Environmental Test Chambers for ASTM D4799 Accelerated Weathering Test Method
Lenpure UV Lamp Weathering Test Chambers adopt fluorescent UV lamp as light source to simulate the UV irradiation in natural light and condensation to conduct accelerated weathering test to the materials. It can simulate the UV, rain, high temperature, high humidity, condensate, darkness and other environmental conditions in natural climate and combine them in a circle, and carry out these circles automatically.
This test method covers the test conditions and procedures that are applicable when Practice G53 is employed for the exposure of bituminous roofing and waterproofing materials having a minimum softening point of approximately 200F (95C) as determined by Test Method D36.
The values stated in inch-pound units are to be regarded as the standard.
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 and health practices and determine the applicability of regulatory limitations prior to use.
Thin films of bitumen are uniformly applied to aluminum panels. Shingles and similar materials are cut to size and exposed to specified cycles of temperature, light, and water. A choice of three test cycles is given along with options for determining the period of exposure and evaluating results.
This weathering apparatus is used for comparing the weathering characteristics of bituminous materials against a control material for which the outdoor weathering characteristics are known. It is not possible to establish a precise correlation between accelerated and natural weathering be cause:
(1) There are geographical climatic variations local weather variations, and variations in local pollutants;
(2) The relation between accelerated and natural weathering is material dependent. Acceleration factors differ between mate rials as well as between formulations of the same material Guide G141 provides guidance regarding this issue.
The fuorescent UV and condensation apparatus used shall conform to the requirements defined in Practices G15 and G154.
Lamps-Unless otherwise specified, the lamps shall be fluorescent UVA-340 lamps as described in 6.1.3.1 of Practice G154.
Other fluorescent UV lamps meeting the size and electrical characteristics in 5.2 may be used if mutually agreed upon and provided that the lamp and spectral energy distribution are reported in conformance with Section 9.
Moisture-It is permitted to expose the test specimens to moisture in the form of water spray, condensation, or high humidity.
Water Spray-It is permitted to equip the test chamber with a means to introduce intermittent water spray onto the test specimens under specified conditions. The spray shall be uniformly distributed over the samples. The spray system shall e made from corrosion resistant materials that do not contaminate the water used.
Spray Water Quality-Spray water shall have a conductivity below 5 μS/cm, contain less than 1-ppm solids and leave no observable stains or deposits on the specimens.Very low levels of silica in spray water can cause significant deposits on the surface of test specimens.
Care should be taken to keep silica levels below 0.1 ppm. In addition to distillation a combination of deionization and reverse osmosis can effectively produce water of the required quality. The pH of the water used shall be reported. See Practice G151 for detailed water quality instructions.
Unless otherwise agreed upon, test specimens shall be approximately 3 by 6 in. (75 by 150 mm). Bituminous materials shall be applied as uniform coatings on aluminum panels in accordance with Practice D1669.
Fabricated materials such as bituminous roofing, shingles, and similar products shall be cut to size and their weather surfaces exposed. If these are too flexible to sustain their own weight in a vertical position, they may be mounted on aluminum panels.
Replicate specimens are desirable to provide a record of degradation at different time intervals. Retention of an unexposed specimen is recommended as it is difficult to mask a specimen to prevent exposure to condensation.
Follow the procedures described in Practice G147 for identification, conditioning, and handling of specimens of test and control materials prior to, during, and after exposure.
Proceed in accordance with Section 9 of Practice G154.
Apparatus shall be operated continuously, except for intervals for repositioning of samples or inspection of samples, according to one of the following cycles. The temperature specifications are for an uninsulated black panel thermometer For equipment that requires an irradiance setting for its operation, it shall be 0.89 ± 0.02 W/(m2.nm) at 340 nm Specimens shall 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 G154. Section 9.5, to ensure equal radiant exposure on all specimens or to compensate for differences within the exposure chamber. If the specimens do not completely fill all of the spaces, fill the empty spaces with blank panels of corrosion resistant material to maintain the test conditions within the chamber.
Cycle A-4 h UV at 60 ± 2.5C. alternating with 4 h condensation at 50 ±2.5C.
Cycle B-20 h UV at 60 2.5C. alternating with 4 h condensation at 50 ± 2.50℃.
Cycle C-20 h UV at 80 2.5C. alternating with 4 h condensation.at 50 ± 2.5C.
Cycle D-4 h UV at 60 ± 2.5°C, 15 min water spray, alternating with3.75 h condensation at 50 + 2.5C.
Cycle E-20 h UV at 60 ± 2.5%C. 15 min water spray, alternating with3.75 h condensation at 50 ± 2.5℃.
Cyele F-20 h UV at 80 2.5C. 15 min water spray, alternating with 3.75h condensation at 50 ± 2.5℃.
If inspection of the panels is to be performed at any stage in the cvcle, the interruption of the test procedure shalll ' take only sufficient time to allow for such inspection. The time taken for inspection of the samples shall not be counted as part.
The cycle to be employed shall be specified in the product standard.
The operational fluctuations, that is, the positive and negative deviations from the specified set points for the irradiance and temperature, are allowable deviations from the set points during equilibrium operation of the equipment. They do not imply that the user is allowed to program a set point higher or lower than that specified.
Operate the apparatus to maintain the allowable operational fluctuations. If the latter are greater than the maximum allowable after the equipment has stabilized, discontinue the test and correct the cause of the problem before continuing.
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