1、 FORD LABORATORY TEST METHOD BO 127-03 Date Action Revisions Rev. 05 2017 07 07 Revised See Summary of Revisions L. Schmalz, NA 2016 07 05 Revised See Summary of Revisions L. Schmalz, NA 1994 12 20 Released Controlled document at www.MATS Copyright 2017, Ford Global Technologies, LLC Page 1 of 3 STR
2、ESS CRACKING TEST FOR PLASTICS Application This procedure is used to determine the resistance of thermoplastic materials to stress cracking when they are used in direct contact with other materials, such as oil, grease, cleaners, flexible PVC and elastomers. All amorphous materials (such as PC, PC/A
3、BS ABS, SMA, ASA, PPO, PMMA) should be evaluated for potential incompatibility with other materials that they may come in contact with. For example, polycarbonate should be tested with grease used on fasteners; vinyl should be tested for compatibility with the substrate material they are covering. I
4、f in doubt, contact the Design and Release Engineer for a specific list of agents. Apparatus Required Mechanical Convection Oven Conforming to ASTM E145 Type IIA normal oven or equivalent and capable of maintaining the specified temperature within +/- 1 C. Test Fixtures Construct a mandrel from chem
5、ically inert materials such as wood or aluminum with the radius needed to achieve the required percent strain. The samples should be attached to the mandrel in a manner which will not interfere with the test results. Source: Automate Industries Inc. 1906 Brinston Troy, MI 48083 Phone: 248-740-7022
6、Stereo Microscope 20X magnification AATCC Crockmeter Cloth (style 3) 80 x 84 thread count, combed cotton, desized, bleached (no optical brightener or finishing material present). Source: Test Fabrics, Inc. P.O. Box 26 415 Delaware Ave. West Pittston, PA 18643 Phone: (717) 603-0432 FORD LABORATORY T
7、EST METHOD BO 127-03 Copyright 2017, Ford Global Technologies, LLC Page 2 of 3 Procedure 1. Prepare Type 1A and 1B bars per ISO 527-2 or as agreed upon by the Ford Materials Engineer. A minimum of four tensile bars shall be prepared. In the instance of material suspected of exhibiting anisotropy, sp
8、ecimens should be obtained parallel and perpendicular to the “material flow“ and should be identified as such. 2. Care should be taken to assure that the test fixtures are carefully cleaned prior to each test to avoid possible contamination from previous tests. Assemble the tensile bars in the test
9、fixtures to achieve the 1% strain level (or as specified in the engineering document). The back of the samples should fully contact the test fixture to achieve the desired strain level. 4. Examine the samples throughout the gauge length for cracks using 20X on the stereo microscope (after applicatio
10、n of stress, but prior to application of the chemical agent). This is to establish the initial strained condition. 5. Apply the chemical agent (within 2 hrs. of assembling the test bar onto the test fixture) to a minimum of three tensile bars. (Do not apply the chemical agent to one bar that will se
11、rve as the “control”). . Liquid Chemical Agent (oil or cleaners) 2 pieces of cotton crock cloth should be placed on top of each other in the strained area of the test bar, and saturated with approximately 1 ml of the agent. Replenish every 24 hours with new crock cloth. High Viscosity Chemical Agent
12、s (grease) 0.2 grams applied to the strained area of the test bar. Flexible Chemical Agents (PVC or elastomer sheets) Overlaid on the strained area of the test bar. 6. Expose the samples for 72 hours at 80 +/- 2C. Expose the control sample in a separate oven in order to avoid contamination. 7. At th
13、e end of the test period, remove the chemical agent by wiping with a soft cloth or scraping. DO NOT USE A SOLVENT. 8. Allow the strained sample to condition for 1 h at 23 +/- 2C and 50 +/- 5% relative humidity. 9. Using a stereo microscope, examine the strained sample for cracking and crazing at 20X
14、 magnification while the sample is still in the test fixture. 10. Report the chemical agent, amount, application frequency and the presence of cracking or crazing. Bend Radii Required to Produce 1% Strain for 4.00 mm Thickness Sample Thickness (mm) % Strain Radius (mm) 4.0 1 198 For other sample thi
15、cknesses, the following formula may be used to determine the correct radius: R = T x 100 1 2 E Where R = radius T = test sample thickness E = % strain FORD LABORATORY TEST METHOD BO 127-03 Copyright 2017, Ford Global Technologies, LLC Page 3 of 3 Summary of Revisions 2017 07 07 Removed immersion sta
16、tement for oils in step 5. Clarified removal of chemical agent. 2016 07 05 Removed ASTM D573 reference for oven, as it referenced ASTM E145. Added AATCC Crockmeter Cloth (style 3) Removed initial conditioning Removed Chemical Agent table 2006 06 21 Updated application, test bars, Step #1, 3, 5, 6, 7 Added Possible Chemical Agents for Chemical Compatability 2005 01 12 Revised Text Fixtures, Stereo Microscope; Procedure 1, 3, 5, 6, 8, 9, 10; Chart 1; deleted Figure 2 2001 03 28 Editorial Revision
