Designation:D1148–07a
Standard Test Method for
Rubber Deterioration—Discoloration from Ultraviolet(UV) and Heat Exposure of Light-Colored Surfaces1
This standard is issued under thefixed designation D1148;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.
(This test method was prepared jointly by the Society of Automotive Engineers and ASTM International.)
1.Scope
1.1This test method covers techniques to evaluate the surface discoloration of white or light-colored vulcanized rubber that may occur when subjected to UV or UV/visible exposure from specified sources under controlled conditions of relative humidity,or moisture,and temperature.
1.2This test method also describes how to qualitatively evaluate the degree of discoloration produced under such conditions.
1.3The term“discoloration”applies to a color change of the rubber sample,as distinguished from staining(see Note1),that refers to a color change of a metalfinish in contact with or adjacent to the rubber specimen.
1.4The values stated in SI units are to be regarded as the standard.The values given in parentheses are for information only.
1.5This standard does not purport to address all of the safety concerns,if any,associated with its use.It
is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
N OTE1—Tests for staining are covered by Test Methods D925.
2.Referenced Documents
2.1ASTM Standards:2
D925Test Methods for Rubber Property—Staining of Sur-faces(Contact,Migration,and Diffusion)
D2244Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates
D3182Practice for Rubber—Materials,Equipment,and Procedures for Mixing Standard Compounds and Prepar-ing Standard Vulcanized Sheets
D3183Practice for Rubber—Preparation of Product Pieces for Test Purposes from Products
G151Practice for Exposing Nonmetallic Materials in Ac-celerated Test Devices that Use Laboratory Lig
ht Sources G154Practice for Operating Fluorescent Light Apparatus for UV Exposure of Nonmetallic Materials
G155Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-Metallic Materials
3.Summary of Test Method
3.1Specimens to be tested for discoloration are exposed to UV or UV/visible radiation.The specimens shall include one or more control specimens of known discoloration character-istics.
3.2After exposing the specimens to actinic radiation for specified periods of time,under controlled conditions of relative humidity,or moisture,and temperature,the degree of discoloration is rated against discoloration of the control specimens,which have been exposed simultaneously with the test specimens.
4.Significance and Use
4.1The surface of white or light-colored vulcanized rubber articles,or vulcanized rubber covered with an organicfinish, may discolor when exposed to conditions of humidity,or moisture,heat,and sunlight.This change in color of light-colored rubber surfaces is objectionable to the consumer. 4.2Res
ults obtained should be treated only as indicating the effect of irradiance from the specified source(either UV A-340 lamps or a xenon arc with a Daylight Filter)and not as equivalent to the result of any natural exposure,unless the degree of quantitative correlation has been empirically estab-lished for the material in question.
4.3This test method may be used for producer-consumer acceptance,referee purposes,and research and development work.
1This test method is under the jurisdiction of ASTM Committee D11on Rubber
and is the direct responsibility of Subcommittee D11.15on Degradation Tests.
Current edition approved May1,2007.Published June2007.Originally
approved in1951.Last previous edition approved in2007as D1148–07.
2For referenced ASTM standards,visit the ASTM website,,or
contact ASTM Customer Service at For Annual Book of ASTM
Standards volume information,refer to the standard’s Document Summary page on
the ASTM website.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
5.Apparatus
5.1Fluorescent UV/Condensation Apparatus (Practice G 154)—Use Fluorescent UV test apparatus that conforms to the requirements defined in Practices G 151and G 154.
5.1.1Unless otherwise specified,the spectral power distri-bution (SPD)of the fluorescent lamp shall conform to the requirements of Table 1in Practice G 154(UV A-340Lamp).Refer to Fig.1.
5.2Xenon Arc Light Apparatus (Practice G 155)—Use xenon arc test apparatus that conforms to the requirements defined in Practices G 151and G 155.
5.2.1Unless otherwise specified,the spectral power distri-bution (SPD)of the filtered xenon lamp shall c
onform to the requirements of Table 1in Practice G 155(Xenon Arc with Daylight Filter).Refer to Fig.2.
5.3Color meter capable of measuring tristimulus colors for amber,blue,and green with or without automatic calculation for L a b or L *a *b *values.If without automatic calculations,a computer program should be available for this calculation.
6.Test Specimen
6.1The test specimen shall be prepared from a vulcanized production part or from a test slab prepared in accordance with Practices D 3182and D 3183.The specimen shall be rectan-gular in shape,62by 12mm (2.4by 0.5in.).If a specimen of this size cannot be prepared from a production part,a modifi-cation of the size may be agreed upon between the purchaser and the seller.
6.2An unexposed file specimen of the same compound as that stated in 6.1shall be prepared and reserved for color comparisons without being subjected to exposure.
7.Procedure
7.1The two procedures (Fluorescent UV/Condensation and Xenon Arc)contain different types of exposure sources and test conditions and may produce different test results.They cannot
be used interchangeably without supporting data that demon-strates equivalency of the procedures for the materials tested.7.2Refer to Table A3.1in Practice G 151for the allowed operational fluctuations of the specified set points for irradi-ance,temperature,and relative humidity.If the actual operating conditions do not comply with the maximum allowable fluc-tuations in Table A3.1after the equipment has stabilized,discontinue the test and correct the cause of the problem before continuing.
7.3Specimens should be confined to an exposure area in which the irradiance is at least 90%of the irradiance at the center of the exposure area.Unless it is known that irradiance uniformity meets this requirement,use one of the procedures described in Practice G 151,Section 5.1.4,to ensure equal radiant exposure on all specimens,or to compensate for differences within the exposure chamber.If the specimens do not completely fill the racks,fill the empty spaces with blank metal panels to maintain the test conditions within the cham-ber.The apparatus shall be operated continuously.However,if the test needs to be interrupted to perform routine maintenance or inspection,it should be during a dry period.
7.4Procedure for Exposure in Fluorescent UV/Condensation Apparatus (Practice G 154)—Unless otherwise specified,operate the fluorescent UV test apparatus with UV A-340lamps in accordance with Practice G 154.
7.4.1Use the following exposure cycle:Set the irradiance level to 0.77W /(m2.nm)at 340nm.Expose specimens to a continuous cycle of 8h light at 60ºC uninsulated black panel temperature followed by 4h of condensation at 50ºC uninsu-lated black panel temperature.
7.5Procedure for Exposure in Xenon Arc Apparatus (Prac-tice G 155)—Unless otherwise specified,use the following operating conditions:
7.5.1The xenon arc test apparatus shall be used with a Daylight Filter and conform to the spectral power distribution specifications in Practice G 155
.
FIG.1Spectral Power Distributions of UVA-340Lamp Versus
Daylight
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7.5.2Set the irradiance level at 0.55W /(m2•nm)at 340nm.Consult the manufacturer of the apparatus for equivalent broad band irradiance levels at 300to 400nm and 300to 800nm.
7.5.3The default exposure cycle shall be 102min light only followed by 18min light plus either water spray on the front surface or immersion in water (refer to Note 2).The water spray temperature is typically 2165°C,but may be lower if ambient water temperature is low and a holding tank is not used to store purified water.The immersion water is kept at a constant temperature,which shall be less than 40°C.
N OTE 2—Water spray and immersion in water frequently produce different results.In the immersion technique,the test specimens are placed in a chamber that is periodically flooded with either recirculated or running water,which completely covers the specimens.The maximum temperature attained by a black colored specimen is determined with the black standard thermometer (BST)held un
xposed
der water on the same plane and distance from the surface as the test specimens.The immersion system is made from corrosion resistant materials that do not contaminate the water.
7.5.4Set the uninsulated Black Panel Temperature (BPT)at 63°C during the dry period of exposure to light.Consult the manufacturer of the apparatus for the equivalent insulated black panel temperature (Black Standard Temperature (BST)).7.5.5Relative humidity shall be set at 60%during the dry period of exposure to light in xenon arc apparatus that provides for control of relative humidity.
7.5.6The chamber air temperature shall be set at 44°C in apparatus that provides for adjustment of the chamber air temperature.
7.6One or more control specimens using rubber material of known discoloration characteristics shall be included.
7.7Any change in color of a test specimen in relation to the original sample shall be considered as discoloration.
7.7.1The degree of discoloration can be judged visually to be greater or less than the control specimen and can be given
a numerical rating based on an arbitrary scale of degree of discoloration which may be agreed upon between the purchaser and the seller.
7.7.2The change in color can be measured instrumentally using commercial color meters (refer to Note 3)for specimens prepared according to Section 6.Calculate the difference between an unexposed specimen and the exposed specimen,as follows:
D E 5E U 2E E (1)D E *5E U *2E E *
(2)
where:
D E =difference between unexposed and exposed specimen E U =unexposed specimen E E =exposed specimen
N OTE 3—Some color meters calculate D E and others calculate D E*,while some may calculate both.Either expression is suitable for use in this test method,but one must not mix them together.A complete equation can be found in Practice D 2244.
8.Report
8.1The report shall include the following information:8.1.1Type of radiation used,either UV A-340or filtered xenon arc lamp;
8.1.2Exposure time in hours;8.1.3Date of test;
8.1.4Identification of test and control specimens;
8.1.5Size and shape of specimen(s)if not in accordance with the standard shape and size;
8.1.6An estimate of the degree of discoloration according to a visual estimation,described in 7.7.1,or an instrumental evaluation according to 7.7.2.
9.Precision and Bias
9.1A precision and bias study has not yet been
prepared.
FIG.2Spectral Power Distributions of Xenon Arc with Daylight Filter Versus
Daylight
--`,``,``,````,,,`,,,,,,`,````,`-`-`,,`,,`,`,,`---
9.2Bias—Bias cannot be determined because no acceptable
standard weathering reference materials are available.
10.Keywords
10.1fluorescent UV;heat discoloration;rubber products;
ultraviolet;ultraviolet light discoloration;UV A-340;xenon arc
APPENDIX
(Nonmandatory Information)
X1.COLOR METER
X1.1Set up the color meter according to the directions supplied by the manufacturer for optimum performance.This will include any necessary calibrations.
X1.1.1If the color meter requires a standard plaque,ob-serve any precautions for plaque storage,cleanliness,and re-calibration.
X1.1.2Obtain amber,blue,and green tristimulus reflectance readings for each specimen to be measured,including the unexposedfile specimen(which was not exposed to ultraviolet light).
X1.1.2.1Color meters present data differently;however,L a b and L*a*b*data can be obtained from any color meter either as part of the instrumental calculations or,if not, computer programs can be used to generate the necessary data. X1.2To assess the discoloration of a sample as compared to the unexposedfile specimen,subtract the E E or E E*value of the exposed specimen from the E U or E U*value of the unexposed specimen.This is the difference(D E)or(D E*)on which the discoloration evaluation is based.See7.7.2.
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