How to make plastic repairs with adhesives properly and profitably

by Douglas Craig, Structural Adhesives Applications Engineering Manager & Collision Repair Industry Liaison

Douglas Craig, Structural Adhesives Applications Engineering Manager & Collision Repair Industry Liaison
Douglas Craig

While making plastic repairs with structural adhesives is relatively simple, it is important to understand the product being used and to carefully follow instructions to guarantee optimal results. Profitability comes from doing repairs properly – the first time.

A good rule of thumb is, “Slow down to go faster!” You only want to make a repair once. There is no profit gained in having to redo a repair, especially since the second repair might have to be done free-of-charge to gain customer satisfaction.

Spend the time needed to make the repair properly and be sure to follow the procedures recommended by the adhesive supplier.

Here are some guidelines to follow when using adhesives to guarantee successful plastic repairs:


  • Surface preparation – clean the front and back of the surface using the recommended cleaner.
  • Backing patch – a backing patch is required if the damage penetrates through the part, such as a bumper cover.
  • Sanding – for certain repairs use a sander or sandpaper to prepare the surface for proper adhesion.


  • Surface modifier or adhesion promoter – use the recommended surface modifier or adhesion promoter before applying the adhesive.
  • Equal mix – two component adhesives require leveling of the plungers. Typically, a bead of adhesive should be dispensed through the mixer before it is applied to the repair area.


  • Curing times – follow the manufacturer’s suggested curing times to guarantee optimal repair adhesion. In some instances, parts may require clamping or taping during the curing process, or the use of a heat gun.
  • Sanding – follow the manufacturer’s recommended sand times to finish sanding the adhesive.

One of the biggest failure situations that occur in the automotive repair industry is not allowing the proper time for each procedure to reach its finishing point, before moving to the next step. This is where “Slow down to go faster” can really make a difference in the final outcome. Make sure that cleaning solvents and surface modifiers are allowed to dry for the recommended time. Rushing these procedures or steps may result in failure. If the repair adhesive is applied before the proper drying time is reached, the adhesive may not hold and the repair may fail.

When repairing plastic automotive components, apply the adhesive and spread it evenly to ensure the best adhesion.
When repairing plastic automotive components, apply the adhesive and spread it evenly to ensure the best adhesion.

Respect written cure times before sanding or other finishing procedures. Do not rely on observation to determine if the adhesive is cured. Follow the recommended curing time before handling or completing work on the repaired part. When using primer or paint, follow the paint manufacturer’s instructions for proper use.

When used properly, some manufacturers’ repair adhesives carry a lifetime warranty. Repairing plastic car parts is both practical and profitable, and will garner customer satisfaction. It is crucial, though, to respect each adhesive manufacturer’s product line to guarantee the best results.

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Spend the time needed to make the repair properly and be sure to follow the procedures recommended by the adhesive supplier.

Do not combine repair products from different suppliers; they could be chemically incompatible and compromise the outcome of the repair or cause harm to repair personnel. Use the complete product line of repair products recommended from the repair product manufacturer. Not doing so could negate the warranty.

Always stay within one manufacturer’s process – bottom-to-top – from surface preparation to final finishing.

Adhesives provide a solution to making durable repairs and increase a body shop’s profitability, all while ensuring customer satisfaction.

Are you using crash-durable adhesives at your facility? Tell us about it here.


What you need to know about aluminum vehicle repair and crash-durable adhesives

by Douglas Craig, Technical Application Engineer & Collision Industry Liaison, Structural Adhesives Tech Service, LORD Corporation

Aluminum’s light weight makes it an ideal autobody substrate as an environmentally-friendly, cost-effective method for increasing performance, boosting fuel economy and reducing emissions while maintaining or improving safety and durability.

Douglas-Craig-edited photo
Douglas Craig

Auto OEMs are using crash durable adhesives in the manufacturing process, and will be recommending similar type adhesives for repair operations to return vehicles to pre-accident condition.

Two-component crash-durable adhesives for repair have been formulated to replace all OEM one-component crash-durable adhesives. The crash-durable adhesives allow you to duplicate the original vehicle right down to the adhesive.

Reference is often made to one-component and two-component, or 1K and 2K, materials. This designation refers to how many materials are applied as a bead or are mixed to be applied as a bead. A one-component material is applied as received from the supplier, whereas a two-component material is mixed together during the application.

Most of the vehicles produced today, whether aluminum- or steel-bodied, are assembled with a one-component crash-durable adhesive, whereas the repair version of the crash-durable adhesive is a two-component formulation. Here’s the reason for the differences:

When OEMs assemble cars with crash-durable adhesives, the vehicles go through a heat-curing process for the adhesive, along with drying processes for the paint and/or e-coating. The one-component crash-durable adhesive is made to withstand temperatures up to 400° F. All of this heat allows the chemistry in the one-component adhesive to cure.

In the collision repair shop, it is not possible to place a repaired vehicle into such high temperatures for the curing process. The two-component epoxy formulation allows repairs to be made to vehicles that match the original adhesive application.

Crash-durable adhesives not only have the strength of structural adhesives, they also provide exceptional toughness. This is why they are sometimes referred to as “impact-toughened” adhesives. Crash-durable adhesives are extremely flexible, with the ability to stretch without losing their effectiveness.

Flexibility is especially crucial in crash mode situations. Crash-durable adhesives will not “micro-fracture” in a “crush-and-crash” mode as with standard structural adhesives. Therefore, joints will hold together better and not lose their strength during a crash. This is especially important when considering that thinner substrates, such as aluminum, tend to “move around” more during a crash, and the flexibility of the adhesives helps to hold the joints together.

Crash-durable adhesives, for repair procedures, are used to replace all the original equipment locations of OEM-applied crash-durable adhesives. Typically, these areas are between all the metal panels and in sections such as A-, B- and C-pillars, and other locations including roof joints and engine box joints. They can be used for panel bonding, weld bonding and rivet bonding of aluminum panels.

Though application methods for these adhesives are similar to conventional structural adhesives, technicians might be “startled” by their appearance. Crash-durable adhesives are highly pigmented and come in colors such as purple, orange, red, and blue.Offering both strength and sealing functions, crash-durable adhesives provide a sealant to the vehicle‘s body structure and a bonding method. If there is any doubt as to whether the OEM adhesive is crash durable, use a crash-durable adhesive in the repair.

For repair, it is important to understand that colors do not need to be matched. For example, a purple OEM adhesive can be replaced with a blue repair adhesive as long as that repair adhesive meets the OEM requirements.