RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
Roof and Associated Components: Service and Repair
Types of Structural Adhesive
Types of Structural Adhesive
Overview:
There are three basic chemistries used in aftermarket structural bonding and repair:
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Epoxy, urethane, and Acrylic. To achieve optimum results, it is best to use the chemistry that bonds best to the substrate to be repaired, is easiest
to use, and offers the most permanent, non-detectable repair at the lowest overall repair cost. All three chemistries have their strengths and
vveaknesses.
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Epoxy adhesives bond well to rigid and semi rigid plastics and are generally easy to sand and featheredge. Some may be too rigid for flexible
substrates and they often require primers on most bare metal applications. Epoxies can be heat cured to increase strength and accelerate the curing
process and have a very stable long shelf life. The mix ratio can vary by +/- 5O% and still cure, however, the performance properties will vary
when the mix ratio is off. Epoxies are more forgiving than urethanes with regards to mix ratio accuracy.
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Acrylic adhesives bond all types of bare metals and are excellent for cross bonding aluminum to steel. They have good NVH properties and some
offer anti-corrosion properties so primer on hare metal are not necessary. Most acrylics have a fast room temperature cure, and are stable with
regards to temperature and moisture during cure. However, both of these can effect shelf life Mix ratio is modestly important although the
performance properties can vary some with a change in mix ratio. Acrylics are the most forgiving of the three chemistries with regards to mix ratio
accuracy
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Urethane adhesives are typically flexible and bond well to plastics. However they usually require primers on metal surfaces to protect against
corrosion. Urethanes have good seam sealing and NVH qualities and are frequently the optimal choice for seam scalers. They are sensitive to
moisture during cure, packaging and storage.
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One component urethanes usually have a much shorter shelf life than two component urethanes. Mix ratio is critical for urethanes. In most cases it
cannot vary more than +/- 5%. Therefore, hand mixing is not recommended. Urethanes are the most unforgiving of the three chemistries with
regards to mix ratio accuracy.
