PPG Training

OVERVIEW: When repairing to a factory-like finish, the substrate being refinished determines the process and products recommended. To reproduce the color, gloss level, and texture of the factory finish on plastic parts requires a different process than painting metal. 1 Successfully preparing plastic parts for painting requires more complete scuffing/sanding and more thorough cleaning than what is needed for metal parts. If water "sheets" off the part, then it is ready for paint. If water "beads up" on the part, recleaning is necessary. There are special cleaners designed specifically for this process. 2 When refinishing bare plastic, use the appropriate preparation products and adhesion promoters to ensure a successful outcome. These products are explained and demonstrated in our technical training materials and courses. 3 Due to the nature of a flexible substrate, it must be able to absorb a slight impact and not crack or chip. Additives are used in undercoats and clearcoats to maintain this flexibility. Years ago, these additives were just a solvent that would evaporate. Today, our flex additives contain resins that actually remain with the paint film after any solvent has left. These resins improve long-term flexibility and durability. 4 Basecoat film does not require flexing. However, to get the most durable finish when painting flexible leading edges, a best practice is to activate the basecoat (especially solvent). 5 PPG does not recommend using flexed materials to paint metal parts. While compatibility and adhesion may be unaffected, there are three reasons to avoid this practice: decreased productivity since the flexed material takes a little longer to dry, the increased material costs of the flex agent, and adding flex agent may result in VOC non-compliance. 6 Metal parts can be baked on or off the car with relative ease. Non-rigid plastic parts, if baked off the car, must be adequately supported to avoid warping and deforming of the part or baked longer at lower temperatures. ! Note: Bumper failure due to poor preparation is NOT a warranty issue. More attention to detail during preparation will reduce potential customer satisfaction issues in the future. Page 2-1 PLASTIC REFINISHING

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