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Plastic Pointers - Volume 2 Number 4

click here to view the Adobe Acrobat version of Plastic Pointers

Repairing Polyethylene — From ATV Fenders to Windshield Washer Bottles

Polyethylene, that clearish, whitish, semi-translucent plastic that is often used on windshield washer bottles, overflow tanks, and ATV fenders is one of the easiest types of plastic to repair with the airless plastic welder.

Polyethylene is often used to store liquids because it is almost impervious to attack by solvents. For that reason, polyethylene is used in laboratories to store acids and other chemicals. That's why PE is used for battery cases.

	This mounting tab on a radiator overflow bottle has a crack nearly all the way across (arrow).
	This type of damage is very easily and quickly repaired with the 5600HT Mini-Weld Model 6 airless plastic welder. After cleaning and v-grooving the crack, weld with 5003R4 Polyethylene Welding Rod. Melt the base material and rod together for maximum strength.>

Welding is the best way to fix polyethylene. First of all, it's an olefinic plastic, so adhesives won't stick well to it. Second, there's no way to duplicate that translucent appearance without welding.

Welding is the fastest and most efficient way to fix most thermoplastics. There's no cure time and you're ready to go as soon as the weld cools down.

Warm Up the Welder

It's very easy to weld polyethylene because its melting point is so low. Set your airless plastic welder to the "clear rod" setting, which is near the low end of the scale. Our latest welders, the Models 4 and 5, have an indicator for "R4" on the dial to match the part number for the polyethylene rod, 5003R4. Allow the welder to reach the operating temperature while you prepare the damaged area for welding.

Clean and Prep

As with any welding procedure, you need to get the plastic good and clean before you repair it. First, wash the area with soap and water to remove dirt and oils. Dry it, then spray it with 1000 Super Clean plastic cleaner. Our plastic cleaner is an alcohol-based product that will remove any oil-based contamination including mold release agents. Don't mess around with substitutes -- use something you know is going to work on plastics.

Spray on the plastic cleaner in a heavy wet coat to bring the contaminants into solution. Before the cleaner evaporates, wipe it with a clean cloth in one direction only, exposing a clean surface of the cloth to the plastic each time you wipe. It's not hard to do; you've been doing it ever since you were potty trained!

Once you've got the surface clean, you can prepare the damaged area for welding. If you start grinding on the plastic before you clean it, you'll just imbed the contaminants into the plastic, causing adhesion problems during the welding process.

If the part is torn open, you'll need to get the pieces lined up. Use a heat gun to heat the parts if necessary. Once softened, move the parts together and cool the plastic with a wet rag so it stays in position.

Grind a tight v-groove down the crack using our 6121-T Teardrop Cutter Bit for the Dremel tool, or you can melt the v-groove in using the 6200VG V-Groovin' Tool. Once you've got the v-groove in there, you're ready to weld.

Make the Weld

By now, you've got the welder warmed to the proper temperature and the damaged area prepped for welding. Start by feeding the 5003R4 Polyethylene Rod into the 6027HT Tube Welding Tip on your airless plastic welder. If there's any blackened residue from a previous welding job, run about an inch of rod slowly through the welder tip until it turns clear before you start welding on the part.

Lay the welder tip down onto the part at the beginning of the v-groove. Feed the rod in slowly so that it comes out the bottom clear. Pass the welder slowly along the v-groove, keeping a puddle of clear, melted rod in front of the tip.

Lay down a bead about 1 1/2 or two inches long, then remove the rod from the welder tip and go back to the beginning of the weld to melt it in and smooth it out. It's better to weld in short sections -- that way the rod material is still hot, making it easier to melt it into the base material.

Since polyethylene is a thermoplastic, you'll want to melt the rod together with the base material. Let the welder's heat do the job; just linger the tip over the weld and smear the rod into the base material and vice versa.

You can also do what is called the "stitch-tamp method" to mix the rod and base materials. Dig the edge of the welder into the plastic across the weld bead, melting the rod and base materials. Then immediately smooth and blend the rod and base together.

Ideally, you are striving to melt the rod completely into the base material. This way, if you're working on a colored PE like a dirt bike fender, the color of the base material should be completely blended across the joint.

Once you've blended the rod and the base material thoroughly in one section, continue the process by laying down another two inch section of weld rod.

If you can access both sides of the damage, it's best to weld on both sides. Many times it's not possible on polyethylene parts because it is so often used to hold liquids, like windshield washer bottles and batteries. However, on ATV fenders and the like, welding on both sides will be stronger than a single sided weld.

Polyethylene is also very easy to repair with the EZ-Weld Hot Air Welder. Airless welders are much more popular because they're easier to use, but if you work with polyethylene a lot, a hot air welder might speed up your work.

Tech tips Reinforce Tears to the Edge with Stainless Steel Mesh

In stressed areas, you can use the 2045W Stainless Steel Reinforcing Wire Mesh to strengthen the tear. This is one of the techniques we developed for the Uni-Weld Ribbon, but it can also be used even when you're not using the Ribbon. Cut a piece of the mesh to bridge over the tear. If the part is torn to the edge, you can wrap the mesh around the edge and melt it in on both sides to further strengthen this critical area. This is especially helpful on dirt bike fenders where the part is likely to see some stress again.

I-CAR's UPCR

I-CAR, the collision repair industry's premier training organization, has begun to publish the UPCR, or Uniform Procedures for Collision Repair.

I-CAR states that the UPCR "outlines industry-accepted, uniform repair processes for technicians, insurers, suppliers, auto makers, educators and others. They enable the Collision Repair Industry to produce uniform, safe, quality repairs for the consumer. They are an easy-to-use reference source that will be revised and updated with the latest, most accurate repair procedureal information."

I-CAR publishes UPCR on a CD-ROM that allows the user to instantly transfer to related articles within the disc. For example, if you're looking at a procedure on plastic repair and you need to see the MSDS for Urethane Supply Company's Plastic Magic adhesion promoter, you can bring the document up instantly with a click of the mouse.

Urethane Supply Company has been a supporter of I-CAR since its inception, and we are proud to announce that we are one of the first manufacturers to have our product literature included within the UPCR. On the UPCR disc you'll find Urethane Supply's instructional literature, product literature, and MSDS sheets.

We urge you to contact I-CAR and get a copy of the UPCR for your shop. For more information, contact Cindy Landwehr at 920-749-0444.

IMPORTANT UPDATE: I-CAR has discontinued the UPCR program.

Bumper Texture Colors Now Available

Flkexible Bumper Color Coat Urethane Supply Company is proud to introduce two new problem-solving products for the automotive plastic repair industry. Primarily intended for our bumper recycling customers, the 3301-1 Gray-Green Flexible Color Coat and the 3302-1 Dark Gray Flexible Color Coat match the OEM colors on many late model textured TPO bumpers. The 3301 Gray-Green is tinted to match many of the Chrysler Minivan shades, and the 3302 will match many applications including the Jeep Grand Cherokee. These are tints only; if you need to restore the texture, spray on 3800 Flex Tex first, then apply the appropriate color coat.