Methyl methacrylate adhesives are acrylic adhesives made of two parts, a resin and hardener. Most MMAs also contain rubber and additional strengthening agents. MMAs cure quickly at room temperature, and have full bond strength soon after application. The adhesive is resistant to shear, peel and impact stress. These adhesives are able to form bonds between dissimilar materials with different flexibility, like metal and plastic. Unlike some other structural adhesives like two-part epoxies, MMAs do not require heat to cure.
MMAs are widely used in field work and production lines within aerospace, automotive, marine, composites, transport, facilities, and MRO applications. The bond excellently with most metals including steel, stainless steel and aluminum. They also bond excellently withcomposites including fiberglass and carbon fiber, unsaturated polyester, vinyl ester, gel-coat, sheet molding compound and even epoxy. And in particular, MMA's are excellent choices for bonding thermoplastics like acrylics, acrylonitrile butadiene styrene (ABS), polycarbonates and polyvinyl chloride (PVC).
some specific uses include:
- Bonding magnets in loudspeakers and transformers.
- Bonding panels of aluminum to other panels.
- For trucks and construction equipment like side and roof panels, door panels, and aerodynamic components.
- With Electric motor manufacturing like the bonding of magnets to metal housings made of steel or aluminum.
- Composite bonding of truck trailer beds using aluminum, and composite parts such as fenders, stiffeners to door panels, sliding roofs.
- Bonding hulls, deck liners, ski boats, yachts, internal fixtures, canoes and kayaks.
MMAs require less surface preparation than other adhesives. When using MMAs to bond metal and plastics for example, you only need to use a solvent or alcohol wipe to remove any oils from the surface instead of having to clean and scoff the surface with an abrasive material. Using methyl methacrylate adhesives allows you to work with many different materials and requires less preparation than other adhesives. “Pre-Mix” MMAs are also available and can be used in dispensing guns or automatic dispensing equipment, they are packaged in cartridges with mixing nozzles. These products have the added benefit of good gap fill capability, and allow for easy dispensing and accurate application.
Advantages of MMAs
Methyl methacrylate adhesives can replace mechanical fasteners and welding joints. They also offer advantages over other adhesive technologies. Using fasteners like bolts and screws requires more time and labor, and the bolts can corrode and loosen over time. Welding two different metals together is sometimes possible, but it is expensive and labor intensive. Epoxy adhesives do not bond different metals well because they are more brittle and do not allow for expansion and contraction, which leads to cracks and ultimately bond failure. Polyurethane adhesives need more surface preparation and often require priming of the surface, adding an additional step. MMAs are less brittle than epoxies and can fill large gaps. They have higher bond strength than urethanes and better impact and fatigue resistance. They also offer good chemical and environmental resistance, and fast cure speed. Features of MMAs include:
- High tension strength
- No primer needed
- Excellent impact and peel strength
- Varying cure times
- High toughness and flexibility
- Cure at room temperature
- Good flexibility at low temperatures
- Minimal bond shrinkage
- Less surface preparation
- Very high resistance to fatigue
- Can bonds a wide range of materials together
- Tolerant of off ratio mixing
- Can fill large gaps
- Resistant to solvents and weathering
- Easy application
- Tolerant of oily surface and other types of surface contamination
MMAs have higher peel strength and are more temperature resistant. They develop strength faster allowing parts to be used sooner. It is also worth noting the different processing conditions used for MMAs. For example, the two components of MMAs can each be applied separately to one of the materials being bonded together, and the MMA will not begin to cure until the joints are brought together, combining the components. This means that you do not have to deal with precise mixing ratios to get a good bond. It is important to remember that MMAs do tend to have a strong smell, meaning you should have good ventilation when applying them and they are flammable so some care is needed.
