Patent Application
20180208779
Not applicable.
Not applicable.
The disclosure relates generally to fire resistant, thermal barriers thermally-resistant for protecting components exposed to relatively high thermal energies. More particularly, the disclosure relates to slurry cast thermally-resistant coatings for protecting polymer substrates from thermal damage.
A significant portion of fire-related injuries and damage occur in the home and in connection with transportation vehicles such as cars and airplanes. For example, components in a vehicle positioned near an internal combustion engine (e.g., near a jet engine of an airplane) experience relatively high thermal loads. If not adequately shielded or protected from the thermal loads, such components may be damaged and/or catch fire. One conventional technique for protecting components from thermal energy is to simply position such components at a greater distance from the source of the thermal energy. However, this technique necessitates the availability of space, which may be limited, particularly in aerospace applications. Other conventional techniques for protecting components from thermal energy include manufacturing such components from more exotic, fire resistant materials, and attaching fire resistant panel to such components. However, such techniques can increases costs (materials and manufacturing costs) and add weight, which is also undesirable in many aerospace applications.
In an embodiment, a method for manufacturing a thermally-resistant component, the method comprising: forming a first homogenous coating solution by mixing a first aqueous solution including an cationic polymer and a second aqueous solution including an anionic clay; and applying the first homogenous coating solution to a first side of a substrate.
In an embodiment, a thermally-resistant component, comprising: a polymeric substrate; and a thermally insulating coating mounted to the substrate, wherein the coating comprises a mixture of one or more cationic polymers and one or more anionic clays.
Embodiments described herein comprise a combination of features and advantages intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical advantages of the invention in order that the detailed description of the invention that follows may be better understood. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:
The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.
Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.
In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to an axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis.
Discussed herein are embodiments of thermally-resistant barriers or coatings, as well as methods for applying such coatings, for polymer substrates. Such thermally-resistant coatings and methods enable tailorable properties, decreased coating times, and use in connection with a variety of substrates including polymers, metals, and ceramics. In general, the substrates described herein may be 2D or 3D components that can be coated on one or more sides, faces, or surfaces. In addition, the manufacture and application of embodiments of the thermally-resistant barriers and coatings described herein can be scaled up for mass production. For example, embodiments described herein can be applied to components used in or near internal combustion engines such coated components are not only resistant to and protected from anticipated thermal loads, but are also fire resistant. Such fire-resistance may, for example, not only exhibit improved thermal resistance properties during normal use, but also advantageously enable continued operation of vehicles (e.g., airplanes) despite an engine fire.
In various embodiments, a coating comprising at least one anionic component and at least one cationic component is applied to at least one side of a polymeric substrate. In some embodiments, non-ionic components may be included, these may include polymers such as poly(vinyl alcohol) instead of or in addition to chitosan. The coating is applied as an aqueous, homogenous solution formed from a first aqueous solution of one or more cationic polymers (e.g., chitosan) and a second aqueous solution of one or more anionic clay (e.g., vermiculite (VMT), sodium montmorillonite (MMT), etc.). In some embodiments, the cationic polymers employed exhibit a charring property such as polysaccharides that comprise at least one nitrogen groups. For example, while chitosan is discussed herein, the cationic polymer employed in various embodiments of the present disclosure may comprise other polysaccharides that comprise ring structures and nitrogen groups. In general, embodiments of thermally-resistant coatings described herein can be applied directly to a substrate (e.g., polymer substrate) by spraying, roll-to-roll coating technology such as a blade coating, dip coating, or other suitable method. In addition, the coatings can be applied to one or both sides of the substrate as desired. In some embodiments, a primer layer such as polyethylenimine (PEI) or poly(acrylic) acid (PAA) is applied to the substrate prior to the application of the thermally-resistant coating. Still further, embodiments of thermally-resistant coatings described herein can be applied as a single layer in one application step, or applied in multiple layers in multiple application steps. In embodiments where more than one layer is applied to the substrate, an intermediate drying step can be performed between the application of each layer.
Referring now to
Coating 104 is made of a composition 106 including a homogenous, uniform mixture of one or more cationic (or non-ionic) polymer(s) and one or more anionic clay(s). In embodiments described herein, each of the one or more cationic polymer(s) is preferably a cationic polysaccharide selected from chitosan, cellulose, or starch. The cationic polymer could also be a nitrogen-rich polyelectrolyte, such as polyethylenimine, polyallylamine, polyvinylamine or copolymers containing them. Non-ionic polymers could include polyvinyl alcohol, polyvinylpyrrolidone and polyethylene oxide. In some embodiments, to facilitate charring (as opposed to igniting) when exposed to relatively high thermal energy, one or more of the selected cationic polymers preferably includes at least one nitrogen group per repeat unit. In addition, in embodiments described herein, each of the one or more anionic clay(s) is preferably selected from montomotillonite (MMT) clay (e.g., natural untreated sodium montmorillonite), vermiculite (VMT) clay (e.g., natural vermiculite), kaolinite, halloysite, sepioloite, bentonite, or other inorganic silicate-based materials. Composition 106 preferably comprises 3 to 50 wt % of the one or more cationic polymers and 50 to 97 wt % of the anionic clay(s) when the coating is dried. As will be described in more detail below, coating 104 can be formed by applying composition 106 as a single layer in one application step or by applying composition 106 via multiple layers in a plurality of application steps.
Coating 104 has a thickness T104 measured perpendicular to the surface 102a of substrate 102 on which coating 104 is applied, and substrate 102 has a thickness T102 measured perpendicularly from side 102a to opposite side 102b. The thickness T104 is preferably selected to provide the desired thermal resistance, which may vary from application to application. In embodiments described herein, the thickness T104 is preferably greater than 0.001 mm, and more preferably 0.01 mm to 0.1 mm. In addition, the ratio of the thickness T104 of coating 104 to the thickness T102 of substrate 102 is preferably between 1:10 and 1:1. In some embodiments, the weight of coating 104 is up to about 20% of the weight of the underlying substrate 102.
In the embodiment shown in
As shown in
Referring now to
In this embodiment, primer layer 108 is made of at least one of linear polyethylenimine (L-PEI), branched polyethylenimine (B-PEI), or poly(acrylic acid) (PAA). The primer could simply be a thin layer (0.01-10 micron thick) of polyethylenimine alone. The primer serves to promote strong adhesion between the protective coating and the substrate to be protected. Primer layer 108 can be applied as a single layer in one application step or applied via multiple layers in a plurality of application steps. Coating 104 and substrate 102 have thicknesses T104, T102, respectively, each as previously described. Thus, thickness T104 is preferably greater than 0.001 mm, and more preferably 0.01 mm to 0.1 mm. Further, the ratio of the thickness T104 of coating 104 to the thickness T102 of substrate 102 is preferably between preferably between 1:10 and 1:1. Primer layer 108 has a thickness T108 measured perpendicular to the surface 102a of substrate 102 on which layer 108 is applied. Thickness T108 is preferably greater than 0.00001 mm, and more preferably 0.0001 mm to 0.01 mm.
In the embodiment shown in
As shown in
Referring now to
Coating 204 (including the plurality of layers 204a, 204b) has a thickness T204 measured perpendicular to side 102a to which it is applied, and substrate 102 has a thicknesses T102 as previously described. Similar to thickness T104 previously described, thickness T204 is preferably greater than 0.001 mm, and more preferably 0.01 mm to 0.1 mm. Further, the ratio of the thickness T204 of coating 204 to the thickness T102 of substrate 102 is preferably between 1:1 and 1:10. Each layer 204a, 204b of coating 204 has a thickness T204a, T204b, respectively, and each thickness T204a, T204b is preferably greater than 0.0005 mm, and more preferably 0.005 mm to 0.05 mm. In general, the thickness T204a, T204b of each layer 204a, 204b can be the same or different. Further, the weight of coating 204 is up to about 20% of the weight of the underlying substrate 102.
In general, each layer 204a, 204b of coating 204 can be formed by applying composition 206a, 206b, respectively, as a single layer in one application step or by applying composition 206a, 206b, respectively, via multiple layers in a plurality of application steps. Although only two layers 204a, 204b are shown in
In the embodiment shown in
In general, each layer 204a, 204b of each coating 204 can be formed by applying composition 206a, 206b, respectively, as a single layer in one application step or by applying composition 206a, 206b, respectively, via multiple layers in a plurality of application steps. Although only two layers 204a, 204b are shown in each coating 204 in
Referring now to
Primer layer 108 is as previously described. Namely, primer layer 108 is made of at least one of linear polyethylenimine (L-PEI), branched polyethylenimine (B-PEI), or poly(acrylic acid) (PAA). In general, primer layer 108 can be applied as a single layer in one application step or applied via multiple layers in a plurality of application steps.
Coating 204 has a thickness T204, substrate 102 has a thickness T102, and each layer 204a, 204b of coating 204 has a thickness T204a, T204b, each as previously described. Thus, thickness T204 is preferably greater than 0.001 mm, and more preferably 0.01 mm to 0.1 mm. Further, the ratio of the thickness T204 of coating 204 to the thickness T102 of substrate 102 is preferably between 1:1 and 1:10. Each layer 204a, 204b of coating 204 has a thickness T204a, T204b, respectively, and each thickness T204a, T204b is preferably greater than 0.0005 mm, and more preferably 0.005 mm to 0.05 mm. In general, the thickness T204a, T204b of each layer 204a, 204b can be the same or different.
Primer layer 108 has a thickness T108 as previously described. Thus, thickness T108 is preferably greater than 0.00001 mm, and more preferably 0.0001 mm to 0.01 mm. The weight of coating 204 is up to about 20% of the weight of the underlying substrate 102.
In general, each layer 204a, 204b of coating 204 can be formed by applying composition 206a, 206b, respectively, as a single layer in one application step or by applying composition 206a, 206b, respectively, via multiple layers in a plurality of application steps. In addition, primer layer 108 can be applied as a single layer in one application step or applied via multiple layers in a plurality of application steps. Although only two layers 204a, 204b are shown in
In the embodiment shown in
In general, thickness T204 of each coating 204 can be the same or different, and further, the thickness T108 of each primer layer 108 can be the same or different. Each layer 204a, 204b of each coating 204 can be formed by applying composition 206a, 206b, respectively, as a single layer in one application step or by applying composition 206a, 206b, respectively, via multiple layers in a plurality of application steps. In addition, each primer layer 108 can be applied as a single layer in one application step or applied via multiple layers in a plurality of application steps. Although only two layers 204a, 204b are shown in each coating 204 in
In various embodiments, substrates may be coated on one or both sides with the following layers, where the X % is the weight percentage of the component in a dried coating. Some example trilayer formulations that may be disposed on one or both sides of a substrate, or otherwise disposed on a 3-dimensional component may comprise: (1) CH(12%)-MMT/MMT(12%)/CH(12%)-MMT; (2) CH(12%)-MMT/VMT(12%)/CH(12%)-MMT; CH(12%)-VMT/MMT(12%)/CH(12%)-VMT; or (3) CH(12%)-VMT/VMT(12%)/CH(12%)-VMT.
Referring now to
Referring still to
In embodiments where a primer layer 108 is applied at block 504, the homogenous aqueous coating solution formed at block 510 is applied to one or both sides 102a, 102b of the substrate 102 directly on top of the primer layer 108 (i.e., the pretreatment layer 108 is applied directly onto the substrate 102 and the homogenous aqueous coating solution is subsequently applied to the primer layer 108). However, in embodiments where no primer layer 108 is applied at block 504, the homogenous aqueous coating solution formed at block 510 is directly applied to one or both sides 102a, 102b of the substrate 102. In general, the application of the homogenous aqueous coating solution at block 510 can be performed by roll-to-roll coating methods referred to as “blade coating” or by dip coating such that both sides 102a, 102b of substrate are coated simultaneously, or the homogenous aqueous coating solution can be applied by an optimized spray process to coat one or both sides 102a, 102b. Depending upon the method employed at block 510, both sides 102a, 102b of the substrate 102 may be coated simultaneously, or each side 102a, 102b of the substrate 102 may have one or more layers applied in one or more process steps to form the completed structure.
Moving now to block 514, to form embodiments of coatings 104 previously described, the homogenous aqueous coating solution is allowed to dry (air dried at room temperature or at an elevated temperature) to form thermal insulating coating 104. In some embodiments, the thermal insulating coating 104 is formed by applying the homogenous aqueous coating solution in multiple layers. In such embodiments, the drying at block 514 is performed after each layer of the homogenous aqueous coating solution is applied at block 512. The application of the homogenous aqueous coating solution can be performed on one or both sides 102a, 102b at a time and then allowed to dry. The coating solution may be applied as discussed herein in a single step, in a single layer, or it may be applied in multiple steps in a single process in multiple layers, and there may or may not be intermediate drying steps employed. The coating solution may be applied by roll-to-roll application (blade coating), spraying, and/or dipping. In some embodiments, the coating may be applied to both sides of a substrate and/or to multiple sides of a structure.
Referring still to
While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.
To further illustrate various illustrative embodiments of the present invention, the following examples are provided.
Natural vermiculite (VMT) (formulation HTS-SE) was purchased from Specialty Vermiculite (Enoree, S.C.). Southern Clay Products, Inc. (Gonzales, Tex.) supplied natural, untreated sodium montmorillonite (MMT) (tradename Cloisite NA+). The MMT platelets had a density of 2.86 g/cm3, an average diameter of 300-800 nm, and a thickness of about 1 nm. Cationic chitosan (CH) (M=60,000 g/mol, 95% deacetylated) was purchased from G.T.C. Union Group (Qingdao, China). 2 wt % MMT and VMT solutions were made with 18.2MΩ deionized (DI) water and rolled overnight for full dissolution. 0.2 wt % CH solution was made using pH 2 DI water and readjusted to pH 5 using sodium hydroxyl.
In an embodiment, and as illustrated in the desired aqueous cationic and anionic solutions were prepared to form a homogenous coating solution. In various embodiments, each of the chitosan (cationic), MMT, and VMT materials were mixed with water to form separate aqueous solutions. Both MMT and VMT are discussed herein as the anionic components, and the resultant solutions when those components were mixed with deionized water may be collectively referred to as anionic aqueous solutions. The desired amounts of each of the chitosan and one of the MMT and VMT were mixed together to form a single, homogeneous coating solution. This homogenous coating solution was applied by casting or spraying the mixture into a mold with the polymide laminate substrates inside.
While polyimide laminate substrates were used herein, in other examples, other polymer substrates may be used. These substrates may be hollow, solid, comprise perforations and/or through-holes, or comprise a core structure of a different composition. The samples were dried at room temperature after application of the coating in order to evaporate the water from the coating solution. In alternate embodiments, an oven or other thermal source could be used to accelerate this step. In some embodiments, a pretreatment layer of PEI or PAA may be applied to the substrate prior to the application of the coating. In an embodiment, the weight % of chitosan in a dried coating was less than 13% when MMT was used in combination with the chitosan.
In various embodiments, the experiment was repeated using different concentrations of MMT and chitosan, as well as VMT and chitosan as discussed further below. Table 1 comprises the coating recipes investigated and the difference weight gain among and between the various compositions.
The flame resistant performances of the coatings after burning for 5 minutes are shown in Table 2. Increasing the CH percentage helps to prevent flame burn through, as indicated by a check mark. Increasing the weight gain also prevents flame burn through.
By increasing the dry temperature, the time to make dry coatings greatly decreased. In one example, the results of which are illustrated in 11C, after 0.3 h at 90° C., 0.5 h at 80° C., 1 h at 60° C. and 2 h at room temperature, 20% water was removed and the coatings remain on the surface of laminate. That is, the samples did not exhibit delamination or sliding of the coating even when the samples were tilted. In another example, the results of which are illustrated in
In another example, in a similar fashion to the example described above in the single-sided coating embodiment, a plurality of samples were fabricated by coating a substrate on both sides. In particular, samples were coated on both sides with a dry coating of 5% CH-95% MMT and samples were coated on both sides with a coating solution of 7% CH-93% MMT, both as measured when the coating was dry.
As shown in
In another example, samples were coated with trilayers of CH(12%)-MMT/MMT(12%)/CH(12%)-MMT; CH(12%)-MMT/VMT(12%)/CH(12%)-MMT; CH(12%)-VMT/MMT(12%)/CH(12%)-VMT; CH(12%)-VMT/VMT(12%)/CH(12%)-VMT.
Exemplary embodiments are disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternate embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, Rl, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=R+k*(Ru−Rl), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of broader terms such as “comprises,” “includes,” and “having” should be understood to provide support for narrower terms such as “consisting of,” “consisting essentially of,” and “comprised substantially of.” Each and every claim is incorporated into the specification as further disclosure, and the claims are exemplary embodiment(s) of the present invention.
While exemplary embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the compositions, systems, apparatus, and processes described herein are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order and with any suitable combination of materials and processing conditions.
