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Magnet Bonding Adhesives

Permanent magnet motors come in an every expanding number of designs and magnet bonding adhesives are available to meet every new challenge.

The primary driver for the vast array of industrial adhesives available for magnet bonding is the diversity of the size and performance characteristics required in the electric motors, speakers and other applications that require magnet bonding.  The primary industrial adhesive categories are 1. Structural acrylic adhesives, 2. Single part epoxy adhesives and 3. Cyanoacrylate adhesives.

So many types of industrial adhesives are used for magnet bonding – let’s have a look at the features of each.

CYANOACRYLATE MAGNET BONDING ADHESIVES

Cyanoacrylate adhesives are ideal magnet bonding adhesives for many of the new very small motors and speakers.  They are single component easy to apply and develop strength rapidly.  Products vary in viscosity, adhesion to various substrates, set speeds and temperature resistance.  Cyanoacrylate adhesives have very high shear strength but are not as resistant to impact as structural adhesives like structural acrylics and epoxies.  Structural acrylic adhesives and single component epoxy adhesives both offer very high strength, very durable bonds.  For many the choice comes down to the application process.

SINGLE PART EPOXY MAGNET BONDING ADHESIVES

Single part epoxy adhesives are available in various flow rates.  Free flowing single component epoxy is applied at the junction of the magnet and the can and when heated to cure, the epoxy flows down between the two components.  Alternatively a no flow or non-sag epoxy can be applied to the magnet then upon assembly the epoxy spreads to cover the bond area.  Both options provide very high strength magnet bonding.

STRUCTURAL ACRYLIC MAGNET BONDING ADHESIVES

Structural acrylic adhesives are often preferred to epoxy for magnet bonding as no heating ovens are required.  There are several types to choose from and again all provide high strength.  External mix systems are ideal for large magnets (~3” and greater).  The application involves two dispense nozzles that point toward each other such that the two components of the magnet bonding adhesive contact each other mid-stream before they fall onto the magnets – pressing this mixture into the can completes the mixing process.

Some products can be applied separately such that a bead of one component is dispensed on top of a bead of the other component.  This method is also used on larger magnets.

In both external mix and bead on bead magnet bonding adhesives, care must be taken to assemble and clamp parts quickly to avoid the adhesive setting before assembly.  Although these systems would work very effectively on smaller parts, it can be challenging to get the dispensing lined up for very small components so surface activated structural acrylic adhesives are often preferred.

Surface activated structural acrylic adhesives can be used on small and large magnets alike.  The activator is applied to one surface, (generally the can) and the adhesive is applied to the other.  Surface activated structural acrylic adhesives are ideal when additional time is needed between dispensing and assembly.

Still too many choices!

Permabond has been manufacturing magnet bonding adhesives for several decades!  Our chemists are experienced at asking all the right questions to assist in selecting the best industrial adhesive for your unique application.  Although we have a large selection of proven products, we also customer formulate to meet unique requirements.  Contact Permabond at info.americas@permabond.com.