WO2006084117A2 - Method for forming and bonding thermoformable composites - Google Patents

Method for forming and bonding thermoformable composites Download PDF

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Publication number
WO2006084117A2
WO2006084117A2 PCT/US2006/003819 US2006003819W WO2006084117A2 WO 2006084117 A2 WO2006084117 A2 WO 2006084117A2 US 2006003819 W US2006003819 W US 2006003819W WO 2006084117 A2 WO2006084117 A2 WO 2006084117A2
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WO
WIPO (PCT)
Prior art keywords
thermoplastic
composite
honeycomb
adhesive
facing sheets
Prior art date
Application number
PCT/US2006/003819
Other languages
French (fr)
Other versions
WO2006084117A3 (en
Inventor
Thomas St. Denis
Gabriel M. Karamanis
Original Assignee
Panterra Engineered Plastics, Inc.
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Application filed by Panterra Engineered Plastics, Inc. filed Critical Panterra Engineered Plastics, Inc.
Publication of WO2006084117A2 publication Critical patent/WO2006084117A2/en
Publication of WO2006084117A3 publication Critical patent/WO2006084117A3/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
    • B32B37/146—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers whereby one or more of the layers is a honeycomb structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B38/18—Handling of layers or the laminate
    • B32B38/1866—Handling of layers or the laminate conforming the layers or laminate to a convex or concave profile
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/12—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
    • B32B37/1207—Heat-activated adhesive
    • B32B2037/1215—Hot-melt adhesive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
    • B32B2309/02—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
    • B32B2309/12—Pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2310/00—Treatment by energy or chemical effects
    • B32B2310/14—Corona, ionisation, electrical discharge, plasma treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/08—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the cooling method
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/12—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
    • B32B37/15—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state
    • B32B37/153—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state at least one layer is extruded and immediately laminated while in semi-molten state
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B38/0008—Electrical discharge treatment, e.g. corona, plasma treatment; wave energy or particle radiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B38/12—Deep-drawing

Definitions

  • the present invention relates to a method of producing thermoformable composites by thermoforming expanded thermoplastic honeycomb and extruded or co-extruded thermoplastic facing materials and bonding them with appropriate adhesives in a cost-effective and efficient manner.
  • thermoforming and bond expanded thermoplastic honeycomb and extruded or co-extruded facing materials into a composite structure involve a number of different steps. The most common of these methods involves thermoforming the facings individually to a specific geometry, thermoforming the expanded honeycomb to a specific geometry, applying adhesive to the mating materials, and bonding the mating materials in a male or female tool with the desired geometry under pressure and heat.
  • Another variation of the process is to twin form the facing materials simultaneously to a specific geometry, thermoform the expanded honeycomb to a specific geometry, apply adhesive to the mating materials, and bond the mating materials in a male or female tool with the desired geometry under pressure and heat.
  • thermoforming the facings individually to a specific geometry thermoforming the expanded honeycomb to a specific geometry, applying adhesive to one facing material and one side of the honeycomb, and bonding them in a male or female tool with the desired geometry under pressure and heat.
  • adhesive is applied to the second facing and the other side of the expanded honeycomb, and these materials are bonded to the other half of the structure in a male or female tool with the desired geometry under pressure and heat.
  • thermoforming and bonding extruded or co-extruded thermoplastic facing materials and expanded honeycomb cores into composites that avoids the aforementioned disadvantages.
  • the present invention overcomes all of the disadvantages of the methods for thermoforming composites discussed above.
  • the present invention provides a unique method in which the thermoformable composites are thermoformed and bonded in the same step.
  • the present invention further provides a method for producing thermoformable composites that significantly improves on the manufacturing costs of currently available methods.
  • the present invention further provides a method for producing thermoformable composites that improves on the product cycle time and production capacity of currently available methods.
  • the present invention further provides a method for producing thermoformable composites that significantly reduces the amount of equipment used in the manufacturing processes of currently available methods.
  • the present invention provides a cost-effective and energy efficient method for producing thermoformable composites that includes thermoforming expanded honeycomb and thermoformable facing sheets and bonding them with appropriate adhesives in the same step. This method reduces the cycle times and improves the throughput of currently available methods.
  • the method of the present invention encompasses the steps of: applying the appropriate adhesives in liquid, paste or film form to extruded or co-extruded sheets of thermoplastic material or to thermoplastic honeycomb (such as that made by Panterra Engineered Plastics, Inc.); placing a pre-assembled composite in a closed mold tool, the pre-assembled composite comprising layers of a thermoformable facing sheet, adhesive, thermoplastic honeycomb, adhesive, and another thermoformable facing sheet, in that order; heating the pre-assembled composite to a temperature in the range of about 200°F to about 600°F at a pressure of about 0.1 to about 20 p.s.L; thermoforming and bonding the pre- assembled composite into the final assembly; and cooling the composite to between about 70-150°F on the tool to facilitate release from the tool.
  • thermoplastic honeycomb such as that made by Panterra Engineered Plastics, Inc.
  • Fig. 1 is a cross-sectional view of a pre-assembly composite formed using the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION
  • Pre-assembly composite 10 has honeycomb 20, upper facing sheet 40, and lower facing sheet 60.
  • An appropriate adhesive in liquid, paste or film form may first be applied to one side of either upper facing sheet 40 or lower facing sheet 60, or alternatively the upper or lower face of honeycomb 20.
  • Another layer of adhesive is then applied on the uncoated facing sheet or uncoated face of honeycomb 20.
  • Adhesive can be applied to the upper and lower facing sheets 40 and 60 or honeycomb 20 by spraying, roll coating, film application, or any other suitable method. The adhesive thus forms two layers, upper adhesive layer 30 and lower adhesive layer 50.
  • thermoplastic polymeric materials in the pre-assembly composite that have similar rheological, thermal, melt index/flow and softening/melting point indices. Use of materials that are dissimilar in these characteristics will make processing of the pre-assembly composite more difficult.
  • the thermoformable honeycomb 20 and the upper and lower facing sheets 40 and 60 are made of a thermoplastic material. Suitable candidates for this material include, but are not limited to, high impact polystyrene, polycarbonate, acrylonitrile butadiene styrene, homo- or co-polymer polypropylene, low- and high- density polyethylene, and other thermoplastic materials. It should be emphasized that this list is a small representation of the many thermoplastic compounds that can be used in the method of the present invention.
  • thermoformable honeycomb 20 and the upper and lower facing sheets 40 and 60 may be pre-treated prior to the application of the adhesive with plasma or corona techniques, which increases the surface energy of the materials and facilitates bonding of the materials in the process. These pre- treatment processes are well known to those skilled in the art.
  • the choice of the adhesives used in the present invention is paramount to the success in producing a composite structure that can be thermoformed and bonded in the one step process.
  • the liquids, pastes or films used in the invention must inherently have an appropriate degree of flexibility to allow the composite structure to initially be thermoformed and also have rigidity characteristics that will produce a structurally sound component.
  • Suitable candidates for the adhesives of the present invention include, but are not limited to, polyurethanes, methacrylates, flexible epoxies, ethylene vinyl acetates, polyvinyl acetates, hot melt urethanes, polyethylene and polypropylene films.
  • the adhesive can be a thermoset or thermoplastic adhesive, although other kinds of adhesives are contemplated by the present invention.
  • thermoformable facing sheet 40 After the adhesive has been applied to upper thermoformable facing sheet 40, lower thermoformable facing sheet 60, and/or honeycomb 20, the materials are placed in the mold as shown. Upper facing sheet 40 contacts upper mold plate 70, and lower facing sheet 60 contacts lower mold plate 80, with honeycomb 20 disposed between the upper and lower facing sheets 40 and 60.
  • Upper facing sheet 40, upper adhesive layer 30, honeycomb 20, lower adhesive layer 50, and lower facing sheet 60 are then heated in the mold to a temperature in the range of from about 200°F to about 600 0 F, and subjected to a pressure of between about 0.1 to about 20 p.s.i. This consolidates the materials into one composite assembly 10.
  • the proper temperature and pressure to be applied will depend on the specific materials used.
  • the amount of time that the pre-assembly composite is subjected to these temperatures and pressures can be a predetermined value.
  • thermoforming temperatures and pressures be closely controlled and monitored. Excessive heat and/or pressure in the mold will cause the distortion of the facing materials and/or the collapse of the honeycomb cell structure. Mold design is also crucial in that the composite structure will have the same geometry as that of the mold. Coefficients of expansion and contraction of the mold and materials must be taken into consideration so as to produce a tight tolerance and high quality composite.
  • Mold release agents may also be incorporated into the thermoformable facing sheet materials or onto the mold surfaces to aid in releasing the composite from the mold. In some cases, the thermoplastic material selected for the facing sheets will contain release agents. The release agent can also be added to the surface of the facing sheet and/or the mold plate to facilitate release of the assembled composite. Such a release agent can be a Teflon-based compound, which can be sprayed onto the facing material and/or the mold.
  • thermoplastic material used to form the composite 10 can be a non-reinforced polymer or a polymer alloy.
  • the thermoplastic material can also contain additives such as fibers, fillers, nano-reinforced polymers, or recycled materials.
  • the thermoplastic material can also be a flexible polymeric material. This allows for tremendous flexibility in the choice of materials that can be used to manufacture the final composite. Suitable materials for the fiber additives include glass, mineral, carbon, ceramic, boron, wood or aramid fibers, or a combination thereof.
  • Suitable filler materials include calcium carbonate, calcium silicate, calcium sulfate, aluminum silicate, magnesium silicate, alumina trihydrate, glass microspheres, carbon black, paste pigments, silicon dioxide, nanoclays or carbon nanotubes, or a combination thereof.
  • Suitable flexible polymeric materials include butadiene, acrylonitrile, or carboxyl terminated butadiene nitrile rubber. The methods for adding the fiber and filler materials to the thermoplastic materials are well known to those skilled in the art. Nano-reinforced polymers are state of the art polymers that have reinforcements in micron sizes, which add strength and durability to the base polymer system. Such polymers are also well known to those skilled in the art.
  • thermoformable composite comprises two layers of facing material sheets and a thermoformable honeycomb core
  • present invention contemplates the assembly of other thermoformable composites, such as one having one layer of facing material and one layer of honeycomb core, or one having two or more honeycomb cores and three or more layers of facing material.
  • the method of the present invention can also be repeated, so that consecutive thermoformable composites can be processed. Additionally, the time that the pre-assembled composites are heated to the above mentioned temperature range and placed under pressure at the above mentioned range can be set to a predetermined value. This value represents the period of time necessary to make the assembly thermoformable, and to cure or set the adhesive being used, which consolidates the assembly into the final configuration.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Nanotechnology (AREA)
  • Physics & Mathematics (AREA)
  • Composite Materials (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Laminated Bodies (AREA)

Abstract

A method for efficiently producing composite structures by thermoforming expanded thermoplastic honeycomb and extruded or co-extruded thermoplastic facing materials and bonding them with appropriate adhesives in a one-step, energy efficient and throughput-enhancing process, comprising the steps of: applying the appropriate adhesives in liquid, paste or film form to extruded or co- extruded sheets of thermoplastic material or to thermoplastic honeycomb; placing a pre-assembled composite in a closed mold tool, the pre-assembled composite comprising layers of facing, adhesive, thermoplastic honeycomb, adhesive, and facing, in that order; heating the pre-assembled composite to a temperature in the range of about 2000F to about 600°F at a pressure of about 0.1 to about 20 p.s.i.; thermoforming and bonding the pre-assembled composite into the final assembly; and cooling the composite to between about 70-150°F on the tool to facilitate release from the tool.

Description

METHOD FOR FORMING AND BONDING THERMOFORMABLE COMPOSITES
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing thermoformable composites by thermoforming expanded thermoplastic honeycomb and extruded or co-extruded thermoplastic facing materials and bonding them with appropriate adhesives in a cost-effective and efficient manner.
2. Description of the Prior Art
Processes typically used to thermoform and bond expanded thermoplastic honeycomb and extruded or co-extruded facing materials into a composite structure involve a number of different steps. The most common of these methods involves thermoforming the facings individually to a specific geometry, thermoforming the expanded honeycomb to a specific geometry, applying adhesive to the mating materials, and bonding the mating materials in a male or female tool with the desired geometry under pressure and heat.
Another variation of the process is to twin form the facing materials simultaneously to a specific geometry, thermoform the expanded honeycomb to a specific geometry, apply adhesive to the mating materials, and bond the mating materials in a male or female tool with the desired geometry under pressure and heat.
One other variation of the process involves thermoforming the facings individually to a specific geometry, thermoforming the expanded honeycomb to a specific geometry, applying adhesive to one facing material and one side of the honeycomb, and bonding them in a male or female tool with the desired geometry under pressure and heat. After these steps, adhesive is applied to the second facing and the other side of the expanded honeycomb, and these materials are bonded to the other half of the structure in a male or female tool with the desired geometry under pressure and heat.
The problems associated with the currently available processes are numerous, with the multiple steps required to manufacture a composite structure utilizing extruded or co-extruded thermoformed facings and expanded honeycomb being of major concern. The steps required to produce a composite structure are extremely time-consuming, which lowers productivity and increases cycle times. The multiple steps required with these processes are also labor intensive and involve significant energy costs. A further disadvantage with presently available methods that adds greatly to the cost of manufacturing the composite products is the need for multiple tools to thermoform the facing and honeycomb core materials, and the need for a bonding tool to mate the materials together. These costs can all be significant deterrents to manufacturing thermoformable composite products.
Accordingly, there is a need for an improved method of thermoforming and bonding extruded or co-extruded thermoplastic facing materials and expanded honeycomb cores into composites that avoids the aforementioned disadvantages.
The present invention overcomes all of the disadvantages of the methods for thermoforming composites discussed above.
The present invention provides a unique method in which the thermoformable composites are thermoformed and bonded in the same step.
The present invention further provides a method for producing thermoformable composites that significantly improves on the manufacturing costs of currently available methods. The present invention further provides a method for producing thermoformable composites that improves on the product cycle time and production capacity of currently available methods.
The present invention further provides a method for producing thermoformable composites that significantly reduces the amount of equipment used in the manufacturing processes of currently available methods.
SUMMARY OF THE INVENTION
The present invention provides a cost-effective and energy efficient method for producing thermoformable composites that includes thermoforming expanded honeycomb and thermoformable facing sheets and bonding them with appropriate adhesives in the same step. This method reduces the cycle times and improves the throughput of currently available methods.
The method of the present invention encompasses the steps of: applying the appropriate adhesives in liquid, paste or film form to extruded or co-extruded sheets of thermoplastic material or to thermoplastic honeycomb (such as that made by Panterra Engineered Plastics, Inc.); placing a pre-assembled composite in a closed mold tool, the pre-assembled composite comprising layers of a thermoformable facing sheet, adhesive, thermoplastic honeycomb, adhesive, and another thermoformable facing sheet, in that order; heating the pre-assembled composite to a temperature in the range of about 200°F to about 600°F at a pressure of about 0.1 to about 20 p.s.L; thermoforming and bonding the pre- assembled composite into the final assembly; and cooling the composite to between about 70-150°F on the tool to facilitate release from the tool.
BRIEF DISCRIPTION OF THE DRAWING
Fig. 1 is a cross-sectional view of a pre-assembly composite formed using the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION
Referring to Fig. 1, a cross-sectional view of a pre-assembly composite formed using the method of the present invention is shown. Pre-assembly composite 10 has honeycomb 20, upper facing sheet 40, and lower facing sheet 60. An appropriate adhesive in liquid, paste or film form may first be applied to one side of either upper facing sheet 40 or lower facing sheet 60, or alternatively the upper or lower face of honeycomb 20. Another layer of adhesive is then applied on the uncoated facing sheet or uncoated face of honeycomb 20. Adhesive can be applied to the upper and lower facing sheets 40 and 60 or honeycomb 20 by spraying, roll coating, film application, or any other suitable method. The adhesive thus forms two layers, upper adhesive layer 30 and lower adhesive layer 50.
Generally speaking, it is desirable to utilize thermoplastic polymeric materials in the pre-assembly composite that have similar rheological, thermal, melt index/flow and softening/melting point indices. Use of materials that are dissimilar in these characteristics will make processing of the pre-assembly composite more difficult. The thermoformable honeycomb 20 and the upper and lower facing sheets 40 and 60 are made of a thermoplastic material. Suitable candidates for this material include, but are not limited to, high impact polystyrene, polycarbonate, acrylonitrile butadiene styrene, homo- or co-polymer polypropylene, low- and high- density polyethylene, and other thermoplastic materials. It should be emphasized that this list is a small representation of the many thermoplastic compounds that can be used in the method of the present invention.
The surfaces of the thermoformable honeycomb 20 and the upper and lower facing sheets 40 and 60 may be pre-treated prior to the application of the adhesive with plasma or corona techniques, which increases the surface energy of the materials and facilitates bonding of the materials in the process. These pre- treatment processes are well known to those skilled in the art.
Additionally, the choice of the adhesives used in the present invention is paramount to the success in producing a composite structure that can be thermoformed and bonded in the one step process. The liquids, pastes or films used in the invention must inherently have an appropriate degree of flexibility to allow the composite structure to initially be thermoformed and also have rigidity characteristics that will produce a structurally sound component. Suitable candidates for the adhesives of the present invention include, but are not limited to, polyurethanes, methacrylates, flexible epoxies, ethylene vinyl acetates, polyvinyl acetates, hot melt urethanes, polyethylene and polypropylene films. The adhesive can be a thermoset or thermoplastic adhesive, although other kinds of adhesives are contemplated by the present invention.
After the adhesive has been applied to upper thermoformable facing sheet 40, lower thermoformable facing sheet 60, and/or honeycomb 20, the materials are placed in the mold as shown. Upper facing sheet 40 contacts upper mold plate 70, and lower facing sheet 60 contacts lower mold plate 80, with honeycomb 20 disposed between the upper and lower facing sheets 40 and 60.
Upper facing sheet 40, upper adhesive layer 30, honeycomb 20, lower adhesive layer 50, and lower facing sheet 60 are then heated in the mold to a temperature in the range of from about 200°F to about 6000F, and subjected to a pressure of between about 0.1 to about 20 p.s.i. This consolidates the materials into one composite assembly 10. The proper temperature and pressure to be applied will depend on the specific materials used. The amount of time that the pre-assembly composite is subjected to these temperatures and pressures can be a predetermined value.
It is imperative that the thermoforming temperatures and pressures be closely controlled and monitored. Excessive heat and/or pressure in the mold will cause the distortion of the facing materials and/or the collapse of the honeycomb cell structure. Mold design is also crucial in that the composite structure will have the same geometry as that of the mold. Coefficients of expansion and contraction of the mold and materials must be taken into consideration so as to produce a tight tolerance and high quality composite. After the composite 10 is thermoformed and bonded the assembly is cooled to a range from about 7O0F to about 150°F to facilitate release of the composite 10 from the mold. Mold release agents may also be incorporated into the thermoformable facing sheet materials or onto the mold surfaces to aid in releasing the composite from the mold. In some cases, the thermoplastic material selected for the facing sheets will contain release agents. The release agent can also be added to the surface of the facing sheet and/or the mold plate to facilitate release of the assembled composite. Such a release agent can be a Teflon-based compound, which can be sprayed onto the facing material and/or the mold.
In addition, the thermoplastic material used to form the composite 10 can be a non-reinforced polymer or a polymer alloy. The thermoplastic material can also contain additives such as fibers, fillers, nano-reinforced polymers, or recycled materials. The thermoplastic material can also be a flexible polymeric material. This allows for tremendous flexibility in the choice of materials that can be used to manufacture the final composite. Suitable materials for the fiber additives include glass, mineral, carbon, ceramic, boron, wood or aramid fibers, or a combination thereof. Suitable filler materials include calcium carbonate, calcium silicate, calcium sulfate, aluminum silicate, magnesium silicate, alumina trihydrate, glass microspheres, carbon black, paste pigments, silicon dioxide, nanoclays or carbon nanotubes, or a combination thereof. Suitable flexible polymeric materials include butadiene, acrylonitrile, or carboxyl terminated butadiene nitrile rubber. The methods for adding the fiber and filler materials to the thermoplastic materials are well known to those skilled in the art. Nano-reinforced polymers are state of the art polymers that have reinforcements in micron sizes, which add strength and durability to the base polymer system. Such polymers are also well known to those skilled in the art.
Although in the shown embodiment the thermoformable composite comprises two layers of facing material sheets and a thermoformable honeycomb core, the present invention contemplates the assembly of other thermoformable composites, such as one having one layer of facing material and one layer of honeycomb core, or one having two or more honeycomb cores and three or more layers of facing material.
The method of the present invention can also be repeated, so that consecutive thermoformable composites can be processed. Additionally, the time that the pre-assembled composites are heated to the above mentioned temperature range and placed under pressure at the above mentioned range can be set to a predetermined value. This value represents the period of time necessary to make the assembly thermoformable, and to cure or set the adhesive being used, which consolidates the assembly into the final configuration.
The present invention having been thus described with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as defined herein.

Claims

1. A method for efficiently producing a thermoplastic composite assembly, said assembly comprising a thermoplastic honeycomb and extruded or co-extruded thermoplastic facing sheets, said method comprising:
applying an adhesive to at least one surface of said thermoplastic facing sheets and/or to at least one surface of said thermoplastic honeycomb;
forming a pre-assembled composite wherein said adhesive treated surface of said thermoplastic facing sheets and/or said adhesive treated surface of said thermoplastic honeycomb are disposed adjacent to each other; and
heating said pre-assembled composite to a temperature in the range between about 200°F to about 600°F, at a pressure in the range between about 0.1 p.s.i. to about 20 p.s.i, thereby forming said thermoplastic composite assembly.
2. The method of claim 1, where the thermoplastic honeycomb and the thermoplastic facing sheets comprise a thermoplastic material selected from the group consisting of: high impact polystyrene, polycarbonate, acrylonitrile butadiene styrene, homo- or co-polymer polypropylene, low density polyethylene, and high density polyethylene.
3. The method of claim 1, further comprising cooling said composite assembly to a temperature in the range between about 700F to about 150°F.
4. The method of claim 1, wherein said pre-assembled composite is placed in a mold tool, said mold tool being made of steel, aluminum, copper or composite.
5. The method of claim 1, wherein said adhesive is a material selected from the group consisting of: thermoset adhesives and thermoplastic adhesives.
6. The method of claim 5, wherein said adhesive is sprayed, roll coated, or film applied onto said thermoplastic honeycomb and/or said thermoplastic facing sheets.
7. The method of claim 6, wherein said adhesive is applied in a layer having a thickness of between about 0.005 to about 0.020 inches when wet, and between about 0.001 to about 0.005 inches when dry.
8. The method of claim 1, wherein said thermoplastic facing sheets have a thickness of between about 0.060 to about 0.250 inches.
9. The method of claim 1, wherein said thermoplastic honeycomb has a thickness of between about 0.25 to about 3.00 inches.
10. The method of claim 1, wherein said thermoplastic honeycomb and/or said thermoplastic facing sheets are made from at least one material selected from the group consisting of: non-reinforced polymers, polymer alloys, fiber-, filler-, or nano-reinforced polymers, flexible polymeric materials, and recycled materials.
11. The method of claim 10, wherein said fiber-reinforced polymers comprise at least one fiber material selected from the group consisting of: glass, mineral, carbon, ceramic, boron, wood, and aramid fibers.
12. The method of claim 10, wherein said filler-reinforced polymers comprise at least one filler material selected from the group consisting of: calcium carbonate, calcium silicate, calcium sulfate, aluminum silicate, magnesium silicate, alumina trihydrate, glass microspheres, carbon black, paste pigments, silicon dioxide, nanoclays and carbon nanotubes.
13. The method of claim 10, wherein said flexible polymeric materials are at least one polymer selected from the group consisting of: butadiene, acrylonitrile, and carboxyl terminated butadiene nitrile rubber. 4. A thermoforaiable composite made according to the method of claim 1.
PCT/US2006/003819 2005-02-02 2006-02-02 Method for forming and bonding thermoformable composites WO2006084117A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US64929005P 2005-02-02 2005-02-02
US60/649,290 2005-02-02

Publications (2)

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US10618210B2 (en) 2018-05-30 2020-04-14 Corning Incorporated High capacity print station, method of making a polymer composite part, and polymer composite part

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