John Kuthe wrote:
On Oct 18, 7:39 pm, Bill Tuthill wrote:
John Kuthe wrote:
What *I* want to know is:
OK, if Teflon plastic, AKA polytetrafluoroethylene, is a "...is a
white solid at room temperature..." (much like many other polmerized
ethylenes!) as is said he
http://en.wikipedia.org/wiki/Polytetrafluoroethylene
then what's that dark brownish coating on cookware made of? Not JUST
Teflon, I'm sure!! The above page says nothing about cookware coating,
or how they take a white plastic and make it into that brownish
coating. I'm curious!
I can totally understand Teflon's low low frictional coefficient, what
with only fluorine atoms on it's molecular outside. Fluorine is THE
most electronegative atom, I believe, resulting in extremely low Van
Der Waal forces which cause friction. So low in fact that Teflon is
the only substance a gecko lizard can't stick to! Someone tell Geico
insurance, quick! ;-)
LOL, great post. "degrades above 260°C (500°F)," hmmm.
Teflon frying pans must have some coloring agent because a white surface
would get dirty quickly. I have a Creuset pot (enamel inside & out)
with blue exterior and off-white interior, now stained halfway up
from cooking black beans.
Teflon coating on cookware is probably colored due to the stuff they
have to use to get Teflon to stick to the metal of the pan! I doubt
it's for cosmetic reasons. Think about it: Teflon plastic, AKA
polytetrafluoroethylene, is a white plastic, I'd imagine very close in
appeaance and feel to Nylon or polyethylene. You know, white kinda
soft plastic.
So how do they get this super-low coefficient of drag plastic to be
this thin brownish coating that sticks to cookware but little else
once it's on the cookware? I wanna know!
John Kuthe...
I couldn't help responding to this post.
I lurk in this news group on occasion because it's full of good advice
and I like to canoe.
I use to work with manufacturers of Teflon coated pans ( a while ago -
so the information provided is dated, abridged and subject to the
accuracy of my recollections) - At the time I was involved, Teflon was a
3 coat system.
A base coat which was a polymer mix to adhere to the sand blasted and
etched pan surface, a second coat of PTFE with decorative speckles
(and/or pigments) and a clear over coat of translucent PTFE
The durability of the coating is more a function of the cook ware
manufacturing process than the resin composition.
DuPont got burned on their original Teflon coating by selling the resin
(emulsion) to anybody and allowing them to use the Teflon brand name.
Later coatings like the SilverStone required process approval and
auditing by DuPont in order to use the SilverStone name.
Other companies may use the same coating, but if their process is not up
to par, they can not use the SilverStone trade name.
The white "Teflon" components for lab ware etc. are typically ETFE which
is a thermoplastic as opposed to a thermo set resin (emulsion) system
like PTFE Teflon coatings.
The coating adhesion is mainly mechanical in nature and substrate
preparation is extremely important.
The Teflon has a very low surface tension which prevents it from being
wetted in solid form - However, when melted, it is a low surface tension
liquid and it will wet a substrate very efficiently and creep into every
nook and cranny on the surface.
I hope this information helps to satisfy your curiosity ;-)
Gregg