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Plastics-Bonding (fwd)



---------- Forwarded message ----------
Date: Thu, 02 May 96 10:53:00 PDT
From: Richard Hull <RICHARDH-at-whitlock-dot-com>
To: bin <bin-at-poodle.pupman-dot-com>
Subject: Plastics-Bonding


To all interested,

I sat down with our plastics expert/resident phyicist, Kim Goins, and here 
is the result of the chat which bounces the ball back towards Methylene 
chloride for poly carbonate.

Polycarbonate, Lexan, Tuffak.... All the same stuff

Virgin polycarbonate is glued with and soluable in methylene chloride!!!
The problem is that virgin polycarbonate is almost never encountered!!  All 
polycarbonate normally distributed is specially coated and treated to 
prevent scuffing and scratching.  This tough and tenacious over-layer is 
impervious to all known solvents and this standard material is un-gluable. 
 Period!  It can be specially fusion welded (expensive) or bolted together 
(most normal).  * note*  virgin polycarbonate when glued with Methylene 
chloride forms a singularly, bubble free, flawless weld which is a marvel to 
behold.

Plexiglass, lucite, acrylic....All the same stuff

Methylene chloride is the solvent of choice here, too, and all the 
commerical product responds well to this stuff.  It is virtually impossible 
to exclude bubbles from a lucite weld as the solvent outgases micro bubbles 
of chlorine just as the stuff starts to setup.  Weldon #3 is just  methylene 
chloride with a small amount of dissolved lucite in it.  Weldon #16 is a 
thick glue like substance and is in a tube and not as runny as #3.  These 
are the normal commercial glues for the non-chemical buyer.

Styrene, Poly-Styrene

These plastics are welded by their solvent Toluene.  Testors model airplane 
cement is a thicked version of this solvent.  Many good low loss capacitors 
can be made from "modified styrene".  The dielectric loss in this material 
is very low. .0002%.  Styrene is used in a lot of ultra low loss high 
frequency radio applications for insulators, spreaders, etc.  Ultra cheap 
low loss plastic  like polyethylene, but gluable.
This stuff tends to craze and show sleeks and stress marks  when 
 mechanically stressed.

PVC

A very normal material for Tesla coil forms.  This material uses a "MEK" 
 Methyl Ethyl Chloride base in its glues, all of which are ready made and in 
the stores world wide.

Polyethylene, Polypropelene

The number one choice of capacitor makers.  These materials have no real 
solvent!  They are linked by fusion welding only and are themselves used in 
a number of "hot glues".  Common hot glue is ultra-low density polyethylene. 
 *note* there is a supposed glue offered by some few plastics distributors 
for polyethylene.  The joke is that they ship it in a polyethylene bottle!!! 
 One of the distributors told me this joke on the plastics industry.  The 
great value of polyethylene is that almost nothing attacks it, short of very 
hot acids.  This is why so many bottles for holding all manner of vile and 
Eco-unfriendly materials are made from the stuff.  Billions of years from 
now all the polyethylene bottles will still be in bottle form. 
  Non-biodegradable.

Teflon

Would be the best capacitor material in the world, but for the fact that all 
teflon has countless trillions of micro and larger size holes in it!!! 
(dissapation factor .0001%)  The thinner the sheet, the more like swiss 
cheese it is!!  I have made a number of excellent, small, flat plate caps 
from this stuff and they remain at ambient temperature after many minutes of 
operation.  You must use many thin layers to avoid puncture and the best use 
of this material is in caps for small table top coil units which use 
voltages under 9,000 volts for input.  I prefer to use it for under 5000 
volt micro- coils.  Teflon is also not really gluable, although there is a 
glue offered, and even tape for teflon.  They are all very expensive, as is 
teflon, itself.  As a side note, Teflon coated wire is great for Tesla coils 
provided that it is tight wound at  room temperature and this temperature 
never varies!!  The coils in my lab, which I have wound with teflon wire, 
have all come unraveled and the layers of wire just separate and fall over 
the outside of the other turns with expansion and contraction  as the 
temperatures rises and falls.  This stuff is slick!!  No coating holds to it 
and there is little hope for coils wound with teflon insulated wire in a 
highly variable temperature environment.

I hope this has been informative to all you Tesla coil buffs.  Plastics are 
the very reason that even the most novice of our number can build systems 
which easily outperform anything  "Nik" could have ever assembled in his 
world of gutta-percha and wax impregnation coil building.  Plastics have 
delivered us from wood and paper form materials (high loss) and have vastly 
improved capacitor construction where only expensive mica units were 
available in Tesla's day.

Note*  All solvents are nasty and toxic.  Many are mutanogenic and  are 
known Teratogens.  Breathing them is a no-no over the long haul.  Use lots 
of ventilation and try and work out of doors with all of them.

Richard Hull, TCBOR