ASTM D7238-20

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7238 − 06 (Reapproved 2017) D7238 − 20
Standard Test Method for
Effect of Exposure of Unreinforced Polyolefin
Geomembrane Using Fluorescent UV Condensation
Apparatus
This standard is issued under the fixed designation D7238; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This standard covers the specific procedures and test conditions that are applicable for exposure of unreinforced polyolefin
geomembranes to fluorescent UV radiation and condensation.
NOTE 1—Polyolefin geomembranes include high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), flexible polyproplyene
(fPP), etc.
1.2 Test specimens are exposed to fluorescent UVA 340 UVA-340 lamps under controlled environmental conditions. UVA 340
UVA-340 lamps are standard for this method.
NOTE 2—Other types of fluorescent UV lamps, such as UVB-313, can also be used based upon discussion between involved parties. However, if the
test is run with another type of fluorescent UV lamps,lamp, such as UVB-313, this should be considered as a deviation from the standard and clearly stated
in the test report. UVB-313 and UVA-340 fluorescent lamps generate different amounts of radiant power in different wavelength ranges; thus, the
photochemical effects caused by these different lamps may vary.
1.3 This method covers the conditions under which the exposure is to be performed and the test methods for evaluating the
effects of fluorescent UV, heat, and moisture in the form of condensation on geomembranes. General guidance is given in Practices
G151 and G154.
1.4 The values listed in SI units are to be regarded as the standard.
1.5 This 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 appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1238 Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer
D5885D5885/D5885M Test Method for Oxidative Induction Time of Polyolefin Geosynthetics by High-Pressure Differential
Scanning Calorimetry
D6693D6693/D6693M Test Method for Determining Tensile Properties of Nonreinforced Polyethylene and Nonreinforced
Flexible Polypropylene Geomembranes
G113 Terminology Relating to Natural and Artificial Weathering Tests of Nonmetallic Materials
G151 Practice for Exposing Nonmetallic Materials in Accelerated Test Devices that Use Laboratory Light Sources
G154 Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic Materials
G156 Practice for Selecting and Characterizing Weathering Reference Materials
3. Terminology
3.1 Definitions: (According to Terminology G113.)
This test method is under the jurisdiction of ASTM Committee D35 on Geosynthetics and is the direct responsibility of Subcommittee D35.02 on Endurance Properties.
Current edition approved July 1, 2017July 1, 2020. Published July 2017July 2020. Originally approved in 2006. Last previous edition approved in 20122017 as D7238 – 06
(2012).(2017). DOI: 10.1520/D7238-06R17.10.1520/D7238-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7238 − 20
3.1.1 control, n—a material which is of similar composition and construction to the test material used for comparison, exposed
at the same time.
3.1.2 irradiance, n—the radiant power per unit area incident on a receiver, typically reported in units of W/(m .nm)·nm) at
specified wavelength of measurement or in W/m in a specified spectral range.
3.1.3 reference material, n—a material with known performance.
3.1.4 ultraviolet regions, n—the UV region of the spectrum is divided into three regions: UVA, radiation in wavelengths
between 315 nm and 400 nm; UVB, radiation in wavelengths between 280 nm and 315 nm; and UVC, radiation in wavelengths
shorter than 280 nm (Ref. CIE Publication No. 20 (1972)).
4. Summary of Test Method
4.1 Geomembrane coupons are exposed to repetitive cycles consisting of ultraviolet radiation at a specified temperature
followed by moisture in the form of condensation at a specified temperature in the absence of ultraviolet radiation.
4.2 The UV source is provided by fluorescent UVA-340 lamps, with lamp emissions peaking at 343 nm.
4.3 Water vapor shall be generated by heating water and filling the chamber with hot vapor, which then is made to condense
on the front of the test coupons. The reverse side of the coupons is exposed to the cooling influence of ambient room air.
4.4 While this standard prescribes a particular set of exposure conditions, such conditions may be varied by agreement between
the parties involved in the agreement or contract. Such variation may include the irradiance, the selection of the fluorescent UV
lamps, the duration of the UV and condensation exposure periods, the temperature of UV exposure, and the temperature of the
condensation exposure.
4.5 The periodically removed coupons are cut into test specimens, appropriately tested, and the results compared to unexposed
samples for determination of a percent retained for each property evaluated.
5. Significance and Use
5.1 The use of this apparatus is intended to induce property changes associated with the end-use conditions, including the effects
of the UV portion of sunlight, moisture, and heat. Exposures are not intended to simulate the deterioration caused by localized
weather phenomena, such as atmospheric pollution, biological attack, and saltwater exposure.
NOTE 3—Refer to Practice G151 for cautionary guidance applicable to laboratory weathering devices.
5.2 Variation in results may be expected when operating conditions are varied within the accepted limits of this method.
5.3 Test data for one thickness of a geomembrane cannot be used as data for other thickness geomembranes made with the same
formula (polymer, pigment, and stabilizers) since the degradation is thickness related.
NOTE 4—It is recommended that a similar material of known performance (a control) be exposed simultaneously with the test material to provide a
standard for comparative purposes. When control material is used in the test program, it is recommended only one coupon be used for each UV exposure
period to allow for OIT testing.
6. Apparatus
6.1 Fluorescent UV/Condensation Apparatus, complying with Practices G151 and G154.
6.2 Unless otherwise specified, the spectral power distribution of the fluorescent UV lamp shall conform to the requirements
in Practice G154 for a UVA-340 lamp.
6.3 The apparatus must include a feedback loop controller and be capable of controlling the irradiance level within the
guidelines set in Practice G154, Table X2.3, Operational Fluctuations On Exposure Conditions.
6.4 Exposure Chamber Location:
6.4.1 The apparatus shall be located in an area maintained at temperature range between 18 and 27 °C (64 and 81 °F) measured
at a maximum distance of 150 mm (5.9 in.) from the plane door of the apparatus.
6.4.2 It is recommended that the apparatus be located at least 0.3 m (12 in.) from walls or other test devices. Nearby heat
sources, such as ovens or heated test devices, shall be avoided or shielded because such sources can influence the results.
6.4.3 The room where the apparatus is located shall be adequately ventilated to remove the heat and moisture produced and to
maintain the temperatures specified in 6.4.1.
6.5 Instrument Calibration:
6.5.1 To ensure standardization and accuracy, the instruments associated with the exposure apparatus (that is, timers,
thermometers, UV sensors, radiometers) require recurrent calibration to ensure repeatability of test results. The calibration
frequency recommended by the equipment manufacturer should be used.
NOTE 5—It is recommended that a weathering reference material should be evaluated at least once per year to assess the operation of the device.
Practice G156 describes procedures for selecting and characterizing weathering reference m
...