Report of the Climate Working Group meeting 23-03-2022

In October 2021, we started a new topic with the Climate working group, namely UV/Solar testing. The second meeting regarding this topic is at Accell Group in Heerenveen. We were welcomed here with a delicious lunch and also a very nice location for the Climate working group to meet! Thanks for this invitation!

Proposal round
Some participants are joining this meeting for the first time. That is why an introduction round is held where everyone has the opportunity to introduce themselves.

Discussing test plan (Marcel van Doesburg – Eurofins Materials Science Netherlands)
During this presentation the difference between “weathering” and “solar testing” was discussed. Weathering is the effect of weather and climate on materials and products, while solar testing only looks at the effects of sunlight.

When conducting artificial weathering tests, there are many variables that can be controlled.

Think about

• Radiation intensity
• Spectral radiation distribution
• Temperature surface samples or reference
• Temperature test chamber
• Relative humidity test chamber
• Cycles (dry/rain or light/dark)
• Calibration of equipment
• Indoor/outdoor (filters)
• Backed/open backed
• Test duration

Next we discussed a portion of the MIL-STD-810G. Detailed guidance on solar radiation testing. A distinction has been made between the effects that can occur as a result of sunlight.

Two types of effects occur:

• Heat effects
• Actinic effects (photo degradation))

This standard is very detailed and makes a good translation from actual environmental conditions to laboratory testing. Carrying out these tests is not always easy and sometimes requires “tailor-made solutions”.

To set up the correct solar test, it is important to characterize the climate where a product is used. Various maps can be used for this. For example, there are maps where the horizontal solar radiation is indicated (Solargis) and maps where the climate is defined using a 3-letter coding (hanschen kopen).

A distinction can be made between UV-A/B testing and solar testing. UV testing is suitable for quickly degrading materials. The amount of UV radiation is much higher than in sunlight. The disadvantage is that a good correlation with the lifespan of a product cannot be made because the spectrum does not resemble sunlight. There are many wavelengths missing. Solar testing does have a good correlation with the lifespan of a product, but that often means a longer test time.

Within the working group we will carry out a number of field tests and laboratory tests. The data from these tests will be used to examine a correlation between the various tests.

 The various participants in these tests will draw up a verification protocol for the samples they supply themselves. This includes color point measurements, tensile strength, bending tests and visual inspection.

Experiences testing solar products Accell (Frits van der Galien)

Characteristics of aging/weathering

• Color change
• Fading
• Gloss loss
• Strength loss
• Degradation
• Cracking
• Peeling
• Chalking

The standard ISO4892-2 is used to carry out Solar tests. These tests are performed with Q-Sun Xenon Test Chamber Model Xe-3.

Color point measurements are often made on the various samples. Color and perception of color is often a subjective matter. However, colors can be measured according to the so-called CIE-lab method. The colors are identified by their “L” value (gray value), “a” value (position between red and green) and the “b” value (position between blue and yellow). Once the position of a color has been determined, it is possible to determine the “distance” to a second color, in other words the color difference. Color differences are expressed in ΔE. A colorimeter is used for this.

In addition, the ISO Blue wool standards are also used. This method is used to determine which of the eight strips on the blue wool standard card is discolored to the same extent.

For the solar test

After the solar test

After this presentation we have a guided tour at the Accell Group Reliability lab. Various mechanical tests and solar systems were discussed.

Boudwijn Jacobs (Signify) will be discussed in more detail in the next presentation UV testing within Signify, what standards are available on this topic, and important tools for this type of testing. The so-called “irradiance maps” clearly show that there is a 1-to-1 relationship between the amount of solar radiation and UV radiation here on earth. We can distinguish 3 types of areas here:

High severity, relative weight 1.3: South West of USA, Mexico, Australia, North of Africa;

Moderate severity, rated 1 by default. 1700 kW.h/m² is used as annual horizontal irradiation:

South of Europe, Mid part of USA, India, East of China

Low severity, relative weight 0.7: Central and North Europe, North of USA and Canada, China

There are many standards available that can provide information for carrying out a UV/Solar or weathering test. Below is a summary of a number of available standards.

ASTM G154 Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp

Apparatus for Exposure of Non-metallic Materials ≡ ISO 4892-3

ASTM G155 Standard Practice for Operating Xenon Arc Light Exposure of NonMetallic Materials ≡ ISO 4892-2

IEC 60068-2-5 Ed. 3.0 en:2018 – Simulated Solar Radiation at Ground Level

ISO 13468-1 Plastics — Determination of the total luminous transmittance of

transparent materials — Part 1: Single-beam instrument.

ISO 4892-2 Plastics – Methods of exposure to laboratory light sources — Part

2: Xenon arc lamps

ISO 4892-3 Plastics — Methods of exposure to laboratory light sources — Part

3: Fluorescent UV lamps

MIL-C-48497A Military specification on durability requirements for coatings.

SEPAP 12/24 Photovieillissement accéléré and SEPAP adapted by the French

National Center for Photoprotection Assessment (CNEP).

UL 4599 Resistance of Plastics to Chemical Reagents, equivalent to ASTM

D543

Show two ways to determine the yellowing of transparent materials:

Method A: Yellow Index this examines the difference in transmission coefficient between measurements at 450 and 550 nm.

Method B: transmission at a certain wavelength. This looks at the absolute transmission at a certain wavelength.

Yellowing effects of transparent materials

Finally, it has Harry Roossien (R2R) gave a brief overview of the problems he has encountered with certain products. Common issues are materials becoming brittle and discoloration. This also raises questions about what the failure mechanism is and how can we find this out. There are many techniques available to determine the failure mechanism. If this is clear, it will be easier to find a solution to the problem.

With this explanation we have come to the end of our meeting. We have made the necessary agreements for carrying out the field tests and will continue to do so in the coming period.

The next meeting is expected to take place in September bee Thales Hengelo. Thank you in advance for the invitation. See you soon at the next PLOT members meeting!