Silicone Bonding Sheeting + Static Electricity - Lightning like patterns of sticking

[Dr. Electron]

Good Afternoon everyone!

We've been witnessing an incredible phenomena where our silicone sheeting bonds with the polycarbonate surface it is spread onto during manufacturing in a lightning like pattern. We believe that after it is cured...a static charge is somehow baking the silicone to the poly...and is causing these crazy patterns of sticking. The static electricity would have to reach temperatures about 312 F though...and we are skeptical that is possible.

Has anyone ever experienced this kind of phenomena?

[Marc]

Why are you looking at static electricity as the cause?

[Tim Folkerts]

Originally Posted by Dr. Electron

and is causing these crazy patterns of sticking

I'm not an expert with plastics, but your use of the word "crazy" reminded me of a phenomemon called "crazing" which is is cracking of materials (plastics & ceramics mostly) into patterns that could resemble "lightning". Sometimes it goes all the way throuhg a material; sometimes just the surface. Typically it is caused by thermal, mechanical or chemical stress.

If the problem is just patterns in the adhesion of the materials, then crazing probably isn't related.

A quick web search found
"A major electronics equipment and computer manufacturer first encountered the polycarbonate compatibility problem with dissipative polymers. Their field service people noticed that polycarbonate-containing components were "crazed" which then cracked when used. Later, they found another crazing problem that was time related and was traced back to their static dissipative shipping and storage bags. This second polycarbonate compatibility problem became critical when a costly worldwide product recall was required to replace the crazed parts.

In general, polycarbonates can be seen as polar, rigid thermoplastics. As expected with chemistry's "like dissolves like" rule, a polar solvent or molecule with a polar end will try to dissolve into the polycarbonate surface. However, because polycarbonate is rigid, it cannot expand or swell to accommodate the solvent. It accommodates the solvent molecule by surface cracking or crazing at a stress point, which leads to further surface attack and ultimately breaks in two."

Don't know if that is at all related, but it might give an idea or two.

Tim F

[Dr. Electron]

Originally Posted by Marc

Why are you looking at static electricity as the cause?

We are able to peel all the other silicone off the carrier, but the lightning like sections appear as if they're baked in and do not peel off at all. Other than static electricity...we can't imagine anything else being able to charge the material and polycarbonate to a temperature that could cause such strong adhesion.

Thanks!

[Dr. Electron]

Originally Posted by Tim Folkerts

" Later, they found another crazing problem that was time related and was traced back to their static dissipative shipping and storage bags. In general, polycarbonates can be seen as polar, rigid thermoplastics. As expected with chemistry's "like dissolves like" rule, a polar solvent or molecule with a polar end will try to dissolve into the polycarbonate surface. However, because polycarbonate is rigid, it cannot expand or swell to accommodate the solvent. It accommodates the solvent molecule by surface cracking or crazing at a stress point, which leads to further surface attack and ultimately breaks in two."

Thank you so much for this answer. I did a lot of research on crazing yesterday and found some very interesting material. It is particularly interesting because we believe that something is done to the polycarbonate before we use it...that is further inticing this kind of behavior out of it. Thus the part with the "traced back to their static dissipative shipping and storage bags" really caught my eye. I took a look at a lot of crazing pictures and it does look similar...and is also mainly on the edges of the polycarbonate which is supposedly typical of crazing.

Of course the kicker is...the fact that it adheres so prominently to the polycarbonate when it does this...and that throws me for a loop.

Thanks again!!