Solar radiation testing is a method of testing used to determine the consequences of actinic ray exposure (also known as UV rays from sun) touching on the physical surface or “Device under test” with the intention to see its operational integrity after significant exposure.

There are many standards which prescribe the duration and method of exposure and thereafter verifying the integrity. Some of the common and popular methods are described below:

Solar Radiation Testing as per MIL STD 810 G – Test Method 505.5 – Solar Radiation (Sunshine)

Solar radiation testing as per MIL-STD 810 is conducted to determine the consequences of radiation on instrument that will be exposed to sunshine during operation or unsheltered storage on the Earth’s surface. Some times even devices which are to be used in the lower atmosphere are also tested as per this standard.

The heating effects of radiation are different from just the high temperature alone, because of this reason, temperature cycling test method do not fully validate the DUT for effects of sun radiation including UV radiation. It is also not just the radiation absorbed by the DUT but also reflected by the DUT that has a impact on its functionality and appearance.

Additionally, changes within the intensity of radiation could cause elements to expand or contract at completely different rates, which might result in severe stresses and loss of structural integrity within different elements of the DUT.

AATCC TM16

Colorfastness to Light: This test method provides the general principles and procedures which are currently in use for determining the colorfastness to light of textile materials

AATCC TM169

Weather Resistance of Textiles: Xenon Lamp Exposure -This test method provides the procedure for the exposure of textile materials of all kinds, including coated fabrics and products made thereof, in a xenon solar radiation chamber using controlled conditions of test. This can be conducted by either wetting the sample or dried sample.

The intent of this test is to measure the degradation due to exposure of Solar radiation including UV radiation. Degradation will be either as percent strength loss or percent residual strength (breaking, tearing, or bursting) and/or colorfastness of the material when evaluated under standard textile testing conditions.

ASTM C1257

Standard test method for accelerated weathering of solvent-release-type sealants: This test method includes two laboratory accelerated exposure procedures for predicting the effects of ultraviolet or ultraviolet/visible radiation, heat, and moisture on color, chalking, cracking, and adhesion of solvent-release sealants. It is applicable on sealants.

ASTM C1442

Practice for Conducting Solar radiation Tests on Sealants Using Artificial Weathering Apparatus : This standard practice covers three types of laboratory weathering exposure procedures for evaluating the effect of actinic radiation, heat, and moisture on sealants.

There exists a comparable ISO standard related to this – ISO 11431. However there are some differences between ISO 11431 and ASTM C 1442 test methodology. In the ISO standard, test material is exposed through glass and is stretched prior to evaluation for loss of adhesion or cohesion, or both after continued solar radiation exposure.

ASTM C1519

It is a Solar radiation test method for evaluating durability of building construction sealants by simulated Accelerated Weathering. This test method covers the method for the determination of the durability of a sealant based on its ability to function in cyclic movement maintaining adhesion and cohesion after repeated exposure to laboratory accelerated weathering procedures

ASTM C732

This standard specifies the test method for “Aging Effects” of Artificial weathering on latex sealants. It describes the procedure for determination of aging effects of artificial weathering on latex sealants through application of solar radiation.

ISO 16474-2

This standard specifies test method for exposing specimens of paints and varnishes to xenon-arc light in a solar radiation chamber, in the presence of moisture. This is done with the intention to reproduce the weathering effects that occur when materials are exposed in actual end-use environments to daylight and even to daylight filtered through window glass.

The specimens of paints and varnishes are exposed to filtered xenon-arc light under controlled conditions (temperature, humidity and/or wetting). ITC India has facility and experience for conducting this test for paints and varnishes.

ISO 105-B02

ISO 105-B02 specifies a test methodology which is useful for finding out effects of solar radiation testing on the colour of textiles. In this test procedure a artificial light source such as a xenon lamp which is representative of natural daylight is used. This Solar radiation testing methodology is also useful to test white (bleached or optically brightened) textiles.

ISO 9022-9

ISO 9022-9:2016 describes the test methodology of environmental tests of optical instruments for their ability to resist the effects of simulated solar radiation or laboratory weathering, which is a combination of simulated solar radiation, heat, and moisture. It is applicable to instruments that may be exposed to sunlight during operation or unsheltered storage on the earth’s surface, or in the lower atmosphere

ISO 12040

Graphic Technology – Prints and Printing Inks – Assessment of Light Fastness Using Filtered Xenon Arc Light

MIL STD 810 G

This method is used to evaluate material likely to be exposed to solar radiation during its life cycle in the open in hot climates, and when heating or actinic effects are of concern. This method is valuable in evaluating the effects of direct exposure to sunlight (solar spectrum and energy levels at sea level).

Procedure I is useful in determining the temperature increase (over ambient) of material caused by solar loading.

In addition to using Procedure I to evaluate the effects of direct sunlight (actinic effects as well as directional heating for exposed materiel), use Procedure I for determining the heating effects (response temperature) for materiel enclosed within an outer container.

Procedure II may be used to simulate the ultraviolet effect of solar radiation at different locations and altitudes by using various radiation sources that allow reasonable comparison to measurements of these natural solar radiation conditions.

Use Procedure II of this method when the spectrum of the lamp bank has been measured and conforms to the spectrum identified in Table 505.5-I. Deviations from this table may be justified if the test requirements are based on the tailoring process, or if a specific frequency band is of concern. Detail and justify any deviation.

Limitations

This test method does not consider all of the effects related to the natural environment (see Annex A, paragraph 7.2) and, therefore, it is preferable to test materiel at appropriate natural sites.

If the installed environment for an item is within an enclosure, then to properly address the heating effects, the enclosure must be provided to characterize the environment. Once the enclosed environment has been characterized, further testing could be done using Method 501.

This method is not intended to be used for space applications due to the possible change in irradiance.

TEST PROCESS

Procedure I – Cycling

Step 1. Adjust the chamber air temperature to the minimum value of the temperature cycle at which radiation is non existent.

Step 2. Expose the test item to continuous 24-hour cycles of controlled simulated solar radiation and dry-bulb temperature as indicated on Figure 505.5-1 or as identified in the requirements document, measuring and recording test item temperatures throughout the exposure period. For convenience, and if the test facility is unable to perform the continuous curve of Figure 505.5-1, to approximate the curve increase and decrease the solar radiation intensity in a minimum of eight levels (see Annex C, Figures 505.5C-5 and C-6 for the stepped levels) for each side of the cycle, provided the total energy of the cycle as well as the spectral power distribution (above 1000 w/m2 – see Table 505.5-I and Annex B, paragraph 1.4) is maintained. Perform the longer of the following number of cycles, and record the results:

The minimum necessary to ensure the peak response temperature of the most critical area of the test item achieved during a cycle is within 2°C (3.6°F) of the peak response temperature achieved during the previous 24-hour cycle,

or

Three continuous cycles,

or

The number of cycles as identified by the requirements document (not to exceed 7 cycles, unless otherwise specified in the test plan).

Step 3. Based on the requirements document, the test item may or may not be operated throughout the test. If operation is required, operate the test item when the peak response temperature occurs. For some single-use items (e.g., rockets), use thermocouples affixed to critical portions of the test item to determine the time and value of peak temperature. Operate the test item at the peak cycle temperature. Conduct the operational checkout of the test item as in paragraph 4.4.1.2, Step 4. Document the results as well as the peak temperature. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure.

Step 4. Adjust the chamber air temperature to standard ambient conditions and maintain until temperature stabilization of the test item has been achieved.

Step 5. Conduct a complete visual examination of the test item and document the results. For comparison between pre and post test items, photograph the test item and take material samples (if required).

Step 6. Conduct an operational checkout of the test item as in paragraph 4.4.1.2, Step 5. See paragraph 5 for analysis of results.

Step 7. Compare these data with the pretest data.

Procedure II – Steady State

Step 1. Adjust the chamber air temperature to 49°C (120°F) or the temperature identified in the test plan.

Step 2. Adjust the solar radiation source to a radiant energy rate of 1120 ±47 W/m2 or as identified in the materiel specification. Use sufficient air speed to maintain the test item temperature to the peak response temperature obtained in procedure I or obtained from field data.

Step 3. Maintain these conditions for 20 hours, measuring and recording the test item temperatures. If required, conduct operational checks during the last four hours of each 20-hour exposure when test temperatures are maximized. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure.

Step 4. Turn off the solar radiation source for four hours.

 Step 5. Repeat Steps 1 through 4 for the number of cycles identified in the test plan.

Step 6. At the end of the last radiation cycle, allow the test item to return to standard ambient conditions.

Step 7. Conduct a visual examination and an operational check as in paragraph 4.4.1.2, Steps 3 and 5, and document the results. Take photographs of the test item and material samples (if required) for comparison between pre and post-test items. See paragraph 5 for analysis of results.

What are the Benefits of Testing?

• Save money & save energy as well
• Provide faith in the product
• Improve the safety of the product

Other Standards for Solar Radiation testing

• VDA 230-219
• MBN 55555-5
• DIN 75220