Golf GTI L4-1781cc 1.8L SOHC (HT) (1985)
Paint: All Technical Service Bulletins
Body Trim - Identifying/Painting/Repairing Plastic Parts
Applies To
ALL
Group
50
Subject
Body Trim
Part Identifier N/A
Key Points
Identifying/painting and repairing plastic parts
Supercedes Product Circular, Group 50, No. 84-02
D
Number
85-04
October 11, 1985
Plastic Identification
Since many varieties of plastics are being used in the manufacture of our vehicles, proper identification of these plastics is of extreme importance when
repairing or repainting these parts.
Automotive plastic parts 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 PC - Polycarbonate PE - Polyethylene PVC - Polyvinyl chloride
PPO - Polyphenylene oxide (Noryl)
Thermoplastic parts soften when heat is applied, hence are the easiest of the two to repair.
Inner tender shields, some front spoilers and fender flares are examples of thermoplastic parts.
Thermosets
PUR - Polyurethane UP - Unsaturated polyester, better known as:
GFR-UP - Glassfiber reinforced unsaturated polyester
Thermosetting plastics harden (set) under heat, therefore, in most instances once a part is manufactured, nothing further may be done to alter its original
shape.
Grills, Vanagon camper pop-top, and those parts reinforced by fiberglass are examples of thermosetting plastic parts.
In order to determine whether you have a thermoplastic or thermosetting plastic, hold a hot air welder an inch from the material for approximately ten
seconds, if a softening or melt occurs you have a thermoplastic.
Parts formed from thermoplastics and some thermosets can be repaired in a multitude of ways:
1.
Bent or misshapen pans can be reformed after the application of heat to make them pliable. Hot water, infrared lamps and heat guns can also be
used to supply the necessary heat.
2.
Some plastics (ABS, PC, PPO) can be repaired using solvents (Acetone or MEK (Methyl-Ethyl Ketone)).
3.
Parts that have cracks or fractures can be refused by welding with a hot air welding torch..