WO2024078234A1

WO2024078234A1 - Heater, preparation method therefor, and application thereof

Info

Publication number: WO2024078234A1
Application number: PCT/CN2023/118280
Authority: WO
Inventors: 谢宗蕻; 袁培毓; 唐超; 王海瑞
Original assignee: 中山大学
Priority date: 2022-10-13
Filing date: 2023-09-12
Publication date: 2024-04-18
Also published as: CN115334701B; CN115334701A

Abstract

The present invention belongs to the technical field of energy conversion materials, and particularly relates to a heater, a preparation method therefor, and an application thereof. The heater comprises, successively stacked, a first insulating layer, a functional layer, and a second insulating layer; the functional layer is a graphene heating film, and the graphene heating film is formed via the screen printing of a water-based graphene conductive slurry containing 0.5-3wt% graphene powder, 0.8-10wt% dispersing agent, and 10-40wt% organic resin, with the remainder being water. The heater of the present invention has advantages such as being light, thin and high strength, low voltage, high efficiency, low energy consumption, of having a long service life, being highly reliable, and having a high degree of integration, and can relatively easily achieve large-area high-curvature conformal heating.

Description

A heater and its preparation method and application

Technical Field

The present invention belongs to the technical field of energy conversion materials, and in particular relates to a heater and a preparation method and application thereof.

Background technique

Heaters are widely used in daily life and various industrial production. Current heaters are mainly electric heaters, which use electric energy to achieve heating effects. Traditional heaters often use heating elements such as resistance wires and thermistors to convert electrical energy into thermal energy. They generally have problems such as heavy weight, large volume, high energy consumption, low reliability, poor heating uniformity, and it is difficult to achieve heating requirements for large areas and large curvatures. In addition, in existing electric heaters, the heat source and the heat radiator are often not an integral structure. During the heat transfer process, a large amount of heat will be lost, the thermal energy utilization efficiency is low, and the power consumption is high.

To overcome the above problems, relevant research uses graphene film as a heating element to make a graphene composite heater. At present, the heaters using graphene materials as heating elements generally have the following problems: (1) Existing graphene coating heaters are often packaged by thermoplastic forming, which are large in size and weight, and are greatly affected by working environment conditions (temperature, humidity, etc.). The heating effect is unstable and fluctuates within a large range. Even with intelligent temperature control, it is difficult to achieve a good heating effect. (2) The graphene film heaters involved in the existing publicly published literature and patents only describe the ideal structural configuration, and do not comprehensively consider the rationality of the heating structure in combination with the manufacturing method and heating effect. In engineering applications, for the application requirements of light weight and thin-walled structures, many ideal structural configurations cannot be successfully manufactured, or after being manufactured, the heating structure as a whole cannot achieve a high electric-to-heat conversion efficiency, and the actual engineering application is of little significance. (3) Existing graphene film heaters can only be used in the temperature range below 100°C. At higher temperatures, the surface of the film heater is prone to oxidation reaction, and the heating power will decay, which cannot meet the use requirements. (4) Existing graphene film heaters are often flexible heaters that cannot be used as load-bearing structures, and the film is easily damaged under external loads (such as external impact loads).

Summary of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first aspect of the present invention is to provide a heater, which has the advantages of being light, thin, high-strength, low-voltage, high-efficiency, low-energy consumption, long life, high reliability, high integration, etc., and can easily achieve large-area and large-curvature conformal heating.

The second aspect of the present invention is to provide a method for preparing the heater, which integrates the various layers of the heater into a composite structure through a hot pressing process, thereby meeting the requirements of practical engineering applications.

A third aspect of the present invention is to provide use of the heater.

Specifically, the present invention adopts the following technical solutions:

The first aspect of the present invention is to provide a heater, which includes a first insulating layer, a functional layer, and a second insulating layer stacked in sequence, wherein the functional layer is a graphene heating film, and the graphene heating film is formed by screen printing an aqueous graphene conductive paste containing 0.5-3wt% graphene powder, 0.8-10wt% dispersant and 10-40wt% organic resin, with the remainder being water.

Graphene can adsorb various atoms and molecules for separation, and has good electrothermal conversion efficiency and thermal conductivity. The formation method of the graphene film has an important influence on its heating performance. The present invention uses water-based graphene conductive slurry to form a graphene heating film by screen printing, and uses it as a key heating component of the heater, so that when the temperature rises, the components in the graphene heating film produce molecular adhesion different from other film-forming methods, thereby affecting the heating effect of the heater. After testing, the heater of the present invention is efficient and stable, the heating effect is less affected by temperature, and it has the advantages of light, thin, high strength, low voltage, high efficiency, low energy consumption, long life, high reliability, high integration, etc., and can easily achieve large-area and large-curvature conformal heating.

In some embodiments of the present invention, the aqueous graphene conductive slurry comprises 0.5-3wt% graphene powder, 0.8-10wt% dispersant and 30-40wt% organic resin, and the balance is water. The graphene heating film of the functional layer is mainly composed of graphene and is designed for high electrothermal conversion efficiency.

In some examples of the present invention, the aqueous graphene conductive slurry comprises 2-3 wt% of graphene powder, 5-10 wt% of dispersant and 30-40 wt% of organic resin, and the balance is water.

In some examples of the present invention, in the water-based graphene conductive paste, the dispersant includes any one or more of PVP and BYK-2150; the organic resin includes any one or more of alkyd resin, acrylic resin, epoxy resin, polyester resin, and amino resin. The water-based graphene conductive paste uses water as a solvent, which not only affects the adhesive force of each component of the graphene heating film, thereby affecting the heating effect, but also has the advantage of being green and environmentally friendly.

In some embodiments of the present invention, the number of meshes of the screen printing is 120-220 meshes, preferably 150-200 meshes. After screen printing, the film is cured at 130-180° C. (preferably 140-160° C.) for 10-50 minutes, preferably 20-40 minutes. The film thickness formed by this parameter is generally ≤2 mm.

In some examples of the present invention, the heater also includes a plurality of composite plies and a heat-averaging layer. The heater includes a first composite ply, a first heat-averaging layer, a second composite ply, a first insulating layer, a functional layer, a second insulating layer, a third composite ply, a second heat-averaging layer, and a fourth composite ply stacked in sequence. The first composite ply, the second composite ply, the third composite ply, and the fourth composite ply are independently selected from fiber-reinforced resin-based composite layers.

In some examples of the present invention, the first composite material layer, the second composite material layer, the third composite material layer, and the fourth composite material layer independently include any one of glass fiber, carbon fiber, basalt fiber, and aramid fiber. or multiple fiber-reinforced resin-based composite materials. The first composite material ply, the second composite material ply, the third composite material ply, and the fourth composite material ply can play a role in structural reinforcement. Preferably, the first composite material ply, the second composite material ply, the third composite material ply, and the fourth composite material ply have the same size.

In some embodiments of the present invention, the first insulating layer and the second insulating layer are independently selected from any one of a polyimide (PI) film and a composite material layer with an insulating function (such as a fiber-reinforced resin-based composite material such as glass fiber, basalt fiber or aramid fiber). Among them, using the PI film as the insulating layer can enable the heater to be used in a high temperature environment, enhance its insulation, and avoid circuit short circuit.

In some examples of the present invention, the first heat-averaging layer and the second heat-averaging layer are both graphene thermal conductive films. The graphene thermal conductive film has good thermal uniformity, and when the size of the functional layer is small, it can also quickly conduct heat to the entire outer surface of the heater. The heat-averaging layer can quickly and effectively conduct and diffuse the high heat generated by the functional layer in the plane to increase the overall structure's ability to withstand thermal stress caused by local rapid temperature rise. Preferably, the heat-averaging layer is prepared from graphene heat-averaging slurry, and the composition of the graphene heat-averaging slurry includes 1-10wt% graphite powder (general graphite powder contains a small amount of graphene, so the resulting heat-averaging slurry can be called graphene heat-averaging slurry), 0.002-0.3wt% stripping agent and 18-40wt% diluent, and the balance is solvent. The graphite powder can be commercially available graphite powder; the stripping agent is a general stripping agent used for mechanical stripping to prepare graphene, such as one or more of soluble carbonates, bicarbonates, ammonium salts, ammonia, urea, azo compounds, sulfonyl hydrazide compounds, chitosan, etc.; the diluent includes any one or more of epoxy diluent, anhydrous ethanol, etc. The graphene heat-isolating slurry is an organic slurry (with an organic solvent as a solvent) or an aqueous slurry (with water as a solvent), preferably an aqueous slurry. The graphene heat-isolating slurry is filtered, dried, and pressed into a film (such as screen printing) to form a heat-isolating layer. When the screen printing method is used to form a film, the screen printing parameters of the heat-isolating layer can be the same as or different from the screen printing parameters of the functional layer, for example, the number of grids is 120 to 220 meshes, preferably 150 to 200 meshes; after screen printing, it is cured at 130 to 180°C (preferably 140 to 160°C) to form a film, and the curing time is 10 to 50 minutes, preferably 20 to 40 minutes. The graphene thermal conductive film of the heat-dissipating layer is mainly composed of carbon particles and is designed for the purpose of high thermal conductivity.

In some examples of the present invention, the size of the functional layer is smaller than the first insulating layer and the second insulating layer in both length and width directions. When the heater further includes a first composite material layer, a second composite material layer, a third composite material layer, and a fourth composite material layer, the size of the functional layer is smaller than the first composite material layer, the second composite material layer, the third composite material layer, and the fourth composite material layer in both length and width directions. By setting this size, it is ensured that the functional layer obtains a good fixing effect.

In some embodiments of the present invention, the functional layer is provided with an electrode. Preferably, the electrode is any one of copper and silver. For example, two parallel long strips of copper foil can be glued to the functional layer by a high temperature resistant hot melt adhesive as electrodes, or conductive silver paste can be applied to the functional layer by screen printing or conductive ink can be printed on the functional layer by inkjet printing technology. Electrodes are formed on the energy layer. The spacing between the two electrodes can be flexibly adjusted as needed to achieve the desired heating effect. The width of the overlapping area between the electrode and the functional layer can be flexibly changed as needed, and generally greater than 2mm can ensure circuit conduction; the size of the electrode in its lead-out direction is larger than the functional layer/first insulating layer/second insulating layer/(first to fourth) composite material ply, and can be flexibly adjusted as needed to lead out the electrode to connect to an external power source.

In some examples of the present invention, the heater further comprises one or two outer surface layers, and the outer surface layers are arranged on the outer surface of the heater. Specifically, when the heater comprises a first insulating layer, a functional layer, and a second insulating layer stacked in sequence, at least one outer surface layer is arranged on the outer surface of the first insulating layer or the second insulating layer, and the heater then comprises a first outer surface layer, a first insulating layer, a functional layer, a second insulating layer, and a second outer surface layer stacked in sequence, or comprises a first outer surface layer, a first insulating layer, a functional layer, and a second insulating layer stacked in sequence. When the heater includes a first composite material layer, a first heat-averaging layer, a second composite material layer, a first insulating layer, a functional layer, a second insulating layer, a third composite material layer, a second heat-averaging layer, and a fourth composite material layer stacked in sequence, at least one outer surface layer is arranged on the surface of the second composite material layer or the fourth composite material layer; in this case, the heater includes a first outer surface layer, a first composite material layer, a first heat-averaging layer, a second composite material layer, a first insulating layer, a functional layer, a second insulating layer, a third composite material layer, a second heat-averaging layer, a fourth composite material layer, and a second outer surface layer stacked in sequence, or includes a first outer surface layer, a first composite material layer, a first heat-averaging layer, a second composite material layer, a first insulating layer, a functional layer, a second insulating layer, a third composite material layer, a second heat-averaging layer, and a fourth composite material layer stacked in sequence. The outer surface layer includes any one or two of a metal layer and a composite material layer (i.e., a fiber-reinforced resin-based composite material), which can be flexibly selected according to application needs. Preferably, the outer surface layer is a metal layer, and specifically any one or more of aluminum, titanium, and steel can be used. The use of metal materials as the outer surface layer can be directly used for further thermal use; this layer can enhance the overall rigidity of the heater, greatly improve the impact resistance and increase safety. At the same time, similar to the heat-spreading layer, the outer surface layer can quickly and effectively conduct and diffuse the high heat generated by the functional layer within the plane to increase the overall structure's ability to bear the thermal stress caused by local rapid temperature rise.

In some examples of the present invention, the size of the outer surface layer is the same as that of the heat-saturating layer. At the same time, preferably, the size of the outer surface layer in the electrode lead-out direction is smaller than that of the first composite material layer, the second composite material layer, the third composite material layer, and the fourth composite material layer.

In some examples of the present invention, the sizes of the first composite material layer, the second composite material layer, the third composite material layer, and the fourth composite material layer in the electrode lead-out direction are independently larger than the outer surface layer, the first heat-dissipating layer, the second heat-dissipating layer, and the functional layer.

In some examples of the present invention, the sizes of the first heat-dissipating layer and the second heat-dissipating layer are the same as those of the outer surface layer.

In some embodiments of the present invention, the size of the first heat-dissipating layer and the second heat-dissipating layer in the electrode lead-out direction is smaller than that of the first heat-dissipating layer and the second heat-dissipating layer in the electrode lead-out direction. The functional layer.

In some examples of the present invention, the sizes of the first insulating layer and the second insulating layer are independently larger than the functional layer. The first insulating layer and the second insulating layer can be closely attached to the functional layer by means of a high temperature resistant insulating adhesive. The first insulating layer and the second insulating layer can well isolate the air to protect the functional layer and avoid oxidation of the functional layer during use and the resulting power attenuation problem.

In some embodiments of the present invention, the heater has any one of a flat plate structure and a curved structure. The heater of the present invention can be made into a flat plate structure or a curved structure, which can meet the requirements of large curvature conformal heating.

The thickness of each layer of the heater can be adjusted according to actual needs. As an example, the thickness of the (first and/or second) outer surface ply can be set to 0.1-1 mm, preferably 0.1-0.3 mm; the first to fourth composite material plies can be independently set to 0.1-1 mm, preferably 0.2-0.5 mm; the thickness of the first and second heat-dissipating layers can be independently set to 0.05-0.5 mm, preferably 0.1-0.2 mm; the thickness of the first and second insulating layers can be independently set to 0.02-1 mm, preferably 0.02-0.5 mm, more preferably 0.04-0.2 mm; the thickness of the functional layer can be set to 0.02-0.5 mm, preferably 0.1-0.2 mm. The layer structure of the heater of the present invention has a small thickness and is characterized by being light and thin.

The second aspect of the present invention is to provide a method for preparing the heater, comprising the following steps: laying a first insulating layer, a functional layer, and a second insulating layer on the surface of a substrate in order, sealing, evacuating, and heating to cure to obtain the heater.

In some examples of the present invention, according to the structure of the heater, the method for preparing the heater also includes the steps of laying a (first or second) outer surface layer, (first to fourth) composite material layers, and (first and second) heat-absorbing layers according to the stacked structure of the heater.

In some examples of the present invention, the preparation method of the heater includes the following steps: laying a first outer surface layer, a first insulating layer, a functional layer, a second insulating layer, and a second outer surface layer on the surface of the substrate in order, sealing, evacuating, heating and curing, and obtaining the heater.

In some examples of the present invention, the preparation method of the heater includes the following steps: laying a first outer surface layer, a first insulating layer, a functional layer, and a second insulating layer on the surface of the substrate in order, sealing, evacuating, heating and curing, and obtaining the heater.

In some examples of the present invention, the preparation method of the heater includes the following steps: sequentially laying a first outer surface layer, a first composite material layer, a first heat-averaging layer, a second composite material layer, a first insulating layer, a functional layer, a second insulating layer, a third composite material layer, a second heat-averaging layer, a fourth composite material layer, and a second outer surface layer on the surface of the substrate, sealing, evacuating, heating and curing, and obtaining the heater.

In some embodiments of the present invention, the preparation method of the heater comprises the following steps: laying a first outer surface layer, a first composite material layer, a first heat-absorbing layer, a second composite material layer, a first insulating layer, a functional layer on the surface of the substrate in sequence; The heater is formed by sealing a first insulating layer, a second insulating layer, a third composite material layer, a second heat-dissipating layer, and a fourth composite material layer, evacuating the layer, and heating and curing the layer to obtain the heater.

In some examples of the present invention, the vacuum pressure is -90 to -70 kPa, including but not limited to -90, -80, -70 kPa, etc.

In some examples of the present invention, the curing temperature is 100-150°C, including but not limited to 100, 110, 120, 130, 140, 150°C and the like.

In some embodiments of the present invention, the curing time is 30 to 120 minutes, including but not limited to 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 minutes, etc.

In some examples of the present invention, the paving process further includes a step of extracting electrodes from the functional layer.

The third aspect of the present invention is to provide the application of the heater in electric deicing, battery heating, and electric heating of industrial or civilian consumer products. Among them, electric deicing includes electric deicing of aircraft wings or aerodynamic leading edges of fan blades, battery heating includes heating of power battery packs of new energy vehicles, and electric heating of industrial or civilian consumer products includes electric mosquito coils, electric aromatherapy stoves, electronic cigarettes, electric heaters, etc.

In some examples of the present invention, the application temperature of the heater is -50 to 300° C., preferably -20 to 100° C. The heater of the present invention has a wide range of uses and can be applied to different application scenarios.

Compared with the prior art, the present invention has the following excellent effects:

The present invention uses reasonable ply arrangement and size arrangement to ensure that the graphene functional layer and electrodes are well encapsulated and solidified inside the insulating material. At the same time, the electrode lead-out method can ensure the safety and stability of the functional layer circuit. The heat-averaging layer and the outer surface ply can greatly improve the thermal conductivity and reduce heat loss. The various layers of the structure are integrated and composited through a hot pressing process to obtain a thin-walled functional structure heater that is light, high-strength, low-voltage, high-efficiency, low-energy consumption, long-life, high-reliability, and highly integrated, and can easily achieve large-area and large-curvature conformal heating.

Specifically, (1) the heater of the present invention has the advantages of being light, thin, high-strength, highly reliable, highly integrated, and highly designable. This is reflected in the designability of the overall shape of the structure, which can be flat or curved, and can be as close to the desired shape as possible according to the specific application; it is also reflected in the designability of the ply angle so that the ply structure has the desired mechanical properties.

(2) After being formed by a hot pressing process (i.e., formed under specific temperature and pressure conditions), the various structures of the present invention have the characteristics of fast thermal response, rapid temperature rise, stable heating effect, and little influence by environmental conditions. The functional layer circuit can be adjusted according to the specific use environment to easily obtain the desired heating effect.

(3) The outer surface layer of the heater of the present invention can be a metal foil or a composite material layer. When the functional layer is a graphene heating layer, the structure of the present invention can be directly applied to a large number of heater fields. The graphene heating film contains a certain proportion of graphene and is a thin film that can generate heat energy after being energized, with a high heat conversion rate. Compared with existing products, the heater structure of the present invention uses graphene heating. When the thermal film is used as a heating source, its power consumption is greatly reduced and its heating efficiency is greatly improved.

(4) The combination of metal and composite material greatly improves the impact resistance and environmental adaptability of the heater structure of the present invention, and the structure is safer and more stable. The heater structure of the present invention can well isolate the air and the heat source, so that the oxidation effect on the graphene heating film is almost negligible.

(5) The heater structure of the present invention can quickly and effectively conduct and diffuse the high heat generated by the functional layer through the heat-averaging layer, so that the entire structure can bear the thermal stress generated by the rapid heating of the functional layer. At the same time, the heater structure of the present invention has good two-dimensional heat-averaging performance, which can make the entire structure quickly heat-averaged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a layer relationship structure of a heater of the present invention.

FIG. 2 is a schematic diagram of the structure of the heater applied to the leading edge of the wing in Example 1.

FIG3 is a physical diagram of the heater preparation process in Example 1.

Figure 4 is a composite material curing process curve.

FIG. 5 is a physical picture of the heater in Example 1 before freezing.

FIG. 6 is a physical picture of the heater in Example 1 after freezing.

FIG. 7 shows the deicing process of the heater in Example 1. FIG.

FIG. 8 is a temperature variation curve of the heater in Example 1.

FIG. 9 is a physical picture of the heater in Comparative Example 1 after freezing.

FIG. 10 is a temperature variation curve of the heater in Comparative Example 1.

FIG. 11 is a schematic diagram of the structure of the heater in Example 2.

FIG. 12 is a physical picture of the heater in Example 3 applied to the electric mosquito coil.

FIG. 13 is a temperature curve of the heater applied to the electric mosquito coil in Example 3.

FIG. 14 is a physical picture of the heater in Example 4 applied to an electric aromatherapy furnace.

FIG. 15 is a temperature curve of the heater in Example 4 applied to the electric aromatherapy furnace.

FIG. 16 is a schematic diagram of the structure of the heater in Example 5 applied to an electric heater.

Detailed ways

The technical scheme of the present invention is further described below in conjunction with specific examples. The raw materials used in the following examples, unless otherwise specified, can all be obtained from conventional commercial sources; the processes used, unless otherwise specified, all adopt conventional processes in the art.

The present invention provides a heater having a thin-walled functional laminated structure. In some embodiments, the outer surface layer 101, composite material layer 102, heat-averaging layer 103, composite material layer 102, insulating layer 104, functional layer 105, insulating layer 104, composite material layer 102, heat-averaging layer 103, composite material layer 102 and outer surface layer 101 are laminated in sequence and compositely molded by a hot pressing molding process, wherein the functional layer is a graphene heating film, and an electrode 106 is led out of the graphene heating film, and the ply relationship is shown in Figure 1 (S in the figure represents the electrode lead-out direction). The entire laminated structure is formed by a composite material hot pressing process, and the obtained product can be a flat plate or a curved plate. Combined with a molding mold, a large curvature spatial structure of any curved surface can be manufactured in theory. In some embodiments, the heater can also be formed by sequentially stacking an insulating layer, a functional layer, an insulating layer and an outer surface layer. The heater is described in detail below in conjunction with several specific application examples.

Example 1

The present embodiment provides a heater based on a fiber graphene laminated composite functional structure (Fiber Graphene Laminated Composite, referred to as FGL), and applies it to the electric thermal deicing of the leading edge of the wing as a functional skin device for the local area of the wing that is prone to icing.

In this application scenario, the structural schematic diagram of the heater is shown in Figure 2, which is a curved structure. Figure 2 (a) is an overall top view of the heater, and (b) is a schematic diagram of the heater structure decomposition. The heater includes an outer surface layer 101, a composite material layer 102, a heat-saturating layer 103, a composite material layer 102, an insulating layer 104, a functional layer 105, an insulating layer 104, a composite material layer 102, a heat-saturating layer 103, a composite material layer 102 and an outer surface layer 101, which are composited by a hot pressing process, and electrodes are drawn out on the functional layer by copper foil/silver paste printing (not shown in the figure). The outer surface layer is a titanium sheet with a thickness of 0.2mm and a size of 200mm*100mm; each composite material layer is an epoxy resin-based glass fiber reinforced material layer with a thickness of 0.2mm and a size of 200mm*100mm; the heat-spreading layer is a graphene thermal conductive film, which is prepared by screen printing a water-based graphene heat-spreading slurry composed of 2.5wt% graphite powder, 0.1wt% stripping agent and 40wt% diluent, and the balance is water, and its thickness is 0.1mm. The size is 180mm*80mm; the upper insulating layer and the lower insulating layer are both PI films, with a thickness of 0.04mm and a size of 180mm*80mm; the functional layer is a graphene heating film, which is prepared by screen printing a water-based graphene conductive paste composed of 2wt% graphene powder, 8.6wt% dispersant (BYK-215) and 35wt% organic resin (alkyd resin), and the balance is water, with a thickness of 0.15mm and a size of 180mm*80mm. The parameters of the screen printing are: the number of grids is 180 meshes, and the film is cured at 150°C for 30 minutes after printing.

The preparation method of the heater of this embodiment comprises the following steps:

First, wipe the leading edge of the wing with a cotton ball dipped in alcohol to make sure it is clean and free of other impurities, then follow the steps below.

(a) Composite material

The various layers of the heater are laid in sequence on the surface of the leading edge of the wing, namely the outer surface layer, the composite material layer, the heat-saturating layer, The composite material layer, the upper insulating layer, the functional layer, the lower insulating layer, the composite material layer, the heat-spreading layer, the composite material layer and the outer surface layer are pressed flat, as shown in FIG3( a ).

(b) Auxiliary vacuum

Then, auxiliary vacuum materials such as release cloth, breathable felt, isolation film, and a silicone flexible heating device (for providing curing temperature for subsequent steps) are laid in sequence on the structure pressed flat in step (a), as shown in FIG3(b).

(c) Vacuum extraction

Then cover and seal with a vacuum bag and sealant, as shown in Figure 3 (c). After ensuring airtightness, start vacuuming, and set the vacuum degree to -80kPa. Refer to the composite material curing process curve (see Figure 4), and cure at 120℃ for 90min.

(d) Cooling and demoulding

Finally, the hot pressing process of the part is completed, and the part is demoulded after cooling. The part molding quality is checked: it is found that the heater structure is tightly fitted to the leading edge of the wing, the thickness of the part is 0.75mm, the area is 200mm*100mm, and the surface density is 0.0827g/ ^cm2 , achieving the effect of conformal integration, as shown in Figure 3 (d).

The leading edge of the wing with the heater laid and cured was placed under -20.2℃/23%RH conditions for freezing and icing. The ice range was 175mm×61mm, and the average thickness of the ice layer was 2.37mm. The actual pictures before and after icing are shown in Figures 5 and 6 respectively. Then the heater was powered on, with a voltage/current of 32V/5.47～5.59A. The results showed that the actual power of the heater was 174～178W, the power density was 17.6～18.0KW/m ² , and the time for the bottom interface of the ice layer to completely melt was 37s.

By changing the voltage and current to make the power density of the heater 15kW/ ^m2 , the wing de-icing can be completed within 55s [see Figure 7. In the present invention, the time when the ice layer interface begins to melt is defined as the initial melting point, and the time when the ice layer interface is completely melted is defined as the final melting point. The relatively gentle temperature platform area between the initial melting and the final melting is called the melting range. In Figure 7, after the ice layer is powered on for heating (a), it goes through the initial melting stage (b) and the final melting stage (c), and finally the de-icing is completed (d)].

Three points (heater 1, heater 2, and heater 3) were selected at an even distance on the heater, and the temperature changes of the three points during the heating and deicing process were recorded over time. The temperature curve is shown in Figure 8. It can be seen from the figure that the heater is used to de-ice the leading edge of the wing with high efficiency and stability, and the heating effect is less affected by temperature.

Comparative Example 1

This comparative example provides a heater, and applies it to the electric heating deicing of the leading edge of the wing, as a functional skin device for the local area of the wing that is prone to ice formation. The difference between this heater and Example 1 is that: the functional layer is a graphene heating film, which is prepared by a blade coating printing method using a graphene conductive slurry composed of 2wt% graphene powder, 9.5wt% dispersant and 26wt% organic resin, and the remainder is an organic solvent (the solvent is an organic solvent); and the outer surface is paved with a titanium sheet. The other structures and the laying method of the heater on the wing are the same as those in Example 1.

The leading edge of the wing after the heater is laid and cured is placed under -20.4℃/27%RH for freezing and icing. The icing range is 200mm×70mm, the average thickness of the ice layer is 2.52mm, as shown in Figure 9. Then the heater is powered on, the voltage/current is 32V/5.41～3.52A. The results show that the actual power of the heater is 173～113W, the power density is: 17.4～11.3KW/m ² , and the time for the bottom interface of the ice layer to completely melt is: 60s.

Three points (heater 1, heater 2, and heater 3) were selected at an even distance on the heater, and the temperature changes of the three points during the heating and deicing process were recorded over time. The temperature curve is shown in Figure 10. It can be seen from the figure that the heating effect of deicing the leading edge of the wing using this heater is unstable, and the heater power decreases as the temperature increases.

The deicing data of Example 1 and Comparative Example 1 are as follows:

Embodiment 1:

Ice range: 175mm×61mm;

Average ice thickness: 2.37mm;

Voltage and current: 32V/5.47～5.59A;

Ambient temperature and humidity: -20.2℃/23%RH;

Actual power: 174~178W;

Power density: 17.6～18.0KW/ ^m2 ;

Time for the bottom interface of the ice layer to completely melt: 37s.

Comparative Example 1:

Ice range: 200mm×70mm;

Average ice thickness: 2.52mm;

Voltage and current: 32V/5.41～3.52A;

Ambient temperature and humidity: -20.4℃/27%RH;

Actual power: 173~113W;

Power density: 17.4～11.3KW/ ^m2 ;

Time for the bottom interface of the ice layer to completely melt: 60s.

By comparing Example 1 and Comparative Example 1, it can be seen that the change of the heater structure will lead to a change in the final heating effect. When the graphene heating film (functional layer) formed by screen printing of a graphene conductive paste of a specific composition in Example 1 is replaced by the graphene heating film obtained by coating and printing of a graphene conductive paste of a different composition in Comparative Example 1, an efficient and stable heating effect cannot be achieved. On the one hand, this may be due to the different distribution of graphene in the coatings formed by screen printing and blade coating and printing, and the different adhesion between the various components of graphene in the coating when the temperature rises, resulting in different heating effects; on the other hand, it may also be related to the composition of the graphene conductive paste.

Example 2

The present embodiment provides a heater based on a fiber graphene laminated composite material functional structure (Fiber Graphene Laminated Composite, referred to as FGL), and applies it to the heating of lithium iron phosphate batteries for new energy vehicles, as a heating device for maintaining sufficient working efficiency of the power battery within a certain temperature range.

In this application scenario, the structural schematic diagram of the heater is shown in Figure 11, which has a flat plate shape, and includes, from top to bottom, successively stacked composite layers 102, composite layers 102, heat-averaging layers 103, composite layers 102, composite layers 102, functional layers 105, composite layers 102, composite layers 102, heat-averaging layers 103, composite layers 102, and composite layers 102. The composite layers located on the two outer surfaces of the heater serve as outer surface layers, and the composite layers located on the two surfaces of the functional layer act as insulating layers. Each layer is composited by a hot pressing process, and electrodes 106 are led out on the functional layer by silver paste printing. In the figure, S represents the electrode lead-out direction. All composite material layers are epoxy resin-based glass fiber reinforced material layers, with a thickness of 0.2mm and a size of 585mm*80mm; the functional layer is a graphene heating film, which is prepared by screen printing of an aqueous graphene conductive slurry composed of 2wt% graphene powder, 8.6wt% dispersant and 35wt% organic resin, with the balance being water, with a thickness of 0.1mm and a size of 480mm*72mm; the heat-dissipating layer is a graphene thermal conductive film, which is prepared by coating and printing of an aqueous graphene heat-dissipating slurry composed of 2.5wt% graphite powder, 0.1wt% stripping agent and 40wt% diluent, with the balance being water, with a thickness of 0.15mm and a size of 540*72mm. The parameters of the aqueous graphene conductive slurry, aqueous graphene heat-dissipating slurry and screen printing are the same as those in Example 1. The preparation method of the heater of this embodiment comprises the following steps:

1. Clean the mold. Use an absorbent cotton ball soaked in alcohol to wipe the 700mm*400mm mold 2 times or more until there is no stain on the cotton ball; then use an absorbent cotton ball dipped in a release agent to wipe 4 to 5 times, with an interval of 2 to 3 minutes between each time. Wait until the mold is dry before wiping it again.

2. Cut the release cloth, adhesive and isolation film according to the size of the mold.

3. Lay out the heater. The order of laying the layers is isolation film, adhesive tape, release cloth, test piece (i.e., including composite material layer, composite material layer, heat-spreading layer, composite material layer, composite material layer, functional layer, composite material layer, composite material layer, heat-spreading layer, composite material layer, composite material layer), release cloth, adhesive tape, isolation film; stick the isolation film on the mold and smooth it out, stick the adhesive tape on the isolation film and smooth it out, stick the release cloth on the adhesive tape and smooth it out; handle the test piece, lay the test piece flat on the release cloth; then lay the release cloth, adhesive tape, and isolation film in sequence.

4. Vacuum and put into oven. Cover the mold with silicone and seal the mold with high temperature sealant and silicone; put it into oven; set the molding temperature corresponding to the material, and heat it (120℃, 90min) according to the curing process curve of composite materials (see Figure 4), and set the vacuum degree to -80kPa.

5. Natural cooling

Place the cured heater under the lithium iron phosphate battery pack, cover it with insulation cotton, and place it in a -20℃ low temperature environment. The temperature is lowered in the box until the battery core temperature is about -17°C. Then the heater is powered on with a supply voltage of 32V.

As a comparison, a conventional PTC heater was used to heat the battery under the same low temperature conditions, with a supply voltage of 93V.

The heating indicators of the two different heaters are as follows.

(1)PTC heater:

Test environment (℃): -20;

Battery cell temperature (℃): -17.6;

Supply voltage (V): 93;

Average heating power (W): 140.5;

Energy consumption (W·h): 153.8;

Temperature rise efficiency (℃/h): 16.1;

Weight (g): 226.9;

Power to weight ratio (W/g): 0.62.

(2) FGL heater

Test environment (℃): 20

Cell temperature (℃): -17.7

Supply voltage(V):32

Average heating power (W): 170.6

Energy consumption (W·h): 148.5

Temperature rise efficiency (℃/h): 20.3

Weight(g):93.2

Power to weight ratio (W/g): 1.83.

The change ratio of FGL heater compared to PTC heater is as follows:

Supply voltage (V): ↓65.6%

Average heating power (W): ↑21.4%

Energy consumption (W·h):↓3.5%

Temperature rise efficiency (℃/h): ↑26％

Weight (g): ↓59%

Power to weight ratio (W/g): ↑195%.

During the heating process, it was found that the FGL heater of this embodiment achieved the effect of raising the battery core temperature from -15°C to 0°C in about 45 minutes under a low temperature (-20°C) environment, reaching and exceeding the heating effect of the existing PTC heater. Compared with the traditional PTC heater, the FGL heater has a 65.6% lower supply voltage, a 59% lower weight, a 21.4% higher power, a 3.5% lower energy consumption, a 26% higher temperature rise efficiency, and a 1.95-fold higher power-to-weight ratio.

Comparative Example 2

This comparative example provides a heater, and uses it to heat a lithium iron phosphate battery for a new energy vehicle. The difference from Example 2 is that the vacuum degree used when preparing the heater is 0. The rest is the same as Example 2.

The heater was powered on at a voltage of 28.8 V, and its power was tested and compared with the heater of Example 2 under the same conditions. The results were as follows:

Example 2: At a voltage of 28.8 V, the power of the long plate heater and the short plate heater are 90.4 W (sample number 0807-A-1c-1-L) and 75.5 W (sample number 0807-A-1c-1-S) respectively;

Comparative Example 2: At a voltage of 28.8V, the power of the long plate heater and the short plate heater are 56.16W (sample number 0801-A-1c-1-L2) and 68.8W (sample number 0801-A-1c-1-S), respectively.

It can be seen from the above data that when the vacuum pressure is insufficient, the power of the molded FGL heater at the same voltage is significantly lower than that of the molded FGL heater manufactured when the vacuum pressure is -80 kPa.

Therefore, if the vacuum degree and sealing are not good when the vacuum is extracted, the electrode cannot be tightly attached to the graphene film and the graphene film will not be dense enough in the thickness direction, resulting in increased resistance, which will affect the heat generation and thermal conductivity.

Example 3

The present embodiment provides a heater, and applies it to electric mosquito coil heating. In this application scenario, the structure of the heater has a flat plate structure, which is formed by a sequentially stacked outer surface layer, an insulating layer, a functional layer, and an insulating layer through a hot pressing process, and the functional layer is printed with copper foil/silver paste to lead out the electrode. The outer surface layer is aluminum foil with a thickness of 0.2mm and a size of 30mm*40mm; the upper insulating layer and the lower insulating layer are both epoxy resin-based glass fiber reinforced material layers, with a thickness of 0.2mm and a size of 30mm*42mm; the functional layer is a graphene heating film, which is prepared by screen printing of a water-based graphene conductive slurry composed of 2wt% graphene powder, 8.6wt% dispersant and 35wt% organic resin, and the remainder is water, with a thickness of 0.1mm and a size of 35mm*5mm. The water-based graphene conductive slurry and screen printing parameters are the same as those in Example 1.

1. Clean the mold. Use an absorbent cotton ball soaked in alcohol to wipe the 300mm*400mm mold 2 times or more until there is no stain on the cotton ball; then use an absorbent cotton ball dipped in a release agent to wipe 4 to 5 times, with an interval of 2 to 3 minutes between each time. Wait until the mold is dry before wiping it again.

3. Lay out the heater. The order of laying is isolation film, adhesive tape, release cloth, test piece, release cloth, adhesive tape, and isolation film; stick the isolation film on the mold and smooth it out, stick the adhesive tape on the isolation film and smooth it out, stick the release cloth on the adhesive tape and smooth it out; handle the test piece and lay it flat on the release cloth; then lay the release cloth, adhesive tape, and isolation film in sequence.

4. Vacuuming and hot pressing. Put it into a self-made aluminum alloy mold and evacuate it to -80kPa. Use a hot pressing instrument to heat and cure it according to the curing process curve of the composite material (epoxy resin-based glass fiber reinforced material) (see Figure 4).

5. Natural cooling.

Note: The above mold can produce 5 to 10 electric mosquito coil heaters at the same time.

The actual picture of the prepared electric mosquito coil heater is shown in FIG12 .

The heater is powered on with a voltage of 5V, and the recorded temperature curve is shown in Figure 13. From the temperature curve, it can be seen that the heater can achieve stable heating at a low voltage, and the heating power is about 5W, which has the characteristics of low voltage and high power.

Example 4

The present embodiment provides a heater and applies it to an electric aromatherapy furnace. In this application scenario, the structure of the heater has a flat plate/curved plate structure, which is formed by a sequentially stacked outer surface layer, an upper insulating layer, a functional layer, and a lower insulating layer through a hot pressing process, and the electrodes are drawn out on the functional layer by copper foil/silver paste printing. The outer surface layer is an epoxy resin-based glass fiber reinforced material layer with a thickness of 0.2mm and a size of 40mm*40mm; the upper insulating layer and the lower insulating layer are both epoxy resin-based glass fiber reinforced material layers, with a thickness of 0.2mm and a size of 40mm*40mm; the functional layer is a graphene heating film, which is prepared by screen printing of a water-based graphene conductive slurry composed of 2wt% graphene powder, 8.6wt% dispersant and 35wt% organic resin, and the remainder is water, with a thickness of 0.1mm and a size of 40mm*5mm. The water-based graphene conductive slurry and screen printing parameters are the same as those in Example 1.

The manufacturing process of the electric aromatherapy stove heater of this embodiment can refer to the manufacturing process of the electric mosquito coil heater in Example 3.

The actual picture of the prepared electric aromatherapy furnace heater is shown in FIG14 , and the electric aromatherapy furnace heater is filled with a mixture of essential oil and water.

The heater is powered on with a voltage of 5V, and the temperature curves of the electric aromatherapy heater and the mixture of essential oil and water are recorded as shown in Figure 15 (FGLH in the figure is the electric aromatherapy heater). It can be seen from the temperature curve that the heater can achieve stable heating at low voltage, with a heating power of about 5W, and has the characteristics of low voltage and high power.

Example 5

This embodiment provides a heater, and it is applied to an electric heater. In this application scenario, the structure of the heater has a flat plate structure, and its structural schematic diagram is shown in FIG16, which is composed of an outer surface layer 101, a composite material layer 102, a heat-absorbing layer 103, a composite material layer 102, an insulating layer 104, a functional layer 105, an insulating layer 104, a composite material layer 102, a heat-absorbing layer 103, a composite material layer 102 and an outer surface layer 101 stacked in sequence through a hot pressing molding process. The electrode 106 is drawn out by silver paste printing, and S in the figure indicates the direction of electrode drawing. The outer surface layer is aluminum foil with a thickness of 0.2mm, and each composite material layer is a high-temperature epoxy resin-based glass fiber reinforced material layer with a thickness of 0.2mm and a size of 400mm*300mm; the functional layer is a graphene heating film, which is prepared by screen printing of a water-based graphene conductive paste composed of 2wt% graphene powder, 8.6wt% dispersant and 35wt% organic resin, and the balance is water, with a thickness of 0.1mm and a size of 380mm*280mm; the heat-dissipating layer is a graphene thermal conductive film, which is prepared by coating and printing of a water-based graphene heat-dissipating paste composed of 2.5wt% graphite powder, 0.1wt% stripping agent and 40wt% diluent, and the balance is water, with a thickness of 0.15mm and a size of 380*280mm. The aqueous graphene conductive paste, aqueous graphene isothermal paste and screen printing parameters are the same as those in Example 1.

The manufacturing process of the heater of the electric heater of this embodiment can refer to the manufacturing process of Example 2, and the only difference is that the curing temperature in the manufacturing process is 180°C.

The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

A heater, characterized in that: the heater comprises a first insulating layer, a functional layer, and a second insulating layer stacked in sequence, the functional layer is a graphene heating film, and the graphene heating film is screen-printed with an aqueous graphene conductive paste containing 0.5-3wt% graphene powder, 0.8-10wt% dispersant and 10-40wt% organic resin, with the remainder being water.
The heater according to claim 1 is characterized in that the aqueous graphene conductive slurry contains 0.5-3wt% graphene powder, 0.8-10wt% dispersant and 30-40wt% organic resin, and the balance is water.
The heater according to claim 1 or 2 is characterized in that: the heater also includes a plurality of composite material plies and a heat-averaging layer, and the heater includes a first composite material ply, a first heat-averaging layer, a second composite material ply, a first insulating layer, a functional layer, a second insulating layer, a third composite material ply, a second heat-averaging layer, and a fourth composite material ply stacked in sequence, and the first composite material ply, the second composite material ply, the third composite material ply, and the fourth composite material ply are independently selected from fiber-reinforced resin-based composite material layers.
The heater according to claim 3 is characterized in that the first composite material ply, the second composite material ply, the third composite material ply and the fourth composite material ply independently include any one or more fiber-reinforced resin-based composite materials selected from the group consisting of glass fiber, carbon fiber, basalt fiber and aramid.
The heater according to claim 3 is characterized in that the first heat-dissipating layer and the second heat-dissipating layer are both graphene thermal conductive films.
The heater according to claim 1 is characterized in that the functional layer is smaller than the first insulating layer and the second insulating layer in both length and width directions.
The heater according to claim 1 or 2 is characterized in that the heater has any one of a flat structure and a curved structure.
The method for preparing the heater according to any one of claims 1 to 7 comprises the following steps: laying a first insulating layer, a functional layer, and a second insulating layer on the surface of a substrate in order, vacuuming after sealing, and heating and curing to obtain the heater.
The preparation method according to claim 8 is characterized in that the vacuum pressure is -90 to -70 kPa.
The heater according to any one of claims 1 to 7 is used in electric deicing, battery heating, and electric heating of industrial or civilian consumer products.