Safety precautions on using trichlorosilanes 1

[DHT83]

thread334-270573

This question is directed towards Chris (demon3) and your comment on creating your own hydrophobic coating. That sounds very neat! and I am thinking of trying it.

However, I have some questions from a safety point of view. How sensitive are the final coating solution (~5 wt% chlorosilane in hexane) to ambient moisture or retained water in the fabric? The chlorosilanes are listed as very reactive with water. Did you dry your fabric thoroughly before you applied the coating? I was thinking a hair-dryer treatment might be a good pre-coating step but I wonder if this is even necessary. Please let me know what your thoughts are.

Thanks.

 

[Demon3]

Hi,

We made up the solution and sprayed it right onto a Tenson brand jacket I bought at a second hand clothes store. The treatment was done with no pre-drying. Probably we had enough silane (5 weight%) in there to react with any surface water.

The hydrophobic treatment was stunning. You could literally hold a litre of water in that jacket for days and get a mirror like sheen where the water sat on the jacket. Then we did the same with an umbrella. It was hilarious because the water would literally bounce off the surface and jump several feet, hitting the person next to you.

Then we did the same on the cement outside and wrote in water-proof ink. This is the same as commercial water-proofing for cement like Ronson Water Shield or whatever it's called only they use the less reactive trialkoxy silanes.

Trichlorosilanes liberate hydrochloric acid vapor when they react so do it in a well ventilated area.

Chris DeArmitt PhD FRSC CChem

 

[DHT83]

Thanks for the reply Chris!

I have a follow up question on this coating method, I hope you don't mind .

Do you think these silane molecules chemically react with the surface of the fabric (I imagine this would require -OH groups presiding on the surface being coated...) or do these molecules only being physically adsorbed on the surface? I suppose to relate my question to real life, did you see a performance reduction with your jacket after you wash it multiple times? I think this would indicate whether the silane molecules are only physically adsorbed or chemically tethered to the surface. I love to hear your thoughts on this.

Thanks again!

Best,

Dawud

 

[Demon3]

I think the trichlorosilanes react chemically with polyesters and nylons but can't react with for example PP fibers (no sites for reaction). I didn't wash the jacket as the experiment was for fun, not a commercial project.

Chris DeArmitt PhD FRSC CChem

 

[Demon3]

I remembered to mention that Gelest are now selling some silanes that are very reactive but safer than the trichlorosilanes as they don't liberate HCl gas. They were presented at a conference I organized recently in Atlanta.

Cyclic azasilanes: "Meeting the environmental demands of
surface modi?ed minerals"
Mr. Joel Zazyczny, Vice President - Silanes Silicones and
Metal-Organics
GELEST INC., United States

Chris DeArmitt PhD FRSC CChem