Patent Application
20200384687
The technical field relates to 3D printing method.
Two of the most well-known methods for rapid prototyping are the selective laser sintering process and the liquid binder three-dimensional printing process. The laser-sintering and liquid binder techniques are advantageous, because they create parts directly from computer-generated design data and can produce parts having complex geometries. Moreover, three-dimensional printing can be quicker and less expensive than machining of prototype parts or production of cast or molded parts using conventional “hard” or “soft” tooling techniques, which can take from a few weeks to several months, depending on the complexity of the item.
While liquid binder techniques has an advantage in high speed and lower cost for dispensing the liquids compared to the laser sintering process, there exists a need in the art of the liquid-based 3D printing process to improve production efficiency. For example, 3D object of TPEE cannot be manufactured by binder process, it can only be manufactured by selective laser sinter (SLS) at present.
One embodiment of the disclosure provides a method of 3D-printing, including: (1) forming a first powder layer of a polymer; (2) applying an ink to the first powder layer to form a first pattern in the first powder layer, wherein the ink includes a compound; (3) pre-heating the first powder layer; (4) forming a second powder layer of the polymer on top of the pre-heated first powder layer; (5) applying the ink to the second powder layer to form a second pattern in the second powder layer; (6) pre-heating the second powder layer; (7) removing parts of the first powder layer and the second powder layer not in contact with the ink; and (8) baking the remained parts of the first powder layer and the second powder layer interacted with the compound to obtain an object. The polymer and the compound have similar molecular structure.
One embodiment of the disclosure provides a composite material, including: powder of a polymer uniformly distributed in a blend of the polymer and a compound, and the polymer and the compound have similar molecular structure. The compound has a first initially melting temperature and a first completely melting temperature, the polymer has a second initially melting temperature and a second completely melting temperature, and the first completely melting temperature is lower than the second initially melting temperature.
One embodiment of the disclosure provides an ink for 3D printing an object of a polymer, including: a compound, wherein the polymer and the compound have similar molecular structure.
A detailed description is given in the following embodiments with reference to the accompanying drawings.
The disclosure can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.
In one embodiment, a method of 3D-printing is provided. As shown in
As shown in
In some embodiments, the compound contains a hydrophilic group to be dissolved in water to form an aqueous ink 21, and the hydrophilic group includes hydroxyl, carboxylic acid, amino, ammonium, phosphate, sulphate, sulfonic, sulfhydryl, or polyethylene oxide. In some embodiments, the ink 21 also includes pigment, dye, surfactant, rheology modifier, defoamer, leveling agent, or a combination thereof. In some embodiments, the ink further comprises wetting agent, solvent, or co-solvent, and the compound is dissolved or dispersed in the solvent to form the ink 21. For example, the solvent includes toluene, xylene, ethyl acetate, butyl acetate, methoxy propyl acetate, 2-ethoxyethanol, tetraethylene glycol dimethyl ether, propylene glycol methyl ether acetate, diethylene glycol diethyl ether, water, or a combination thereof.
The ink 21 is in contact with the polymer powder 13 in the pattern 23, and not in contact with the polymer powder 13 outside the pattern 23. The method of applying the ink 21 to the powder layer 11 can be inkjet, screen printing, roll printing, another suitable method, or a combination thereof. As shown in
As shown in
As shown in
As shown in
In the above description, the steps of
As shown in
As shown in
In some embodiments, the polymer of the polymer powder 13 is polyester-type polymer, and the compound 31 of the ink 21 is ester-type monomer, oligomer, pre-polymer, or polymer. The polymer has a weight average molecular weight of 10000 to 100000, and the compound has a weight average molecular weight of 200 to 100000. For example, the polymer can be thermoplastic polyester elastomer, polylactic acid, polyethylene terephthalate, polybutylene terephthalate, polyesteramide, copolyester, or another suitable polyester-type polymer. The compound can be polyglycolic acid, polylactic acid, polycaprolactone, polyhydroxyalkanoate, polyhydroxybutyrate, polyethylene adipate, polybutylene succinate, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, another suitable polyester-type polymer, monomer thereof, oligomer thereof, or pre-polymer thereof.
In some embodiments, the polymer of the polymer powder 13 is polyurethane-type polymer, and the compound 31 of the ink 21 is urethane-type monomer, oligomer, pre-polymer, or polymer. The polymer has a weight average molecular weight of 10000 to 200000, and the compound has a weight average molecular weight of 200 to 200000.
In some embodiments, the polymer of the polymer powder 31 is polyamide-type polymer, and the compound 31 of the ink 21 is amide-type monomer, oligomer, pre-polymer, or polymer. The polymer has a weight average molecular weight of 10000 to 100000, and the compound has a weight average molecular weight of 200 to 100000. The weight average molecular weight of the polymer is related to the initial melting point and the completely melting point of the polymer of the polymer powder 31. For example, the polymer can be TPAE, nylon 12, nylon 6, or another suitable polyamide-type polymer. The compound can be nylon 6, nylon 66, nylon 6T, copolyamide, another suitable polyamide polymer, monomer thereof, oligomer thereof, or pre-polymer thereof.
In some embodiments, the polymer of the polymer powder 13 is polyacrylate-type polymer, and the compound 31 of the ink 21 is acrylate-type monomer, oligomer, pre-polymer, or polymer. The polymer has a weight average molecular weight of 10000 to 1200000, and the compound has a weight average molecular weight of 50 to 1200000. For example, the polymer can be polymethyl methacrylate, polyacrylate, polyacrylic acid, or another suitable polyacrylate-type polymer, and the compound includes polyacrylate, polyacrylic acid, another suitable polyacrylate-type polymer, monomer thereof, oligomer thereof, or pre-polymer thereof.
In some embodiments, the polymer of the polymer powder 13 is polyolefin-type polymer, and the compound 31 of the ink 21 is olefin-type monomer, oligomer, pre-polymer, or polymer. The polymer has a weight average molecular weight of 10000 to 1500000, and the compound has a weight average molecular weight of 200 to 1500000. For example, the polymer can be polyvinyl alcohol, polyolefin, or another suitable polyolefin-type polymer, and the compound can be polyethylene, polypropylene, polystyrene, polyvinyl chloride, another suitable polyolefin-type polymer, monomer thereof, oligomer thereof, or pre-polymer thereof.
In some embodiments, the compound 31 is dissolved or dispersed in the solvent to form the ink 21. The solvent can be water, toluene, xylene, ethyl acetate, butyl acetate, methoxy propyl acetate, 2-ethoxyethanol, tetraethylene glycol dimethyl ether, propylene glycol methyl ether acetate, diethylene glycol diethyl ether, ethylene glycol monobutyl ether, Carbitol solvent, butyl Carbitol, DPnB glycol ether, dipropylene glycol n-butyl ether, another suitable solvent, or a combination thereof. In some embodiments, the compound 31 contains a hydrophilic group to be dissolved in water to form an aqueous ink 21. For example, the hydrophilic groups include hydroxyl, carboxylic acid, amino, ammonium, phosphate, sulphate, sulfonic, sulfhydryl, or polyethylene oxide.
In addition, the ink 21 of the compound 31 can further include dye, pigment, colorants, surfactant, rheology modifier, defoamer, leveling agent, or another suitable additive to help the 3D-printing or change the properties or appearance (such as the color) of the final product (e.g. object).
Below, exemplary embodiments will be described in detail with reference to accompanying drawings so as to be easily realized by a person having ordinary knowledge in the art. The inventive concept may be embodied in various forms without being limited to the exemplary embodiments set forth herein. Descriptions of well-known parts are omitted for clarity, and like reference numerals refer to like elements throughout.
Thermoplastic polyester elastomer powder (TPEE, Hytrel 4056 commercially available from Dupont) was spread to form a powder layer with a thickness of 0.16 mm. 15 parts by weight of polyester (which was synthesized from 23 parts by weight of dimethylsulfoisophthalate, 24 parts by weight of ethylene glycol, and 52 parts by weight of terephthalic acid under 250° C. for 8 hours), 6 parts by weight of diethylene glycol (DEG), 8 parts by weight of triethylene glycol (TEG), 10 parts weight of 5-chloromethylfurfural (CMF), 2 parts by weight of wetting agent BYK-333 (commercially available from BYK), 0.05 parts by weight of wetting agent BYK-348 (commercially available from BYK), 0.275 parts by weight of wetting agent BYK-3455 (commercially available from BYK), 1.05 parts by weight of wetting agent Surfynol 465 (commercially available from Evonik), and 57.625 parts by weight of water were mixed to form an aqueous ink. The aqueous ink was inkjetted to the powder layer to form a pattern. The aqueous ink was in contact with the TPEE powder in the pattern, and not in contact with the TPEE powder outside of the pattern. The powder layer was pre-heated to 90° C. and kept at 90° C. for 2 seconds. During the pre-heating step, the solvent of the aqueous ink was removed, and the polyester in the aqueous ink was melted to interact with the TPEE powder. Thereafter, the steps of spreading the TPEE powder to form a powder layer, inkjetting the aqueous ink to the TPEE powder layer, and pre-heating the powder layer were repeated 50 times. Parts of the TPEE powder layers not in contact with the aqueous ink were removed. Thereafter, the pre-heated powder layers were heated to 165° C. for baking step and kept at 165° C. for 20 minutes to obtain a product. The product was a block of 246 mm×29 mm×2 mm. During the baking step, the melted polyester and surface of the TPEE powder were fused to form a blend, and the shrunk TPEE powder (the surface part of the TPEE powder was fused and blended with the melted polyester) was uniformly distributed in the blend. Because the baking temperature was lower than the completely melting point of the TPEE powder and higher than the initially melting point of the TPEE powder, the TPEE powder would not be completely melted and the fused portion blended with the melted polyester. However, the TPEE powder and the polyester in the aqueous ink were the same type of polymer (e.g. the polyester type), the blend and the shrunk TPEE powder were strongly fused without a heterogeneous interface therebetween. The product had a tensile strength of 180 kgf/cm2 (tested by the standard ASTM D412).
Polybutylene terephthalate powder (PBT, Toraymill™ PBT commercially available from Toray) was spread to form a powder layer with a thickness of 0.16 mm. 15 parts by weight of copolyester (which was synthesized from 23 parts by weight of dimethylsulfoisophthalate, 24 parts by weight of ethylene glycol, and 52 parts by weight of terephthalic acid under 250° C. for 8 hours), 72.9 parts by weight of parts by weight of 2-ethoxyethanol, 17 parts by weight of ethyl acetate, and 0.1 parts by weight of wetting agent BYK-333 were mixed to form a solvent-based ink. The solvent-based ink was inkjetted to the powder layer to form a pattern. The solvent-based ink was in contact with the PBT powder in the pattern, and not in contact with the PBT powder outside of the pattern. The powder layer was pre-heated to 90° C. and kept at 90° C. for 2 seconds. During the pre-heating step, the solvent of the solvent-based ink was removed, and the copolyester in the solvent-based ink was melted to interact with the PBT powder. Thereafter, the steps of spreading the PBT powder to form a powder layer, inkjetting the solvent-based ink to the PBT powder layer, and pre-heating the powder layer were repeated 50 times. Parts of the PBT powder layers not in contact with the solvent-based ink were removed. Thereafter, the pre-heated powder layers were heated to 160° C. for baking step and kept at 160° C. for 20 minutes to obtain a product. The product was a block of 246 mm×29 mm×2 mm. During the baking step, the melted copolyester and surface of the PBT powder were fused to form a blend, and the shrunk PBT powder (the surface part of the PBT powder was fused and blended with the melted copolyester) was uniformly distributed in the blend. Because the baking temperature was lower than the completely melting point of the PBT powder and higher than the initially melting point of the PBT powder, the PBT powder would not be completely melted and the fused potion blended with the melted copolyester. However, the PBT powder and the copolyester in the solvent-based ink were the same type of polymer (e.g. the polyester type), the blend and the shrunk PBT powder were strongly fused without a heterogeneous interface therebetween. The product had a tensile strength of 300 kgf/cm2 (tested by the standard ASTM D412).
Thermoplastic polyurethane powder (TPU, Ultrasint 3D TPU01 commercially available from BASF) was spread to form a powder layer with a thickness of 0.16 mm. 15 parts by weight of polyurethane (which was synthesized from 47 parts by weight of hexamethylene diisocyanate, 5 parts by weight of 1,4-butanediol, 14 parts by weight of 5-sulfoisophthalic acid sodium salt and 34 parts by weight of polyethylene glycol with molecular weight 200 under 80° C. for 1 hour), 6 parts by weight of ethanol, 2 parts by weight of wetting agent BYK-333, 0.05 parts by weight of wetting agent BYK-348, 0.275 parts by weight of wetting agent BYK-3455, 1.05 parts by weight of wetting agent Surfynol 465, and 57.625 parts by weight of water were mixed to form an aqueous ink. The aqueous ink was inkjetted to the powder layer to form a pattern. The aqueous ink was in contact with the TPU powder in the pattern, and not in contact with the TPU powder outside of the pattern. The powder layer was pre-heated to 90° C. and kept at 90° C. for 2 seconds. During the pre-heating step, the solvent of the aqueous ink was removed, and the polyurethane in the aqueous ink was melted to interact with the TPU powder. Thereafter, the steps of spreading the TPU powder to form a powder layer, inkjetting the aqueous ink to the TPU powder layer, and pre-heating the powder layer were repeated 50 times. Parts of the TPU powder layers not in contact with the aqueous ink were removed. Thereafter, the pre-heated powder layers were heated to 160° C. for baking step and kept at 160° C. for 20 minutes to obtain a product. The product was a block of 246 mm×29 mm×2 mm. During the baking step, the melted polyurethane and surface of the TPU powder were fused to form a blend, and the shrunk TPU powder (the surface part of the TPU powder was fused and blended with the melted polyurethane) was uniformly distributed in the blend. Because the baking temperature was lower than the completely melting point of the TPU powder and higher than the initially melting point of the TPU powder, the TPU powder would not be completely melted and the fused portion blended with the melted polyurethaner. However, the TPU powder and the polyurethane in the aqueous ink were the same type of polymer (e.g. the polyurethane type), the blend and the shrunk TPU powder were strongly fused without a heterogeneous interface therebetween. The product had a tensile strength of 65 kgf/cm2 (tested by the standard ASTM D412).
TPU powder (Ultrasint 3D TPU01 commercially available from BASF) was spread to form a powder layer with a thickness of 0.16 mm. 15 parts by weight of TPU (which was synthesized from 32 parts by weight of methylene diphenyl diisocyanate, 51 parts by weight of DIEXTER® G200, 13 parts by weight of 5-Sulfoisophthalic acid sodium salt, and 5 parts by weight of 1,4-butanediol under 80° C. for 1 hour), 72.9 parts by weight of parts by weight of 2-ethoxyethanol, 0.1 parts by weight of ethyl acetate, and 17 parts by weight of wetting agent B410 (commercially available from BYK) were mixed to form a solvent-based ink. The solvent-based ink was inkjetted to the powder layer to form a pattern. The solvent-based ink was in contact with the TPU powder in the pattern, and not in contact with the TPU powder outside of the pattern. The powder layer was pre-heated to 90° C. and kept at 90° C. for 2 seconds. During the pre-heating step, the solvent of the solvent-based ink was removed, and the TPU in the solvent-based ink was melted to interact with the TPU powder. Thereafter, the steps of spreading the TPU powder to form a powder layer, inkjetting the solvent-based ink to the TPU powder layer, and pre-heating the powder layer were repeated 50 times. Parts of the TPU powder layers not in contact with the solvent-based ink were removed. Thereafter, the pre-heated powder layers were heated to 160° C. for baking step and kept at 160° C. for 20 minutes to obtain a product. The product was a block of 246 mm×29 mm×2 mm. During the baking step, the melted TPU and surface of the TPU powder were fused to form a blend, and the shrunk TPU powder (the surface part of the TPU powder was fused and blended with the melted TPU) was uniformly distributed in the blend. Because the baking temperature was lower than the completely melting point of the TPU powder and higher than the initially melting point of the TPU powder, the TPU powder would not be completely melted and the fused portion blended with the melted TPU. However, the TPU powder and the TPU in the solvent-based ink were the same type of polymer (e.g. the polyurethane type), the blend and the shrunk TPU powder were strongly fused without a heterogeneous interface therebetween. The product had a tensile strength of 66 kgf/cm2 (tested by the standard ASTM D412).
TPAE powder (thermoplastic polyamide elastomer, Pebax 4533 commercially available from ARKEMA) was spread to form a powder layer with a thickness of 0.16 mm. 15 parts by weight of polyamide (which was synthesized from 21 parts by weight of dimethyl 5-sulfoisophthalate sodium salt, 40 parts by weight of caprolactam, 39 parts by weight of Jeffamine ED-900 under 240° C. for 8 hours), 0.05 parts by weight of wetting agent BYK-333, 0.5 parts by weight of wetting agent B410, and 20 parts by weight of propylene glycol methyl ether acetate (PMA) were mixed to form a solvent-based ink. The solvent-based ink was inkjetted to the powder layer to form a pattern. The solvent-based ink was in contact with the TPAE powder in the pattern, and not in contact with the TPAE powder outside of the pattern. The powder layer was pre-heated to 90° C. and kept at 90° C. for 2 seconds. During the pre-heating step, the solvent of the solvent-based ink was removed, and the polyamide in the solvent-based ink was melted to interact with the TPAE powder. Thereafter, the steps of spreading the TPAE powder to form a powder layer, inkjetting the solvent-based ink to the TPAE powder layer, and pre-heating the powder layer were repeated 50 times. Parts of the TPAE powder layers not in contact with the solvent-based ink were removed. Thereafter, the pre-heated powder layers were heated to 160° C. for baking step and kept at 160° C. for 20 minutes to obtain a product. The product was a block of 246 mm×29 mm×2 mm. During the baking step, the melted polyamide and surface of the TPAE powder were fused to form a blend, and the shrunk TPAE powder (the surface part of the TPAE powder was fused and blended with the melted polyamide) was uniformly distributed in the blend. Because the baking temperature was lower than the completely melting point of the TPAE powder and higher than the initially melting point of the TPAE powder, the TPAE powder would not be completely melted and the fused portion blended with the melted polyamide. However, the TPAE powder and the polyamide in the solvent-based ink were the same type of polymer (e.g. the polyamide type), the blend and the shrunk TPAE powder were strongly fused without a heterogeneous interface therebetween. The product had a tensile strength of 270 kgf/cm2 (tested by the standard ASTM D412).
Nylon 12 powder (VESTOSINT 3D Z2773 PA 12 commercially available from Evonik) was spread to form a powder layer with a thickness of 0.16 mm. 15 parts by weight of polyamide (which was synthesized from 21 parts by weight of dimethyl 5-sulfoisophthalate sodium salt, 40 parts by weight of caprolactam, 39 parts by weight of Jeffamine ED-900 under 240° C. for 8 hours), 0.05 parts by weight of wetting agent BYK-333, 0.5 parts by weight of wetting agent B410, and 20 parts by weight of PMA were mixed to form a solvent-based ink. The solvent-based ink was inkjetted to the powder layer to form a pattern. The solvent-based ink was in contact with the nylon 12 powder in the pattern, and not in contact with the nylon 12 powder outside of the pattern. The powder layer was pre-heated to 90° C. and kept at 90° C. for 2 seconds. During the pre-heating step, the solvent of the solvent-based ink was removed, and the polyamide in the solvent-based ink was melted to adhere the nylon 12 powder. Thereafter, the steps of spreading the Nylon 12 powder to form a powder layer, inkjetting the solvent-based ink to the nylon 12 powder layer, and pre-heating the powder layer were repeated 50 times. Parts of the nylon 12 powder layers not in contact with the solvent-based ink were removed. Thereafter, the pre-heated powder layers were heated to 160° C. for baking step and kept at 160° C. for 20 minutes to obtain a product. The product was a block of 246 mm×29 mm×2 mm. During the baking step, the melted polyamide and surface of the nylon 12 powder were fused to form a blend, and the shrunk nylon 12 powder (the surface part of the nylon 12 powder was fused and blended with the melted polyamide) was uniformly distributed in the blend. Because the baking temperature was lower than the completely melting point of the nylon 12 powder and higher than the initially melting point of the nylon 12 powder, the nylon 12 powder would not be completely melted and the fused portion blended with the melted polyamide. However, the nylon 12 powder and the polyamide in the solvent-based ink were the same type of polymer (e.g. the polyamide type), the blend and the shrunk nylon 12 powder were strongly fused without a heterogeneous interface therebetween. The product had a tensile strength of 310 kgf/cm2 (tested by the standard ASTM D412).
Polyolefin powder (Ultrasint PP nat 01 commercially available from BASF) was spread to form a powder layer with a thickness of 0.16 mm. 10 parts by weight of atactic polypropylene oxide (APAO, Vistamaxx 6502 commercially available from ExxonMobil Chemical), 0.1 parts by weight of wetting agent BYK-333, 0.5 parts by weight of wetting agent B410, and 69.4 parts by weight of toluene were mixed to form a solvent-based ink. The solvent-based ink was inkjetted to the powder layer to form a pattern. The solvent-based ink was in contact with the polyolefin powder in the pattern, and not in contact with the polyolefin powder outside of the pattern. The powder layer was pre-heated to 90° C. and kept at 90° C. for 2 seconds. During the pre-heating step, the solvent of the solvent-based ink was removed, and the APAO in the solvent-based ink was melted to adhere the polyolefin powder. Thereafter, the steps of spreading the polyolefin powder to form a powder layer, inkjetting the solvent-based ink to the polyolefin powder layer, and pre-heating the powder layer were repeated 50 times. Parts of the polyolefin powder layers not in contact with the solvent-based ink were removed. Thereafter, the pre-heated powder layers were heated to 160° C. for baking step and kept at 160° C. for 20 minutes to obtain a product. The product was a block of 246 mm×29 mm×2 mm. During the baking step, the melted APAO and surface of the polyolefin powder were fused to form a blend, and the shrunk polyolefin powder (the surface part of the polyolefin powder was fused and blended with the melted APAO) was uniformly distributed in the blend. Because the baking temperature was lower than the completely melting point of the polyolefin powder and higher than the initially melting point of the polyolefin powder, the polyolefin powder would not be completely melted and the fused portion blended with the melted APAO. However, the polyolefin powder and the APAO in the solvent-based ink were the same type of polymer (e.g. the polyolefin type), the blend and the shrunk polyolefin powder were strongly fused without a heterogeneous interface therebetween. The product had a tensile strength of 180 kgf/cm2 (tested by the standard ASTM D412).
Polymethyl methacrylate powder (PMMA, Solupor commercially available from Voxeljet) was spread to form a powder layer with a thickness of 0.16 mm. 100 parts by weight of polyacrylic emulsion (which was synthesized from 42 parts by weight of methyl methacrylate, 50 parts by weight of n-butyl acrylate, 8 parts by weight of acrylic acid, 0.4 parts by weight of sodium peroxodisulfate, and 100 parts by weight of water), 0.1 parts by weight of wetting agent BYK-333, 0.5 parts by weight of wetting agent B410, and 10 parts by weight of water were mixed to form an aqueous ink. The aqueous ink was inkjetted to the powder layer to form a pattern. The aqueous ink was in contact with the PMMA powder in the pattern, and not in contact with the PMAA powder outside of the pattern. The powder layer was pre-heated to 90° C. and kept at 90° C. for 2 seconds. During the pre-heating step, the solvent of the aqueous ink was removed, and the PA in the aqueous ink was melted to adhere the PMMA powder. Thereafter, the steps of spreading the PMMA powder to form a powder layer, inkjetting the aqueous ink to the PMMA powder layer, and pre-heating the powder layer were repeated 50 times. Parts of the PMMA powder layers not in contact with the aqueous ink were removed. Thereafter, the pre-heated powder layers were heated to 160° C. for baking step and kept at 160° C. for 20 minutes to obtain a product. The product was a block of 246 mm×29 mm×2 mm. During the baking step, the melted PA and surface of the PMAA powder were fused to form a blend, and the shrunk polyolefin powder (the surface part of the PMAA powder was fused and blended with the melted PA) was uniformly distributed in the blend.
Because the baking temperature was lower than the completely melting point of the PMAA powder and higher than the initially melting point of the PMAA powder, the PMAA powder would not be completely melted and the fused portion blended with the melted PA. However, the PMAA powder and the PA in the aqueous ink were the same type of polymer (e.g. the polyacrylate type), the blend and the shrunk PMAA powder were strongly fused without a heterogeneous interface therebetween. The product had a tensile strength of 20 kgf/cm2 (tested by the standard ASTM D412).
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed methods and materials. It is intended that the specification and examples be considered as exemplary only, with the true scope of the disclosure being indicated by the following claims and their equivalents.
This application claims the benefit of U.S. Provisional Application No. 62/859,287, filed on Jun. 10, 2019, the entirety of which is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 62859287 | Jun 2019 | US |
