Painted Plastics Flammability Requirements - Outer shell

[RollingStock]

Hello everyone.

In my company we manufacture intraoral scanners, and I'm unsure of the flammability requirements for our PAINTED outer plastic shell. This shell is not in patient contact, however, it is handled by practitioners. I've read several posts in this forum on flammability of plastic, however, none that specifically address the influence of paints (or generally coatings) on those requirements.
The plastic material is rated for UL94 V-0 @ 1.5mm. So far, I've gathered that EN 60601-1:2006/A2:2021 mandates V-2 or better for TRANSPORTABLE ME EQUIPMENT. I was not able to retrieve any flammability data for our cured paint.

My question is: How are the flammability requirements affected when a known plastic is painted (or in general: coated)? Is it normally considered by auditors? If yes, which tests and data will be required?

Any help is highly appreciated. Cheers

 

[Jen Kirley]

Welcome RollingStock!

In general the flammability requirements will be applied to both base material and coating. What does your drawing say?

 

[Hendi]

Isn't the idea of burning down something at work nice?
You've got flammability in your risk assessment.
Talk to the people in power, like workplace security, check if your company has competence to do a - precompliance, if you don't have your own accredited lab - flammability test, set up a test plan, burn it, use it as risk assessment input again, and act accordingly (keep it, change, accredited testing, see if you can declare your own testing as valid, or at least as an intermediate until lab appointment), if it fits your processes.

 

[RollingStock]

Welcome RollingStock!

In general the flammability requirements will be applied to both base material and coating. What does your drawing say?

Hi Jen. Thank you for your answer. However, I'm not sure I understand your question regarding the drawing. If you mean the shell part drawing, it states our V-0 rated material in the "Material" field, and out paint system in the "Surface treatment" field. Or did I misunderstand?

 

[RollingStock]

Isn't the idea of burning down something at work nice?
You've got flammability in your risk assessment.
Talk to the people in power, like workplace security, check if your company has competence to do a - precompliance, if you don't have your own accredited lab - flammability test, set up a test plan, burn it, use it as risk assessment input again, and act accordingly (keep it, change, accredited testing, see if you can declare your own testing as valid, or at least as an intermediate until lab appointment), if it fits your processes.

Hi Hendi. I love your go do attitude and you've definitely sparked my interest in doing this test in-house to substantiate our flammability compliance. Do you have experience with authorities accepting such approach? If in-house testing is not a possibility, do you then see it necessary to do tests on the painted shells at an accredited lab? Or could the effect of the paint be rationalized only by a paper exercise?

 

[Hendi]

The main guide for your continuing effort is your risk evaluation. We do some few tests in-house, acceptance relies on test planning and execution that shows some competence (that might overlap what is required for the product anyway), following test standards, results needs to go into risk assessment again. Sometimes its fully accepted, sometimes it just buys some valuable time because they want to see a proper test next time, its way better then when they find you found the risk and ignored it!

Accredited lab means that the people who did the test are competent and adhered to standard, and it keeps your own personnel free for other stuff.

I guess flammability of combined materials is hard to predict, I vaguely remember a school experiment, you first try to set fire to a sugar cube, which only melts. Putting some ash on it makes it flammable.

 

[Jen Kirley]

Hi Jen. Thank you for your answer. However, I'm not sure I understand your question regarding the drawing. If you mean the shell part drawing, it states our V-0 rated material in the "Material" field, and out paint system in the "Surface treatment" field. Or did I misunderstand?

I usually find flammability callouts in the drawing Notes. When that is the case the callout is for everything on the drawing, whether it is shell, assembly or component. Otherwise I would expect the callout to specify whether the flammability requirement applies to shell, coating etc.

 

[RollingStock]

I usually find flammability callouts in the drawing Notes. When that is the case the callout is for everything on the drawing, whether it is shell, assembly or component. Otherwise I would expect the callout to specify whether the flammability requirement applies to shell, coating etc.

Hi Jen, and thanks for getting back to me. I think I didn't manage to explain our case clearly. We design our products entirely and therefore we create the drawings. Anything stated on the drawings is written by either me or the design engineer.

From the answers above, my understanding is the following:
- Flammability requirements are only explicitly stated for the base material (per EN 60601-1:2006/A2:2021) and NOT for the coating/paint.
- However, it is expected by authorities that you take any coating into account in your risk assessment on flammability.
- The coated material shall be assessed holistically either by (A) justification from data sheets, literature search etc.; (B) in-house testing + justification; or (C) verification test at accredited lab.

Please correct me if I misunderstood.

 

[Jen Kirley]

If authorities have an expectation for something like flammability, it follows that your specifications should address that in some way.

Do you have a specification for coatings? If yes, flammability can be addressed there and the drawing simply state that coating shall be 123 from specification XYZ.

Overall, I am wondering why flammability is a required risk assessment. If so, it seems to me automatic that all of the part adhere to that in some way. How you do it is up to you, what works best for your organization and will ensure it is followed.

I would also look at manufacturer data sheets for the coating. They likely also state combustion temperature as extent of flammability. For the rest, I think your methods are sound but would defer to your customer in deciding whether to go to that effort unless the data sheets are not conclusive.