Tuesday, July 24, 2012

Self Cleaning Plastics

You've probably seen over the years numerous examples of "self-cleaning" ______________, whether it be windows, sculptures or as was mentioned yesterday in the Polymer Solutions Blog, plastic outdoor furniture. While a variety of mechanisms exist for obtaining these surfaces, the most common route is to take advantage of the photocatalytic nature of the anatase [*] phase of titanium dioxide. If organic matter contacts the surface, and the surface is exposed to UV light, the organic material will oxidize, possibly going as far as becoming CO2 and water, leaving the surface pristine again. Hence the name "self-cleaning".

But there is one little glitch in the whole system that prevents the widespread adoption of these coatings. They only work on reduced (non-oxidized) materials. When inorganic materials, such as various clays based on SiO2 contact the surface, nothing happens. You have to then clean your "self-cleaning" surface.

So when the Polymer Solutions Blog says: "Manufacturers of cleaning supplies: Be afraid. Be very afraid.", you don't need to be selling your Chlorox or S.C. Johnson stock anytime soon. Maybe "semi-self-cleaning" would be a better descriptor.

[*] The rutile phase is used as a white pigment. We once had a client that accidentally used the anatase phase as a colorant...and had some major liability issues, but that's another story for another day).

4 comments:

Anonymous said...

I heard of a "self-cleaning" coating, wherein lipases are used to break-down grease/oil (presumably in a restaurant/personal kitchen). I was surprised that those lipases remain active enough in the dried coating to produce such an effect.

George Gough said...

I suppose that self-cleaning plastics are helpful as well to unblock drains as well.

John said...

George,

If you could somehow design them (no UV light down there, but other lesser options exist), they would be better at preventing drain blocks than in unblocking them.

Florence Pfaff said...

Is it safe to say therefore that these self-cleaning plastics when used as outdoor garden furniture should be wiped clean everyday. Anyways, dusting the furniture is all part of the everyday domestic chores.