Our popular Ask Joe Powder blog has made its way to the pages of PCI magazine. What are your powder coating questions and challenges? Joe Powder, aka Kevin Biller of ChemQuest Powder Coating Research, shares his powder coating knowledge and expertise by answering questions sent in from around the world.

Dear Mr. Joe Powder, 

I am looking for a simple respiratory mask to be used during powder coating application. Do you have a mask recommendation, and/or is there any standard we should follow? Or, is there any classification I should be aware of in order to help me select a mask? 

Thank you,

Girdhari Singh

Dubai, United Arab Emirates

Dear Mr. Singh,

In the United States, our National Institute of Occupational Safety and Health (NIOSH) recommends the use of a dust mask that is rated as N95. This designation means the dust mask will remove 95% of particulate materials from the air that you breathe.

It is essential to fit the mask carefully on your face. Thick beards and narrow bridges on one’s nose can make proper fitting a bit of a challenge.

In my laboratory, we use a 3M model 8210. It’s from a very reliable company, but there are plenty of competitive products that I am sure will suffice. If a person has a thick beard, they may have to trim it for a better fit. And if they have a small face, there are other products available. Here is a link to the N95 page for NIOSH: https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/n95list1.html.

Please be aware that these masks are only good for protection from airborne particulates. If your operators handle cleaning solvents, then a respirator with an activated carbon filter is necessary. NIOSH provides information on respirators acceptable for handling acetone here: https://www.cdc.gov/niosh/npg/npgd0004.html. Respirators can be fitted with particulate filters to protect from powders and solvents.

I hope that this helps.

Best regards,

Joe

Dear Joe,

One of my customers is facing a problem when using a polyester powder coating. The coated pieces are aluminum profiles, and their application is vertical.

They are seeing an unknown material that looks like snow, is mostly found inside the baking oven, and causes defects on the coated surface. It seems to happen with the powder we supply, under usual conditions, in the customer’s oven.

Can you advise from your experience what it is and how it happens?

Thank you in advance.

Pongbodin Deacha

Thailand

Dear Pongbodin Deacha,

Thank you for your question. I have seen this problem before. It can be summed up in one word: benzoin.

Nearly all powder coating formulas use a de-gassing agent to assist in the film formation of the coating while it is melting in the oven. Degassing is needed because, as the particles coalesce, air pockets form in between the particles (I like to call it interstitial air). Incorporating benzoin allows the bubbles to escape during this melt phase.

Part of the mechanism of degassing involves the volatilization of the benzoin, as its melting point is 132 °C and it tends to sublime above this temperature. How do we know this? I have taken samples of the snowflake-like residue found in powder-cure ovens and had our analytical lab characterize it. What they found was the majority of the residue is benzoin.

How do you minimize/stop this problem? My experience with finding high concentrations of benzoin in a cure oven usually indicated a very “tight” oven. By that, I mean an oven with very little exhaust. This is a common issue; some oven designers think that since powder coatings are promoted as having no VOCs (volatile organic compounds), they don’t have any volatiles. This is not the case.

VOCs refer to regulated organic compounds that present a deleterious effect on the atmosphere. Powder volatiles do not, but they still exist. Hence, the solution to your problem is to thoroughly clean/vacuum your oven and provide more exhaust to the oven.

This should eliminate the problem. Then, have a trusted analytical laboratory analyze the residue with infrared spectroscopy. Benzoin absorption bands are unmistakable.

Best regards and let me know if you have further questions,

Joe Powder

Do you have a question for Joe Powder? Email kbiller@chemquest.com. And be sure to listen to the Ask Joe Powder “Powdcast” for all the latest news, insights and technology in the powder coatings industry. Click here to listen!