When you are bonding a product that is going to be exposed to the outdoors, you need to choose the right adhesive. If you get it wrong, the weather conditions can ruin the integrity of the bond. When that happens, you have to spend more time and money on finding a suitable adhesive.
When it comes to testing products to determine quality and performance in the outside world, accelerated weathering testing is a popular testing method. You want to ensure that the product can not only withstand normal weathering conditions but also hold its performance even when exposed to harsh conditions. That’s why you are looking into accelerated weathering testing.
After doing a bit of research into the topic, you will come across ASTM G154. It always seems to crop up in the same conversation as weathering testing. Nonetheless, you may have very little idea about what ASTM G154 is. If that sounds like you, don’t worry. We’ve got you covered.
Here at Forgeway, we manufacture structural adhesives and sealants. We use the ASTM G154 testing method to establish whether our products can withstand weathering conditions.
This article will mainly focus on weathering testing for adhesives and sealants as they are our areas of specialism. However, the topics we discuss in this article will mostly apply to other types of products too.
By the end of the article, you will know what ASTM G154 is all about, when you should use it, and what to do once you have completed the testing process.
What is ASTM G154?
ASTM G154 is an American standard for measuring accelerated weather testing. In technical terms, it sets the standard for operating fluorescent light instruments to test the performance of non-metallic materials when exposed to weathering conditions.
It is recognised globally as one of the best ways to test a product’s performance in harsh conditions without actually having to expose them to real-life conditions over long time periods.
ASTM G154 gives you a structure for using your accelerated weathering device (such as a Q-Lab QUV). It allows you to match the conditions your product is likely to experience.
For example, let’s say your adhesive is bonding a plastic panel to the side of a caravan. You need to see whether the adhesive can withstand massive variations in conditions (cold, hot, etc). The caravan will likely experience anything from freezing conditions to temperatures above 40℃. ASTM G154 testing will help you establish whether the adhesive will maintain performance even in those harsh conditions.
Whilst the test results are a very good indication of how the product will perform in those conditions, it is never going to tell you exactly how the product will perform in the outside world. ASTM G154 tests are the closest to the real thing without actually putting the product in those real-life conditions.
What are the alternatives to ASTM G154?
ASTM G154 is the most popular because It’s comprehensive making it widely respected by the adhesive and sealant industry. However, there are some other options you should be aware of as well:
Much like ASTM G154, ASTM G155 is an American standard. The only difference is that it is for machines that use xenon arc lamps rather than fluorescent bulbs. Some say xenon arc lamps are much more similar to the sun’s rays. However, both tests give a good idea of how the adhesive or sealant will perform in typical weathering conditions.
This standard is specifically for the automotive industry. It is for the accelerated exposure of automotive exterior materials. SAE J2020 is also for machines that use fluorescent lights and condensation to provide an accurate representation of real-life weathering conditions.
The ultimate aim of the test is to see how well the materials on the exterior of automobiles perform. The test exposes the materials to conditions similar to those it is likely to face in the real world.
Much like some of the other test methods, ISO 4892 is for machines that use fluorescent lights to simulate real-life conditions. The machine simulates the real-life conditions using a xenon arc bulb and ISO 4892 determines what the level of exposure should be and how long that exposure should be.
When to use ASTM G154?
Whenever you want to see how your adhesive performs in certain weather scenarios, accelerated weather testing will give you the ability to do just that. In our opinion, ASTM G154 will give you the best framework to match the conditions you need. However, there are plenty of other testing methods you could use that will help you establish the performance of your product.
ASTM G154 is an American standard. But even if you aren’t conducting the test in America, you can ensure you tested the product to the same standard by following its guidance.
Effectively, whenever you are conducting an accelerated UV weathering test, we would suggest you use ASTM G154’s framework. However, there are several other testing standards you can use.
What to look out for when ASTM G154 testing?
Before starting the ASTM G154 test, determine what specific issues you want to see from the test. Typically, companies will evaluate the adhesive/sealant’s performance in areas such as:
- Colour change – A common problem with sealants like neutral cure silicones is their susceptibility to turning yellow after exposure to UV. ASTM G154 testing will show you the adhesive/sealant’s ability to retain its colour.
- Embrittlement – All adhesives and sealants have a ‘hardness’ rating. Sometimes after prolonged UV exposure, this hardness can increase to the point that it affects the product’s performance. We call this hardness increase ’embrittlement’.
- Cracking – Cracks can sometimes appear in the adhesive or sealant after a lot of exposure to UV and weathering. If there are any signs of cracking after an ASTM G154 test, the adhesive or sealant is obviously not fit for purpose.
- Chalking – This is where white precipitate makes its way to the surface. This leaves a white residue on the surface of the adhesive or sealant. The residue bears resemblance to chalk, hence the term ‘chalking’.
- Leaching – If UV or humidity exposure causes an adhesives polymer matrix to breakdown, it can allow unbound raw ingredients to migrate to its surface. If these unbound raw ingredients are liquid it can appear as though the adhesives (or substrates) surface is ‘seeping’. If this happens, it can affect the performance of the adhesive or sealant. Leaching out raw materials is an early sign that embrittlement may occur over a longer exposure time. Accelerated weathering testing will tell you if the adhesive or sealant will leach out raw ingredients.
All of these issues could arise when you test any adhesive or sealant. However, you need to know what to look out for before you analyse the final test results.
Evaluating the test results
Obviously, you should analyse the adhesive or sealant test results first. If you aren’t sure, read the section above again to see what we recommend you to look out for.
If the adhesive or sealant has passed in the areas you wanted it to, you should look further at some of the other potential issues that could arise. For example, the sealant may maintain its colour very well, but if there was additional cracking created by the test, then it wouldn’t pass the test.
When conducting accelerated weathering testing, always remember the adhesive or sealant can fail in more than one area.
Make sure there are no other issues with the sealant (like cracking), before you finish analysing the results and come to a conclusion about the sealant’s performance.
But what if the adhesive or sealant fails the test?
Nonetheless, you may have found the product you are testing doesn’t pass the test in the area that mattered most. Perhaps the sealant has experienced severe discolouration. What’s next?
Now you have two options:
- Look to adjust the formulation of the existing adhesive or sealant
- Look for an alternative adhesive or sealant altogether
Adjusting the formulation will mean you can keep the existing adhesive or sealant. It will just allow you to try and work around the problem that arose during the testing (such as chalking). There is no guarantee that you can adjust the formulation to rectify the issue though.
Looking for an alternative product is sometimes the only way forward. If the adhesive or sealant failed in multiple areas, or you have already tried to adjust the formulation, it makes sense to look for an alternative adhesive or sealant solution. However, you need to be sure that you know how to choose the right adhesive or sealant for your application.
ASTM G154; key takeaways
So you were wondering what ASTM G154 is, and why accelerated weathering testing is so valuable. Now you know that ASTM G154 is one of the most popular testing frameworks for accelerated weathering testing. You also know what to look for when conducting accelerated weathering testing.
But what’s next? The answer depends entirely on what stage you are at. If you are at the point where you need to test one of your products to see if it withstands the impacts of weathering, an ASTM G154 test is what you need.
Here at Forgeway, we test our adhesive and sealants in accordance with ASTM G154 with our QUV machine. We don’t do this to earn extra brownie points, we do it because ASTM G154 is the most rigorous and thorough framework for accelerated weathering testing. We know that if our products pass this test, they are likely to be able to withstand the effects of real-life weathering.
However, there are other variables (such as mould growth) that can influence an adhesive or sealant’s performance over time. Weathering testers can’t replicate this. So you shouldn’t wholly rely upon the testing results from accelerated weathering testing to judge an adhesive or sealant’s long-term performance.
If you need help with accelerated weathering testing for your adhesive or sealant, we would be more than happy to help. By reaching out to a member of our team, you will get guidance on how we can help you test your products. We have the facilities to undertake accelerated weathering testing on adhesives and sealants according to ASTM G154. We also have the knowledge to translate the technical results information into data that is easier to understand.
If you want to conduct the testing on your own, we wouldn’t advise buying your own QUV machine. You likely wouldn’t use it enough to warrant the investment. There will be test laboratories in your area that can assist with accelerated weathering testing of your product.
Whatever you decide to do, we are here to help you find the right solution.