[Amps] Dielectric grease for roller inductors ?

[Roger (K8RI)]

Generally dielectric greases are insulators, hence the name 
"dielectric". Being an insulator does not hurt them being used as a 
lubricant for a contact wiper.

Now: Silica (SiO2) = quartz sand. ALL silicones  (As far as I know and I 
worked in the industry from 61 through 97 except for college) start out 
as quartz, but the "silica" is long gone before the Silicones are 
compounded.  The term "dielectric" is quite specific by definition as in 
coax cable dielectric. "The grease" may be an insulator by itself, but 
it allows the wiper to make intimate contact so its insulating 
properties are a non issue. These compounds protect the surface from 
Oxidation and act as a low speed, low pressure lubricant.  I should 
emphasize the "Low Speed" as these compounds do not work well as high 
speed lubricants.

The Silica (SiO2) is turned into Silicon + Oxygen in an arc furnace.  
The Silicon is turned into a Silicone fluid via a chemical reaction.  
The resulting fluid is the basis for nearly all of the Silicone 
compounds.  There is nothing abrasive about these compounds.  An arc 
will cause them to decompose.  Silicones "CAN NOT"  carbonize as there 
is no carbon in the compounds. Organic Greases can carbonize as they 
consist of Hydrocarbons.

As I've said before, Silicone grease, specifically Dow Corning's DC4 
(the first Silicone grease) was developed for sealing spark plug boots 
on B-17s in WWII.  It was to prevent arcing to chassis ground at high 
altitudes.

DC4 and DC5 compounds work well for flooding connectors. They do raise 
the breakdown voltage above plain air gaps. I find they do not create a 
larger impedance bump compared to the original air gap.  From "what I've 
seen" they actually lower the bump in UHF connectors

I do not like Tom's use of the term "low Viscosity" as it's a relative 
term. These are "RELATIVELY low viscosity" for greases, but not for 
Silicones. Yes the RTVs have a much higher viscosity, but there are a 
number of Silicone fluids with muck lower viscosity.  Almost all non DC 
Silicone compounds are made as a result of reverse engineering Dow 
Corning's Silicone compounds which were not patented..  One company 
reverse engineered DC's compounds, applied for a patent and then tried 
to sue DC for patent infringement.   They lost as DC could show prior 
use for over 50 years. I believe that put those Silicone compounds into 
the public domain.

At any rate, DC5 and DC5 compounds make excellent contact wiper lubricants.

73, Roger (K8RI)




On 7/7/2018 10:31 AM, Bob Burns W9BU wrote:
> On 7/5/2018 2:30 PM, Joe wrote:
>> isn't dialectic grease an Insulator?
>
> Maybe. Maybe not.
>
> https://www.w8ji.com/dielectric_grease_vs_conductive_grease.htm
>
> Bob...
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>

-- 
Roger (K8RI)


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