Repairing Other Thermoplastics

Most of the plastics used in vehicles today are thermoplastic, which means they can be melted. If a plastic can be melted, it can be repaired with a nitrogen welding system. There are lots of different thermoplastics, but there are only a few basics used in automobiles. By far the one most commonly used in vehicles is polypropylene. Over 95% of bumper covers are made of this material.

Some of the other common thermoplastics you might run into are ABS, polyethylene, nylon, and polycarbonate. This video will discuss common uses for these types of thermoplastics, and how they can be identified. We briefly go over the plastic repair options for these different types of thermoplastics.

There are a few types of plastics that you cannot weld with a nitrogen welder. Thermoset plastics are not meltable because they are formed by a chemical reaction in the mold. Polyurethane is one of the most common thermosets. Polyurethane can be repaired with the airless plastic welder. Fiberglass, SMC, and metton also cannot be welded. Cross-linked polyethylene can also be welded with the airless plastic welder.

Always wear proper safety gear while working!

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Helpful Resources:

• View our our Plastic Identification Chart for help identifying common plastics. You can also consult The Book of Plastic Repair that came with your welder.
• Text and photo tutorials: Fusion welding thermoplastics with the nitrogen plastic welder | Repairing thermoset plastics with the airless plastic welder
• Videos: Nitrogen/Hot Air Welding | Thermoset Polyurethane Repair | Repair cross-linked polyethylene with the airless plastic welder
• We have a huge selection of welding rod available to match a variety of plastics. View our Welding Rod List to see all of our options.
• Polyvance's current selection of nitrogen plastic welders

Video Notes:

• English Closed Captions have been provided for this video. Click on the CC button to turn them on or off.
• The length of this video is in no way representative of the actual time required to perform a complete repair and therefore should not be used for estimating purposes.

English Transcript:

Most of the plastics used in vehicles today are thermoplastic, meaning they can be melted. If a plastic can be melted, it can be repaired with a nitrogen welding system. There are lots of different thermoplastics, but there are only a few basics that are used in automobiles. By far the most common plastic is polypropylene. Over ninety-five percent of bumper covers are made of this material. It's also used for most headlight housings, side cladding, inner fender liners, and so forth. Look for the symbol "PP" on the backside. Sometimes it will be identified as "TPO" or "TEO".

Some of the other common thermoplastics you'll run into are ABS, polyethylene, nylon, and polycarbonate. Look on the backside of the part to find the ID symbol, identify the plastic, then select the welding rod that matches best.

Polyethylene is often used on inner fender liners, radiator overflow, and windshield washer bottles. Make sure you check the ID symbol, because a lot of these are molded with polypropylene also. Polyethylene is also used on dirt bike and ATV fenders, agricultural tanks, gas tanks, canoes, kayaks, and children's play equipment.

ABS is a more rigid plastic that is used for grilles, trim, and interior plastics. It's also very common on street bike fairings, RV parts, and aircraft parts. ABS has a lower melting point so be sure to turn down the heat setting on the welder.

Nylon has a high heat resistance, so it's commonly used under the hood. Nylon's ID symbol is "PA" which means polyamide. Look for it on radiator tanks, core supports, engine covers, intake manifolds, and so forth. It can also be used on some street bike fairings. Polycarbonate is a rigid plastic that is sometimes used in bumpers. It was use by Ford in the really hard bumpers on the old Taurus and Escorts. Mercedes and BMW have also used it. Its ID symbol is "PC." Weld it with a clear polycarbonate rod.

There are a few types of plastics that you cannot weld with a nitrogen welder. Thermoset plastics are not meltable because they are formed by a chemical reaction in the mold. Polyurethane is one of the most common thermosets. It can be repaired with the airless plastic welder, but not the nitrogen welder. Fiberglass, SMC, and a material called metton, used on big trucks, also cannot be welded. Check the table in The Book of Plastic Repair that came with your welder to help identify the plastic and the proper repair procedure.