Methylmethacrylate Adhesives (MMAs), Acrylic Adhesives
WHAT ARE THEY?
Methylmethacrylate adhesives (MMA’s) are reactive acrylic adhesives normally comprising resin and initiator (or a resin and hardener). They cure quickly at room temperature and strength development is rapid. Once cure is complete, the material forms a strong thermoplastic with excellent resistance to shear, peel and impact stresses. Most MMA adhesives contain rubber which helps give them these strength properties.
WHAT WILL THEY BOND?
MMA adhesives will bond most substrate materials including metal, magnets, plastic, glass, wood, and composite materials and are fairly tolerant of poor surface condition (such as oil contamination). Because of their high strength performance, they are often used to replace welding or riveting and can allow greater freedom of material choice. They can be used to bond dissimilar materials as well as to improve finished appearance. The inbuilt rubber toughening system gives a degree of flexibility required to cope with differential thermal expansion and contraction and thermal shock.
WHERE ARE THEY USED?
They are used widely in the aerospace, automotive, composites and transport market sectors, often for structural bonding of advanced materials. They can also be used for bonding magnets for items such as loudspeakers and electric motors. Their rapid cure speed is desirable on a fast moving production line and their strength performance is above and beyond what is required.
HOW ARE THEY PACKAGED? HOW ARE THEY APPLIED?
“No-Mix” MMA adhesives are packaged as a resin and initiator. The initiator is applied to one surface by brush or spray and the resin the other. When the joint is closed and the resin comes into contact with the initiator it triggers the reaction. Reactive acrylic cure is quite different to other two part systems as the reaction is catalytic and fairly insensitive to the amount of initiator used whereas epoxy and polyurethane adhesives rely on precise mixing in the correct mix ratio.
“Pre-Mix” MMA adhesives are normally packaged in cartridges with static mixing nozzles and can be used in dispensing guns or automatic dispensing equipment. These products have the added benefit of good gap fill capability. Their light consistency and thixotropic rheology allow for easy dispensing and accurate application.
HOW DO THEY DIFFER FROM OTHER STRUCTURAL ADHESIVES SUCH AS EPOXY OR PU?
MMA adhesives normally have a much higher peel strength and better temperature resistance. Also a faster strength development means parts can be put into use much sooner. Applications such as bus manufacturing where adhesive is used for bonding the panels or “skins” require fast strength development so that parts don’t have to be clamped for hours taking up valuable space in the workshop. On the downside they tend to smell more than other adhesives (although the odour does wear off quite quickly). Also, they are flammable and can cost more to ship.
Permabond chemists are able to formulate MMA adhesives to meet your specific requirements. If you have an application you would like to discuss with a technical advisor or would like to receive further information, please contact email@example.com or firstname.lastname@example.org.