1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2012 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/ARP6229 AEROSPACE RECOMMENDED PRACTICE ARP6229 Issued 2012-12 Fluoride Offgassing
5、 in Fluoropolymer Insulations RATIONALE This report provides information to the user community on the potential of fluoride offgassing from fluoropolymer wire insulation and recommendations to protect against potential effects. Although there have been some published advisories related to this subje
6、ct, no publication existed prior to this ARP which pulls together current knowledge for communication to industry OEMs and end-users. 1. SCOPE This SAE Aerospace Recommended Practice (ARP) shall be limited to information about corrosion caused by fluoride offgassing of fluoropolymer-based wire insul
7、ation. It reviews published reports of corrosion caused by this phenomenon, describes scenarios where this may be a concern, mitigation options, and references a test method which can be used to evaluate wire insulations where needed. 1.1 Purpose This document provides basic information to wire manu
8、facturers, OEMs, and end users about fluoride offgassing from wire insulation, including effects, applications of concern, test methods, and recommendations. 2. REFERENCES The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications sha
9、ll apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes appli
10、cable laws and regulations unless a specific exemption has been obtained. 2.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. AS4373 Test Methods for Insulated
11、Electric Wire AIR5717 Mitigating Wire Insulation Damage During Processing and Handling ARP6400 Recommended Practice for Processing and Handling Wire and Cable with Silver Plated Conductors and Shields AS22759 Wire, Electrical, Fluoropolymer-Insulated, Copper or Copper Alloy SAE ARP6229 Page 2 of 4 2
12、.2 Other Publications “Fluoropolymer degradation resulting in corrosion of packaged pre-wired connector assemblies”, FSFC NASA Advisory #: NA-GSFC-2003-03, April 15, 2003 “Cause and effects of fluorocarbon degradation in electronics and opto-electronic systems” Predmore, Roamer E.; Canham, John S. P
13、h.D; NASA Goddard Space Flight Center, Materials Engineering Branch; 2003 “A corrosion puzzle of pre-wired connectors in sealed storage bags” by June Cabourne, Senior Project Manager at Cristek Interconnects, Inc. c. 1998 GIDEP EA-P-98-02 Problem Advisory “Wire outgassing” 1998 “ISS Fiber Optic Fail
14、ure Investigation Root Cause Report”, NASA GSFC, August 1, 2000 “Effect of Insulation on Red Plague Corrosion in Silver-Plated Wire”, Steven Gullerud, Peter Ibarra, Steve Zingheim, and Richard Reimer, TE Connectivity, AEISS Presentation, October 12, 2011 3. BACKGROUND 3.1 Definition and Mechanism Du
15、ring processing of fluoropolymers, exposure to high temperatures can cause the polymer to degrade in the presence of air and water to produce carbonyl fluoride end groups. These end groups remain in the polymer and can later hydrolyze in the presence of moisture to produce carbon dioxide and hydrofl
16、uoric acid. This reaction can occur over a long period of time, at a rate limited by the diffusion of water into the fluoropolymer material. In wire insulation, this phenomenon is referred to as either fluoride offgassing or fluoride outgassing. The total potential of fluoride offgassing from a fluo
17、ropolymer insulation is finite, and limited by the amount of carbonyl fluoride groups present within the polymer. Observed parts per million (ppm) of extractable hydrogen fluoride in wire insulation ranges from 10 to 1000. 3.2 History Insulation off-gassing is a known issue in the satellite manufact
18、uring industry since the late 1990s.The issue was first publically reported by Cristek Interconnects, Inc. in mid-1997 concerning corrosion on pre-wired connectors in sealed bags that were terminated to AS22759/33 insulated wire. This resulted in a subsequent Government Industry Data Exchange Progra
19、m (GIDEP) Problem Advisory in 1998 regarding the offgassing of XL-ETFE insulated wire. A second GIDEP was published by Goddard Space Flight Center in 2003, again observing corrosion on connector assemblies caused by fluoride offgassing in wire assemblies stored in sealed bags for 2 years. While the
20、instances above involved XL-ETFE wire, other fluoropolymers have been shown to generate fluoride offgassing and cause corrosion-related failures. FEP jacketed fiber optic cables were found to have etched pits in the fiber caused by HF released by the FEP insulation layer. 3.3 Effects Hydrogen fluori
21、de is highly corrosive, and will etch glass and corrode plating surfaces of connectors and other components. As a vapor, it is able to penetrate porous coatings and react with underlying materials. Although there are considerable health risks associated with hydrogen fluoride, the potential amount r
22、eleased by a fluoropolymer wire insulation is quite small and unlikely to present an actual health hazard. An investigation has shown evidence that hydrogen fluoride is capable of penetrating the plating of a silver-plated copper conductor and reacting with the underlying copper to form copper fluor
23、ide. If there is enough available hydrogen fluoride, the volume increase caused by this reaction is able to breach the silver plating and expose the underlying copper. The presence of white to bluish-white crystals on a conductor surface may indicate that some copper fluoride has formed, but does no
24、t necessarily mean that the underlying plating has been compromised. SAE ARP6229 Page 3 of 4 Exposure of the underlying copper, with the presence of water, could lead to red plague corrosion of the copper conductor. However, further investigation is necessary before a limit on the amount of fluoride
25、 offgassing sufficient to influence red plague corrosion could be defined. 4. EVALUATION AND RECOMMENDED PRACTICES 4.1 Application and Storage Environment In general airframe wire use, there are no known incidents of corrosion caused by fluoride offgassing. Published incidents are confined to the sa
26、tellite manufacturing industry, specifically in instances where wire harnesses or assemblies are stored in sealed bags for months or years before use. The presence of moisture is required for fluoride offgassing to occur. Environments without moisture present are not at risk. Wire users should evalu
27、ate the environment around the wire both in storage and in the final application. Any small sealed environment or one with no air flow and limited air volume may allow offgassed hydrogen fluroide to accumulate and cause corrosion over time. Users are recommended to avoid placing assemblies containin
28、g fluoropolymer wire into these environments where possible, especially during storage. 4.2 Mitigation Baking fluoropolymer wire in an oven has not been shown to be effective in reducing the potential for fluoride offgassing. Storage of wire in open air is expected to reduce the insulations potentia
29、l for fluoride offgassing, as moisture in the air diffuses into the wire insulation over time and reacts with the finite amount of carbonyl fluoride present there. However, no studies have been published on the conditions required or amount of time necessary to complete this reaction during normal s
30、torage. This is not recommended as an effective mitigation method until more data is collected. Wire manufacturers have the ability to reduce the potential of fluoride offgassing from wire insulation through material selection and manufacturing processes. Since there is no single route to achieve th
31、is and many of these options would be considered proprietary information by the producers, this ARP does not attempt to recommend specific mitigation steps for wire manufacturers. Introducing air flow or air exchanges into an otherwise sealed environment will prevent hydrogen fluoride from accumulat
32、ing and presenting a corrosion hazard, and may be considered as an option for mitigation. 4.3 Evaluation Methods for Wire Insulation SAE has developed a test method, AS4373 Method 608, by which the fluoride offgassing potential of a wire insulation may be measured. While studies have not been done t
33、o correlate this test method to corrosion issues observed in the satellite industry, a level of 20 ppm has been selected for new AS22759/47 through /50 slash sheets for crosslinked ETFE insulated wire. This value was selected based on measurements of extruded PTFE insulated wires, which are also use
34、d in that industry and have not been identified as causing similar corrosion in bagged assemblies. Users who have concerns about applications or storage conditions where mitigation is not viable should test or define a fluoride offgassing requirement for wire used in these environments. A test limit
35、 as low as 20 ppm is only recommended for conditions similar to those seen in the satellite industry - wire assembies placed in small, sealed environments for years or longer. Users should otherwise consider establishing test limits based on the amount of fluoropolymer wire insulation present, expec
36、ted limits on air volume, and susceptibility of components to hydrogen fluoride corrosion. 5. RECOMMENDATION SUMMARY Both users and manufacturers of wire in the Aerospace industry should be aware of fluoride offgassing and the potential for corrosion caused by this phenomenon. Although it is not a c
37、oncern for general airframe use, specific applications can be at risk and corrosion may not be observed until months or years after wire harness assembly or installation. Quality inspection and test methods should be established for those applications where this corrosion may be an issue and other m
38、itigation options are not available. SAE ARP6229 Page 4 of 4 6. NOTES 6.1 A change bar (l) located in the left margin is for the convenience of the user in locating areas where technical revisions, not editorial changes, have been made to the previous issue of this document. An (R) symbol to the lef
39、t of the document title indicates a complete revision of the document, including technical revisions. Change bars and (R) are not used in original publications, nor in documents that contain editorial changes only. PREPARED BY SAE SUBCOMMITTEE AE-8D, WIRE AND CABLE OF COMMITTEE AE-8, AEROSPACE ELECTRICAL/ELECTRONIC DISTRIBUTION SYSTEMS
