CN114010065B

CN114010065B - Non-stick coating for cookware, manufacturing method thereof and non-stick cookware

Info

Publication number: CN114010065B
Application number: CN202111551677.0A
Authority: CN
Inventors: 张明; 李超; 瞿义生; 袁华庭
Original assignee: Wuhan Supor Cookware Co Ltd
Current assignee: Wuhan Supor Cookware Co Ltd
Priority date: 2021-12-17
Filing date: 2021-12-17
Publication date: 2023-06-20
Anticipated expiration: 2041-12-17
Also published as: CN114010065A

Abstract

The invention provides a non-stick coating for cookware, a manufacturing method thereof and a non-stick cookware. The non-stick coating comprises: a base layer having a surface roughness structure at an outer surface thereof and pores inside thereof; and a non-stick resin embedded between the surface roughness structures of the base layer and filling at least a portion of the pores of the base layer, wherein the surface roughness structures include a plurality of composite protrusions distributed along the surface of the base layer, each of the composite protrusions including a large protrusion and a plurality of small protrusions formed on the outer circumference of the large protrusion. Thus, the initial non-tackiness and non-tackiness durability of the non-tacky coating can be improved.

Description

Non-stick coating for cookware, manufacturing method thereof and non-stick cookware

Technical Field

The present invention relates to a non-stick coating, and more particularly, to a non-stick coating for cookware, a method of manufacturing the same, and a non-stick cookware including the same.

Background

Since non-stick cookware such as a non-stick pan has been developed, since it does not stick food to the bottom of the pan during cooking, it is possible to avoid the phenomenon of sticking food to the pan which often occurs in conventional cookware during cooking, thus it is possible to avoid the occurrence of scorching of food and the problem of generation of harmful substances due to scorching. Moreover, the non-stick pan not only has reduced cleaning difficulty, but also can easily fry food, thereby greatly improving the use experience of the pan.

The non-stick properties of a non-stick pan are typically achieved by a non-stick coating disposed on the surface of the non-stick pan. With the development of non-stick coatings for non-stick pans, the use of a pore oil storage mechanism to achieve a non-stick coating has emerged. Such non-stick coatings can cope with the non-stick requirements of most of daily food materials, but still cannot effectively meet the non-stick requirements of some easily-stick pan food materials.

Disclosure of Invention

The present invention is directed to solving the above-mentioned technical problems in the related art.

The aim of the invention is to improve the initial non-tackiness of a non-tacky coating.

The invention also aims to improve the durability of the non-stick coating.

The objects of the present invention are not limited to the above objects, and other objects of the present invention will be apparent from the description.

According to an aspect of the present invention, there is provided a non-stick coating for cookware, the non-stick coating comprising: a base layer having a surface roughness structure at an outer surface thereof and pores inside thereof; and a non-stick resin embedded between the surface roughness structures of the base layer and filling at least a portion of the pores of the base layer, wherein the surface roughness structures include a plurality of composite protrusions distributed along the surface of the base layer, each of the composite protrusions including a large protrusion and a plurality of small protrusions formed on the outer circumference of the large protrusion.

In an embodiment, the matrix layer may have a porosity in the range of 3% to 15% by volume.

In an embodiment, the peak height of each composite bump may be 10 μm to 20 μm, the peak spacing between two adjacent composite bumps may be not more than 20 μm, and the peak height of each small bump may be 1 μm to 4 μm, and the peak spacing between two adjacent small bumps on the same large bump may be not more than 2 μm.

In an embodiment, the large protrusions and the small protrusions may each be arc-shaped.

In an embodiment, the non-stick resin may be a fluororesin.

In an embodiment, the matrix layer may be formed from composite particles.

In an embodiment, the composite particles may include 69wt% to 99wt% ceramic particles, 1wt% to 2wt% binder, and 0wt% to 30wt% metal particles, in weight percent based on the total weight of the composite particles.

In embodiments, the ceramic particles may include one or more materials of titanium oxide, titanium nitride, titanium carbide, ferric oxide, ferrous oxide, aluminum oxide, chromium oxide, and nickel oxide.

In embodiments, the metal particles may include one or more materials of titanium, titanium alloy, iron, stainless steel, mild steel, high carbon steel, cast iron, copper alloy, aluminum alloy, nickel, and nickel alloy.

In embodiments, the binder may include a cellulosic binder and/or an alcohol binder.

In embodiments, the composite particles, ceramic particles, and metal particles may all be spherical or spheroid-like.

In an embodiment, the composite particles may have a porosity in the range of 5% to 30% by volume.

According to another aspect of the present invention, there is provided a method of manufacturing a non-stick coating layer, the method comprising: forming a base layer on a substrate, wherein the base layer has a surface roughness structure at an outer surface thereof and pores inside thereof, the surface roughness structure including a plurality of composite protrusions distributed along a surface of the base layer, each composite protrusion including a large protrusion and a plurality of small protrusions formed on an outer circumference of the large protrusion; immersing the substrate on which the base layer is formed in an immersion liquid containing a non-stick resin for a predetermined time; performing a drying process on the substrate layer adsorbed with the non-stick resin; and performing a sintering process on the dried base layer, thereby forming the non-stick coating layer on the substrate.

In an embodiment, the non-stick resin may be in a particulate form and may have a particle size in the range of 1 μm to 5 μm.

According to a further aspect of the present invention there is provided a non-stick cookware comprising a substrate and a non-stick coating, wherein the non-stick coating at least partially covers the outer surface of the substrate and the non-stick coating is a non-stick coating as described above.

Drawings

The above and/or other features and aspects of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings.

Fig. 1 is a schematic cross-sectional view of a non-stick cookware according to an embodiment.

Fig. 2 is a schematic cross-sectional view showing a surface roughness structure and pores of a non-stick coating according to an embodiment.

Fig. 3 is a schematic cross-sectional view showing composite protrusions of a surface roughness structure according to an embodiment.

Fig. 4 is a schematic plan view showing a non-stick coating according to an embodiment.

Fig. 5 is a schematic enlarged view of the region C in fig. 4.

Fig. 6 is a schematic view of a composite particle according to an embodiment.

Fig. 7 is a schematic flow chart of a method for manufacturing a non-stick coating according to an embodiment.

Detailed Description

Exemplary embodiments of the present invention will be described in more detail below. While exemplary embodiments of the invention are described hereinafter, it should be understood that the invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In the prior art, the non-stick coating which is non-stick by using a pore oil storage mechanism has more or less certain functional defects, such as but not limited to, unsuitable use environment with less oil consumption and poor durability. In addition, conventional non-stick coatings having voids generally have a surface structure with many sharp protrusions, and when used for cooking sticky foods, the foods are easily embedded in the surface structure of the non-stick coating due to being pierced by the sharp protrusions, making it difficult to peel off, thereby resulting in a saucepan.

To this end, the present invention improves the surface structure of the non-stick coating on the one hand and improves the pore structure of the non-stick coating on the other hand, thereby realizing a non-stick coating having excellent initial non-stick properties and non-stick durability.

Fig. 1 is a schematic cross-sectional view of a non-stick cookware according to an embodiment. Fig. 2 is a schematic cross-sectional view showing a surface roughness structure and pores of a non-stick coating according to an embodiment, and fig. 3 is a schematic cross-sectional view showing a composite protrusion of the surface roughness structure according to an embodiment.

Referring to fig. 1, a non-stick cookware 100 may include a substrate 120 and a non-stick coating 140.

The substrate 120 may be the body of the non-stick cookware 100 and may include an inner surface for carrying food and an outer surface opposite the inner surface. The substrate 120 may comprise any suitable material commonly used in the art. In addition, the substrate 120 may have various shapes according to the type of non-stick cookware and/or the needs of the use scenario. For example, as shown in fig. 1, when the non-stick cookware 100 is a non-stick pan, the substrate 120 may have a common pan body shape. It should be understood that the main body portion of the non-stick cookware is shown in fig. 1 by way of example only and other portions are not shown, and that the non-stick cookware according to the present invention may also have a common cookware structure such as a cookware handle (e.g., a pot handle).

The non-stick coating 140 may at least partially cover the substrate 120 to achieve non-stick in the covered area. For example, as shown in fig. 1, the non-stick coating 140 may be disposed on the entire inner surface of the substrate 120, but this is merely an example. Depending on the particular type of non-stick cookware and/or the actual non-stick requirements, a non-stick coating may be formed to cover a portion or all of the surface of the substrate 120. For example, the non-stick coating may be disposed on a portion of the inner surface of the substrate 120 and/or may be further disposed on the outer surface of the substrate 120.

The structure of the non-stick coating 140 will now be described in connection with fig. 2 and 3. Fig. 2 is a schematic enlarged view of the region a in fig. 1, and fig. 3 is a schematic enlarged view of the region B in fig. 2.

The non-stick coating 140 according to an embodiment may include a base layer 141 and a non-stick resin 142. The non-stick resin 142 may be disposed in the base layer 141, and a portion of the base layer 141 may be exposed to the outside.

In some embodiments, the base layer 141 may have a surface roughness structure at its surface. For example, the surface roughness may be distributed along the surface of the base layer 141, and may be a portion (e.g., a top) of the base layer 141. For example, as shown in fig. 1, when the non-stick coating 140 is disposed on the inner surface of the substrate 120, the surface roughness of the base layer 141 may be distributed over the entire surface of the base layer 141 remote from the substrate 120. That is, the surface roughness structure of the base layer 141 may be disposed at a surface of the base layer 141 not in contact with the base material 120 of the non-stick cookware 100.

Referring to fig. 2, the surface roughness structure of the base layer 141 may include a plurality of composite protrusions 10. The plurality of composite protrusions 10 may be distributed along the surface of the base layer 141 and may constitute the top of the base layer. The composite protrusion 10 may be a portion of the base layer 141 protruding in a direction away from the substrate 120.

As shown in fig. 2, the plurality of composite protrusions 10 may form a continuous undulating structure on the surface of the base layer 141, but this is merely for convenience of explanation of the exemplary structure given. For example, as shown in fig. 3, which will be described later, each of the composite projections 10 may include a large projection 20 and a plurality of small projections 30 formed on the outer circumference of the large projection 20. The outer contour of the composite protrusion 10 may be collectively defined by the outer contours of the large protrusion 20 and the small protrusion 30 included in the composite protrusion 10, such that the plurality of composite protrusions 10 as a whole (or macroscopically) assume the contour shape as shown in fig. 2. For example, the surface of the base layer 141 including such composite protrusions 10 may have a wave-like undulating structure having peaks and valleys.

Each of the plurality of composite projections 10 may have a peak height H of 10 μm to 20 μm. For example, the peak height H of each composite protrusion 10 may also be 11 μm to 19 μm, 12 μm to 18 μm, 13 μm to 17 μm, 14 μm to 16 μm, or 15 μm. Further, the peak distance D between two adjacent composite projections 10 among the plurality of composite projections 10 is not more than 20 μm.

Here, "peak height" means a peak-to-peak distance of one peak (e.g., a single composite bump 10 herein) in a macroscopic relief structure formed by a plurality of bumps (e.g., a plurality of composite bumps 10 herein). Here, the "peak pitch" means a distance between peak tops of two peaks adjacent to each other (e.g., two composite projections 10 adjacent to each other) in a macroscopic relief structure formed by a plurality of projections (e.g., a plurality of composite projections 10). It should be understood that while the peak heights and peak spacing are explained herein by way of example for the composite bump 10 shown in fig. 2, the same explanation may be applied to other bump structures in the specification.

In addition, it is shown in fig. 2 that the surface of the base layer 141 has a relatively uniform undulating shape, and the dimensions of the respective composite protrusions 10 are substantially uniform with respect to each other, but the embodiment is not limited thereto. For example, as shown in fig. 4, which will be described later, the plurality of composite projections 10 may be unevenly distributed on top of the base layer 141 and/or may be identical to or different from each other in size (as long as their peak heights H and peak intervals D satisfy the above-described ranges).

Referring to fig. 3, a single composite protrusion 10 may include one large protrusion 20 and a plurality of small protrusions 30. A plurality of small protrusions 30 may be formed on the outer circumference of the large protrusion 20. For example, a plurality of small protrusions 30 may be distributed on the outer surface of the large protrusion 30 and bonded to the large protrusion 30. The plurality of small protrusions 30 may completely or incompletely cover the outer surface of the large protrusions 20 to form a undulating protrusion structure on the large protrusions 20. For example, the outer circumferential profile of each composite protrusion 10 formed by the large protrusions 20 and the small protrusions 30 may have a wavy convex curve structure.

As shown in fig. 3, each tab 30 may have a peak height h. The peak height h of each of the small projections 30 may be 1 μm to 4 μm, for example, 2 μm to 3 μm. Further, as shown in fig. 3, on the same large projection 20, the peak spacing d between adjacent two small projections 30 is not more than 2 μm. This ensures a certain non-tackiness, while making the non-tackiness coating 140 at the valley position between adjacent small projections 30 less likely to be damaged by foreign objects, and thus can improve the non-tackiness lifetime.

In some embodiments, when the non-stick coating 140 is applied to a substrate 120 having an arcuate surface (e.g., without limitation, a concave curved surface, a wavy surface, etc.), the peak spacing d between adjacent small projections 30 on the same large projection 20 may be less than 2 μm.

Although fig. 3 shows that the plurality of small protrusions 30 are relatively uniformly distributed on the surface of the large protrusion 20 and have relatively uniform dimensions, the embodiment is not limited thereto. For example, as shown in fig. 5 to be described, the plurality of small projections 30 may be unevenly arranged on the surface of the large projection 20 and/or may have a difference in size (as long as their peak heights h and peak intervals d satisfy the above-described ranges).

As described above, the plurality of composite protrusions 10 are distributed on the top surface of the base layer 141, and the plurality of small protrusions 30 are distributed on the top surface of the single composite protrusion 10. Such a structure may provide the surface of the base layer 141 with micro-roughened structural characteristics. On the one hand, when food is contacted with the non-stick coating 140, the various protrusions can effectively lift up the food, which reduces the contact area of the food and the non-stick coating 140, and realizes the physical non-stick of the lotus-like structure. On the other hand, the above-mentioned various projections provide a large amount of gaps therebetween, which can substantially wrap and relatively stably store edible oil or the like, thereby achieving good oil storage non-stick.

In some embodiments, referring to fig. 1-3, both the large protrusions 20 and the small protrusions 30 may be arcuate. The large protrusions 20 may protrude from the base layer 141 in a direction away from the base material 120, and may have an outer surface having an arc shape. The small protrusions 30 coupled to the large protrusions 20 may protrude from the outer surfaces of the large protrusions 20 in a direction away from the large protrusions 20, and may have outer surfaces having an arc shape. In other words, the large protrusions 20 may be integrally formed on the protrusions having the convex curved surfaces on the top of the base layer, and the small protrusions 30 may be protrusions having the convex curved surfaces formed (e.g., bonded) on the surfaces of the large protrusions 20. When both the large protrusions 20 and the small protrusions 30 forming the composite protrusions 10 are arc-shaped, the structure of the surface roughness structure formed by the plurality of composite protrusions 10 can be made round, and the problem that the protrusions of the surface roughness structure pierce the food due to being too sharp is avoided. Under the condition, the food is not embedded in the surface layer of the non-stick coating due to puncture, so that the initial non-stick performance of the non-stick coating can be improved, and the application range of the food material of the non-stick coating is enlarged.

Referring again to fig. 1 and 2, the base layer 141 may also have a void p therein. The pores p may be distributed in the matrix layer 141. Although not shown, one or more of the pores p may communicate with each other to form a channel structure, and may also communicate outwardly through gaps between the surface roughness structures. The porosity of the matrix layer 141 on a volume percent basis may be in the range of 3% to 15% (e.g., in the range of 5% to 13%, in the range of 7% to 11%) or may also be 9%. That is, the percentage of the total volume of the pores p to the total volume of the matrix layer 141 may be within the aforementioned range. When the porosity is less than 3%, the pore oil storage amount is reduced, resulting in poor non-tackiness. When the porosity is more than 15%, the coating strength is reduced, resulting in poor abrasion resistance and eventually a shorter tack-free life.

In some embodiments, the matrix layer 141 may be formed using a granular powder material such as a granulated powder. In this case, the particulate material may be formed on the substrate 120 by a process such as spraying. The particulate materials formed on the substrate 120 may be stacked upon one another and form pores therebetween. In addition, when the base layer 141 is formed by a granular powder material, the pores p may be directly formed inside the base layer 141 and the surface roughness structure may be formed on the top of the base layer 141. An example of the granular powder material used herein will be described in detail later with reference to fig. 6. However, embodiments of the present invention are not limited thereto.

When the pores p are formed in the base layer 141, at least a portion of the pores p may communicate with gaps between protrusions of the surface roughness structure, for example, the plurality of composite protrusions 10, the plurality of large protrusions 20 (see fig. 3), and/or the plurality of small protrusions 30 (see fig. 3), to integrally form the pore structure in the base layer 141. The base layer 141 having such a pore structure can further improve the oil storage amount and the oil storage stability of the formed non-stick coating layer 140. Thus, better pore oil storage properties and better non-stick properties can be achieved. In addition, when the base layer having both the surface roughness structure and the pores is formed by the granular powder material, the process can be saved.

As described above, when the non-stick coating 140 has both the surface roughness structure and the pore structure, it is possible to obtain a coating having good initial non-stick properties and excellent pore oil storage non-stick properties. However, the non-tackiness achieved with the pore oil storage mechanism is relatively limited by the cooking scenario. For example, for cooking scenarios where the amount of household oil is small, the amount of oil that can be stored by the pore structure of the non-stick coating 140 is limited, which can lead to problems with the non-stick coating 140 having reduced non-stick properties (e.g., initial non-stick and/or non-stick during use) in the scenario.

Thus, referring to fig. 2 and 3, the non-stick coating 140 according to an embodiment may further include a non-stick resin 142.

As shown in fig. 2, a non-stick resin 142 may be disposed between the base layers 141. The non-stick resin 142 may be disposed between the respective composite protrusions 10 constituting the surface roughness structure of the base layer 141, and allows a portion of the respective composite protrusions 10 to be exposed to the outside. In other words, the non-stick resin 142 may be embedded between the surface roughness structures of the base layer 141 to partially expose the surface roughness structures, be surrounded by the respective composite protrusions 10 of the surface roughness structures of the base layer 141, and fill the space formed by the surrounding of the respective composite protrusions 10. The non-stick resin 142 may be lower than the peaks of the relief structure on the surface of the base layer 141 (for example, may be formed lower than the peaks of the composite projections 10 adjacent thereto). As shown in fig. 3, since each of the composite projections 10 of the base layer 141 includes the large projections 20 and the plurality of small projections 30, the non-stick resin 142 may also be embedded between the large projections 20 and between the small projections 30 of the base layer 141. As a result, the non-stick resin 142 may be formed in a structure embedded between the surface roughness structures of the base layer 141.

As described above, the base layer 141 may include the pores p in addition to the surface roughness. Thus, the non-stick resin 142 may also fill at least a portion of the void p. For example, the non-stick resin 142 may fill the pores p located at the upper portion of the base layer 141 depending on the process conditions, but the embodiment is not limited thereto. For example, the non-stick resin 142 may fill more or all of the pores p in the matrix layer 141.

In some embodiments, non-stick resin 142 may be a fluororesin, a silicone resin, or the like. In embodiments, the fluororesin may include one or more of polytetrafluoroethylene, polytrifluoroethylene, polyvinylidene fluoride, modified polytetrafluoroethylene. In an embodiment, the modified polytetrafluoroethylene may be a perfluoroethylene propylene, a tetrafluoroethylene-ethylene copolymer, or the like. A soaking process may be employed to cause the non-stick resin 142 to fill (e.g., adsorb and/or penetrate) into the surface roughness and pores of the matrix layer 141. This will be described later.

The non-stick resin 142 itself has non-stick properties. When it is filled in the surface roughness and pores of the base layer 141, the non-stick property of the non-stick coating layer that realizes non-stick with the surface roughness and pore oil storage can be further improved. In addition, when it fills the surface roughness of the base layer 141 and the pores in the upper portion, it can replace edible oil and the like to achieve the effect of pore-like oil storage non-stick, and thus, even in the case of a small amount of cooking oil, it is possible to maintain excellent non-stick performance of the non-stick coating 140. In addition, as it fills more or all of the pores of the non-stick coating 140, the aforementioned properties may be maintained over a long period of use, which increases the non-stick life of the non-stick coating.

Fig. 4 is a schematic plan view showing a non-stick coating according to an embodiment, and fig. 5 is a schematic enlarged view of a region C in fig. 4.

As described above, the non-stick coating 140 (see fig. 1) according to an embodiment of the present invention may include a base layer 141 and a non-stick resin 142 disposed in the base layer 141. Fig. 4 schematically shows a top plan view of such a non-stick coating 140 to explain the arrangement relationship between the base layer 141 (see fig. 2 and 3) and the non-stick resin 142 as shown in fig. 2. Fig. 5 schematically shows a top plan view with respect to one composite protrusion 10 to explain the arrangement relationship between the composite protrusion 10 and the non-stick resin 142 as shown in fig. 3.

Referring to fig. 4, in the finally formed non-stick coating 140, the plurality of composite protrusions 10 may be distributed on top of the base layer 141 with a peak pitch D of not more than 20 μm (e.g., in the range of 10 μm to 20 μm). The non-stick resin 142 (shown by hatching) may be distributed between the surface roughness structures of the base layer 141 composed of the plurality of composite protrusions 10 and fill the gaps between the surface roughness structures. As such, the non-stick resin 142 may have a "mosaic" structure in the surface roughness structure. As can be appreciated from a combination of fig. 2 and 3, the non-stick resin 142 may extend from the surface roughness of the base layer 141 toward the inside of the base layer 141 to fill the pores p formed inside the base layer 141.

Referring to fig. 5, in the composite protrusion 10 of the finally formed non-stick coating layer 140, the plurality of small protrusions 30 may be distributed at a peak pitch d of not more than 2 μm (e.g., in the range of 1 μm to 2 μm) on top of the single composite protrusion 10 (e.g., formed on the outer surface of the large protrusion 20 (see fig. 3) included in the composite protrusion 10). The non-stick resin 142 (shown by shading) may be distributed between the relief structures formed by the large protrusions 20 and the small protrusions 30 and fill the gaps formed around the large protrusions 20 (see fig. 3) and the small protrusions 30. As such, the non-stick resin 142 may also have a "damascene" structure on the composite protrusions. As can be appreciated in connection with fig. 2 and 3, the non-stick resin 142 may extend from the surface roughness of the base layer 141 toward the inside of the base layer 141 to fill the pores p formed inside the base layer 141 (e.g., in the large protrusions 20). In this manner, the non-stick resin 142 may be integrally embedded in the top of the base layer 141, and may further extend to the inside of the base layer 141, thereby achieving closure of the entire surface roughness structure and/or pore structure of the base layer 141.

In addition, fig. 4 and 5 show a surface roughness structure in which the non-stick resin 142 substantially completely encloses the base layer 141, but the embodiment is not limited thereto. In some embodiments, depending on the process conditions, the non-stick resin 142 may partially encapsulate the surface roughness of the base layer 141. That is, the non-stick resin 142 may not be formed or filled between some of the composite projections 10 and/or some of the small projections 30. For example, when the gap between two adjacent composite projections 10 is small due to their small peak pitch and/or large peak height, the non-stick resin 142 may not be filled between the two adjacent composite projections 10. For example, when the gap between two adjacent small projections 30 is small due to their small peak-to-peak distance and/or large peak height, for example, the non-stick resin 142 may not be filled between the two adjacent small projections 30.

The non-stick resin 142 may be (integrally) formed lower than peaks of the microscopic surface structure of the non-stick coating 140, and thus, as shown in fig. 4 and 5, the convex structure on the top of the base layer 141 may be partially exposed. In this case, the finally formed non-stick coating 140 may be made to retain a "lotus-like structure" to achieve physical non-stick properties. Further, since the non-stick resin 142 is not higher than the base layer 141 as a whole, the non-stick resin 142 is not in contact with a stirring tool such as a spatula, spoon, or the like during use, scratch and/or peeling of the non-stick resin 142 is prevented, and thus, durability of the non-stick coating 140 can be improved. In addition, it also allows the cooking operation to be performed directly using a conventional hard flipping tool, expanding the application range of the non-stick coating 140 and enhancing its usability.

The substrate layer is provided with the surface roughness structure with a plurality of composite bulges, and the surface roughness structure is sealed by the non-stick resin, so that the overhead capacity of the non-stick coating to food materials can be improved, the initial non-stick performance of the non-stick coating can be improved, and good non-stick performance can be maintained under the condition of low oil consumption. In addition, after the non-stick coating is worn, the exposed surface roughness structure still has good non-stick performance due to the structural characteristics, so that the service life of the non-stick coating is prolonged. At the same time, the surface roughness and/or voids may retain the non-stick resin therein to prevent complete flaking of the non-stick resin, and thus, may still have good non-stick properties (especially with less oil usage).

The base layer of the non-stick coating according to embodiments of the present invention may be formed to have a surface roughness and/or pores by various suitable processes. In some embodiments, the matrix layer may be formed by a granulated powder comprising composite particles.

Fig. 6 is a schematic view of a composite particle according to an embodiment of the invention. Fig. 6 shows a schematic structure of one composite particle 40.

Referring to fig. 6, composite particles 40 according to embodiments of the present invention may generally have a particulate form. The composite particles 40 may include first particles 41, second particles 42, and a binder.

The first particles 41 may have a larger particle size than the second particles 42. The plurality of second particles 42 may be attached to the surface of the first particles 31 to form a structure in which the plurality of second particles 42 encapsulate the first particles 41. The first particles 41 and the plurality of second particles 42 may be bonded to each other by a binder to form the composite particles 40. In this way, the composite particles themselves may have voids, such that the matrix layer formed by the composite particles can also have some voids.

Further, for convenience of explanation, fig. 4 shows only the composite particles 40 as a plurality of second particles 42 formed by wrapping a single first particle 41, but the embodiment is not limited thereto. In some embodiments, in the composite particles 40, the first particles 41 may be formed by a plurality of first particles smaller in particle size than the first particles 41 being bonded to each other, and the second particles 42 may be formed by a plurality of second particles smaller in particle size than the second particles 42 being bonded to each other. In addition, a plurality of composite particles 40 may also be combined with one another to form a larger composite particle. In this way, the porosity of the composite particles themselves can be increased, and the porosity of the finally formed matrix layer can also be increased. Here, the bonding between the particles may be achieved by the interaction of the particles themselves and/or the action of a binder.

In an embodiment, the composite particles 40 having the above structure may have a porosity in a range of 5% to 30% by volume. In this way, when the granulated powder composed of the composite particles 40 is formed into the matrix layer by using spray coating (e.g., thermal spray coating), it is possible to ensure that the porosity of the formed matrix layer is within a desired range. For example, the matrix layer formed may have a porosity in the range of 3% to 15% by volume. Further, in some embodiments, the porosity of the composite particles 40 may be in the range of 8% to 27%, 11% to 24%, 14% to 21%, or 17% to 18%. In this manner, the porosity of the formed matrix layer may be adjusted based on the porosity of the composite particles.

In some embodiments, as shown in fig. 4, the first particles 41 and the second particles 42 may each be spherical or spheroid (e.g., ellipsoidal or oval), and the composite particles 40 formed from the first particles 41 and the second particles 42 may also have a spherical or spheroid shape as a whole. When the various particles have a spherical shape or a spheroid shape, various protrusions including a surface roughness structure of the non-stick coating layer can be directly formed, and each protrusion can be naturally made to have a corresponding arc-shaped structure. In this case, it is possible to save the number of processes, reduce the post-treatment process for the surface roughness structure, and improve the initial non-stick property of the non-stick coating.

In the composite particles 40, the first particles 41 may be ceramic particles or metal particles, and the second particles 42 may be ceramic particles. In other words, the composite particles may comprise ceramic particles, a binder and optionally metal particles. In an embodiment, the particle size of the ceramic particles may be in the range of 1 μm to 10 μm, and the particle size of the metal particles may be in the range of 10 μm to 80 μm. The particle size of the ceramic particles and the particle size of the metal particles may be selected according to the surface roughness structure and the porosity of the base layer as described above.

The weight percent of the ceramic particles is 69 to 99wt%, the weight percent of the binder is 1 to 2wt%, and the weight percent of the metal particles is 0 to 30wt%, based on the total weight of the composite particles.

For example, when the composite particles include ceramic particles, binder, and metal particles, the composite particles may include, in weight percent based on the total weight of the composite particles: 69.5 to 81wt% ceramic particles, 1 to 1.4wt% binder and 17.6 to 29.5wt% metal particles; 75 to 87wt% of ceramic particles, 1.2 to 1.6wt% of binder, and 11.4 to 23.8wt% of metal particles; 81 to 93wt% of ceramic particles, 1.4 to 1.8wt% of binder and 5.2 to 17.6wt% of metal particles; or 97 to 98.9wt% ceramic particles, 1.6 to 1.9wt% binder and 0.2 to 1.4wt% metal particles.

For example, when the composite particles include ceramic particles and a binder but not metal particles, the composite particles may include, in weight percent based on the total weight of the composite particles: 98 to 99wt% of ceramic particles and 1 to 2wt% of binder; 98.2 to 98.8wt% ceramic particles and 1.2 to 1.8wt% binder; 98.4 to 98.6wt% ceramic particles and 1.4 to 1.6wt% binder; or 98.5wt% ceramic particles and 1.5wt% binder.

By including predetermined weights of optional metal particles and ceramic particles, the composite particles can have high stability and good abrasion resistance, thereby enabling a non-stick coating to be formed with good non-stick properties and non-stick lifetime. For example, an increase in the content of ceramic particles contributes to an improvement in non-stick properties. For example, an increase in the content of metal particles helps to increase the bonding force of the non-stick coating to the substrate of the non-stick cookware. In addition, when the weight of the binder is less than 1wt%, granulation cannot be effectively performed due to the small proportion of the binder; when the weight of the binder is more than 2wt%, the caking phenomenon is liable to occur after the subsequent spray sintering process and the like due to the higher proportion of the binder, thereby causing problems such as a decrease in the overall production efficiency.

In an embodiment, the ceramic particles comprise one or more materials of titanium oxide, titanium nitride, titanium carbide, ferric oxide, ferrous oxide, aluminum oxide, chromium oxide, and nickel oxide.

In embodiments, the metal particles comprise one or more materials of titanium, titanium alloy, iron, stainless steel, mild steel, high carbon steel, cast iron, copper alloy, aluminum alloy, nickel, and nickel alloy.

In an embodiment, the binder comprises a cellulosic binder and/or an alcoholic binder. For example, the cellulosic binder may include one or more of hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose. For example, the alcohol binder may include polyvinyl alcohol, polypropylene alcohol, and/or other higher alcohols. For example, higher alcohols refer to saturated or unsaturated alcohols having a carbon number of not less than 6.

By including the ceramic particles, the binder and optionally the metal particles, respectively, of a predetermined material, the composite particles may have a high stability, a high wear resistance, etc., and thus the matrix layer formed thereby may also have corresponding properties.

In an embodiment, the composite particulate material (granulated powder) composed of the composite particles as described above may be produced by means of a "slurry-spray-drying-sintering manner". Further, the composite particles may be formed by a series of processes of grinding, pulping, spray drying, sintering, and sieving, etc.

In the grinding process, the ceramic powder and/or the metal powder used to form the composite particles are ground. For example, the ceramic powder and/or the metal powder may be ball milled. After grinding, the particles in the powder may be spheroidized (or spheroidized). In addition, the polishing treatment method may be any existing technique, and the present invention is not limited thereto.

In the pulping process, the binder and the auxiliary agent are first dissolved in water to obtain a mixed solution. The auxiliary agent may include one or more of a dispersant and a defoamer. In an embodiment, the dispersant may include one or more of citric acid and triethylhexyl phosphoric acid, and the defoamer may include one or more of polyether, modified silicone oil, and silicone oil. The mixed solution may include 1 to 4wt% of a binder, 0.5 to 1wt% of a dispersant, 1 to 2wt% of a defoamer, and the balance deionized water in weight percent based on the total weight of the mixed solution. The dispersant is used for better dispersing the solid powder added to the slurry part and making the spray granulation more uniform; the defoaming agent has the effects of reducing the generation of adhesive foam, reducing the waste of the adhesive and ensuring that the final granulation is better and more accurate. Thus, in the examples, the weight of the dispersant and defoamer are in a positive proportional relationship with the weight of the binder. That is, the higher the weight of the binder, the higher the weight of the dispersant and defoamer, based on the total weight of the mixed solution.

After the mixed solution is obtained, the ground ceramic powder and optionally the metal powder are mixed with the mixed solution to obtain a slurry. Here, the slurry may have a solid content of 20wt% to 70wt% based on weight percentage. When the solid content of the slurry is less than 20wt%, the process cost is too high due to the long granulation time; when the solid content of the slurry is more than 70wt%, the liquid in the slurry occupies less liquid due to more solid content, so that the subsequent spraying process cannot be performed stably, and the production stability is further affected.

In the spray drying process, the slurry obtained is delivered to a high-speed spinning disk at 6000 rpm to 15000 rpm (preferably 6000 rpm to 12000 rpm) to form droplets. Subsequently, the droplets are blown into a drying tower of 100 to 400 ℃ by hot air of 60 to 100 ℃. During the drop descent, a residence time of 5 to 15 seconds is passed, forming a spherical (or spheroidic) powder. Since the primary particle size of the granulated powder is small, the overall particle size of the granulated powder formed after the binder is adhered is also relatively small, so that only a relatively low rotational speed is required to throw out the granulated powder, so as to save the process cost.

In the sintering process, the powder formed by spray drying is sintered to a predetermined temperature to remove moisture in the granulated powder. Here, the sintering curve may be formulated according to physical properties of the granulated powder raw material to sinter to a predetermined temperature. For example, the predetermined temperature may be 95 ℃, 100 ℃, 120 ℃, 150 ℃, or the like. The temperature rise rate of sintering may be 5 deg.c/min to 10 deg.c/min and the duration of the sintering process may be 3 hours to 10 hours. Since the primary particle size of the granulated powder is small, the overall particle size of the granulated powder formed after the binder is adhered is also relatively small, and thus, the sintering process can be completed with a relatively low temperature rising rate and a relatively short holding time, so that the process cost can be saved.

In the sieving process, the sintered granulated powder is sieved, and the granulated powder is sieved into powder with different particle size intervals according to the production requirement of the process. In the granulated powder finally obtained, a structure of particles+binder can be formed. In the particle + binder structure, the particles may be one or more particles, and thus the final granulated powder particle size is larger than the original powder particle size.

Fig. 7 is a schematic flow chart of a method for manufacturing a non-stick coating according to an embodiment of the invention.

The non-stick coating according to the embodiments of the present invention may be formed on a substrate of a non-stick cooker using the following method.

Referring to fig. 7, in step S101, a matrix layer may be formed on a substrate using the granulated powder including composite particles described above. In an embodiment, the process of forming the base layer may be thermal spraying. Specifically, the process parameters of thermal spraying may be: current is 250-600A; main gas (argon) flow of 1000-5000L/h; the hydrogen flow is 20-300L/h; the powder feeding amount is 20-200 g/min. Wherein the porosity of the formed base layer can be controlled by controlling the process parameters. For example, when the current and the hydrogen flow rate are larger, the porosity of the formed base layer is relatively high; the porosity of the formed matrix layer is relatively low as the primary air flow is greater. Furthermore, the process parameters of the thermal spraying may be selected depending on the characteristics of the composite particles used.

Since the composite particles themselves have voids and do not disperse during the spraying process, and the granulated powder containing the composite particles is integrally piled on the surface of the substrate by spraying without substantially losing the characteristics of the particles it contains, the matrix layer formed can be made to have the void structure and the porosity and the surface roughness structure as described above with reference to fig. 2 and 3.

In step S102, the substrate on which the base layer is formed may be immersed in an immersion liquid containing a non-stick resin for a predetermined time.

In an embodiment, the soak solution may be a solution containing 35wt% to 60wt% of the fluororesin particles, 2wt% to 12wt% of the soluble acrylic resin, and 2wt% to 4wt% of the cosolvent, with the balance being deionized water, based on the total weight of the soak solution. In an embodiment, the aforementioned solution may be a suspension formed by dispersing a fluororesin in a solvent. In an embodiment, the matrix layer may have a porosity of 13% to 15%, and the fluororesin particles may have a particle diameter in a range of 1 μm to 5 μm (e.g., 1 μm to 3 μm, 2 μm to 4 μm, or 2 μm to 3 μm). When the particle diameter of the fluororesin particles is within the foregoing range, filling and closing of pores and surface roughness structures of the fluororesin particles to the base layer can be promoted, thereby improving the efficiency and effect of the soaking process, and further ensuring and prolonging the initial performance and service life (especially in the case of less oil consumption) of the finally formed non-stick coating. For example, the soak solution may be a surface oil of a conventional fluororesin coating, but the embodiment is not limited thereto. Furthermore, although the process of adsorbing the non-stick resin to the base layer to fill the surface roughness structure and pores of the base layer is described herein by way of example only, the process or the like is equally applicable to other types of non-stick resins. In addition, although not specifically illustrated, the cosolvent used herein may be one commonly used in the art to which the present invention pertains.

In an embodiment, the predetermined time in step S102 may be 10min to 30min. In an embodiment, the predetermined time may be adjusted according to the roughness of the surface roughness structure of the non-stick coating. For example, the larger the protrusions of the surface roughness structure of the non-stick coating, the longer the soaking time.

In step S103, a drying process may be performed on the base layer to which the non-stick resin is adsorbed. For example, the drying process may be performed at a temperature of 80 ℃ to 100 ℃ for 10min to 30min on the base layer adsorbed with the non-stick resin. For example, the drying process may be performed at a temperature of 83 ℃ to 97 ℃ for 13min to 27min. For example, the drying process may be performed at a temperature of 86 ℃ to 94 ℃ for 16min to 24min. For example, the drying process may be performed at a temperature of 90 ℃ for 20min. By executing the drying process, the substrate layer can more fully absorb the non-stick resin, so that the filling rate of the non-stick resin to the surface roughness structure and the pores of the substrate layer is improved, and the substrate layer can obtain a better sealing effect.

In step S104, a sintering process may be performed on the dried base layer to form a non-stick coating layer. In an embodiment, the sintering temperature may be 380 ℃ to 440 ℃ and the sintering time may be 3min to 10min. For example, sintering may be performed at a temperature of 390 to 430 ℃ for 5 to 8 minutes. For example, sintering may be performed at a temperature of 410 to 420 ℃ for 6 to 7 minutes. Upon sintering, the volume of the fluororesin adsorbed in the base layer may shrink, which makes the fluororesin, which may be higher than the base layer due to capillary action, eventually form no higher than the peaks of the microstructure on the base layer, thereby making the fluororesin form to be embedded between the surface roughness structures of the base layer and fill at least a part of the pores of the base layer.

The non-stick coating manufactured by the above-described process has improved porosity and improved surface roughness, and has a structure in which pores and surface roughness are closed with a non-stick resin (e.g., a fluororesin). It should be understood that the non-stick coating produced by the above-described process has characteristics not limited thereto, depending on the details of the manufacturing process.

The non-stick coating of the present invention and the method of making the non-stick coating will be described below with reference to examples.

Example 1

In example 1, a non-stick coating was formed on a substrate using the following procedure.

Step S10: a substrate is prepared.

Step S20: granulating powder is prepared. Specifically, the granulated powder was formed from titanium nitride powder (as a ceramic powder material) having a D50 of 5 μm, low carbon steel powder (as a metal powder material) having a D50 of 30 μm, and hydroxymethyl cellulose (as a binder) by the above-mentioned "slurry-spray-drying-sintering method".

The composite particles included in the granulated powder had 78.9wt% titanium nitride, 19.7wt% mild steel and 1.4wt% hydroxymethyl cellulose based on the total weight thereof as analyzed by XRD diffractometry. The composite particles were tested to have a porosity of 18.9%.

Step S30: the granulated powder is sprayed on the surface of the base material by a thermal spraying process to form a base layer. The technological parameters of thermal spraying are as follows: current, 500A; main gas (argon) flow, 1500L/h; hydrogen flow, 100L/h; powder feeding amount is 100g/min.

The average thickness of the matrix layer formed was 50 μm and the porosity was 9.5% as measured. Through detection, in the surface roughness structure of the substrate layer, the average peak height of the composite bulges is 14.3 mu m, and the average peak interval is 15.2 mu m; the average peak height of the small protrusions was 3.1 μm, and the peak pitch was not more than 2 μm.

Step S40: preparing soaking solution. The soak solution included 45wt% polytetrafluoroethylene particles, 7wt% soluble acrylic resin, and 2.5wt% 1-methyl-2-pyrrolidone (co-solvent), with the balance being deionized water, based on the total weight of the soak solution in weight percent. Wherein the D50 of the polytetrafluoroethylene particles is 3 μm.

Step S50: the base material on which the base layer was formed was immersed in the immersion liquid for 20 minutes so that the base layer adsorbed the fluorine resin particles.

Step S60: drying was performed at 85 ℃ for 15min on the base layer adsorbed with the non-stick resin.

Step S70: sintering the dried substrate layer at 410 ℃ for 6min to finally form the non-stick coating.

Example 2

Example 2 differs from example 1 in that: titanium powder is used in place of the mild steel powder in step 20.

The composite particles of example 2 had 79wt% titanium nitride, 19.6wt% titanium and 1.4wt% hydroxymethyl cellulose based on their total weight as analyzed by XRD diffractometry. The composite particles were tested to have a porosity of 18.5%. The porosity of the matrix layer of example 2 was detected to be 9.4% and in the surface roughness structure of the matrix layer: the average peak height of the composite bulges is 14.1 mu m, and the average peak distance is 15.1 mu m; the average peak height of the small protrusions was 3.1 μm, and the peak pitch was not more than 2 μm.

Example 3

Example 3 differs from example 1 in that: in step 20, ferroferric oxide powder is used instead of titanium nitride powder.

The composite particles of example 3 had 78.8wt% of ferroferric oxide powder, 19.8wt% of mild steel and 1.4wt% of hydroxymethyl cellulose based on the total weight thereof as analyzed by XRD diffractometry. The composite particles were tested to have a porosity of 18.8%. The porosity of the matrix layer of example 2 was detected to be 9.5%, and in the surface roughness structure of the matrix layer: the average peak height of the composite bulges is 14.2 mu m, and the average peak distance is 15.2 mu m; the average peak height of the small protrusions was 3 μm, and the peak-to-peak distance was not more than 2 μm.

Example 4

Example 4 differs from example 1 in that: titanium nitride powder is used in place of the mild steel powder in step 20.

The composite particles of example 4 had 98.6wt% titanium nitride and 1.4wt% hydroxymethyl cellulose based on their total weight as analyzed by XRD diffractometry. The composite particles were tested to have a porosity of 21.2%. The porosity of the matrix layer of example 2 was detected to be 12.1% and in the surface roughness structure of the matrix layer: the average peak height of the composite bulges is 12.7 mu m, and the average peak distance is 15.2 mu m; the average peak height of the small protrusions was 3.1 μm, and the peak pitch was not more than 2 μm.

Example 5

Example 5 differs from example 1 in that: step S40 to step S60 are omitted.

Example 6

Example 6 differs from example 4 in that: step S40 to step S60 are omitted.

Comparative example 1

Comparative example 1 differs from example 1 in that: according to step S30, a non-stick coating layer was formed directly using titanium nitride powder (78.9 wt%) having a D50 of 5 μm, low carbon steel powder (19.7 wt%) having a D50 of 30 μm, and hydroxymethyl cellulose (1.4 wt%).

Comparative example 2

A pot with fluorine resin coating on the market.

Testing of initial tack-free and tack-free permanence

Specifically, the test method is as follows:

(1) Initial tack-free test method: the method for testing the non-tackiness of the omelette in GB/T32095.2-2015 is an initial non-tackiness test, and the test results are classified into grade I, grade II and grade III, wherein the non-tackiness of the grade I is optimal, and the non-tackiness of the grade III is worst.

(2) Test method of non-stick durability: in the method for testing the non-tackiness durability in GB/T32388-2015, the higher the number of times, the better the non-tackiness durability, namely, the longer the service life of the non-tackiness pot.

The initial tack-free and tack-free durability tests were performed on the tack-free coatings of examples 1-6, comparative example 1, and comparative example 2 as described above. The test results are shown in table 1.

TABLE 1 initial tack free and tack free durability test results

Example	Initial non-tackiness	Non-stick durability (secondary)
			Examples1	Ⅰ	33000
Example 2	Ⅰ	32000
			Example 3	Ⅰ	34000
Example 4	Ⅰ	43000
			Example 5	Ⅰ	22000
Example 6	Ⅰ	26000
			Comparative example 1	Ⅲ	0
Comparative example 2	Ⅰ	8000

As can be seen from table 1, each of the examples according to the invention can have better initial non-tackiness and non-tackiness durability than each of the comparative examples.

As can be seen from table 1, the non-stick coating can be made to have further improved non-stick durability by blocking the surface roughness and pores of the base layer using the fluororesin. That is, the non-stick coating can have longer non-stick property and longer service life by sealing with the fluororesin.

The non-stick coating according to embodiments of the present invention can have improved initial non-stick properties by including improved surface roughness and having a non-stick resin blocking structure, and can maintain good non-stick properties under cooking conditions with less oil usage. Thus, the non-stick coating can be applied to a wider variety of food materials, and can be applied to a wider range of cooking scenarios.

Embodiments according to the present invention can also provide non-stick coatings with improved durability.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. The embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the specific embodiments of the invention but by the claims, and all differences within the scope will be construed as being included in the present invention.

Claims

1. A non-stick coating for a cooker, the non-stick coating formed on a substrate for a cooker, the non-stick coating comprising:

A base layer having a surface roughness structure at an outer surface thereof and pores inside thereof; and

a non-stick resin embedded between the surface roughness structures of the base layer and filling at least a portion of the pores of the base layer,

wherein the surface roughness structure includes a plurality of composite protrusions distributed along a surface of the base layer, each composite protrusion including a large protrusion and a plurality of small protrusions formed on an outer circumference of the large protrusion,

wherein each compound protrusion has a peak height of 10 μm to 20 μm, a peak spacing between adjacent two compound protrusions is not more than 20 μm, and

wherein the peak height of each small bump is 1 μm to 4 μm, and the peak pitch between two adjacent small bumps on the same large bump is not more than 2 μm.

2. The non-stick coating of claim 1, wherein the base layer has a porosity in the range of 3% to 15% by volume.

3. The non-stick coating of claim 1 wherein the large protrusions and the small protrusions are each arcuate.

4. The non-stick coating of claim 1, wherein the non-stick resin is a fluororesin.

5. The non-stick coating of any one of claims 1 to 4, wherein the matrix layer is formed of composite particles,

Wherein the composite particles comprise 69 to 99wt% ceramic particles, 1 to 2wt% binder and 0 to 30wt% metal particles in weight percent based on the total weight of the composite particles,

wherein the ceramic particles comprise one or more materials of titanium oxide, titanium nitride, titanium carbide, ferroferric oxide, ferric oxide, ferrous oxide, aluminum oxide, chromium oxide and nickel oxide,

wherein the metal particles comprise one or more materials of titanium, titanium alloy, iron, stainless steel, low carbon steel, high carbon steel, cast iron, copper alloy, aluminum alloy, nickel, and nickel alloy, and

wherein the binder comprises a cellulose binder and/or an alcohol binder.

6. The non-stick coating of claim 5, wherein the composite particles, the ceramic particles, and the metal particles are all spherical or spheroid.

7. The non-stick coating of claim 5, wherein the composite particles have a porosity in the range of 5% to 30% by volume.

8. A method of manufacturing a non-stick coating, the method comprising:

forming a base layer on a substrate, wherein the base layer has a surface roughness structure at an outer surface thereof and pores inside thereof, the surface roughness structure including a plurality of composite protrusions distributed along a surface of the base layer, each composite protrusion including a large protrusion and a plurality of small protrusions formed on an outer circumference of the large protrusion;

Immersing the base material on which the base layer is formed in an immersion liquid containing a non-stick resin for a predetermined time;

performing a drying process on the base layer to which the non-stick resin is adsorbed; and

performing a sintering process on the dried base layer to form the non-stick coating layer on the substrate,

wherein in the non-stick coating layer, the non-stick resin is embedded between the surface roughness structures of the base layer and fills at least a part of the pores of the base layer,

9. The manufacturing method according to claim 8, wherein the base layer has a porosity in a range of 3% to 15% by volume.

10. The production method according to claim 8 or 9, wherein the non-stick resin is in a particulate form and has a particle diameter in a range of 1 μm to 5 μm.

11. A non-stick cookware comprising the substrate according to any one of claims 1 to 7 and a non-stick coating,

Wherein the non-stick coating at least partially covers the outer surface of the substrate.