How to Repair Thermoset Polyurethane

Thermoset polyurethane was commonly used on domestic bumpers back in the 1980's and 90's. It's pretty much been replaced by polypropylene now, but you'll still see the old yellow plastic out there once in a while.
Polyvance was formed in 1981 as Urethane Supply Company to address the needs of bumper recyclers and to supply products to repair urethane bumper covers. Around that time, many people did not think urethane bumpers could be repaired. We proved they can be repaired.
Polyurethane is a thermoset plastic, meaning that it is NOT meltable. The solid is formed by reacting two liquid components which crosslink in the mold. You will NOT be able to use the nitrogen welder on this type of plastic. You can repair it with the airless plastic welder. This will not provide a fusion weld. The urethane welding rod is used more like a hot melt glue.
Chapters:
Intro: 0:00
Explanation of PUR: 0:10
Prepping the backside: 1:10
Setting the welder: 1:35
Welding the backside: 1:55
Prepping the cosmetic side: 3:06
Welding the cosmetic side: 3:37
Grinding and sanding: 4:04
Flex test: 4:20
Sanding: 4:30
Applying filler: 5:01
Look below for links to some of the products from the video.
View this video on our website for more information and product suggestions for this repair: www.polyvance.com/video/therm...
5700HT Mini-Weld Model 7 Airless Plastic Welder: www.polyvance.com/Airless-Wel...
2000-T Flex Filler 2 Tube Kit: www.polyvance.com/Flex-Filler...
⚠️ Important ⚠️
- Always wear proper safety gear while working!
- 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.
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-Plastic welding rod: www.polyvance.com/Welding-Rod...

[@vivianoni9565]

They got an awesome bond on that repair. Even wrenching it for an intentional break failed. Curiously, molders switched from PU to PP/TPO plastics. If anyone knows why plz share.

[@scottb7600]

They still use urethane in some cases. the reason for the switch is cost. On high production cars, the cost of the mold is high for making bumpers out of Polypropylene, but the high cost of the mold is offset by the low cost of polypropylene plastic resin...so the higher the number of bumpers made, the lower the cost each is with higher production numbers. With low production number cars, its more cost effective to use urethane as the bumper material because the mold cost is much lower, however the materials cost is about 3x that of a polypropylene bumper of equal size. Urethane was also used in the past because paint bonds to it fairly easily and its impact resistant as well. New paint technology has allowed paint to reliably stick to PP modern bumpers are typically made from. I hope this answers your question!

[@vivianoni9565]

Thnx for delineating. Could you touch on the viability of each plastic's useful life. PU, aerated type, degrades pretty quickly according to an article I chanced on discussing its use in footwear. It was a shock to see the extent of PU degradation throughout the shoe's midsoles after 15 years or more. It got me thinking in a very different way about TPs. Do PP/TPO plastics have this problem?

[@scottb7600]

@@vivianoni9565 Urethanes in general are susceptible to decomposition from a wide variety of things ranging from UV light to solvents. On bumpers, this is generally not an issue because the outer surface is covered with paint and the inner surface doesn't see much action from anything at all...however urethanes tend to shrink as they age and deform as a result of external stresses...like gravity. This can cause them to not fit well after a long period of time and have saggy spots. They can also craze and cause the paint to crack, once that happens the deterioration accelerates. PUR bumpers are also not recyclable. PP bumpers don't have any of these issues. their only drawback is that paint can be a challenge to get to adhere. Bumper and Cladding Coat Adhesion primer and Plastic Magic fix this; either can be used to get paint to stick well. They also can only be repaired by welding to get a 100% reliable repair. As an added bonus, they can be recycled and made into other things...Flower pots are a common 2nd life for polypropylene bumper plastic.

[@kartermorgan5795]

@Damon Ahmed i really appreciate your reply. I found the site through google and im waiting for the hacking stuff now. Looks like it's gonna take quite some time so I will get back to you later when my account password hopefully is recovered.

[@koizora3430]

i really enjoy watching your videos

[@polyvance]

Thank you! We are glad you enjoy them!

[@nickem7]

RESPECT! thank you!

[@polyvance]

Thank you for watching!

[@lorenzoguevara837]

👍👈thanks You, guys FOR teaching it.

[@polyvance]

Thank you for watching!

[@polyvance]

Visit this video page on our website to see the full list of products used and other helpful tips: www.polyvance.com/video/thermoset-polyurethane-pur-repair/how-to-repair-thermoset-polyurethane

[@fabmanly1070]

Hello there. I have a boat made from Comptec PE3, a three-layer polyethylene. It has a crack that can only be accessed from one side, it is about 10-15mm in length. How could I repair this?

[@MudMotorsMax]

I myself have a Coleman Scanoe RamX And it is not easy to fix it’s crossed linked high density polyethylene which turns the HDPE from a thermoplastic that can melt into a thermoset plastic which means it no longer melts… at this point It’s not easy to repair, even before adhesives and epoxy’s will NOT stick to HDPE. A guy has to first & foremost clean the area very well with alcohol then with a die grinder creat a groove in the crack… next create a slight bevel around the crack a bit wider in diameter then the groove in like an oval pattern. Then with course sand paper rough up the area to create tooth or bite for your plastic filler to stick too. (I recommend HDPE Welding Rod) and then buy a Polyvance's KCWPRO airless plastic welder (less then $100) melt the rod with the welded and force it down into the crack to create a plug. (Remember not to heat the base material ) fill the whole crack then continue to continue to fill and smooth whole bevel, the smooth. You can sand after you’re done if you need to if it’s sharp or rough

[@AVUKI]

Thanks from Russia 🇷🇺

[@jonnydwolf]

Killer music 🤘

[@polyvance]

Thanks for watching!

[@flyurway]

FINALLY I find a video that helps!! I'm moving the medallion on the nose of my Jaguar to the grille and need to fill the hole(s) left behind. Not thinking of welding to fill the hole, just thinking about using the epoxy filler. So to prime I really won't need an adhesion promoter?? I'm impressed with the strength of that weld in the video!!

[@Franc39A6DD]

What is the temperature for PUR ? Amazing job

[@polyvance]

Thank you! The setting is around 300 degrees.

[@Franc39A6DD]

Polyvance. I want to test this on my bumper of BMW e30 84.

[@Franc39A6DD]

Polyvance. Hello, I've a problem.. I bought polyurethane from your brand + tip. It's very difficult to buy in France. I used a seller in England who charged me a lot of shipping costs. You tell me it's 300 degrees C, I see you're selling an ATV kit with a 40 watt soldering iron. But 40 watt = about 560 degrees. I do not know what to buy ... I buy a 25 watt 300 degrees or 40 watt 560 degrees? Celsius. thank you.

[@scottb7600]

First of all, wattage has little to do with the tip temperature. The tip size, internal thermal conductivity of internal components, ambient temperature, airflow around the welder, and component design have a far greater effect on the temperature....Its impossible to simply plug watts into a calculation and get temperature. The current ATVPRO welder we sell is 200 watts, the ATV welder at 40 watts has been discontinued for years, the 80 watt ATVPRO is also discontinued. The 200 watt ceramic core welder and the 80 watt ni-chrome wire heating element produce roughly the same tip temperature....ALL of the above welders are too hot for urethane. There is a work-around however. If you want to use the ATVPRO for urethane, simply start welding before the welder is fully hot and keep rod moving through the tip to keep the tip temperature down.

[@Franc39A6DD]

Scott B thanks for response. I can not buy the ATVPRO. You imagine, I paid 90€/106 dollars for your tip and the rods in Europe. That's a lot of money for me. I am not rich. And I do not know what soldering iron wattage to buy in Europe at a good price for your standard tip. :-(

[@javiertrujillo1916]

What can I use to repair SMC can I use my fiber flex and my welder

[@scottb7600]

You really can't use the welder to repair SMC. SMC is Sheet Molded Compound, aka Fiberglass. The best repair for it is to sand the area being repaired, beveling the edge gradually, then apply layers of glass cloth saturated with epoxy resin.

[@soufyanedz9688]

Can i use fiber flex to repair radiator nylon

[@polyvance]

FiberFlex will stick to nylon, but it isn't the best option. It would be better to repair it with nylon welding rod (www.polyvance.com/Nylon-1/), which is the rod that comes in our radiator repair kit.

[@sukmyfuk]

I just tried my daughters hot glue sticks and it hold strong as $4 job done

[@scottb7600]

Unfortunately, they do not hold onto urethane as well as the urethane to urethane bond. It may be OK for a temporary fix you don't plan on refinishing, but for a paintable, permanent repair urethane rod is the way to go.

[@Marcoosianism]

So the urethane welding rod is just that, pure polyurethane?

[@scottb7600]

It is thermoplastic urethane, not thermoset urethane.

[@drugsguys914]

How to get this welder

[@polyvance]

www.polyvance.com/Airless-Welders-1/5700HT/

[@hearttouchmotivation6883]

Welding rod name

[@polyvance]

It's our R01-01-03-NT polyurethane welding rod. www.polyvance.com/Polyurethane-1/R01-01-03-NT/

[@STARGAUD]

Instead of requiring two hands to apply the welding rod, it would be nice to have a tool like a glue gun where pulling the trigger applies the rod.

[@scottb7600]

We've actually looked into this, but found that applying urethane that way is not as versatile and produces a lower quality bond than when using the 6027HT welding tip. The reason we think this is so is because you don't have the pressure of the melted rod being forced onto the urethane.

[@STARGAUD]

@@scottb7600 Good point. What’s your opinion of using something like a construction adhesive that is polyurethane? Then you don’t have to melt?

[@scottb7600]

@@STARGAUD Most adhesives will not bond as well to urethane as urethane bonds to itself and in terms of cost, a little welding rod is much cheaper than adhesive. Yes, I know, you still need to make the investment in the tool, but spread out over multiple repairs, the tool will more than pay for itself.

[@STARGAUD]

@@scottb7600 Thank you for the reply. I have the tool! Should I use the clear rod then on a urethane bumper? I am currently looking for an epoxy skim coat. the 2000T would take too long to get here so I am looking at the 3M EZ Sand 35887.

[@scottb7600]

@@STARGAUD Yes, the rod you should use is the clear PUR rod part number R01-01-03-NT. It's clear, but has a yellowish caste. Polyvance has two fillers that work great. One is the epoxy based 2000-T or 2000-C (tubes, cartridges). The other is Putty Flex, which is polyester based; PN 1047.