Description:TECHNICAL FIELD
[0001] The present disclosure described herein, in general, relates to the production of an epoxy resin with high thermal conductivity.
[0002] In particular, the present disclosure relates to a process of producing a filler-modified epoxy resin for high thermal conductive electrical insulation application yielding a desired or targeted thermal conductivity and a filler-modified epoxy resin thereof.
BACKGROUND
[0003] Performance of various electrical devices like a transformer, motor and other high voltage insulation applications is determined by a combination of electromagnetic and thermal design. An improved thermal design used with an existing electromagnetic design can decrease the size of the electrical device, achieve higher output power for a given size of the electrical device, and extend the operational lifetime. Higher power density and longer operating lifetime both are required in many applications such as hybrid vehicle motors, aerospace or ship actuators and motors, and power generation equipment. Improved thermal design can reduce total weight and size of the motor for a required power and torque, and allow cost-saving because the amount of the copper, lamination steel, and even magnet material can be reduced.
[0004] The improvement in heat dissipation by the thermal systems in the electric devices has become a very important issue recently because operating currents and current densities in the electric devices show a consistent tendency to go up in the various electrical devices. When forced-air or liquid cooling is not enough to achieve the heat dissipation requirements, the thermal systems employ the use of thermally conductive epoxy resins that can be used effectively to help meet the design and heat dissipation requirements.
[0005] However, it is a fact that the low thermal conductivity of epoxy resins can be a blocking factor in the improvement of heat dissipation. To overcome the problem fillers are usually added to make up for such lack of thermal conductivity. Hitherto conventional materials, like calcium carbonate, clay or glass have been used as fillers. The thermal conductivity of a conventional epoxy resin is improved with the increase of the filler content and/or increase of thermal conductivity of the actual filler material. However, there is a certain limit of improvement of heat dissipation by the addition of the fillers in the epoxy resins, because the amount of fillers that can be added is limited by the practical requirements of fabrication process conditions and of other properties, and the high thermal conductivity effect of fillers reaches a ceiling beyond which there is no increase in the thermal conductivity of the epoxy. Further, an increase in the content of fillers in the epoxy resins incurs more cost.
[0006] In view of the above, there is a need to provide a solution wherein the addition of low content of the fillers is sufficient in yielding a desired or targeted thermal conductivity for high thermal conductive electrical insulation application and hence saving extra costs.
OBJECTS OF THE DISCLOSURE
[0007] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0008] It is a general or primary object of the present disclosure to provide a process of producing a filler-modified epoxy resin for high thermal conductive electrical insulation application and a filler-modified epoxy resin thereof that requires the addition of only a small quantity or content of the filler into the epoxy resin and hence save extra costs.
[0009] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.
SUMMARY
[0010] This summary is provided to introduce concepts related to a process of producing a filler-modified epoxy resin for high thermal conductive electrical insulation application and a filler-modified epoxy resin thereof. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0011] The subject matter disclosed herein relates to a process of producing a filler-modified epoxy resin for high thermal conductive electrical insulation application and a filler-modified epoxy resin produced by such a process. The process comprises preparing an emulsion of a nanostructured filler material by mixing the nanostructured filler material, a functionalization agent and a hardener taken in a predefined weight ratio with the help of a three-dimensional mixer of a commercial epoxy resin system, preparing a mixture by mixing an epoxy resin, a flexibilizer, and an accelerator taken in a predefined weight ratio with the help of a high shear mixer, mixing the emulsion and the mixture taken in a predefined weight ratio with the help of a vacuum mixer for a first predefined time range to obtain a filler-modified epoxy resin emulsion, casting the filler-modified epoxy resin emulsion in moulds and removing excess gases from the filler-modified epoxy resin emulsion through de-gassing, providing heat treatment to the moulds having the filler-modified epoxy resin emulsion in an air circulated oven at a first predefined temperature range for a second predefined time range to obtain a pre-cured filler-modified epoxy resin and providing heat treatment to the moulds having the pre-cured filler-modified epoxy resin in the air circulated oven at a second predefined temperature range for the second predefined time range to obtain a fully cured filler-modified epoxy resin.
[0012] In an aspect, the process comprises removing the fully cured filler-modified epoxy resin from the moulds and cooling them to room temperature.
[0013] In an aspect, the nanostructured filler material is selected from the group consisting of amorphous alumina, magnesium oxide, beryllium oxide, boron nitride, aluminium nitride, silicon nitride, silicon carbide, aluminium fluoride, and calcium fluoride.
[0014] In an aspect, the first predefined temperature range is 80 to 90°C and the second predefined temperature range is 140 to 150°C.
[0015] In an aspect, the first predefined time range is 0.5 to 1 hour and the second predefined time range is 6 to 8 hours.
[0016] In an aspect, the predefined weight ratio of the nanostructured filler material to the functionalization agent to the hardener is 0.5-5: 1-5: 90-100 and the predefined weight ratio of the epoxy resin to the flexibilizer to the accelerator is 90-100: 5-10: 1-5.
[0017] In an aspect, the predefined weight ratio of the emulsion to the mixture is 1:1.
[0018] In an aspect, the functionalization agent, hardener, epoxy resin, flexibilizer, and the accelerator is silane, carboxylic acid anhydride based liquid, bisphenol-A epoxy resin, polyglycol based liquid, and tertiary amine-based liquid, respectively.
[0019] In an aspect, the moulds are made of stainless steel.
[0020] Therefore, with the above-disclosed process, a desired or targeted thermal conductivity can be achieved with the help of the addition of only a small amount of the nanostructured filler material in an ordinary epoxy resin and hence saving extra costs unlike the conventional filler-modified epoxy resin wherein the filler material used is different and often requires a high quantity of its addition thereby increasing the costs.
[0021] To further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit the scope of the present subject matter.
[0022] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods/processes that are consistent with the subject matter as claimed herein, wherein:
[0024] FIG. 1 illustrates a process of producing a filler-modified epoxy resin for high thermal conductive electrical insulation application in accordance with the present disclosure.
[0025] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0026] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0027] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0028] The terminology used herein is to describe particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0029] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0030] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0031] In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practised. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
[0032] Hereinafter, a description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary, a variety of optional components are described to illustrate the wide variety of possible embodiments of the present disclosure.
[0033] Reference is made to FIG. 1 that shows a flowchart of a process 100 of producing a filler-modified epoxy resin for high thermal conductive electrical insulation application.
[0034] At step 102, the process 100 comprises preparing an emulsion of a nanostructured filler material by mixing the nanostructured filler material, a functionalization agent and a hardener taken in a predefined weight ratio with the help of a three-dimensional mixer of a commercial epoxy resin system. Before preparation of the emulsion, synthesis of the nanostructured filler material takes place. In an aspect, unlike the conventional filler materials like the calcium carbonate, clay or glass, the nanostructured filler material in the present disclosure is selected from the group consisting of amorphous alumina, magnesium oxide, beryllium oxide, boron nitride, aluminium nitride, silicon nitride, silicon carbide, aluminium fluoride, and calcium fluoride. In an aspect, the functionalization agent and the hardener used is silane which is chemically named as ?-glycidoxypropyltrimethoxysilane and carboxylic acid anhydride based liquid, respectively. In a further aspect, the predefined weight ratio of the nanostructured filler material to the functionalization agent to the hardener is 1-5: 1-5: 90-100. Table 1 provided below shows various properties of the nanostructured filler material that can be added into an epoxy resin.
Table 1: Various properties of the filler materials
S. No. PROPERTIES Chemical Formula Appearance Specific Surface Area (m2/g) Average Crystallite/Particle Size (Range) (nm) Tap Density (g/cc)
FILLER MATERIALS
1 Alumina Al2O3 Whitish 15-20 50--150 0.2-0.3
2 Magnesium Oxide MgO Whitish, Odorless 10-20 25-75 2.7-2.95
3 Beryllium oxide BeO Whitish 250-350 10-100 2.5-2.57
4 Boron Nitride BN Whitish 60-65 10-75 2.7-2.77
5 Aluminium Nitride AlN Whitish 50-65 10-100 3.10-3.25
6 Silicon Nitride Si3N4 Blackish 45-150 20-75 3.10-3.20
7 Silicon Carbide SiC Blackish 60-100 20-150 3.10-3.20
8 Aluminium Fluoride Al2F6 Whitish 10-20 10-75 1.90-3.20
9 Calcium Fluoride CaF2 Whitish 45-65 10-50 3.00-3.20

[0035] At step 104, the process 100 comprises preparing a mixture by mixing an epoxy resin, a flexibilizer, and an accelerator taken in a predefined weight ratio with the help of a high shear mixer. In an aspect, the predefined weight ratio of the epoxy resin to the flexibilizer to the accelerator is 90-100: 5-10: 1-5. In an aspect, the epoxy resin, flexibilizer, and the accelerator is bisphenol-A epoxy resin, polyglycol based liquid, and tertiary amine-based liquid, respectively.
[0036] At step 106, the process 100 comprises mixing the prepared emulsion and the mixture taken in a predefined weight ratio with the help of a vacuum mixer for a first predefined time range to obtain a filler-modified epoxy resin emulsion. In an aspect, the predefined weight ratio of the emulsion to the mixture is 1:1. In a further aspect, the first predefined time range is 0.5 to 1 hour. While mixing the emulsion and the mixture in the vacuum mixer, the pressure of vacuum ranges from 0.3 to 0.5 mbar. In a preferred aspect, the vacuum pressure is 0.3 mbar.
[0037] At step 108, the process 100 comprises casting the filler-modified epoxy resin emulsion so obtained in step 106, in moulds and removing excess gases from the filler-modified epoxy resin emulsion through de-gassing. In an aspect, the moulds are made of stainless steel. The inside of the moulds is applied with a certain releasing agent so that the final product can be removed easily from the moulds. In an aspect, the moulds are of different shapes and sizes depending on the area of application or use of the filler modified epoxy resin.
[0038] At step 110, the process 100 comprises providing heat treatment to the moulds having the filler-modified epoxy resin emulsion in an air circulated oven at a first predefined temperature range for a second predefined time range to obtain a pre-cured filler-modified epoxy resin. In an aspect, the first predefined temperature range is 80 to 90°C. In a preferred aspect, the first predefined temperature is 80°C.
[0039] At step 112, the process100 comprises providing heat treatment to the moulds having the pre-cured filler-modified epoxy resin in the air circulated oven at a second predefined temperature range for the second predefined time range to obtain a fully cured filler-modified epoxy resin. In an aspect, the second predefined temperature range is 140 to 150°C. In a preferred aspect, the second predefined temperature is 80°C. In an aspect, the predefined time range is 6 to 8 hours. After step 112, the process 100 further comprises removing the fully cured filler-modified epoxy resin from the moulds and cooling them to room temperature. In an aspect, all the apparatus or machines used to carry out the process are known and are not discussed and shown for the sake of brevity.
[0040] The filler-modified epoxy composites as per the present disclosure can be used as a superior electrical insulation material in the field of high voltage insulation applications for producing numerous insulation components for indoor and outdoor use, various bushings in gas-insulated switchgear (GlS), potential transformers, current transformers, and also for base insulators in the medium-voltage sector, in the production of insulators associated with outdoor power switches, measuring transducers, lead-through, and overvoltage protectors, in switchgear construction, in power switches, dry-type transformers, motors, etc.
Experimental Results
[0041] According to the present disclosure, a validation of the process was made by testing of the produced filler-modified epoxy resin for measurement of thermal conductivity properties as per ISO 22007-2:2015 (Plastics – Determination of thermal conductivity and thermal diffusivity – Part 2: Transient plane heat source (hot disc) method). Table 2 represents the thermal conductivity test profile of the filler-modified epoxy resin using different nanostructured filler materials in a different amount of weight percentage (wt.%) as compared to an ordinary epoxy resin wherein both the types of epoxy resins have been cast under identical conditions and dimensions.
Table 2: Comparison of thermal conductivity of ordinary epoxy resin and filler-modified epoxy resin with different percentage of composition in the epoxy resin
S. No Material Composition Thermal Conductivity, ? (W·m-1·K-1)
a) Ordinary Epoxy Resin 90-100% 0.18-0.19
b) Epoxy + Alumina
(% of Alumina)
1%
2%
3%
4%
5%
0.22
0.25
0.26
0.24
0.24
c) Magnesium oxide + epoxy (% of Magnesium oxide)
1%
2%
3%
4%
5%
0.21
0.21
0.22
0.22
0.22
d) Beryllium oxide + epoxy (% of Beryllium oxide)
1%
2%
3%
4%
5%
0.23
0.24
0.24
0.25
0.24
e) Boron nitride + epoxy (% of Boron nitride)
1%
2%
3%
4%
5%
0.43
0.48
0.49
0.42
0.44
f) Aluminium nitride + epoxy (% of Aluminium nitride)
1%
2%
3%
4%
5%
0.35
0.38
0.38
0.40
0.38
g) silicon nitride + epoxy (% of silicon nitride)
1%
2%
3%
4%
5%
0.41
0.41
0.44
0.42
0.42
h) silicon carbide + epoxy (% of silicon carbide)
1%
2%
3%
4%
5%
0.35
0.38
0.39
0.40
0.38
i) aluminium fluoride + epoxy (% of aluminium fluoride)
1%
2%
3%
4%
5%
0.30
0.31
0.33
0.31
0.30
j) calcium fluoride + epoxy (% of calcium fluoride)
1%
2%
3%
4%
5%
0.35
0.31
0.35
0.35
0.35

[0042] It can be concluded from Table 2 that a filler-modified epoxy resin produced by the process disclosed above has indeed a high thermal conductivity than an ordinary epoxy resin. Based on the requirement, different filler materials with different amount or composition can be used in the ordinary epoxy resin to get the desired or targeted thermal conductivity. The mechanical strength of the filler-modified epoxy resin is also good in comparison to the ordinary epoxy resin. As can be observed from the Table 2, the amount of any presently disclosed nanostructured filler material used to yield a targeted or desired thermal conductivity is also less that saves extra costs, unlike the conventional filler materials that are used in more quantity in the ordinary filler material. Thus the conventional filler-modified epoxy resin fails to disclose a less expensive epoxy resin for the manufacture of high voltage insulating products such as motor/transformers/dry-type transformer and other high voltage insulating applications with a high thermal conductivity that is mechanically strong and also meet the depicted high voltage insulation requirements.
TECHNICAL ADVANTAGES
[0043] The present disclosure provides a process of producing a filler-modified epoxy resin for high thermal conductive electrical insulation application and a filler-modified epoxy resin thereof that requires the addition of only a small quantity or content of the filler material into the epoxy resin and hence save extra costs unlike the conventional filler modified epoxy resin.
[0044] While the foregoing describes various embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The present disclosure is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the present disclosure when combined with information and knowledge available to the person having ordinary skill in the art.

Claims:1. A process of producing a filler-modified epoxy resin for high thermal conductive electrical insulation application, the process comprising:
preparing (102) an emulsion of a nanostructured filler material by mixing the nanostructured filler material, a functionalization agent and a hardener taken in a predefined weight ratio with the help of a three-dimensional mixer of a commercial epoxy resin system;
preparing (104) a mixture by mixing an epoxy resin, a flexibilizer, and an accelerator taken in a predefined weight ratio with the help of a high shear mixer;
mixing (106) the emulsion and the mixture taken in a predefined weight ratio with the help of a vacuum mixer for a first predefined time range to obtain a filler-modified epoxy resin emulsion;
casting (108) the filler-modified epoxy resin emulsion in moulds and removing excess gases from the filler-modified epoxy resin emulsion through de-gassing;
providing (110) heat treatment to the moulds having the filler-modified epoxy resin emulsion in an air circulated oven at a first predefined temperature range for a second predefined time range to obtain a pre-cured filler-modified epoxy resin; and
providing (112) heat treatment to the moulds having the pre-cured filler-modified epoxy resin in the air circulated oven at a second predefined temperature range for the second predefined time range to obtain a fully cured filler-modified epoxy resin.

2. The process as claimed in claim 1, comprising removing the fully cured filler-modified epoxy resin from the moulds and cooling them to room temperature.

3. The process as claimed in claim 1, wherein the nanostructured filler material is selected from the group consisting of amorphous alumina, magnesium oxide, beryllium oxide, boron nitride, aluminium nitride, silicon nitride, silicon carbide, aluminium fluoride, and calcium fluoride.

4. The process as claimed in claim 1, wherein the first predefined temperature range is 80 to 90°C and the second predefined temperature range is 140 to 150°C.

5. The process as claimed in claim 1, wherein the first predefined time range is 0.5 to 1 hour and the second predefined time range is 6 to 8 hours.

6. The process as claimed in claim 1, wherein the predefined weight ratio of the nanostructured filler material to the functionalization agent to the hardener is 1-5: 1-5: 90-100, and wherein the predefined weight ratio of the epoxy resin to the flexibilizer to the accelerator is 90-100: 5-10: 1-5.

7. The process as claimed in claim 1, wherein the predefined weight ratio of the emulsion to the mixture is 1:1.

8. The process as claimed in claim 1, wherein the functionalization agent, hardener, epoxy resin, flexibilizer, and the accelerator is silane, carboxylic acid anhydride based liquid, bisphenol-A epoxy resin, polyglycol based liquid, and tertiary amine-based liquid, respectively.

9. The process as claimed in claim 1, wherein the moulds are made of stainless steel.

10. A filler-modified epoxy resin for high thermal conductive electrical insulation application produced by the process as claimed in claims 1 to 9.