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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
|