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How to Avoid Improper Use of Collision Repair Products and Procedures

( 03/15/2018 ) Written by: Stephanie Faucher

Dennis Beardsley, North American Training Manager for Saint-Gobain (a LORD Corporation distributor-partner) and I-CAR instructor, co-authored this blog post.

Before starting a new collision repair job, it’s critical for technicians to understand where to obtain proper repair information and product instructions and how the use – or misuse – of these products can affect the repair’s final outcome and integrity of the vehicle. 

Incorrectly using a repair product, such as an adhesive or seam sealer, is the most common reason for it to fail. Sometimes improper use stems from simply not reading instructions, but most of the time it is due to these two factors: Not leveling two-component cartridges before use and not purging enough material in the mixing nozzle before application.

Leveling the cartridge

The ratio of Part A to Part B in a two-component cartridge is critical because an unleveled two-component cartridge will result in it being off ratio. It will essentially coat the inside of the mixer and throw off everything. If there is more on one side of the cartridge than the other because a material is sticking to the inside wall of the mixer, it will be difficult to ever get on ratio.

Once the cartridge has been equalized and proper ratio has been confirmed, choose a mixing nozzle, attach it and extrude a full mixer length of mixed material and dispose of it.

Choose the nozzle based on variety of factors, including:

  • Nozzle length,
  • Material being used, including its chemistry,
  • Ideal working temperature,
  • Amount of adhesive being applied per cycle, and
  • Number of times the material is being folded back together.

To ensure the cartridge is producing the proper ratio, examine the material as it is coming out of the mixer and look for an even, homogenous mix without streaks or dark or light spots. If the cartridge is off ratio, throw away the mixing nozzle and start over. It’s especially important to just begin again because being off ratio causes the majority of product failures.

Stick to the instructions

The importance of closely following instructions when using collision repair products to ensure a proper repair can be compared to an everyday task such as baking biscuits. If the biscuit recipe calls for leaving the butter chunky in the dough to make them turn out well, these instructions must be followed.

Like closely adhering to a recipe’s instructions for the best biscuits, following instructions without any variance is important to achieving a proper repair when working adhesives because they differ in chemistry and in best use for an application. Improperly prepping adhesives – epoxies, acrylics, and urethanes – for use has the highest failure rate for this reason.

Although they are all adhesives, they differ in in the strengths they provide and other properties such as flexibility and corrosion protection. Seam sealers also have some level of strength so they can be considered adhesives. It is the level of strength that really begins to define how to use the adhesive.

Understanding the correct adhesive to use in the replacement of metal body panels and plastic parts – which to use and when – is critical. Acrylics and epoxies are primarily – but not always – used for metal only. There are also some epoxies used to hold plastic to metal-framed cars. Acrylic adhesives will accomplish the same task but they tend to be a little rarer.

Within panel bonding, adhesives are broken down even further into panel bonders and crash-durable adhesives (CDAs). The dividing line has to do with the flexibility and strength of the adhesives over time and what they are able to tolerate in a split second of a crash mode.

All the adhesives are strong, but crash-durable adhesives are also flexible. This means when a vehicle is in a collision, they provide more control of the joint. Failure to use impact-toughened adhesives where a manufacturer may have used them in a vehicle’s construction may change many characteristics of the car at some point in its life. It could affect durability, safety, and the ability to absorb energy in a crash. Adding a CDA where no adhesive was previously used also could conceivably cause a change.

When dealing with plastic parts repair, urethane should be used to bond the parts together because it has greater flexibility and sticks better to plastics including fiberglass, Kevlar, and carbon fiber. The differences in adhesive chemistry, design, and suitability also drive application decisions, especially because all adhesives are not designed equally and cannot be placed into one category, simply based on chemistry.

Although chemistry is significant when making repair product decisions, it’s critical that repairers follow OEM standard operating procedures (SOPs) to ensure their proper use because a substantial gray area exists. Be sure to review the OEM’s approved products and determine what the OEM wants in a repair – i.e. all adhesives or adhesive and spot welding, or rivets – and make your repair decision based on this information.

Ultimately, it all comes down to repairing the vehicle correctly to pre-accident condition and “marrying” it to the lifetime of the vehicle. The repair procedure and product used is either right or it’s wrong, and these OEM recommendations must be respected.

For more information on collision repair adhesives and for OEM bulletins on repair recommendations, visit www.Fusor.com. For information on training, visit www.i-car.com. Read more in depth about this topic in the article, “How to Avoid Misuse of Collision Repair Products,” published in the ABRN March 2018 issue.

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