Body Trim - Identifying/Painting Plastic Parts
86audi2Applies To All
Group
5
Subject
Body Trim
Part Identifier N/A
Key Points
Identifying/painting plastic parts
Supercedes Product Circular, Group 50, No. 85-06 D
Number
86-03
September 30, 1986
Plastic Identification
Since many varieties of plastics are being used in the manufacture of Audi vehicles, it is important to identify the type of plastic to be painted (pg. 3).
Plastics are currently divided into two categories:
Thermoplastics and Thermosets.
Thermoplastics
PP - Polypropylene EPDM - Ethylene propylene diene-mixed polymerisate
TPE - Thermoplastic elastomer based on EDPM ABS - Acrylnitrile butadiene styrene PA - Polyamide (Nylon) 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
Painting of plastic parts
Untreated "raw" plastic pans 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 pans 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 822 200 10 for PUR/PC
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 pads 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 70% for PUR.
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 table on page 3 lists the various methods of applying paint to different types of plastics.
Durability of the repair 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 (slow) ALZ 009 002 06 (fast)
+ 325 ml is added in 2:1 proportions = 975 ml of paint ready for spraying
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 attract as a result dust.
Parts painted off the car should be dried at about 50~C (122~F) to minimize 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.
Pearl white metallic paint
The same procedure applies for repainting plastic pans painted with pearl white metallic.
Elastic additive ALZ 011 000 is mixed with base coat ALN 769 90E and also with clear coat ALN 769 001 10.
Elastic additive must never be added to pearl effect paint ALD 645 OAO.
CAUTION
Part numbers are for reference only. Always check with your Parts Department for latest information.
MATERIAL INFORMATION
PAINT PROCEDURE