Structural Adhesives Explained. 

If you want to find out more info about structural adhesives you are at the right place. In this blog we shall be reviewing the MS polymer® type of adhesives because this is the chemical composition of the Bond-Flex range. We will be providing an overview of these adhesives and the reason behind their popularity with motor body manufacturers, smash repair facilities, sheet metal fabricators and many of our customers in building and construction. Comparison adhesive lab testing and trialing often finds the Bond Flex range to be the better option for many bonding applications. MS Polymer® adhesives usually means they are extremely strong, environmentally friendly and fully elastic when cured. Importantly there are no poisonous vapours assoiated with these glues, unlike other adhesive and sealants like silicone, polyurethane etc. Aerobolt has two distinct Bond Flex options each with their very own characteristics so there is  bound to be one that suits your application.  

Option 1 - Bond Flex. 

Bond Flex (BF) is a structural adhesive that is renowned for it's high initial tack and green strength. When seeking a tough flexible bond or joint that can withstand a high degree of movement with great initial grab that reduces the need for support whilst curing - Bond Flex should be your first choice.  

Option 2 - Bond Flex Plus. 

Bond Flex Plus (BFP) is an easier to use glue because it does NOT have the high initail tack or green strength of Bond Flex, but is a stronger adhesive AFTER curing. BFP is 25% stronger than Bond Flex when dry. BFP is also formulated to resist short periods of heat associated with powder coating. 

What are MS polymer adhesives?

MS polymer adhesives are made up of a hybrid polymer called modified silane. The term ‘MS polymer’ is a registered trademark of Kaneka as they created the hybrid silane polymer formulation. Copies of MS polymer are known as hybrid polymers or silyl modified polymers, but it all means the same thing. MS polymer was created as an adhesive product that has the strength of polyurethane and the weathering resistance of silicone. However, MS polymers DO NOT contain any silicone or urethane polymers which is a big deal as silicone and polyuethane are being banned by some overseas automotive manufacturers.

You will rarely find two-part MS polymers as they don’t require a hardener in the curing process. They will almost always be one-part (in a foil pack or cartridge). This is because MS polymers require moisture to cure and most customers are happy with the cure speed of the one-part option. 

Where can you use MS polymer adhesives?

To begin with, we should explain that MS polymer’s versatility is perhaps not as well known as it should be. You will be able to use MS polymers in pretty much any sealing or bonding situation because the range is comprehensive. They easily bond to pretty much all surfaces and are fully primerless.

There are, of course, exceptions. If you need an extremely high-strength bond (such as replacing a weld), you would be better off using an epoxy adhesive. But you should definitely consider using an MS polymer for any bonding or sealing situation, as long as the substrate is compatible and you don’t require a very high-strength bond. 

To give you an idea of MS polymers applications, here is a short list of examples:

• Motor body manufacturers use MS polymer adhesives for panel bonding, this includes metal sheets, glass reinforced panels (GRP) and other plastics/composites panels, floor bonding, and trim finishing.  
• Boat manufacturers uses an MS polymer adhesive to bond and seal the windows of their luxury yacht product. They like the weathering resistance and strength of MS polymer glues. 
• Caravan manufacturer use MS polymer adhesives to bond and seal the plastic sides of their caravan product. MS polymer’s structural, flexible, and sealant properties make it the best solution for their application.
• Bus & Coach manufacturer uses MS polymer for panel bonding, this includes glass reinforced panels (GRP) and plastic/composite bonding, floor bonding, trim finishing, and seam sealing. 

There are plenty more examples of companies that use MS polymers. Nonetheless, these examples should give you an idea of the variety of situations where you could use an MS polymer adhesive.

Advantages of using MS polymer adhesives.

As you will be aware, MS polymers are a very good adhesive and sealant solution. But you will be wanting to know the benefits you will get if you choose to use an MS polymer product. So this section of the blog will go over every advantage of using MS polymers.

MS polymers provide a very good seal for bonding and sealing.

Some MS polymer formulations can have high strength, whilst others have limited strength. BUT all MS polymer products have good sealing properties. Whether you intend to use the MS polymer product for bonding or joint sealing, it will always provide a good seal. The seal is better and more durable than that of other products.

MS polymers are very flexible.

Some manufacturers seek to find the strongest glue possible, but strength isn’t everything. In situations where there is likely to be lots of vibration (such as vehicles, trucks, emergency vehicles etc.), you need a flexible adhesive to deal with the constant movement associated with travelling. MS polymers have better flexibility than other structural adhesives such as methyl methacrylates and epoxies. 

You can overpaint most MS polymers.

There are a lot of talk about the difficulty in painting over sealants like silicone, but you can paint over most MS polymers without any problems. Don’t forget there are many different types of paint, so we’d always recommend testing first.

MS polymers are the safest adhesive for the user and the environment.

Most other adhesives and sealants will have some form of health risk to be aware of. Some manufacturing companies have even banned the use of silicones in their factories because of these health risks. You won’t have to worry about this with MS polymers, you won’t experience any health risks. They are not harmful to the environment either.

MS polymers have very good weathering resistance.

UV resistance is not the only form of weathering resistance that you should consider. Weathering includes the impact that hot and humid climates could have on the adhesive as well as the effect of UV. MS polymers are able to withstand the effects of weathering.

The above-mentioned advantages are the deal-breakers for most companies when deciding which adhesive to use. There are a few more advantages that you should also consider, such as:

• Long shelf life.
• Fire-resistant options.
• No bubbling when curing.
• No staining on substrates.

What are the disadvantages of using MS polymer adhesives?

So you now know that MS polymers are a very competent adhesive and sealant option. But you will be thinking we are biased as the suppliers of Bond Flex and Bond Flex Plus. We have worked with MS polymers for over 20 years, so we know that there are a couple of things that makes them an unsuitable option for some companies, here are some drawbacks. 

Cure time require moisture. 

As we mentioned earlier, they also require moisture to cure. Limited moisture (such as lack of airflow or very cold weather) will either reduce the cure time or prevent it from happening at all. There are other factors that can affect the cure time, but moisture will always affect the cure time of MS polymers.

So you should bear this in mind when considering MS polymers as an adhesive or sealant option. Methyl methacrylates have a very fast cure that is much more consistent if that is something that is a big issue for you.

MS polymers aren’t the strongest structural adhesive.

We have already mentioned that MS polymers aren’t the strongest, but there are a couple of reasons why this might not work for you. Epoxies are the strongest structural adhesive. So if you are purely looking for high-strength glue, you should go with them. 

But, we have also mentioned flexibility too. Flexibility can be just as important as strength. And epoxies are very brittle. So what can you do?

DEpending on the strength you are seeking, we would suggest using a MS polymer adhesive if you want something that is mid strength strength but also remains flexible.

Sometimes, MS polymers are too strong.

Yes, MS polymers can be too strong for certain situations. Companies often compare silicones and MS polymers because they are the two best sealants. However, an MS polymer sealant will always have more strength than a silicone sealant. 

Most people would struggle to see why having more strength is an issue. But it can be. 

The simple reason is on the rare occasion you make a mistake, silicones will be a lot more tolerant. They allow you to remove and replace anything you think should be replaced. MS polymers’ strength will be a lot less forgiving and you will struggle to remove and replace the sealant if you get a poor finish.

It can be more difficult to get a good finish.

Silicones are popular for a reason. They always used to be cheaper than MS polymers (now they are about the same price), and they are still a lot easier to work with.

All silicones are easy to work with as you won’t need a significant amount of skill to apply and get a good finish. You won’t always find the same with MS polymers. It can take a lot of skill to apply MS polymer in a way that gets a good finish.

How do you know an MS polymer is the best option for you?

The answer ultimately lies with what you want from your glue. However, MS polymer is a very popular adhesive option for a reason. It is great at most things required of glue, whilst not having as many drawbacks as other structural adhesives. 

We wouldn’t recommend using an MS polymer if you want an adhesive that has extremely high strength, although it depends also on your interpretation of “High Strength”. MS polymers are usually more than strong enough for bonding most structural situations. However, we definitely recommend at least considering an MS polymer for your bonding or sealing (or both) applications. 

If you are interested in having a look at our range of MS polymer adhesives click here to view the Bond Flex & Bond Flex Plus options. Should you still be unsure about whether MS polymers can be the best adhesive solution for you, we recommend contacting the office for further discussions. 

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