USH1252H - Method of increasing dielectric break-down strengths of thermoplastic films - Google Patents
Method of increasing dielectric break-down strengths of thermoplastic films Download PDFInfo
- Publication number
- USH1252H USH1252H US07/888,227 US88822792A USH1252H US H1252 H USH1252 H US H1252H US 88822792 A US88822792 A US 88822792A US H1252 H USH1252 H US H1252H
- Authority
- US
- United States
- Prior art keywords
- thermoplastic resin
- films
- electrons
- ceresine wax
- act
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 230000015556 catabolic process Effects 0.000 title claims abstract description 16
- 238000000034 method Methods 0.000 title claims abstract description 13
- 229920001169 thermoplastic Polymers 0.000 title claims description 4
- 239000004416 thermosoftening plastic Substances 0.000 title claims description 4
- 239000004743 Polypropylene Substances 0.000 claims abstract description 43
- 229920001155 polypropylene Polymers 0.000 claims abstract description 43
- 229920005989 resin Polymers 0.000 claims abstract description 32
- 239000011347 resin Substances 0.000 claims abstract description 32
- JXTHNDFMNIQAHM-UHFFFAOYSA-N dichloroacetic acid Chemical compound OC(=O)C(Cl)Cl JXTHNDFMNIQAHM-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229960005215 dichloroacetic acid Drugs 0.000 claims abstract description 25
- 239000000843 powder Substances 0.000 claims abstract description 15
- -1 polypropylene Polymers 0.000 claims abstract description 12
- 229920005992 thermoplastic resin Polymers 0.000 claims description 9
- 229930195733 hydrocarbon Natural products 0.000 claims description 7
- 150000002430 hydrocarbons Chemical class 0.000 claims description 7
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 claims description 6
- MWPLVEDNUUSJAV-UHFFFAOYSA-N anthracene Chemical compound C1=CC=CC2=CC3=CC=CC=C3C=C21 MWPLVEDNUUSJAV-UHFFFAOYSA-N 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 5
- 239000002033 PVDF binder Substances 0.000 claims description 3
- 239000004698 Polyethylene Substances 0.000 claims description 3
- 229920001577 copolymer Polymers 0.000 claims description 3
- 229920000573 polyethylene Polymers 0.000 claims description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 3
- 239000004215 Carbon black (E152) Substances 0.000 claims 6
- MIZLGWKEZAPEFJ-UHFFFAOYSA-N 1,1,2-trifluoroethene Chemical group FC=C(F)F MIZLGWKEZAPEFJ-UHFFFAOYSA-N 0.000 claims 1
- 239000010408 film Substances 0.000 abstract description 27
- 239000010409 thin film Substances 0.000 abstract description 2
- 239000001993 wax Substances 0.000 description 23
- IVSZLXZYQVIEFR-UHFFFAOYSA-N m-xylene Chemical group CC1=CC=CC(C)=C1 IVSZLXZYQVIEFR-UHFFFAOYSA-N 0.000 description 16
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 12
- 239000003990 capacitor Substances 0.000 description 5
- 238000009835 boiling Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000001125 extrusion Methods 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229920006254 polymer film Polymers 0.000 description 2
- 125000003118 aryl group Chemical group 0.000 description 1
- 239000012185 ceresin wax Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000009965 odorless effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/10—Homopolymers or copolymers of propene
- C08L23/12—Polypropene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2323/10—Homopolymers or copolymers of propene
- C08J2323/12—Polypropene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L91/00—Compositions of oils, fats or waxes; Compositions of derivatives thereof
- C08L91/06—Waxes
Definitions
- This invention relates in general to a method of increasing the dielectric breakdown strength of thermoplastic films such as polypropylene (PP) films obtained from PP resin powder, and in particular to such a method wherein the PP resin powder is melt extruded into a PP film containing small amounts of ceresine wax uniformly distributed throughout the film.
- PP polypropylene
- High quality, high reliability, spirally wound, film capacitors for industrial applications require high quality dielectric films.
- Film limitations are generally due to poor insulation resistance and/or low dielectric breakdown strengths.
- V b Dielectric breakdown strengths, V b , of thin polymer films play a key role in determining ultimate attainable energy densities when these films are used as dielectrics in capacitor applications. This is because attainable energy densities of film capacitors increase as the square of the voltage across the capacitor. If V b of polymer films can be increased these films can be made thinner, or in other words, capacitors can be operated at higher voltages that translate into higher electrostatic energy densities.
- the general object of this invention is to provide a method of increasing the dielectric breakdown strength of thermoplastic films such as PP films obtained from PP resin powder.
- a more particular object of the invention is to provide such a method wherein the PP film is formed from the PP resin powder by melt extrusion.
- Polypropylene pellets are first ground to a powder using a 20 mesh delivery tube and an intermediate size grinding mill. In order to uniformly disperse ceresin wax in PP powder, the following procedure is used. Approximately 0.24 grams of Ceresine wax dissolved in 100 cc of m-xylene is added to approximately 24 grams of ground up PP resin and gently heated to the boiling point of m-xylene. Upon cooling the solution, a rubbery gel is formed. This gel contains m-xylene which must be removed. We chose not to remove m-xylene by simply boiling it off since the high temperatures cause PP to turn orange, probably due to oxidation.
- the odorless material is milled in the grinding mill using a 20 mesh delivery tube and sieved by vibrating it through a series of stainless steel sieves. Only those portions captured on 30 or 40 mesh sieves are used for extruding films whose dielectric properties are reported here.
- Translucent films approximately 25 microns thick and 40 mm wide, are melt extruded from PP resin powder with and without 1% or 2% added ceresine wax.
- the resin is extruded through a half inch (12.7 mm) lab scale, screw type, microextruder under the following conditions: length to diameter ratio 24:1, screw RPM: 50, die temperature: 450 F.; temperature of barrel zone 1: 350 F.; barrel zone 2: 400 F. and barrel zone 3: 450 F.
- PP resins containing 1% and 2% ceresine wax that have been melt extruded under identical conditions yield films having distinctly different thicknesses. This may be due to different flow characteristics of the resin containing added ceresine wax. Assuming that added ceresine wax increases the flow rates of resin through the extruder, more resin will be extruded per second and the resulting films will be thicker. This is indeed observed. For example, under identical extrusion conditions, films extruded from baseline PP resin are 11 micron thick; films extruded from resin containing 1% and 2% ceresine wax are 24 microns thick. In order to obtain measurements on comparable film thicknesses, the screw speed for extruding baseline resin has to be increased (from 50 RPM to 100 RPM). Voltage breakdown of these films is measured at room temperature by placing them between two pools of mercury and ramping the voltage at 500 volts per second until breakdown occurs and the film can not hold off additional voltage.
- Dielectric properties including breakdown voltages for films of approximately similar thicknesses containing 1% and 2% added ceresine wax are listed in Table 1.
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
Abstract
A method is provided of increasing the dielectric breakdown strength of tmoplastic films such as thin films of polypropylene obtained from polypropylene resin powder. The method involves melt extruding the resin powder with a small amount of ceresine wax.
Description
The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.
This invention relates in general to a method of increasing the dielectric breakdown strength of thermoplastic films such as polypropylene (PP) films obtained from PP resin powder, and in particular to such a method wherein the PP resin powder is melt extruded into a PP film containing small amounts of ceresine wax uniformly distributed throughout the film.
High quality, high reliability, spirally wound, film capacitors for industrial applications require high quality dielectric films. Film limitations are generally due to poor insulation resistance and/or low dielectric breakdown strengths.
Dielectric breakdown strengths, Vb, of thin polymer films play a key role in determining ultimate attainable energy densities when these films are used as dielectrics in capacitor applications. This is because attainable energy densities of film capacitors increase as the square of the voltage across the capacitor. If Vb of polymer films can be increased these films can be made thinner, or in other words, capacitors can be operated at higher voltages that translate into higher electrostatic energy densities.
The general object of this invention is to provide a method of increasing the dielectric breakdown strength of thermoplastic films such as PP films obtained from PP resin powder. A more particular object of the invention is to provide such a method wherein the PP film is formed from the PP resin powder by melt extrusion.
It has now been found that the aforementioned objects can be attained by melt extruding PP resin powder with a small amount of ceresine wax uniformly distributed throughout the resin. Melt extruding PP resin powder with 1 weight percent to 2 weight percent ceresine wax yields thin films with significantly increased dielectric breakdown strengths but with virtually no change in bulk dielectric properties. Ceresine wax is believed to act as a trapping center for electrons and by minimizing ionization of the host molecules, dielectric breakdown strength is increased. In lieu of PP resin powder, one can use other thermoplastic resin powders such as polyethylene, polyvinylidene fluoride or trifluorethylene or copolymers of these materials. In lieu of ceresine wax, one can use other hydrocarbons that can act as tripping centers for electrons, such as naphthalene, anthracene, or other long chain molecules such as paraffins.
Polypropylene pellets are first ground to a powder using a 20 mesh delivery tube and an intermediate size grinding mill. In order to uniformly disperse ceresin wax in PP powder, the following procedure is used. Approximately 0.24 grams of Ceresine wax dissolved in 100 cc of m-xylene is added to approximately 24 grams of ground up PP resin and gently heated to the boiling point of m-xylene. Upon cooling the solution, a rubbery gel is formed. This gel contains m-xylene which must be removed. We chose not to remove m-xylene by simply boiling it off since the high temperatures cause PP to turn orange, probably due to oxidation. In order to remove the m-xylene at lower temperatures, approximately 100 cc of ethyl ether is added to the gel and mixed well. We use ethyl ether as the extracting solvent since m-xylene is infinitely soluble in it, but ethyl ether does not dissolve either PP or ceresine wax. This mixture (PP, ceresine wax, m-xylene, ethyl ether) is then filtered through a fritted glass funnel in a sidearm distillation flask and the resulting white, fluffy material is vacuum dried at room temperature for at least three hours. After drying, the odorless material is milled in the grinding mill using a 20 mesh delivery tube and sieved by vibrating it through a series of stainless steel sieves. Only those portions captured on 30 or 40 mesh sieves are used for extruding films whose dielectric properties are reported here.
Translucent films, approximately 25 microns thick and 40 mm wide, are melt extruded from PP resin powder with and without 1% or 2% added ceresine wax. The resin is extruded through a half inch (12.7 mm) lab scale, screw type, microextruder under the following conditions: length to diameter ratio 24:1, screw RPM: 50, die temperature: 450 F.; temperature of barrel zone 1: 350 F.; barrel zone 2: 400 F. and barrel zone 3: 450 F.
PP resins containing 1% and 2% ceresine wax that have been melt extruded under identical conditions yield films having distinctly different thicknesses. This may be due to different flow characteristics of the resin containing added ceresine wax. Assuming that added ceresine wax increases the flow rates of resin through the extruder, more resin will be extruded per second and the resulting films will be thicker. This is indeed observed. For example, under identical extrusion conditions, films extruded from baseline PP resin are 11 micron thick; films extruded from resin containing 1% and 2% ceresine wax are 24 microns thick. In order to obtain measurements on comparable film thicknesses, the screw speed for extruding baseline resin has to be increased (from 50 RPM to 100 RPM). Voltage breakdown of these films is measured at room temperature by placing them between two pools of mercury and ramping the voltage at 500 volts per second until breakdown occurs and the film can not hold off additional voltage.
Dielectric properties including breakdown voltages for films of approximately similar thicknesses containing 1% and 2% added ceresine wax are listed in Table 1.
TABLE 1
______________________________________
Comparison of dielectric constants, dielectric losses
and breakdown voltages for films formed by melt extruding PP
resin containing 1% and 2% ceresine wax. PP refers to resin
that has been milled and melt extruded. PP* refers to baseline
PP resin that has been milled, mixed with m-xylene and
extracted with ethyl ether but not containing any added ceresine
wax. PP* + 1% wax refers to PP resin containing 1% added
ceresine wax as described in the text.
PP PP* PP* + 1% wax
PP* + 2% wax
______________________________________
Thickness, 25 26 19 24
microns
Dielectric
constant
@ 1000 Hz 2.19 2.13 2.12 2.10
@ 10,000 Hz
2.19 2.13 2.12 2.09
Dielectric loss
(× 10.sup.4)
@ 1000 Hz 6.6 6.1 4.1 5.1
@ 10,000 Hz
5.5 5.7 4.4 4.9
Breakdown
Voltage
KV/mil 5.2 5.4 7.7 8.0
______________________________________
Although dielectric properties are essentially unchanged for the different PP samples, their breakdown voltages are apparently quite different. The first important point to notice is that there is no appreciable difference in dielectric breakdown voltage between baseline PP resin and PP resin that has undergone the extraction procedure with ether. This shows that baseline PP resin is relatively pure and that no significant amount of removable impurities are present. Had the resin contained extractable impurities, films prepared from PP resin that had undergone extraction should have yielded significantly higher Vb values,
Addition of only 1% or 2% ceresine wax to PP resin yields a film having more than 40% increase in Vb. One explanation for this increase upon addition of ceresine wax may be the following. When high energy electrons are injected from contacting metal electrodes under D.C. fields, they become trapped around resonating aromatic rings of the added trapping molecule so rapidly that they do not reside in any one bond long enough to break it. Since these electrons become localized around the trap molecule, their mean free path is reduced and their energies are dissipated as heat without ionizing and/or causing damage to host molecules. Vb is therefore increased. All of this can be accomplished without substantially decreasing bulk dielectric constants or increasing bulk dielectric losses. The addition of wax may trap electrons and thereby strongly contribute to increased Vb.
We wish it to be understood that we do not desire to be limited to the exact details of construction as described for obvious modifications will occur to a person skilled in the art.
Claims (7)
1. Method of increasing the dielectric breakdown strength of thin thermoplastic films from a thermoplastic resin powder comprising melt extruding the resin powder with a small amount of a hydrocarbon that can act as a trapping center for electrons.
2. Method according to claim 1 wherein the thermoplastic resin is selected from the group consisting of polypropylene, polyethylene, polyvinylidene fluoride, and trifluoroethylene and copolymers of these materials and wherein the hydrocarbon that can act as a trapping center for electrons is selected from the group consisting of ceresine wax, naphthalene, anthracene, and paraffins.
3. Method according to claim 2 wherein the thermoplastic resin is polypropylene and wherein the hydrocarbon that can act as a trapping center for electrons is ceresine wax.
4. Method according to claim 3 wherein the small amount of ceresine wax is about one weight percent to about two weight percent.
5. A thin thermoplastic resin film with a small amount of a hydrocarbon that can act as a trapping center for electrons uniformly distributed throughout the resin films.
6. A thin thermoplastic resin film according to claim 5 wherein the thermoplastic resin film is selected from the group consisting of polypropylene, polyethylene, polyvinylidene fluoride, trifluorethylene, and copolymers of these materials and wherein the hydrocarbon that can act as a trapping center for electrons is selected from the group consisting of ceresine wax, naphthalene, anthracene and paraffins.
7. A thin thermoplastic resin film according to claim 6 wherein the thermoplastic resin is polypropylene and wherein the hydrocarbon that can act as a trapping center for electrons is ceresine wax.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/888,227 USH1252H (en) | 1992-05-26 | 1992-05-26 | Method of increasing dielectric break-down strengths of thermoplastic films |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/888,227 USH1252H (en) | 1992-05-26 | 1992-05-26 | Method of increasing dielectric break-down strengths of thermoplastic films |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| USH1252H true USH1252H (en) | 1993-11-02 |
Family
ID=25392792
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US07/888,227 Abandoned USH1252H (en) | 1992-05-26 | 1992-05-26 | Method of increasing dielectric break-down strengths of thermoplastic films |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | USH1252H (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3792304A1 (en) * | 2019-09-10 | 2021-03-17 | Solvay SA | Compositions and films comprising a vinylidene fluoride (co)polymer and an aromatic compound, and their preparation and uses |
| CN116218008A (en) * | 2022-12-13 | 2023-06-06 | 安徽省宁国市海伟电子有限公司 | Polypropylene metallized film and metallized film capacitor |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4551499A (en) | 1983-08-09 | 1985-11-05 | International Standard Electric Corporation | Polymeric dielectrics |
-
1992
- 1992-05-26 US US07/888,227 patent/USH1252H/en not_active Abandoned
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4551499A (en) | 1983-08-09 | 1985-11-05 | International Standard Electric Corporation | Polymeric dielectrics |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3792304A1 (en) * | 2019-09-10 | 2021-03-17 | Solvay SA | Compositions and films comprising a vinylidene fluoride (co)polymer and an aromatic compound, and their preparation and uses |
| CN116218008A (en) * | 2022-12-13 | 2023-06-06 | 安徽省宁国市海伟电子有限公司 | Polypropylene metallized film and metallized film capacitor |
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