PUR bumper covers

K

Karmin

Hi all,

Another noob question. I have 2 PUR bumper covers that will be painted off body. My questions are:

- flex additive needed if factory finish is still on it?
- does adding flex additive affect the final color?
- (on some forums) flex additive has been identified as the culprit for fading paint. True?
- do you add the additive to primer, sealer, base and clear?

Thanks,
Karmin
 
Pur does not need an adhesion promoter, best bet is coat with epoxy first, the epoxy will give more flex to the base and you will not need a flex agent.

Flex agents do not cause products to go bad but they are really a waste of money if you are using a good system.
 
Pur does not need an adhesion promoter, best bet is coat with epoxy first, the epoxy will give more flex to the base and you will not need a flex agent.

Flex agents do not cause products to go bad but they are really a waste of money if you are using a good system.

I know this post is old but I thought bare polyurethane needed an adhesion promoter. Everything I’ve read has said to use it.
 
I know this post is old but I thought bare polyurethane needed an adhesion promoter. Everything I’ve read has said to use it.

Whatever you read was wrong.:) One thing about this forum is all the information is given is correct. Many of us are Profesionals here with many years of experience doing quality work so you can trust what you read here. So much stuff gets passed around on the Internet as truth by people who think they know what they are talking about when in fact theyh do not.

PUR does not need adhesion promoter. If you have any doubts as to what the material is try this test. Take a sliver off the backside of the part. Place it in a glass of water, if it floats you need adhesion promoter. If it sinks you do not. Example of PUR would be Fox Body Mustang Factory bumper covers and ground effects. Most everything these days is one of the thermoset plastics like TPO or TEO which do need adhesion promoter. But if in doubt just do the above test for an answer.
 
Whatever you read was wrong.:) One thing about this forum is all the information is given is correct. Many of us are Profesionals here with many years of experience doing quality work so you can trust what you read here. So much stuff gets passed around on the Internet as truth by people who think they know what they are talking about when in fact theyh do not.

PUR does not need adhesion promoter. If you have any doubts as to what the material is try this test. Take a sliver off the backside of the part. Place it in a glass of water, if it floats you need adhesion promoter. If it sinks you do not. Example of PUR would be Fox Body Mustang Factory bumper covers and ground effects. Most everything these days is one of the thermoset plastics like TPO or TEO which do need adhesion promoter. But if in doubt just do the above test for an answer.

Oh man I feel stupid.

This is labeled pur on the backside of the bumper. I had to make a few repairs and stripped it to raw pur. Yesterday I got in a hurry and was finishing the first coat of primer when I remembered I never applied adhesion promoter. I stopped priming, poured out my primer, and gave it time to dry and started stripping the bumper again.

FYI this is a bumper off an 88 camaro. I filled a couple cuts with a 2 part bumper repair epoxy. Do these spots not need adhesion promoter either?
 
No need to feel stupid, it can be confusing with so many types of plastics out there. And no you don't need any on the repair spots.
What type of primer are you using?
 
No need to feel stupid, it can be confusing with so many types of plastics out there. And no you don't need any on the repair spots.
What type of primer are you using?

I went straight to surfacer but I’m considering giving it a light coat of epoxy pre surfacer next time. What’s the best method?
 
Epoxy is ALLWAYS best on any bumper for adhesion and flexibility.

My original thought was to keep the primer layer as thin as possible so I skipped epoxy but now I think it’s needed for good adhesion. Next time I’ll do one coat of epoxy then surfacer.
 
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