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This paper proposes and demonstrates a repair strategy for “Thermoplastic-Substrate/Coating Composite” body panels. A systematic approach is presented that allows automotive design and material engineers to evaluate polymer repair systems and test their compatibility and long term durability with thermoplastic body panel substrate materials (figure 1). This paper systematically categorizes the degree of thermoplastic body panel damage into four specific levels: (1) abrasion of the coating without substrate damage or penetration, (2) damage to the surface coating and substrate excluding cracks or punctures, (3) small cracking or punctures, (4) massive coating/substrate damage beyond that which could be feasibly repaired. Repair systems were evaluated by focusing on substrate preparation techniques to optimize adhesion characteristics without adversely effecting the impact behavior.

The automotive industry has been challenged in the 1980's to evaluate and commercialize an increasing number of new plastic materials for exterior body panels. An important and often critical consideration, during the selection of polymers for body panels is the issue of “paintability”. Usually the paintability of a new plastic candidate is addressed from the perspective of assuring desired surface aesthetics, coating durability, coating-plastic substrate adhesion, processing and heat resistance in the paint ovens. Many times, the mechanical properties of the composite system resulting from the marriage of several coats of paint to the plastic substrate are not given priority consideration in the initial evaluation stages. This paper proposes that a “Technology Advancement Partnership” (1) be forged early in the development of a “plastic substrate-coating composite” system for a specific car platform.