Body Trim - Painting Plastic Parts
84VW02Applies To
ALL
Group
50
Subject
Body Trim
Part Identifier N/A
Key Points
Painting plastic parts
D
Number
84-02
December 20, 1984
The following plastic materials are used in Volkswagen vehicles:
Thermoplastics
PP - Polypropylene EPDM - Ethylene propylene diene-mixed polymerisate
TPE - Thermoplastic elastomer based on EDPM ABS - Acrynitrile butadiene styrene PC - Polycarbonate PE - Polyethylene PVC - Polyvinyl chloride PPO - Polyphenylene oxide (Noryl)
Thermosets
PUR - Polyurethane UP - Unsaturated polyester, better known as:
GFR-UP - Glassfiber reinforced unsaturated polyester
Untreated "raw" plastic parts may be painted for use on a vehicle only with special attention to the problems of paint adhesion, flexibility color match and service repair.
Successful painting of plastic parts is accomplished with the addition of two chemicals to the paint process:
1 - A bonding agent which is sprayed directly onto the untreated, "raw" parts (parts not primed or which have not been previously painted):
Part No. ALO 822 000 04 for EPDM Part No. ALO 822 100 06 for PUR
Note
When stock of Part No. ALO 822 100 06 has been used up, the new bonding agent for PUR, as well as for PC, will be Part No. ALO 822 200 10.
2 - An elastic additive, Part No. ALZ 011 000, which is mixed with 2K unicolor acrylic paint
CAUTION
Never add elastic additive to metallic base coats. The additive is to be combined with the 2K Acrylic Clear Lacquer on metallic paint applications..
The bonding agents will not adhere to PE and PP. These two thermoplastics are considered to be unpaintable.
No bonding agent is used when repainting plastic parts which have already been painted or parts supplied primed from the factory.
Depending on the type of plastic, the amount of elastic additive added to the spray coat varies from 30% for EPDM to 100% for PUR soft foam.
Increasing the quantity of elastic additive naturally reduces the covering capability which, in turn, leads to thicker coats. A thicker coat requires a longer drying time.
Painting procedure
The tables on page 3 list the various methods of applying paint to different types of plastics.
Durability of the paint job relies on:
^ thorough cleaning of the surface and selecting the correct bonding agent
^ adhering to the specified mixing proportions
EXAMPLE:
500 ml 2K Acrylic paint ALN 769 . . . + 150 ml 30% elastic additive ALZ 011 000 650 ml "basic" paint to which 2K hardener ALZ 009 001 06 (fast) or ALZ 009 002 06 (slow)
+ 325 ml is added in 2:1 proportions = 975 ml of paint ready for spraying
CAUTION
Put the elastic additive into the paint or clear lacquer first, then add hardener in correct (2:1) proportion.
Note
To prevent an abnormal amount of dirt in the paint when spraying, ground the spraying equipment properly. Most parts, especially PUR, tend to become electrostatically charged and tend to attract dust.
Parts painted off the car should be dried at about 50~C (122~F) to minimize the risk of distortion. The temperature should not exceed 70~C (158~F) for parts installed on the car. A lower drying temperature will also keep air bubbles (blisters) to a minimum.