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RE: Dielectric
Nice data. The tables came through scrambled
on my machine. Do I need to match my tab
settings to yours to get them on order?
Barry
[NOTE: I reformatted the message below to take out the tabs. You
may have trouble with word wrapping, as the line exceeds 80 chars.
If you have a decent windowing system, it's no problem. :-)
-- Chip "Linux Rules" Atkinson ]
----------
|From: "tesla-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|To: Benson Barry; "Tesla-list-subscribers-at-poodle.pupman-dot-com"-at-PMDF-at-PAXMB1
|Subject: Dielectric
|Date: Monday, October 21, 1996 2:45AM
|
|<<File Attachment: 00000000.TXT>>
|From richard.quick-at-slug-dot-orgSun Oct 20 22:21:29 1996
|Date: Sun, 20 Oct 1996 23:43:00 GMT
|From: Richard Quick <richard.quick-at-slug-dot-org>
|To: tesla-at-poodle.pupman-dot-com
|Subject: Dielectric
|
|> Could someone post a dielectric chart?
|
|
|update 8/1/1995
|Compiled by Ed Harris
|174 W 18th Ave
|Columbus, OH 43210
|New inclusions to the old stuff:
|Info on magnet wire coatings!
|
|
|>From all the discussion on this group about building ones own capacitors
|and what types of materials make good coil forms, I became interested in
|obtaining some hard (or semi-hard) data on different types of polymers. I
|was also interested when someone (?) asked whether ABS was a good material
|for coil forms - I had no idea. It seems that it is much preferable to PVC.
|
|I thought I'd share the results of my library searches:
|
|First, I'd like to list some of the plastics with their chemical name and
|their abreviations. Trade names are listed if they are well known.
|
|chemical name abreviation aka notes
|------------- ----------- --- ------
|polyethylene PE polythene-British!
| CH2-CH2 monomer
|
| HDPE High density PE
| LDPE Low density PE
|
|polypropylene PP replace one H in PE
| by CH3
|
|polyvinyl chloride PVC replace one H in PE
| by one Cl atom
|
|polyvinylidene chloride CPVC PVDC replace two H in PE
| by two Cl
|
|polystyrene PS replace H in PE by
| a benzene ring
|
|polyvinyl flouride PVF replace H in PE by
| F atom
|
|polyvinylidene flouride PVDF Kynar repace two H in PE
| by two F atoms
| *wire wrap insul.
|
|polymethyl methacrylate PMMA Plexiglas
| Lucite
| Perspex (British)
|
|polytetraflouroethylene PTFE Teflon replace all H in PE
| by F atoms
|
|polychlorotrifloroethylene PCTFE Kel-F replace 3 H in PE
| with F one with Cl
|
|polyamide 6 PA 6 Nylon 6
|
|polyamide 66 PA 66 Nylon 66
|
|polyamide-imide PAI Torlon
|
|polyurethane PUR
|
|polycarbonate PC Lexan
|
|Polyacetal POM Delrin
|
|polyethlene terephthalate PET Mylar co-polymer of PE
|
|cellulose actetate butyrate CAB Butyrate
|
|cellulose nitrate CN "Laquer" *typical constituent
| laquers
|
|acrylonitrile-butadiene-styrene ABS Cycopac ter-polymer of
| polystyrene
| * warning Jim Oliver says
| this name may apply to
| may many diff materials
|
|polyimide PI Kapton
|
|polyvinyl formal ? Formvar wire coating
|
|OK, there are zillions of others, but these are the ones I picked because I
|heard of them before...
|A couple of comments: Notice that there are many polymers which share a
|common structure with polyethylene, all that changes is replacing one or
|more of the H atoms in (PE) with some other atom or group of atoms. Then
|there are plastics which are called co-polymers or ter-polymers. A co-
|polymer is just taking two different monomers and sticking them together in
|a unit cell before polymerizing. Example: PET. Likewsie, a ter-polymer is
|just sticking three monomers into a unit cell and then polymerizing. A very
|common example is ABS which is used as sewar and drainage pipe.
|
|
|Now for the useful stuff. What are the electrical properties of some of
|these polymers? The most useful properties in my mind are the dielectric
|constant (or permittivity), the dielectric strenght, and the dissipation
|factor. All of these properties are dependent on temperature and frequency,
|but amazingly they also depend somewhat on the actual thickness of the
|material (as in thin films).
|
|----A couple of notes:
|All three properties mentioned above depend on frequency, but it turns out
|that for many non-polar polymers (ie PE) that the dielectric constant and
|dissipation factor do not depend much on frequency. I'll show some data for
|some of the plastics I could find. However, nobody seems to have data on
|the frequency dependence of the dielectric strength. It is best just to
|assume that this was done at DC.
|
|One property which is not well known for polymers is that the breakdown
|electric field or dielectric strength (VOLTS/INCH etc...) depends on the
|actual thickness of the film. Typically, as the film gets thinner, the
|dielectric strength goes up!!! For example, LDPE has a strength of 800volts
|per mil at 80 mils, but this goes up to 1400volts/mil at 20mils!!
|Polystyrene exceeds even this! I have personally done measurements on LDPE
|which show DC breakdowns of 3000Volts/mil at 2mils...
|
|Finally what is dissipation factor? It is a measure of how lossy the
|material is to alternating electric fields (as in Tesla coils and tank
|capacitors). It is defined by
|
| Ir
| --- = tangent (delta) = DF
| Ic
|
|where Ir is the resistive or dissipative current and Ic is the capacitive
|or displacement or reactive current. Delta is the phase angle between
|these currents (in the complex plane). Another expression which contains
|the same information is the Power Factor. For those familiar with this term
|they are related by:
|
| PF=DF/SQRT(1+DF^2)
|
|For small DF, then PF is approximately equal to DF. Obvisously, one would
|like to have DF as small as possible for low loss, high Q systems. In fact,
|for the purposes of approximation, the Q of a capacitor with low DF or PF
|is simply Q=1/DF=1/PF
|
|Absolute power lost in the system is:
|1. goes up with the square of the voltage gradient (electric field)
|2. goes up linearly with the volume of the dielectric in the field
| ( make your coil forms thin)
|3. goes up linearly with increasing dielectric constant
| ( don't use barium titanate primary caps!)
|4. generally increases with frequency
|
|
|polymer dielectric dielectric dissipation
| constant strength factor
| 50Hz / 1Mhz (Kv/cm) 50Hz / 1Mhz (x10^-3)
|-------- ----------- ----------- -----------
|LDPE 2.29 / 2.28 370 .15 / .08
|HDPE 2.35 / 2.34 -- .24 / .20
|PP 2.27 / 2.25 240 .40 / .50
|PVC-plasticized 4-8 / 4-5 270 80 / 120
|PS 2.5 / 2.5 200-300 .1-.4/.05-.4
|ABS 2.4-5/2.4-3.8 ~400 3-8 / 2-15
|PMMA 3.3-3.9/2.2-3.2 140 40-60/4-40
|POM 3.7 / 3.7 400 5 / 5
|PTFE 2.1 / 2.1 480 .2 / .2
|PCTFE 2.3-2.8/2.3-2.5 550 1 / 20
|PA-6 3.8 / 3.4 400 10 / 30
|PA-66 8 / 4 600 140 / 80
|PC 3.0 / 2.9 380 .7 / 10
|PET 4.0 / 4.0 420 2 / 20
|PI 3.5 / 3.4 560 2 / 5
|PUR-linear 5.8 / 4.0 >300 120 / 70
|PUR-thermoset 3.6 / 3.4 240 50 / 50
|PUR-thermoplas 6.6 / 5.6 300 30 / 60
|CAB 3.7 / 3.5 400 6 / 21
|Silicone 3.6 200 5-13 / 7
|
|
|Another comparison:
|
|polymer Dielectric constant / Dissipation Factor (x10^-3)
|
| 100 Hz 1000 Hz 1 Mhz 10 Mhz
|
|ABS 2.8/5 2.8/6 2.8/8 2.8/7
|PMMA 3.6/62 3.2/58 3.1/40 2.9/33
|PC 3.1/1 3.1/1.3 3.1/7 3.1/11
|PE 2.3/.1 2.3/.1 2.3/.1 2.3/.1
|PA-6 4.2/31 3.8/24 3.8/31 4.0/20
|
|**************************************************************************
|Magnet wire coatings from Phelps-Dodge:
|All data pertain to 18 gauge magnet wires
|Build= thickness of coating
|
|Coating What's it made of Build DC
|---------- ----------------- ----- breakdown
|
|Thermaleze-T (TZT) polyester-imide 2.8mils 11kV
|
|Armored Polythemaleze 3.05mils 11kV
|(APTZ) modified polyester&
| modified polyamide-imide
|
|Imideze (ML) Aromatic polyimide 2.9mils 12kV
|
|Formvar modified polyviynyl 3.0mils 10kV
| formal
|
|Sodereze modified polyurethane 2.9mils 8.5kV
|
|Nyleze Polyurethane 2.9mils 8.5kV
| & polyamide
|
|* Note: for the dielectric breakdown - These numbers are much bigger than
|for bulk materials because they are very thin coatings. As mentioned
|previously, the breakdown field increases as the thickness goes down.
|{a similar effect happens in gases and liquids and was studied by Paschen}
|
|Anyway, here's the dielectric constant/DF numbers for these matearials:
|
|Material Dielectric Const. / DF x 10^-3
|
| 1kHz 100kHz 1Mhz rating
|TZT 3.7/5.6 3.56/16.4 3.58/21.5 3rd
|
|APTZ 3.86/6.9 3.69/22.1 3.67/26.6 5th
|
|ML 3.34/0.9 3.3/5.7 3.36/9.8 2nd to
| teflon
|
|Formvar* 3.6/11.2 3.41/25.2 3.37/28.4 5th
|
|Soldereze 3.85/11.3 3.66/20.7 3.66/23.1 4th
|
|Nyleze 4.07/19.7 3.78/27.1 3.75/27.2 6th
|
|* This shows that Formvar is far from an ideal coating for magnet wire
|used in Tesla Coils when compared to something like Polyimide coatings
|
|
|References:
|1. Polymer Engineering Principles, Richard C. Progelhof and James Throne
|2. Plastics for Electronics, Martin T. Goosey
|3. Handbook of Plastics in Electronics, Dan Grzegorczyk and George Feineman
|4. SPI Plastics Engineering Handbook, Society of the Plasitics Industry
|5. Electrical Engineer's Handbook, Pender - 4th Edition
|6. Phelps-Dodge magnet wire product data
|
|Plastics sources: probably best to check your local distributors, but there
|is a mail order company called US Plastic Corp -at-800-537-9724 (catalog).
|They have rod/sheet/tubing of PVC, PMMA, CAB, POM, PE, PS. Of particlular
|note:
| Butyrate tubing up to 6 " diameter * lower loss coil forms
| Polystyrene tubing to 4 " dia * very low loss coil form
| 4x8ft LDPE sheet 60mil or other * Capacitors
|
|... If all else fails... Throw another megavolt across it!
|___ Blue Wave/QWK v2.12
|