Flex additive...?

[The Z'eer]

Seeking a little advice on flex additive here, never used the product before and shedding some light may help on making a decision.

Front and rear bumper from my late second generation Camaro is made from urethane. It's rather flexible and sort of rubber like (impressions from fingernails can be left quite easily when pressing) it's certainly not as hard as modern plastics. I have done a little research and the jury is out on whether or not a flex additive is needed, apparently modern paints flex more than older ones ? I am working on the bumpers off the car and thus they do flop a little as opposed to when fixed in place.

I was considering using my Lechler 29107 as a primer for it, I hear it's pretty flexible. However, I've found that it doesn't block sand too well above 400 grit, paper becomes blocked (Mirka Abranet) and scratches are left. So I was thinking of using the high build primer I have (U-pol S2025) it'll certainly help since there are suspect areas which will need leveling out slightly.

Also, and again this some info I've come flex additive can be used in primer and clear but not normally the base coat ??

Advice appreciated

 

[ajlelectronics]

However, I've found that it doesn't block sand too well above 400 grit, paper b - . ecomes blocked (Mirka Abranet) and scratches are left.

Nonsense, it can only be your technique. How long do you let it cure for? I have used it on a rubber bumper with great success. If you need to level hollows, that is what stopper is for, not layers of paint.

 

[norsa]

The flexible additives in modern paint is a thing of the past in most panels of the car and once the bumpers are fitted, they won't flex enough to warrant additives to every layer. It will only fracture following a blunt trauma and no panel will take that without leaving a scar.
Nick

 

[The Z'eer]

Nonsense, it can only be your technique. How long do you let it cure for? I have used it on a rubber bumper with great success. If you need to level hollows, that is what stopper is for, not layers of paint.

It wasn’t my technique. Long block and cross hatch pattern. I think the panel had been left for circa three days before attempted to work on it.

Even the data sheet says as much https://portal.lechler.eu/DesktopMo...oad.aspx?Command=Core_Download&EntryId=136093 if the manufacturer thought it would be suitable to dry sanded at 500 then they would’ve said so.

 

[The Z'eer]

The flexible additives in modern paint is a thing of the past in most panels of the car and once the bumpers are fitted, they won't flex enough to warrant additives to every layer. It will only fracture following a blunt trauma and no panel will take that without leaving a scar.
Nick

Thanks for the info there Nick. I did wonder if the urethane may expand and contract with different weather conditions but it sounds like there may be no need to use flex additive.

 

[ajlelectronics]

Even the data sheet says as much

Perhaps you might like to point out exactly WHERE?

I should have known better than to respond again, you are only interested in responses that match the answer you want to see.

 

[The Z'eer]

Perhaps you might like to point out exactly WHERE?

I should have known better than to respond again, you are only interested in responses that match the answer you want to see.

There’s no need to have an attitude and bear umbrage simply because my findings are different to yours.

Put your specs on read through the data sheet, the section entitled SANDING !

 

[ajlelectronics]

There’s no need to have an attitude and bear umbrage simply because my findings are different to yours.

Put your specs on read through the data sheet, the section entitled SANDING !

Then YOU need to learn to read and understand the information you are being given.

 

[Wildefalcon]

Great that both of you are so invested in this. I'm sure neither of you meant it, but some of the responses came across as a bit crabby.

I know that this can happen to me when I'm tired, which I am right now, but if you could double check your posts before you press the blue button, then you might spot that, and change the tone of the comment a bit.

Remember, it's not worth falling out over.

If this comes across as a bit snippy, I'm sorry. It's just that this is a very good humoured forum, which I like. Plus I've not slept.

Thanks for your patience.

 

[ajlelectronics]

Put your specs on read through the data sheet, the section entitled SANDING !

SANDING
When using EPOXYPRIMER as a primer dry sand with P180 - 220
When using EPOXYPRIMER as a sealer-filler dry sand with P280 - 320

So where does it say what you allege? Those instructions are for sanding BEFORE applying primer. 180 for initial bond and 280 for overcoating with itself or a surface in good condition, to seal it.

 

[The Z'eer]

Then YOU need to learn to read and understand the information you are being given.

SANDING
When using EPOXYPRIMER as a primer dry sand with P180 - 220
When using EPOXYPRIMER as a sealer-filler dry sand with P280 - 320

So where does it say what you allege? Those instructions are for sanding BEFORE applying primer. 180 for initial bond and 280 for overcoating with itself or a surface in good condition, to seal it.

NO Andy, those are not the instructions for BEFORE applying, they are after!! The data sheet has a section prior to that entitled Substrate Preparation.

 

[ajlelectronics]

NO Andy, those are not the instructions for BEFORE applying, they are after!! The data sheet has a section prior to that entitled Substrate Preparation.

OK have it your way.

 

[indy4x]

Not sure why the grumpiness either, I've never used epoxy primer of any sort although that is likely to change so I read the spec sheet

Looks to me as if the tech doc is laid out in the order of events I.e.

PREP
APPLICATION
DRYING
SANDING
and so on

If it was me interpreting the document it suggests the sanding bit comes after the painting bit

 

[The Z'eer]

Not sure why the grumpiness either, I've never used epoxy primer of any sort although that is likely to change so I read the spec sheet

Looks to me as if the tech doc is laid out in the order of events I.e.

PREP
APPLICATION
DRYING
SANDING
and so on

If it was me interpreting the document it suggests the sanding bit comes after the painting bit

Yeah, I agree. That's a normal logical interpretation of the instructions.

 

[richie00boy]

AJL is actually correct.

If you look in the Substrate Preparation section it tells you to sand, however the grit to sand with is actually listed in the Sanding section.

If you are having issues sanding the primer using 400 grit, it is probably not cured properly. It is too cold to use epoxy primer in an unheated garage at the moment, note in the drying time section it says "Try not to dry the product under 15 °C".

I have sanded 29107 with 600 grit without issue when adhering to the temperature guidelines.

 

[The Z'eer]

AJL is actually correct.

If you look in the Substrate Preparation section it tells you to sand, however the grit to sand with is actually listed in the Sanding section.

If you are having issues sanding the primer using 400 grit, it is probably not cured properly. It is too cold to use epoxy primer in an unheated garage at the moment, note in the drying time section it says "Try not to dry the product under 15 °C".

I have sanded 29107 with 600 grit without issue when adhering to the temperature guidelines.

I disagree and that's not how the data sheets reads. Preparation, application, drying and then the section on sanding. The details on sanding don't not relate to substrate preparation. I'm pretty sure the manufacturer would not be recommending bare steel to be prepped between 180 to 320 grit considering the higher solid content of this product. The details for substrate prep appear in that particular section.

The parts I've painted were left to cure in heated workshop, a temperature which didn't drop below 17 degrees celsius and is dehumidified too.