Written by Caleb Shaw.
MMA is a 2 component structural adhesive.
Unlike an epoxy, an MMA will cure at room temperature without the need for heat. It consists of a resin and a hardener; some also contain rubber to increase the impact resistance.
There are 2 basic families of MMA, 1:1 ratio and 10:1 ratio.
1:1 tends to be lower cost but the 10:1 often have much greater flexibility and adhesion to more difficult substrates. Both families of MMAs are used to bond metals, plastics, powder coated materials and GRP.
What are the advantages?
MMA (over epoxies) offer much greater flexibility (impact resistance) and are not so affected by ambient temperatures. Users can develop an allergy to epoxies and while MMAs do create an odour when they’re curing, it is relatively harmless.
MMA will generate heat as they cure (exothermic reaction) – this can be up to 140C depending on the product and the volume of curing material. Sometimes you must be careful when bonding to a painted surface as the exotherm can affect the paint integrity.
When do I use MMA?
MMA will bond a wide variety of materials however, you need to consider the joint design before selecting any adhesives. If you want the joint to flex and absorb impact you should consider an adhesive that is more flexible than the substrates to be bonded. For example, GRP will delaminate at approximately 5 MPA. An MMA will not start to flex until it has reached approximately 10MPA meaning that the GRP will break in the event of an impact. Many MS polymer adhesives will flex to over 500% before the adhesive shears at around 4MPA making this a more durable bond for some automotive applications.
2 component polyurethanes are also an option for structural bonding, offering no/limited exotherm reaction and low odour. However, 2P PU adhesives require more surface preparation, they contain isocyanate (carcinogen) and they offer limited heat resistance.
Not many manufacturers produce MMA based adhesives, below I have listed a few that do:
- Plexus, Also known as ITW performance polymers is a well known manufacturer of MMA based adhesives. All of the Plexus products are currently made in the USA
- IPS, also known as Scigrip in the UK, have manufacturing sites in the USA and in the UK
- Scott Bader is another UK manufacturer of MMA – they call their products Crestabond.
- Bostik have a range of MMAs known as their SAF range
- Other MMA manufacturers include Sikafast, Henkel Loctite, Acralock and probably more that we don’t know about.
Typical applications for MMA include composites, marine, transportation and recreation vehicles.
If you have any questions regarding MMA, feel free to contact our specialists for some friendly, non – biased advice.
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