Dissimilar Material Bonding

Application overview

When a product is made from two different substrates, in many cases, “traditional” joining methods, such as welding or riveting cannot be used or are not desirable. Rivets and screws can add extra steps and loosen over time creating issues such as leaks, that lead to warranty claims. Welding is not suited to join dissimilar materials. This is where Plexus adhesives help solve these problems. Being versatile, select Plexus adhesives are primer-less to most substrates and can easily cross-bond with limited to no surface preparation. Plexus adhesives are designed to be strong, yet flexible enough to withstand high loads and differences in thermal expansion. The high degree of toughness that Plexus adhesives have contribute to extremely high resistance to fatigue. Such versatility helps increase your engineering and design freedom.

Click on the Adhesive Selector Guide to help you find the Plexus adhesives most suited for a particular substrate:

US Adhesive Selector Guide

EMEA Adhesive Selector Guide

Clamping

Plexus adhesives are engineered to be thixotropic (non-sag), but also spread very easily. Best practice is to ensure even clamp pressure across the bondline. 

Here are some tips for clamping:

• Only 0.75PSI – 1.75PSI clamp pressure is needed to spread out most Plexus products
• For flat sections, bar clamps help provide even pressure
• Mechanical fasteners can be used as clamps to help move products down line faster
• Certain plexus products contain glass beads to prevent excess squeeze out
• Engineered standoffs or gaps can help contain the adhesive and guarantee certain bond gaps

Thermal Cycling and Different CTE's

Plexus adhesives have high strength and good elongation, this combined with the ability to cure at room temperature, makes them excellent for handling stresses from the thermal cycling of two materials with different coefficients of thermal expansion (CTE).

Surface Preparation for Adhesives

Plexus adhesives are engineered to be very robust with minimal or no surface preparation.

• Thermoplastics - A simple wipe (to remove any dust) is sufficient in most cases
• Composites – Depends on the chemistry; many RTM, and traditional resin composites can be bonded after a dry rag wipe or light solvent wipe to remove any excess shop dust. Other composites may need light abrading
• Raw Metal – Plexus has a line of primer-less to metal adhesives, which can often bond with no surface preparation or as little as a solvent wipe. For a heavily oxidized metal, surface abrasion followed with solvent wipe is typically recommended.
• Coated Metals – Can often be bonded as is, or after a wipe to remove any excess dust.

Testing the exact material you are bonding is important to any successful project. Contact our Technical Services Department to learn more on how Plexus adhesives can bond your specific material.