FORD FLTM BP 101-01-2018 RUBBER - DEGRADATION BY OZONE.pdf

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1、 FORD LABORATORY TEST METHOD BP 101-01 Date Action Revisions 2018 04 18 Revised See Summary of Revisions L. Pollard, NA 2001 08 23 Revised Editorial no technical change A. Cockman 1991 10 03 Controlled document at www.MATS Copyright 2018, Ford Global Technologies, LLC Page 1 of 10 RUBBER - DEGRADATI

2、ON BY OZONE PROCEDURE A: STATIC-STRAIGHT PROCEDURE B: STATIC-MANDREL PROCEDURE C: STATIC-SIMULATED INSTALLATION PROCEDURE D: DYNAMIC FLEX-SEVERE SERVICE-BENT LOOP Application These procedures are used to assess the resistance of rubber materials to accelerated ozone attack. These procedures are for

3、estimating the comparative ability of elastomeric materials to withstand the effects of cracking in a controlled ozone environment when held under constant strain or when subjected to dynamic strain. Tests can be performed on flat sheet (slab stock), standard specimens prepared from parts, or actual

4、 parts. Apparatus and Materials Required Ozone Test Cabinet The cabinet interior shall be constructed of a material that will not be affected by ozone and shall be designed to allow suspending mounted test specimens without shielding or masking any specimen from the ozone/air flow. The ozone-air mix

5、ture must be introduced into the chamber and circulated in a manner that provides uniformity of temperature and ozone concentration throughout the chamber. The ozone concentration and chamber temperature shall be continuously controlled and recorded. Equipment is available that automatically control

6、s the ozone concentration, temperature, and provides a record of these conditions. As additional assurance of uniform ozone exposure over and above that which is provided by air handling provisions of the chamber, a moving specimen carrier for circulating the specimens along a predetermined path in

7、a plane normal to the gas flow is permissible. Intake air should be filtered to remove particles. Dynamic flex apparatus in conformance to ASTM D1149 with adjustable shaft movement of 12 - 50 mm incorporated in the chamber design are recommended. Unless defined in the applicable Engineering Material

8、s Specification, Engineering Specification, or Engineering print, the following standard conditions are to be met: Ozone concentration: 50 mPa partial pressure (50 +/- 5 pphm) Temperature: 38 +/- 1 C Duration of exposure: 70 + 2 h Air-Ozone replacement rate (throughput): 1.2 - 2.0 changes/minute Air

9、-Ozone velocity over specimens: 60 +/- 5 cm/s Sources for equipment capable of meeting the requirements of this method are as follows: SATRA Technology Centre Mast Development Co. Wyndham Way, Telford Way 2200 Dickerson Rd. Kettering, Northamptonshire NN16 8SD Reno, Nevada 89503 United Kingdom USA

10、 FORD LABORATORY TEST METHOD BP 101-01 Copyright 2018, Ford Global Technologies, LLC Page 2 of 10 OREC 221 Beaver St. Akron, Ohio 44304 USA Clamps For holding test specimens at the specified elongation and constructed from material inert to ozone - e.g. steel, aluminum, or polymethylmethacrylate. M

11、andrels For wrapping specimens to achieve specified surface elongation of rubber hose, tubing, weather-strip, etc., constructed from extruded aluminum tubing, varnished wood “dowel rod“, steel rod or any material capable of retaining a known diameter and is inert to ozone. Compression Plates Accordi

12、ng to ASTM D 395 for compressing components, or portions of components, to simulate service conditions. Ozone-Resistant Coatings For protection of heavily-stressed areas adjacent to clamps or wire. It is recommended that all exposed rubber surfaces not required for evaluation be protected in order t

13、o minimize ozone stress-crack “relaxation“ of the specimen in tension. Care should be taken to ensure that the area of the specimen to be evaluated is not contaminated with the protective coating. For the static procedures A, B, and C, a paraffin wax or water based coating verified to be a protectiv

14、e barrier against ozone may be used. Magnifier Hand-held/table-mounted 2X or 7X magnifier, or as specified in the engineering specification, and good light source. Fixtures (various) Fixtures of non-reactive materials to simulate service conditions for mounting specimens to a mobile test piece carri

15、er in the chamber, mandrel mounting, clamps and brackets for dynamic ozone testing, and actual component assemblies for installations of elastomeric parts according to simulated in service conditions. Specimen Holder Per ASTM D 1149, a device, constructed of a material with minimal reaction to ozone

16、, such as stainless steel or aluminum, with dimensions suitable to stretch the test specimen 20 +/- 2% and allowing for a minimum space between specimens of 3.2 mm. The specimen grip area shall be grooved or crosshatched to prevent slippage. Available from CCS Instruments, Inc. (http:/www.ccsi-) (or

17、 equivalent). Refer to Figure 1. Flexible Scale Typical plastic “pocket scale“ graduated in 1 mm divisions for measuring distance increase between bench marks on both straight and mandrel-mounted specimens. Marketing Devices For applying “bench marks“ to establish elongation of specimens. Marking te

18、chniques may include use of aluminum powder with wedge applicators, and light-colored opaque inks and vinyl “flags“ for dark materials or various dark ink pens for light materials. FORD LABORATORY TEST METHOD BP 101-01 Copyright 2018, Ford Global Technologies, LLC Page 3 of 10 Fastening Wire Non-rea

19、ctive wire for securing mandrel-mounted specimens. See Figure 2. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities. Conditioning and Test Conditions All test va

20、lues indicated herein are based on material conditioned in a controlled atmosphere of 23 +/- 2 C and 50 +/- 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. Procedure Conditioning Minimal handling of the specimens during a

21、nd after installation into test fixturing is recommended in order to not disturb protective anti-ozonants that migrate to the polymer surface. Coat non-test areas with ozone-resistant coating as appropriate (see Ozone Resistant Coatings section of Apparatus). Unless otherwise specified, the pre-stre

22、ssed materials are to be conditioned according to ASTM D 1349 at 23 +/- 2 C and 50 +/- 5 % RH for 24 h minimum in a draft free plastic bag and stored in a light free environment, e.g. drawer or empty oven. Note: Omit conditioning for dynamic testing (Procedure D) unless otherwise specified. Procedur

23、e A (Static-Straight) Prepare test specimens from slab materials or actual parts into either uniform width and thickness or tensile-shaped (ASTM D 412 and ISO 37) specimens. For straight specimens, cut into lengthwise strips by sharp die or surgical blade and metal guide to a uniform width of 2.0 -

24、12.0 mm and a length of not less than 35 mm. Unless otherwise specified, strain to an elongation of 20 +/- 2%, established by the measurement of “bench marks“ placed upon the specimen and measured according to ASTM D 412 and ISO 37. Elongate specimens as described in ASTM D 1149 using wood mounting

25、blocks, clamps, frames, or other suitable means of achieving accurate elongations (see Figure 1). Report die type or sample dimensions and observe for cracking with specified magnification prior to specimen relaxation after exposure. Note 1: Testing of straight specimens imparts greater stress at th

26、e clamping region than that of tensile-shaped specimens making the use of protective coatings in the clamp region advisable. Procedure B (Static-Mandrel) Continuous extrusions (or molded, if of sufficient length) of hose, tube, weatherstrip and composite constructions that would otherwise be difficu

27、lt or impractical to elongate by Procedure A may be evaluated by wrapping about a mandrel. Select a mandrel of suitable diameter to elongate the surface 20 +/- 2% unless otherwise specified. Determine elongation by observing the increased distance between initial “bench marks“ (10 mm minimum, 50 mm

28、maximum) applied to a relaxed sample to the nearest 1 mm and secure the assembly by wire or any inert fastening (see Figure 2). Note 1: Because accurate measurement of the increase in distance between benchmarks when on the mandrel becomes increasingly difficult as thickness becomes less, the use of

29、 Procedure A is encouraged when evaluating unreinforced slab or sheet materials that are easily elongated. FORD LABORATORY TEST METHOD BP 101-01 Copyright 2018, Ford Global Technologies, LLC Page 4 of 10 Note 2: For non-extensible thin-coated fabrics (diaphragm, etc.) where determination of surface

30、of elongation is not practical, use mandrel-mounted techniques described in ASTMD 1149 “Bulldog“ style clamps or binder clips in place of varnished wood mounting strips are permitted. Evaluate cracking on those materials with 7X magnification or as specified. Note 3: Molded rings and seals may be ci

31、rcumferentially elongated by carefully sliding onto a polished metal mandrel using the procedures described in FLTM BP 116-01. Select a mandrel diameter to achieve 20 +/- 2% elongation unless otherwise specified. Seals with rigid housings may require removal of the elastomer from the housing unless

32、the seal is to be evaluated at engineered stress. In the latter case, refer to FLTM BP 116-01 and Procedure C below. Procedure C (Static-Simulated Installation) This procedure is to evaluate the effects of ozone on finished parts in their assembly condition while under inherent design strain (undete

33、rmined), on extruded or molded lengthwise parts subject to strain from bending or curving about a radius, and on components under compression. Examples are bushings in compression or in torsion (or a combination of both), seals, and O-rings compressed, or circumferentially elongated while installed

34、in their assemblies, and cut tubing and hose installed on actual production fittings with production clamps. Tests on specified parts are to be described in the applicable Engineering Specifications and Drawings. Observe for cracking by using 2X magnification, or as specified, on exposed external su

35、rfaces of the component prior to removal from any fixturing. Report percent strain (if determinable) in compression or tension and rate cracking according to Table I. Describe location of cracking. Procedure D (Dynamic Flex-Severe Service-Bent Loop) This procedure is for evaluating reinforced or non

36、-reinforced rubber materials and components for ozone resistance during continuous flexing. Although this procedure provides a specific example for using brake hoses for illustrative purposes, other composite materials/components such as engine belts and tire valves may be evaluated as described in

37、their applicable Engineering Specification or Drawing. Under the reciprocating shaft of the dynamic ozone flex apparatus and attached mounting fixtures at the minimum opening position, install a length of material to achieve desired maximum surface elongation when forming a loop. Determine elongatio

38、n of the bent-loop by observing the distance increase between “bench marks“ when the material is flexed from its relaxed position (see Procedure B). For typical brake hoses, a 200 mm length forming a loop when installed at a 35 mm minimum opening gives 25 - 30% surface elongation (see Figure 3 for a

39、ppropriate fixturing). With the reciprocating shaft positioned at its maximum opening, observe and record the minimum surface elongation of the loop. For brake hoses, this elongation should be approximately 10 - 15%. Observe and record both maximum and minimum elongations. Note: Material thickness w

40、ill govern the ability to achieve a desired elongation when forming a loop using standard flex equipment presently available from ozone chamber manufacturers. Adjustment of stroke length, material length and/or fabrication of fixturing to achieve the desired maximum elongation will be required. Mini

41、mum elongation will vary accordingly. Caution: The length of material between fixturing should be sufficient to prevent the specimen from being subjected to tensile forces when the fixture cycles to the maximum open position. Verify adequate length by manually cycling the flex apparatus before start

42、ing the test to avoid damage to cycling apparatus and fixtures. Unless otherwise specified, all tests are to be conducted at 0.5 + 0.05 Hz for 500 continuous hours (approximately 1,000,000 cycles) at standard concentration and temperature. At the end of FORD LABORATORY TEST METHOD BP 101-01 Copyrigh

43、t 2018, Ford Global Technologies, LLC Page 5 of 10 this period, examine the surface of the material in the area forming the loop and areas adjacent to attachment with 7X magnification, or as specified. Report maximum and minimum elongation and rate according to Table I. Evaluation Report procedure u

44、sed and sample mounting description. If simulating actual in-service installations, include a drawing or photograph of fixturing and mounting. Observe cracking in the stressed areas prior to relaxation and report classification rating or report the percent retention derived from the three-digit rati

45、ng method from 24 h interval observations as described in ASTM D 1171 using the rating scale designated in the specification (see Table I or Table II). Images of example ratings can be found in ASTM D 1171. Report percent strain, duration, temperature, and ozone concentration. Note: Photographs at 2

46、X magnification are particularly useful when reporting and describing ozone effects on actual components. FORD LABORATORY TEST METHOD BP 101-01 Copyright 2018, Ford Global Technologies, LLC Page 6 of 10 RUBBER - DEGRADATION BY OZONE Table I - Evaluation (all procedures) Classification of Rating Inte

47、rpretation 0 No checking or cracking visible at 2X or 7X magnification 1 Checking or cracking visible at 2X or 7X but not visible to the unaided eye 2 Small checks or cracks visible to the unaided eye 3 Medium or large cracks visible to the unaided eye Table II - Optional Evaluation (Quality Retenti

48、on Rating Based on Three Successive Observations at 24, 48, and 70 h Intervals - Reproduced from ASTM D 1171) Observed Crack Rating at Resistance to Ozone (%) Three Successive Intervals 000 100 001 95 011 90 111 85 002 80 012 75 112 70 022 65 122 60 222 55 003 45 013 40 113 35 023 30 123 25 223 20 0

49、33 15 133 10 233 5 333 0 FORD LABORATORY TEST METHOD BP 101-01 Copyright 2018, Ford Global Technologies, LLC Page 7 of 10 Reference Documents ASTM D 395, Rubber Properties in Compression ASTM D 412, Rubber Properties in Tension (Die-C Tensile Specimens) ASTM D 1149, Standard Test Methods for Rubber Deterioration-Cracking in an Ozone Controlled Environment ASTM D 1349, Practice for Rubber, Standard Tempe