1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW14759 Determination of the Permeability of Elastomers to Liquids or Vapor Copyright 2012 General Motors Company All Rights Reserved September 2012 Originating Department: North American Engineering Standards Page 1 of 5 1 Scope Note: Nothing in this
2、 standard supercedes applicable laws and regulations. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. The object of this standard is to determine the permeability of elastomers to liquids, or liquid/vapor mixtures to
3、which they are in contact during service. 1.2 Foreword. Not applicable. 1.3 Applicability. Not applicable. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ISO 188 2.2 GM Standards/Specifications. None 3 Resources
4、 3.1 Facilities. Not applicable. 3.2 Equipment. 3.2.1 Test Equipment. 3.2.2 Thickness Gauge. The thickness gauge must be capable of indicating the test piece thickness to an accuracy of 0.01 mm. The two contact members consist of domed surfaces of spherical radius 12.5 mm, formed on rods of 10 mm di
5、ameter, between which the test pieces are placed. The force between the contact members shall be 0.85 N 0.03 N. The thickness gauge shall normally consist of one fixed contact member, with the other moving vertically above it, linked to a suitable dial gauge. 3.2.3 Test Apparatus. The test apparatus
6、 shall consist of cylindrical aluminum vessel with internal dimensions of 35 mm 0.5 mm diameter, and 50 mm 0.5 mm height. Around the opening, there shall be a recess, 54 mm diameter and 1.5 mm 0.1 mm deep for the test piece (in case of test piece thickness of 2 mm 0.1 mm). In case of test pieces wit
7、h deviating thickness, supporting discs or spacer rings shall be used. It shall be ensured that the thickness of the test piece is compressed to about 75% of its original height. The test piece shall be clamped between the vessel and the clamp ring, which also has an internal diameter of 35 mm 0.5 m
8、m. The ring shall also have on the side, which is close to the test vessel, a recess 42 mm 0.5 mm diameter and 2 mm 0.5 mm depth for the installation of a support mesh. The support mesh shall consist of suitable gauze, and of such spacing that, while the area in contact with the test piece is at a m
9、inimum, it is sufficiently strong to resist the test piece being displaced from its position by the internal pressure developed within the vessel during the test. The ring shall be clamped to the test vessel by means of six (6) equally spaced screws. Other dimensions are shown in Figure A1, Appendix
10、 A. 3.2.4 Heating oven capable of maintaining the required temperatures within the specified tolerances (e.g., heat oven to ISO 188 Method B). Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without licen
11、se from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14759 Copyright 2012 General Motors Company All Rights Reserved September 2012 Page 2 of 5 3.2.5 Balance with a capacity of 1000 g maximum, and an accuracy 0.01 g. 3.2.6 Test medium shall be specified on the relevant engineering drawings or mater
12、ial specifications. 3.3 Test Vehicle/Test Piece. 3.4 Test Time. Not applicable. 3.4.1 Test Material. 3.4.2 Shape and Size. Unless otherwise specified, the following test pieces shall be used. 3.4.3 Standard Test Piece: Cylindrical discs of diameter 50 mm 1 mm, thickness 2.0 mm 0.1 mm, either molded
13、or cut from sheet. 3.4.4 Test pieces from complete components: where complete components are supplied for test, standard test pieces as described shall be cut from the component. The thickness of the complete component shall be used as thickness of the test piece. 3.4.5 In special cases the complete
14、 component will be used as test piece, here an appropriate test vessel must be provided. 3.4.6 Number of Test Pieces. For initial sample approval and arbitration purposes, at least three (3) test pieces cut from at least two (2) components shall be tested, for routine quality control purposes at lea
15、st one (1) test piece shall be tested. 3.5 Test Required Information. Not applicable. 3.6 Personnel/Skills. Not applicable. 4 Procedure 4.1 Preparation. 4.1.1 Test Sample Preparation. The minimum time period between vulcanization and testing of elastomers shall be 72 h. The test piece shall remain a
16、t a temperature of 23 C 5 C for at least 8 h before testing, and shall be free from strain during this period. 4.1.2 Test Procedure. 4.1.3 Prior to test the thickness of the test piece shall be measured at five (5) positions minimum equally distributed over the test area, at a temperature of +23 C 5
17、 C. The mean thickness shall be calculated from these individual values. 4.1.4 The test vessel shall be completely filled with the test medium in the case of tests to Method A, or to a depth of 40 mm in the case of tests to Method B. The test piece shall then be placed into the recess on top of the
18、vessel, the support mesh carefully placed above it, and the ring attached by the six screws. 4.1.5 The test assembly shall be weighed to the nearest 10 mg (= m1) and placed in the heating oven at the specified temperature for the specified time. In the case of tests to Method A the test assembly sha
19、ll be inverted, and stood upon the screws, which attach the ring, during the test. For tests to Method B it shall remain as assembled. 4.1.6 After the specified test period, the test assembly shall be removed from the oven and allowed to cool at +23 C 5 C for 0.5 h to 2 h, then be weighed to the nea
20、rest 10 mg (= m2). 4.2 Conditions. 4.2.1 Environmental Conditions. 4.2.2 Test Conditions. Deviations from the requirements of this standard shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports, etc. For tests carried out in accordance wi
21、th the test method, the permeability of an elastomer to liquids or vapors shall be recorded as the arithmetic mean of the individual results rounded to the nearest 10 mg/m2 24 h. 4.2.3 Summary of Test Method. Samples of elastomers are tested for their permeability to liquids, or liquid/vapor mixture
22、s, to which they are in contact during service. 4.2.3.1 Method A (Coding A). Liquid only is in direct contact with the elastomer. 4.2.3.2 Method B (Coding B). Vapor only is in contact with the elastomer. 4.2.4 Test Temperature. The test temperature shall be specified with consideration of the servic
23、e usage and type of elastomer concerned. See Table 1. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14759 Copyright 2012 General Motors
24、 Company All Rights Reserved September 2012 Page 3 of 5 Table 1: Test Temperature Codes Coding Test Temperature A +23 C 5 C B +70 C 3 C C +100 C 3 C D +125 C 3 C E +150 C 3 C F +175 C 3 C G +200 C 3 C H +250 C 3 C J as defined 4.2.5 Test Period. The test temperature shall be selected from one of the
25、 following preferred ranges in Table 2. Table 2: Test Period Codes Coding Duration of Test 1 24 h + 0 h,-2 h 2 72 h + 0 h,-2 h 3 168 h + 0 h,-2 h 4 672 h + 0 h,-2 h 5 as defined 4.3 Instructions. See. 4.1. 5 Data 5.1 Calculations. Not applicable. 5.2 Interpretation of Results. Not applicable. 5.3 Te
26、st Documentation. Not applicable. 6 Evaluation and Rating The liquid or vapor permeability shall be calculated as the loss in mass expressed in g/m2 per 24 h, for an individual test piece thickness. The permeability shall be calculated as: hmgtdmtyP e r m e a b ili24222 m = m1 - m2 Copyright General
27、 Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14759 Copyright 2012 General Motors Company All Rights Reserved September 2012 Page 4 of 5 Where: m = Chan
28、ge in mass after test in grams m1 = Mass of test assembly before test in grams m2 = Mass of test assembly after test in grams t = Test period in days (24 h) d = Diameter of test area in meters (normally 0.035) 7 Safety This standard may involve hazardous materials, operations, and equipment. This st
29、andard does not propose to address all the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 8 Notes 8.1 Glossary. Permeability: T
30、he mass of liquid or vapor, which diffuses through an elastomeric sheet under specified conditions in a given time. 8.2 Acronyms, Abbreviations, and Symbols. Not applicable. 9 Coding System This standard shall be referenced in other documents, drawings, etc., as follows: Test to GMW14759 Example: Pe
31、rmeability to GMW14759 A - Hydraulic Fluid C3 - 45 g/m Where: A = Method A to paragraph 4.2.3.1 liquid only is in direct contact with the elastomer Hydraulic Fluid = Test media C = Test temperature to Table 1, Code C: 100 C 3 = Test period to Table 2, Code 2: 168 h 45 g/m24 h maximum at 2 mm 0.1 mm
32、test piece thickness = Requirement 10 Release and Revisions This standard was originated in October 2005. It was first approved by the Rubber Technical Development Group in December 2006. It was first published in February 2007. Issue Publication Date Description (Organization) 1 FEB 2007 Initial pu
33、blication. 2 SEP 2012 5 Year Refresh. (Elastomers Global Subsystem Leadership Team) Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14759
34、 Copyright 2012 General Motors Company All Rights Reserved September 2012 Page 5 of 5 Appendix A Figure A1: Vessel for Measuring the Permeability Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
