[TowerTalk] Silicone on coax connector's ?

[Roger (K8RI)]

There are many kinds of silicones all of which use silicon (the metal) 
as a base.
Any company that just says to use silicones (generic term) is doing the 
materials a dis-service.
Silicone dielectric greases have been around since WWII. They 
(specifically DC-4 compound by Dow Corning) were a new family of 
compounds developed by DC to prevent arcing in the connectors to the 
sparkplugs on aircraft engines at high altitudes.  These dielectric 
greases, although messy do make great flooding compounds for connectors 
and can raise the breakdown voltage considerably for the connectors when 
properly flooded. They do prevent moisture and air gaps from causing 
arcing, BUT if you run enough power to get the voltage high enough to 
arc through them you will break the compound down and end up with SiO2 
which is Quartz sand.  They do not work well in distributors that have a 
gap between the rotor and electrodes. <:-))

BTW the metal, Silicon is made by using an arc furnace to break SiO2 
(pure Quartz sand) down into Silicon (Sill-ah-con, or Sill-uh-con) and 
O2. From there, a number of  propritary processes and steps results in 
the material familes we recognize a silocones (Sill-uh-cones). Most of 
these products are created by proprietary processes and are not patented.

The Silastic Room Temperature Vulcanizing materials or Silastic RTV's 
(TM) are a different animal. These come in both insulating and 
conductive varieties along with different types of curing. Most types 
use the moisture in the air for curing and contain Acetic acid. Those 
designed specifically for electronics with out corrosive properties use 
other catalysts such as alcohol. Some might use Amines as they sure do 
stink.  Typically these silicones, regardless of who makes them 
(Silastic RTV is a Dow Corning trademark, RTV is a generic term. ) are 
water proof, but not moisture proof.  There is also a family of two part 
silicones including potting compounds.  I've used these to get rid of 
particularly pesky arcing problems in compact, very high voltage 
transformers using vacuum impregnation techniques.

73

Roger (K8RI)

On 7/2/2010 1:02 AM, Jim Thomson wrote:
> Ok...  Andrew  heliax co sez to use silicone on coax connectors... to eliminate ... 'microscopic arcing'.
>
> Ken at Cal-Av sez the same thing.   The silicone is to fill the voids..since u always end up with tiny
> air pockets, even with connectors cranked tight.
>
> This is a silly question, but when did silicone start to conduct anything ??   [Dc/60hz/RF]
> 'Conducto-lube'  which is grnd up silver powder in grease would probably work better,
> but I would be leery of using conductive grease.. as it can bunch up at the bottom..
> and cause an arc from base of pin, over to braid/shell.
>
> Conducto lube is made by 'cool-amp'   co in Ore.
>
> So what's the real story on silicone on coax connector's ??    If it is ok to use... is there
> a certain type to obtain??    I think there is several different types of silicone.  Some
> comes in a tube.  [ like toothpaste].. and some in spray bombs.   Seems to me the stuff
> in tubes comes in a doz diff formulations... and some of em are NOT good for electrical
> use.... like coax connectors.
>
> tnx.......... Jim  VE7RF
>
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