Among the several adhesive types available in the marketplace, each one is appropriate and preferred for a specific application. In this context, the term ‘structural adhesives’has gained increased prominence in recent times. Because of their ability to join dissimilar materials, structural adhesives are used for an extensive list of assembly operations.
Owing to their ability to improve durability and reduce the effects of vibration, structural adhesives are being designed to suit an increasing number of applications. Methyl Methacrylate Monomer (MMA-m) is one such structural adhesive that is a relatively new concept which has gained traction in the last few years.
In this blog, we’ve tried to answer some FAQs on what Methyl Methacrylate (MMA) adhesives are and why they are gaining significant ground in the context of acrylic adhesives.
What are they and what are their characteristic properties?
MMAs are reactive acrylic adhesives usually comprising methyl methacrylate resin and initiator or a resin and a hardener. As far as their properties are concerned, it is observed that they cure quickly at room temperature, thus leading to rapid strength development. Upon completion of cure, methyl methacrylate monomer forms a strong thermoplastic with excellent resistance to peel and impact stresses. Most MMA adhesives contain rubber and this is usually attributed to MMA’s strength properties.
What materials do they bond?
Methyl methacrylate is known to produce a hard-wearing bond that has excellent environmental and chemical resistance. MMA adhesives generally tend to bond most substrate materials such as metal, magnets, plastic, glass, wood, and composite materials. 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 and to improve finished appearance. A unique quality of MMA is the inbuilt rubber toughening system, which provides a greater degree of flexibility. This is required to cope with differential thermal expansion-contraction and thermal shock.
Where are they used?
MMA adhesives are commonly preferred structural adhesives owing to their excellent strength, impact resistance, thermal shock, fatigue resistance and peel strength. They are based on thermoset adhesives formulations that give excellent structural properties to bond a wide-variety of durable substrates. They are also extremely versatile in the sense that they can be cured with a host of different cure methods in order to provide different gap-filling and speed of cure characteristics.
Typically, they are used in the aerospace, automotive, composites and transport market sectors, often for structural bonding of advanced materials. Additionally, they are also used for bonding magnets for loudspeakers and electric motors. Their rapid cure speed is desirable on a fast-moving production line and their strength performance is exemplary.
How are they packaged?
MMA adhesives are packaged as a resin and initiator. The initiator is applied to one surface by brush or spray and the resin on the other. When the joint is closed and the methyl methacrylate resin comes in contact with the initiator, it triggers the reaction.
How do they differ from other adhesives?
MMA adhesives have a relatively higher peel strength and better temperature resistance than other adhesives. Also, faster strength development implies parts can be put into use much sooner. For applications such as bus manufacturing where adhesive is used for bonding the panels, fast strength development is required.
Key properties for a structural adhesive are strength, toughness and flexibility. The latter is particularly important when bonding dissimilar materials with high differential flexibilities, such as a rigid metal and a flexible plastic. According to research forecasts, the major driver identified for the global MMA adhesive market is the growing demand from commercial vehicle, marine, and wind energy industries. Extensive use of advanced materials, compliance with environmental regulations, reduction of manufacturing cost, and increasing speed of production process resulted in several MMA manufacturers increasing production for end users to adopt MMA adhesive for bonding.
As one of the leading manufacturers of MMA-m, we at Sumitomo Chemical are happy to assist you on any queries that you may have. You can reach out to us here.