KR102616752B1 - Mold for Polymer Composites by Using Inductive Heating of Dielectric Materials - Google Patents

Abstract

The present invention relates to a mold device for molding polymer composites, and in particular, to a mold device for molding polymer composites for molding polymer resins or polymer composites by utilizing the induced heat generation of carbon nanomaterials contained in the mold body.

Description

Mold for polymer composites using inductive heating of dielectric materials {Mold for Polymer Composites by Using Inductive Heating of Dielectric Materials}

The present invention relates to a mold device for molding polymer composites, and in particular, to a mold device for molding polymer composites that can mold polymer resins or polymer composites by utilizing the induced heat generation of carbon nanomaterials contained in the mold body.

Recently, with the trend of high-strength and lightweight materials throughout the industry, there are cases of applying fiber composite materials made of not only high-strength metal materials or lightweight non-ferrous metal materials, but also fiber reinforced plastics (FRP). It has become frequent.

In particular, fiber composite materials are generally provided in the form of prepregs in which liquid synthetic resin is infiltrated into fiber reinforcement, and when subjected to heat and pressure within a mold, they have excellent mechanical and thermal properties and can be used to create high-strength, lightweight composite parts. Suitable for production.

Fiber reinforcement materials used as raw materials for the above fiber composite materials are mainly aramid fibers such as glass fiber, carbon fiber, and Kevlar, and boron, which is less frequently used. Ceramic fibers such as boron fiber and silicon carbide are also used.

In addition, liquid synthetic resins that penetrate into fiber reinforcement and are used as base materials are generally epoxy resin and unsaturated polyester resin, and for high temperature use, phenol resin and polyimide are generally used. Thermosetting resins such as polyimide resin are used, and recently, thermoplastic resins are also being used.

In this way, fiber composite materials, which have not only high strength and rigidity but also lightweight properties through an efficient combination of materials, are replacing existing materials by effectively utilizing their properties, and are used in aerospace, automobiles, sports, and industrial machinery. , It is applied in various industrial fields such as medical devices, military supplies, construction, and civil engineering materials.

In the case of metal molds used to mold these polymer composites, most of them were heated to the molding temperature through heating by the heat generated by the electric resistance using a heating cartridge.

As a prior art related to this, Korean Patent Publication No. 10-2014-0148081 (publication date: December 31, 2014) manufactures a fiber-reinforced prepreg by impregnating fibers into a low-temperature curing epoxy resin composition, and laminates them to form a shape. A technology for molding polymer composite materials by supplying heat energy from a heating mold using a heater or a heating wire inserted into the mold has been known.

However, when molding polymer materials or polymer composites using a metal mold, the difference in thermal expansion coefficient between the molded product and the metal mold is high, so internal stress is formed in the molded product during the molding process. In this case, internal stress relief after final molding leads to distortion of the product and separation between layers, which leads to product defects.

In addition, the molding of fiber-reinforced polymer composites is basically manufactured through a molding cycle of heating, cooling, and reheating of a metal mold. In particular, in the case of fiber-reinforced polymers using thermoplastic polymer materials as a matrix, the glass transition of the material occurs during the cooling process. The molding cycle is completed only when it is cooled to a temperature below that temperature.

Accordingly, the conventional heating method, such as a heating cartridge or steam method, has a low energy conversion rate because heat transfer occurs due to collision of molecules. In particular, during the heat transfer process, not only is it impossible to heat the local area of the metal mold (the contact area between the molding and the metal mold), but unnecessary areas are heated and cooled at the same time, which prolongs the molding cycle, which reduces economic efficiency.

Meanwhile, in the case of carbon nanotubes (CNTs), a type of dielectric material, several studies have shown that when carbon nanotubes (CNTs) are exposed to microwaves, their high dielectric loss (bound charge) and conductivity (free electrons) decrease. Due to this, strong energy absorption was observed, resulting in strong heating, degassing and light emission. In one study, single-walled carbon nanotubes (CNTs) exposed to microwave irradiation generated local temperatures reaching ~2000°C.

Additionally, as a result of our research on topics related to CNT/polymer bonding by microwave irradiation, we demonstrated the feasibility of microwave processing for welding thin layers of multi-walled carbon nanotubes (CNTs) to plastic parts. Additionally, researchers have shown that microwave radiation can provide many desirable functions in other areas of polymer and composite processing.

Therefore, this research team used a mold made of a polymer composite material with a similar thermal expansion coefficient as the target molded product to improve the quality of the final molded product, and also shortened the molding process time by selectively heating and processing local areas of the molded product. A mold for molding made of a polymer composite containing carbon nanomaterials that generates induced heat by high-frequency electromagnetic radiation was developed.

Korean Patent Publication No. 10-2014-0148081 (publication date: December 31, 2014)

The main purpose of the present invention is to solve the above-mentioned problems, by introducing a dielectric material that generates induced heat by high-frequency electromagnetic radiation into a mold without using an external heat source such as a heating cartridge, thereby producing high-quality polymer materials or The object is to provide a mold device for molding polymer composites capable of molding processes for polymer composites.

In order to achieve the above object, the present invention includes a first insulating material into which an induction coil is inserted; a first mold body; an upper part and a second mold body arranged sequentially; and a second insulating material into which an induction coil is inserted. It includes a lower part in which a sequentially arranged lower part is formed, wherein the first and second mold bodies are made by mixing polymer resin and carbon nanomaterial with carbon fiber chemically bonded with carbon nanomaterial. It is manufactured by impregnating the prepared polymer mixture and then curing the impregnated material. The carbon nanomaterial chemically bonded to the carbon fibers in the first and second mold bodies is less than 1 wt% based on the polymer resin, and is directly mixed with the polymer resin. The carbon nanomaterial is less than 1 wt% relative to the polymer resin, and the mold for forming a polymer composite is characterized in that the molding temperature of the polymer composite is set by inductively heating the first mold body and the second mold body with high-frequency electromagnetic radiation ( Mold) device is provided.

In a preferred embodiment of the present invention, the insulating material may be a ceramic component.

In a preferred embodiment of the present invention, the carbon fibers in the mold body may be surface modified.

In a preferred embodiment of the present invention, the surface of the carbon fiber in the mold body can be modified by sizing or flame treatment.

In a preferred embodiment of the present invention, the carbon nanomaterial in the mold body introduces a hydrophilic functional group to the surface, and the carbon nanomaterial prepared in the form of water dispersion is applied and dried on the carbon fiber, so that the carbon fiber and the carbon nanomaterial are chemically bonded. bonds can be formed.

In a preferred embodiment of the present invention, the carbon nanomaterial in the mold body may include any one or more selected from pulverized carbon fiber, carbon nanotube, carbon black, and graphene.

In a preferred embodiment of the present invention, the carbon nanomaterial chemically bonded to the carbon fiber in the mold body is less than 0.5 wt% with respect to the polymer resin, and the carbon nanomaterial directly mixed with the polymer resin is 0.5 wt% with respect to the polymer resin. It may be less than %.

In a preferred embodiment of the present invention, the polymer resin in the mold body may include one or more selected from Novolac-modified epoxy, aromatic amine, and bismaleimide.

In another preferred embodiment of the present invention, the present invention provides a method for molding a polymer composite material, characterized in that forming a thermoplastic polymer composite or thermosetting polymer composite by generating induced heat by high-frequency electromagnetic radiation in the mold device for molding the polymer composite. do.

In a preferred embodiment of the present invention, the polymer composite containing the thermoplastic polymer is heated with high-frequency electromagnetic radiation to mold the polymer composite at the melting point (Tm), or the polymer composite containing the curable polymer is heated with high-frequency electromagnetic radiation. Polymer composites can be molded at the curing point (Tc).

In a preferred embodiment of the present invention, the molding temperature by the induced heat generation may be in the range of 200 to 1000 ˚C.

In a preferred embodiment of the present invention, the high frequency electromagnetic radiation may be in the frequency range of 50 - 300 kHz.

The mold device for molding polymer composites according to the present invention enables rapid heating or rapid cooling by induced heat generation by introducing a dielectric material that generates induced heat generation by high-frequency electromagnetic radiation, and has the effect of improving economic efficiency by shortening the molding cycle. can be expected.

In addition, the mold device for molding polymer composites according to the present invention uses a durable polymer as a polymer resin to reduce the weight of the mold and improve durability by maintaining excellent mechanical properties.

Figure 1 shows the components and driving flow of the high-frequency electromagnetic field generating equipment used in the present invention.
Figure 2 is a schematic diagram of a mold device for molding a polymer composite material to which the mold body according to the present invention is applied.
Figure 3 is a schematic diagram of an induction coil array inserted into an insulating material in a mold device for molding polymer composites.
Figure 4 is a side view of an induction coil array inserted into an insulating material in a mold device for molding polymer composites.
Figure 5 is an SEM photograph observing the surface of a carbon fiber filament anchored with carbon nanomaterials (MWCNT) in a mold body according to the present invention.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

Throughout the specification of the present application, when a part "includes" a certain component, this means that it may further include other components rather than excluding other components unless specifically stated to the contrary.

The present invention includes: a first insulating material into which an induction coil is inserted; A first mold body; The upper part and the second mold body arranged sequentially; And a second insulating material into which the induction coil is inserted; It includes a lower part in which these are sequentially arranged,

The mold body is manufactured by impregnating carbon fibers chemically bonded with carbon nanomaterials with a polymer mixture prepared by mixing a polymer resin and carbon nanomaterials and then curing the impregnated material, and chemically bonding the carbon fibers in the mold body. The combined carbon nanomaterial is less than 1 wt% with respect to the polymer resin, and the carbon nanomaterial directly mixed with the polymer resin is less than 1 wt% with respect to the polymer resin, and the first mold body and the second mold body are induced by high-frequency electromagnetic radiation. Provided is a mold device for molding polymer composites, which is characterized in that the molding temperature of the polymer composite is set by heating.

In the mold device for molding a polymer composite, a molding object made of polymer resin or polymer composite is positioned between the first mold body and the second mold body, and the first molding object is generated by high-frequency electromagnetic radiation generated from an induction coil inserted into the first insulation material. The molded object is formed due to induction heat generated in the mold body and induction heat generated in the second mold body due to high-frequency electromagnetic radiation generated in the induction coil inserted into the second insulating material.

In a preferred embodiment, the first and second insulators into which the induction coil is inserted prevent the induced heat generated by high-frequency electromagnetic radiation from being dissipated to the outside, and the material of the insulator may be a ceramic component, and specifically, aluminum oxide. , it may be any one selected from silicon oxide, silicon carbide, and zirconium oxide, and ceramic composites containing high permeability sintered ferrite, amorphous alloy, permalloy, etc. to prevent reduction in induction heating efficiency due to external outflow of electromagnetic fields may be used. You can.

Figure 3 below is a rough diagram of the arrangement of the induction coil inserted inside the insulation material. As the direction of electromagnetic field formation is determined depending on the direction of the current from the power source, the current direction is divided into In and Out. By doing so, cancellation of eddy currents due to interference of electromagnetic fields can be prevented.

Figure 4 below shows a side view of the insertion of the induction coil shown in Figure 3, and shows the division of current into In and Out.

In addition, as a preferred embodiment, the surface of the carbon fiber in the first mold body or the second mold body can be modified to improve the material properties of the mold body, such as strength, elastic modulus, lightness, and stability.

Carbon fiber has a weak interfacial bonding force due to the low activity and smoothness of the fiber surface, so to prevent damage to carbon fiber due to friction during the manufacturing process and to improve bonding strength with the surface of carbon nanomaterials, such as sizing or flame treatment of carbon fiber, etc. It is preferable that the fiber surface is modified through the process.

In other words, the surface treatment process for carbon fibers aims to effectively introduce carbon nanomaterials into carbon fibers by inducing a chemical bond between the carbon fibers and the carbon nanomaterials added to the polymer composite.

The main component of the sizing agent used in the sizing process is preferably an amino functional silane, such as 3-Aminopropyltriethoxysilane, 3-Aminopropylmethoxydiethoxysilane, amino Aminopropylmethoxydimethoxysilane, aminoethylaminopropyltrimethoxysilane (3-(2-Aminoethyl)aminopropyl]trimethoxysilane), etc.; Sulfur functional silanes, such as Bis(3-(triethoxysilyl)propyl) tetrasulfide, Mercaptopropyltrimethoxysilane, Mercaptopropyltriethoxysilane ( Mercaptopropyltriethoxysilane), etc.; Epoxy functional silanes, such as Glycidoxypropyltrimethoxysilane, Glycidoxypropyltriethoxysilane, Glycidoxypropylmethyldiethoxysilane, glycidoxypropylmethyl Dimethoxysilane (Glycidoxypropylmethlydimethoxysilane), etc.; Vinyl functional silane, for example, vinyltrimethoxysilane, vinyltriethoxysilane, etc.; at least one selected from the group consisting of vinyl functional silane, more preferably epoxy functional silane. You can use it.

The exposure time of the carbon fiber to the sizing bath is preferably in the range of 10 seconds to 10 minutes. If it is less than 10 seconds, the amount of sizing on the surface of the carbon fiber is small due to insufficient diffusion and reaction time of the solution by immersion, which is undesirable. If it exceeds 10 minutes, it is difficult to use as a reinforcing agent due to hydrolysis and phase separation inside the solution.

In addition, the flame treatment exposes the carbon fiber to a premixed flame in order to improve the wettability of the carbon fiber or the adhesion between the carbon fiber and the carbon nanomaterial, thereby breaking the molecular chains on the surface of the fiber and adding polar functional groups to the carbon fiber. The surface can be modified to be hydrophilic.

In a preferred embodiment, the carbon nanomaterial in the first mold body or the second mold body introduces a hydrophilic functional group to the surface, and the carbon nanomaterial prepared in water-dispersed form is applied to the carbon fiber and dried to form the carbon fiber and carbon. Nanomaterials can form chemical bonds.

The carbon nanomaterial is a material that generates induced heat due to high-frequency electromagnetic radiation, and can stably provide a heating function for the forming mold by being evenly dispersed within the mold body through a chemical bond with carbon fiber.

Here, the carbon nanomaterial may be any one or more selected from pulverized carbon fiber, carbon nanotube, carbon black, and graphene, but is not limited thereto.

At this time, surface treatment of carbon nanomaterials can be performed by using an acidic aqueous solution such as dilute nitric acid or sulfuric acid, or by using an oxidizing agent such as an aqueous hydrogen peroxide solution.

In addition, the method of introducing hydrophilic functional groups into carbon nanomaterials involves introducing hydrophilic functional groups to the particle surface using an oxidizing agent such as aqueous hydrogen peroxide after the primary oxidation reaction using an acidic aqueous solution such as dilute nitric acid and sulfuric acid aqueous solution. You can.

Carbon nanomaterials surface-modified with hydrophilic functional groups are prepared as carbon nanomaterial dispersions in the form of water dispersions, and then the carbon nanomaterial dispersions are applied and dried on unsurface-treated carbon fibers or surface-modified carbon fibers to obtain carbon nanomaterials and carbon. Forms chemical bonds in the fiber.

At this time, the sum of the weight of carbon nanomaterials in the carbon nanomaterial dispersion prepared in the form of water dispersion may preferably be less than 10 wt.%, and preferably less than 5 wt.%, based on the total carbon nanomaterial dispersion.

In other words, the carbon nanomaterials in the polymer composite form a chemical bond to the carbon fibers and are dispersed together with the carbon fibers, so they can be highly dispersed at a high content. The high dispersion of the carbon nanomaterials in the mold body is then used as a polymer resin or polymer. In the composite molding process, high-quality polymer moldings or polymer composite moldings can be manufactured by effectively controlling the temperatures of the first mold body and the second mold body.

In addition, the mold device for molding polymer composites according to the present invention not only uses carbon nanomaterials chemically bonded to carbon fibers in the mold body (first mold body, second mold body), but also carbon nanomaterials directly mixed with polymer resin. By including it, it is characterized by containing carbon nanomaterials in high content and high dispersion.

Specifically, the first mold body or the second mold body preferably contains less than 1 wt% of carbon nanomaterials chemically bonded to the carbon fibers relative to the polymer resin, and carbon nanomaterials directly mixed with the polymer resin are polymers. It may contain less than 1 wt% relative to the resin, and more preferably, the carbon nanomaterial chemically bonded to the carbon fiber is less than 0.5 wt% relative to the polymer resin, and the carbon nanomaterial mixed directly into the polymer resin is less than 0.5 wt% relative to the polymer resin. It may be less than 0.5wt%.

Here, the polymer mixture can be prepared using a mechanical mixing method to introduce carbon nanomaterials into the polymer resin.

Here, the polymer resin preferably contains at least one selected from thermosetting polymer resins such as Novolac-modified epoxy, aromatic amine, and bismaleimide, which contain a large amount of benzene rings and have low flow of molecular chains. These polymer resins have high temperature durability. Because of its properties, the mold device for forming final polymer composites can exhibit excellent mechanical properties and durability in a processing environment of 300°C.

Thereafter, the carbon nanomaterial is impregnated with a polymer mixture prepared by mixing the carbon fiber chemically bonded with the polymer resin and the carbon nanomaterial, and then the impregnated material is cured to produce a mold body.

The process of impregnating the carbon fibers chemically bonded with the carbon nanomaterial into the polymer mixture resin is not particularly limited, and for example, a resin injection method using a vacuum environment or an impregnation method through hand layup can be used.

The current applied to the carbon nanomaterial in the mold device for molding polymer composites according to the present invention is an induced current due to an externally applied induced electromotive force, that is, an external coil surrounding the carbon nanomaterial without directly contacting it, e.g. For example, when high-frequency induced electromotive force is applied to a conductive metal coil such as a copper coil, an induced heating phenomenon occurs in the carbon nanomaterial due to the induced current.

Therefore, an induced current is generated due to the high-frequency induced electromotive force applied to the mold device for molding a polymer composite according to the present invention, and Joule heat is generated from the carbon nanomaterial in the polymer composite due to this induced current, making it possible to heat the mold body. .

In addition, the present invention provides a polymer composite molding method characterized in that thermoplastic polymer composite or thermosetting polymer composite is formed by generating induced heat by high-frequency electromagnetic radiation in the mold device for molding polymer composite.

At this time, when a thermoplastic polymer resin is used, the polymer composite can be molded at the melting point (Tm) through induced heating by high-frequency electromagnetic radiation. Additionally, when a thermosetting polymer resin is used, the polymer composite can be subjected to high-frequency electromagnetic radiation. It is possible to mold polymer composites at the hardening point (Tc) through induced heat generation.

As an example, the molding temperature due to the induced heat generation may specifically range from 120 to 400˚C.

Specifically, when manufacturing epoxy resin-based composites, the molding temperature is preferably in the range of 120 to 150˚C, and polyethylene (PE), polypropylene (PP), and polyacrylate (PA) )-based composites, the molding temperature is preferably in the range of 120 ~ 250˚C, and when manufacturing polyetheretherketone (PEEK) and polyphenylene sulfide (PPS)-based composites, the molding temperature is is preferably in the range of 120 to 400˚C.

It is preferable that the induced electromotive force applied externally is a high-frequency current in the frequency range of 50 to 300 kHz. The frequency of the high-frequency current determines the penetration depth of the induced current, so it is set according to the size and thickness of the molded object. If the size of the molded object is large or thick, it is desirable to use a low frequency to deepen the penetration depth of the induced current.

As the specific parts of the present invention have been described in detail above, it is clear to those skilled in the art that these specific techniques are merely preferred embodiments and do not limit the scope of the present invention. will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

101: mold body
102: insulation
103: induction coil
104: Molding object

Claims (12)

A first insulating material into which an induction coil is inserted; a first mold body; an upper part and a second mold body arranged sequentially; And a second insulating material into which the induction coil is inserted; includes a lower portion in which these are sequentially arranged,
The first and second mold bodies are manufactured by impregnating carbon fibers chemically bonded with carbon nanomaterials with a polymer mixture prepared by mixing a polymer resin and carbon nanomaterials, and then curing the impregnated material,
The carbon nanomaterial chemically bonded to the carbon fibers in the first and second mold bodies is less than 1 wt% with respect to the polymer resin, and the carbon nanomaterial directly mixed with the polymer resin is less than 1 wt% with respect to the polymer resin,
A mold device for molding a polymer composite, characterized in that the molding temperature of the polymer composite is set by inductively heating the first mold body and the second mold body with high-frequency electromagnetic radiation.
According to paragraph 1,
A mold device for molding a polymer composite, wherein the insulating material is a ceramic component.
According to paragraph 1,
A mold device for molding polymer composites, wherein the carbon fibers in the mold body are surface modified.
According to paragraph 3,
A mold device for molding polymer composites, characterized in that the surface of the carbon fiber in the mold body is modified by sizing or flame treatment.
According to paragraph 1,
The carbon nanomaterial in the mold body is a polymer characterized in that a hydrophilic functional group is introduced to the surface, and the carbon nanomaterial prepared in water dispersion is applied to the carbon fiber and dried to form a chemical bond between the carbon fiber and the carbon nanomaterial. Mold device for forming composite materials.
According to paragraph 1,
A mold device for molding polymer composites, wherein the carbon nanomaterial in the mold body includes at least one selected from pulverized carbon fiber, carbon nanotube, carbon black, and graphene.
According to paragraph 1,
Polymer composite molding, characterized in that the carbon nanomaterial chemically bonded to the carbon fiber in the mold body is less than 0.5wt% with respect to the polymer resin, and the carbon nanomaterial directly mixed with the polymer resin is less than 0.5wt% with respect to the polymer resin. Mold device.
According to paragraph 1,
A mold device for molding polymer composites, wherein the polymer resin in the mold body contains at least one selected from Novolac-modified epoxy, Aromatic amine, and Bismaleimide.
A polymer composite molding method characterized by forming a thermoplastic polymer composite or thermosetting polymer composite by generating induced heat by high-frequency electromagnetic radiation in the mold device for molding a polymer composite of claim 7.
According to clause 9,
The polymer composite containing the thermoplastic polymer is heated with high-frequency electromagnetic radiation to form the polymer composite at the melting point (Tm),
A polymer composite molding method characterized by heating the polymer composite containing the curable polymer with high-frequency electromagnetic radiation to mold the polymer composite at the curing point (Tc).
According to clause 9,
A polymer composite molding method, characterized in that the molding temperature due to the induced heat is in the range of 200 to 1000 ˚C.
According to clause 9,
A method of molding a polymer composite material, characterized in that the high-frequency electromagnetic radiation has a frequency in the range of 50 - 300 kHz.