazed the second specimen shall be tested at 1000 psi. If the specimen did not craze the second specimen shall be tested at 4000-psI. Should crazing at 4000 psi not occur the stress Is continually increased by 2000 psi until crazing occurs.

7.4 If the second specimen at 1000 psi Is not crazed, the third specimen shall be tested at 1500 psi; if this specimen crazes the stress shall be reduced to 500 psi. The fourth specimen is tested at a lower or higher stress depending upon whether the third specimen did or did not craze. This procedure shall be continued until all specimens are tested and the critical crazing stress determined. (The Physics Laboratory tests their first specimen at 4000 psi and works up or down accordingly.)

7.5 The critical crazing stress shall be reported as the stress midway between the stress at which crazing was and was not observed. Example: Crazing was observed at 2000 psi and none at 1938 psi. The critical crazing stress would be 1969 + 31 psi.

(thickness)2 x width x psi

7.6 In the examination of crazing, all cracks at the edge of the specimen shall be noted as "edge crazing" and disregarded in determining the end point unless they grow and extend more than half way across the width of the specimen. (The Physics Laboratory disregards "edge crazing" unless it grows and extends across the entire width of the specimen.)

8. REPORT:

8.1 The report shall include the following:

8.1.1 The identification of the material.

8.1.2 The nominal thickness of the material.

8-1-3 The conditioning procedure used.

8.1.4 The critical crazing stress in psi.

8.1.5 The date of the test.

ARTC CRAZE TEST CONDITION #3
PLACE SAMPLES IN 180°F LYDON OVEN OVERNIGHT. TAKE SAMPLES OUT OF OVEN THE NEXT MORNING AND PLACE THEM IN WATER (1 GAL. JARS). LEAVE SAMPLES IN WATER FOR 24 HRS. NEXT MORNING TAKE EACH SAMPLE OUT OF WATER 1.75 -2 HOURS PRIOR TO TESTING AND TOWEL DRY SAMPLE. MAKE SURE EACH SAMPLE IS OUT OF WATER NO MORE THAN A PERIOD OF 2.25 HRS.

The statements, technical information and recommendations obtained herein are believed to be accurate as of the date hereof. Since the conditions and methods of use of the product and of the information referred to herein are beyond our control, Arkema expressly disclaims any and all liability. NO WARRANTY OF FITNESS FOR ANY PARTICULAR PURPOSE, WARRANTY OR MERCHANTABILITY, OR ANY OTHER WARRANTY, EXPRESS OR IMPLIED, IS MADE CONCERNING THE GOODS DESCRIBED OR THE INFORMATION PROVIDED HEREIN. The information provided herein relates only to the specific product designated and may not be applicable when such product is used in combination with other materials or in any process. The user should thoroughly test any application before commercialization. Nothing contained herein should be construed as an inducement to infringe any patent, and the user is advised to take appropriate steps to be sure that any proposed use of the product will not result in patent infringement.

See MSDS for Health and Safety Considerations.