Chemistry Forum

Hello,
I own a BK Precision 391A DMM. It's a nice, if minimalistic DMM. I took it outside one day and the top surface, that was the one exposed to the sun, turned into a sticky liquid plastic. I tried cleaning it with Isopropyl alcohol, as that was all I had on hand, without effect. I ended up using an abrasive method to remove the liquefied plastic.

IDK what plastic the exterior is made of. I have had similar problems before with plastics, but it was always exposure to heat over a prolonged period of time that caused the plastic or rubber to liquefy. I'd like to be able to use it in the sun at least for a little while. If that's not possible, okay, but I thought I'd ask here. I've attached some photos of the aftermath. Here's the official webpage: https://www.bkprecision.com/products/multimeters/391A

Is there was a way to protect it outside of keeping it in the shade? I'm also curious, why does it break down so quickly? Literally, under 3 hours of exposure till the top of the plastic becomes totally liquid.

Thanks!

I don't see any liquid. It looks like the case used very often and scratched the surface.

The liquid plastic I removed, as I said, using an abrasive method. I showed pictures of the plastic in case it helps identify the plastic. I could go further with tests, but IDK how to test nor what to use to do it with.

You can still see some shards of loose plastic that had softened during exposure to the sun still adhering to the case.

jesse99 wrote: ↑Mon Aug 25, 2025 9:40 pm DELETED

Thanks for the info, but the link you gave goes to a site for gaming. Maybe you posted the wrong link by accident?

heat is key

I'm not so sure. I took it out again about a week later and placed it into the shade (for several hours), and the plastic did not melt.