What is the purpose of primer in some adhesive systems?

• A. Primer improves adhesion to the vehicle substrate and promotes a stronger bond
• B. To color-match the adhesive
• C. To accelerate curing by heat
• D. To soften the glass

Answer: (A)

Primer is used to improve adhesion between the adhesive and the vehicle surface by preparing and conditioning the substrate so the adhesive can form a stronger, more durable bond. It does this by enhancing how the adhesive wets the surface, offering compatible chemical groups that can bond with the adhesive, and often sealing or cleaning the surface to prevent contaminants or moisture from weakening the bond. This leads to increased bond strength and better long-term performance in terms of adhesion and durability. The other ideas aren’t the main purpose: color matching isn’t the primary role of primer in this context, curing speed is governed by the adhesive system itself rather than the primer, and softening the glass would undermine the bond rather than help it.