Scott Bader’s Crestabond MMA primerless structural adhesive range is specially formulated to bond different substrates with minimal preparation and no primer, significantly improving production efficiency and reducing costs and waste.
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In this article, Scott Bader discusses the main characteristics and advantages of MMA structural adhesives compared to other currently available.
What are MMA Structural Adhesives?
A structural adhesive is typically defined as an adhesive that, when cured, bonds two substrates together, becoming a key part of the structure itself. It is an interface between two substrates bonded together, increasing a structure’s strength, toughness, and durability.
Although opinions can slightly differ, structural adhesives generally provide a strength of at least 10 MPa once cured. They are based on methyl methacrylate technology, often abbreviated as MMA.
MMAs have been broadly employed for around 10 years, meaning they are not as well-established as their two main competitors; polyurethane and epoxy-based structural adhesives.
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MMAs vs Epoxy and Polyurethane Adhesives
MMA adhesives are in the middle of the two other main types of structural adhesives (polyurethanes and epoxies) in terms of mechanical properties. While polyurethanes are well-known for their flexibility, they often have a low strength profile. The opposite is true for epoxy adhesives; they have exceptional strength but reduced flexibility. MMA structural adhesives have properties that combine both strength and flexibility.
MMA structural adhesives are two-part systems, meaning two components must be mixed before use. At Scott Bader, they are known as “adhesives” and “activators.”
Once mixed, the adhesive should be applied within a designated “working time” before curing. If applied outside of this time window, the adhesive may have only partially cured and may not be able to wet the surfaces sufficiently to establish a sufficient bond. The mix ratio between the two components also profoundly impacts the cured adhesive’s final characteristics.
The Benefits
MMA structural adhesives provide exceptional performance. Their reputation reflects the strength, toughness, gap-filling, and flexibility they provide.
Flexibility is an especially desired characteristic as typical users typically bond dissimilar substrates like metal to GRP. Dissimilar materials have different expansion coefficients in operation, so a sufficiently flexible adhesive is required to account for this.
Scott Bader’s Crestabond range bonds composites, metals, and plastics, including difficult-to-bond PP, PE, and TPO.
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MMA adhesive technology is also flexible. Multiple physical/handling characteristics, such as viscosity, specific gravity, working time, and even color, may be altered in the formulation while maintaining optimal structural characteristics.
This means that, while limitations remain, it is possible to develop MMA adhesives that meet the demands of a broad spectrum of markets and use cases. Due to this, MMA adhesives are often utilized in the marine, land transport, construction, renewable energy, electric vehicles, and electronics markets, among others.
Comparing with Other Technologies
Welding
MMAs are more cost-effective, less labor-intensive, and easier to use. They also provide a superior aesthetic finish and may be sanded down for further aesthetic improvements, but their uses are often also constrained by the materials that can be joined by welding.
Mechanical Fasteners
MMAs provide significant advantages compared to mechanical fasteners. They are lighter, corrosion-resistant, suitable for use in difficult-to-access areas, less labor-intensive, more robust, and offer even strength distribution across the bonded area.
Using a mechanical fastening like a screw or bolt would require a hole to be made in the substrates that need to be bonded. This hole is a possible point of ingress for moisture or dust and introduces a weak spot as it is a stress concentration point.
This information has been sourced, reviewed and adapted from materials provided by Scott Bader Company Ltd.
For more information on this source, please visit Scott Bader Company Ltd.