The present invention relates to a process for manufacturing reinforced composite products such as composite panels, the process providing at least one of improved control, reduced emissions, and reduced costs.
Prior art manufacturing methods of composite parts include traditional processes involving Resin Transfer Molding (RTM) and Vacuum Assisted RTM (VARTM). Although these processes may be suitable in particular applications, there remains a need for improved processes and systems for manufacturing reinforced composite products such as panels that provide at least one of improved control, reduced emissions, and reduced costs.
Panel Production Assembly (Equipment Assembly and Subassemblies)
According to one aspect of the invention, a system is provided for producing composite products including a substrate and a resin integrated with the substrate, the system including: a press located between an upstream end portion of the system, which is configured to receive the substrate into the system, and a downstream end portion of the system, which is configured to deliver the composite products from the system; a lower film supply located at the upstream end portion of the system and configured to introduce a lower film into the system and in a downstream direction toward the press; a substrate supply located at the upstream end portion of the system and configured to introduce the substrate into the system, onto the lower film, and in the downstream direction toward the press; a resin dispenser located upstream of the press and downstream of the substrate supply and configured to apply the resin to the substrate to form a resin-substrate combination; an upper film supply located downstream of the resin dispenser and configured to introduce an upper film into the system, in the downstream direction toward the press, and onto the resin-substrate combination; and a film removal station located at a downstream end portion of the system and configured to remove the lower film and the upper film from the resin-substrate combination; the press being located downstream of the upper film supply and upstream of the film removal station, the press being positioned to apply pressure to the resin-substrate combination through the upper film and the lower film when the resin-substrate combination is co-located with the press.
Die Assembly
According to another aspect of the invention, a die is provided for use with a press for forming composite products including a substrate and a resin integrated with the substrate, the die including: a lower film configured for movement relative to the press in a downstream direction extending from an upstream end of the press toward a downstream end of the press, the lower film having an upper surface positioned to support a combination of the substrate and the resin, the lower film having a continuous length selected to extend beyond the upstream end of the press in an upstream direction and beyond the downstream end of the press in the downstream direction; an upper film configured for movement relative to the press in the downstream direction extending from the upstream end of the press toward the downstream end of the press, the upper film having a lower surface positioned to contact the combination of the substrate and the resin, the upper film also having a continuous length selected to extend beyond the upstream end of the press in the upstream direction and beyond the downstream end of the press in the downstream direction; and a seal formed by contact between the upper surface of the lower film and the lower surface of the upper film, the seal being positioned to at least partially surround the substrate, the seal extending along portions of the continuous lengths of the lower film and the upper film, and the seal extending lateral to the continuous lengths of the lower film and the upper film; the lower film, the upper film, and the seal together defining a die interior configured to enclose the combination of the substrate and the resin.
Panel Production Process (Steps for Panel Production)
According to yet another aspect of the invention, a process is provided for producing composite products including a substrate and a resin integrated with the substrate, the process including: supplying a lower film to introduce the lower film in a downstream direction; supplying a substrate to introduce the substrate in the downstream direction and onto the lower film; dispensing a resin to apply the resin to the substrate to form a resin-substrate combination; supplying an upper film to introduce an upper film onto the resin-substrate combination; applying pressure to the resin-substrate combination through the upper film and the lower film; and removing the lower film and the upper film from the resin-substrate combination.
VOC Capture Assembly
According to still another aspect of the invention, a system is provided for capturing Volatile Organic Compound (VOCs) during the production of composite products including a substrate and a resin integrated with the substrate, the system including: a resin dispenser positioned to apply the resin to the substrate to form a resin-substrate combination, the resin dispenser including an enclosure into which the substrate can be introduced when the enclosure is open, the enclosure being configured to contain VOCs emitted in the enclosure when the enclosure is closed; a filter coupled to receive VOCs from the enclosure of the resin dispenser; and an exhaust configured to reduce pressure within the enclosure and positioned to purge the VOCs from the enclosure and into the filter, the exhaust being operable when the enclosure is open to allow the substrate to enter the enclosure and to allow the resin-substrate combination to exit the enclosure.
VOC Capture Process
According to another aspect of the invention, a process is provided for capturing VOCs while producing composite products including a substrate and a resin integrated with the substrate to form a resin-substrate combination, the process including: opening an upstream gate of an enclosure; actuating an exhaust to reduce pressure within the enclosure when the upstream gate of the enclosure is open; receiving the substrate in the enclosure through the upstream gate of the enclosure; closing the upstream gate of the enclosure; applying the resin to the substrate to form the resin-substrate combination in the enclosure; and exhausting VOCs from the enclosure and into a filter.
Reinforced Composite Product
According to yet another aspect of the invention, a reinforced composite product is provided including: a substrate; and a resin integrated with the substrate; the reinforced composite product having an exterior surface characterized by uniformity of at least one of color, weave pattern, and surface veil appearance.
Reinforced Composite Product
According to another embodiment of the invention, a reinforced composite product is provided including: a substrate; and a resin integrated with the substrate; the reinforced composite product characterized by uniformity of at least one of thickness, fiber content, thickness after secondary pressing, noise generation in ultrasonic C-scan, fiber content, and cross-section.
According to another aspect of the invention, a Resin Content Uniformity Index of the reinforced composite product is 16 or greater, a Resin Content Covariance of the reinforced composite product is 5% or less, and/or a Resin Content Uniformity of the reinforced composite product is 83% or greater.
According to another aspect of the invention, a Thickness Uniformity Index of the reinforced composite product is 8 or greater, a Thickness Covariance of the reinforced composite product is 7% or less, and/or a Thickness Uniformity of the reinforced composite product is 61% or greater.
The foregoing summary and the following description will be better appreciated and understood in conjunction with the non-limiting examples illustrated in the attached drawing figures, of which:
Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.
Additionally, various forms and embodiments of the invention are illustrated in the figures. It will be appreciated that the combination and arrangement of some or all features of any of the embodiments with other embodiments is specifically contemplated herein. Accordingly, this detailed disclosure expressly includes the specific embodiments illustrated herein, combinations and sub-combinations of features of the illustrated embodiments, and variations of the illustrated embodiments.
Panel Production System
It has been recognized that some processes, including for example those employing resin injection concepts to impregnate substrates with resins for the production of composite materials, can result in a greater risk of fabric pattern distortion. For example, a non-uniform surface appearance may result from the radial flow path of polymer resin across a substrate in a resin injection process, which may generate different levels of resin distribution across the composite product. The radial resin flow front in a resin injection process can also result in excess waste of the resin. Additionally, the radial resin flow in a resin injection process can result in prolonged substrate impregnation times in situations where the substrate material may be non-circular. For example, it would take additional time for the resin to reach and impregnate the corners of a square or rectangular shaped substrate in a resin injection process. In addition, such manufacturing methods tend to use metallic tool dies, which can make the laminate handling and curing process cumbersome.
In contrast to a resin injection process, some processes may improve upon resin injection processes include steps of wrapping, stacking, and cooling of pre-pressed sections of material for subsequent unwrapping and pressing. Referring to
In step (A) of the first process, ingredients of the resin system are weighed and formulations of the ingredients are determined and prepared. Though the duration of mixing can vary, the resin mixing can take about 3 hours or more. Thereafter, the mixed resin is stored in a freezer for future use (perhaps the next day).
In step (B), the prepared resin formulation is applied to a desired substrate. Specifically, the resin is held in a dispensing trough and then applied with a doctor blade. Further, resin coated substrates are separately packaged in a layer of plastic film for storage and placed into a freezer to allow for the polymer to impregnate the substrates without kicking off an exothermic reaction. This step may take 24 hours or more and includes removing the resin from the freezer, applying the resin to the substrate, and storing the resin coated substrate in the freezer (in some examples, a minimum of 16 hours may be required and this can take up to 3 days).
In step (C), the resin-impregnated substrates are removed from the freezer after a predetermined time that can last from a few hours to ten hours. The external plastic film layer is then removed from each substrate. A new layer of plastic film is added to either side of the resin impregnated substrate. Additionally, more layers of release film or paper, fabric with special coating, such as polytetrafluoroethylene (PTFE), etc. might be added optionally if or as necessary or beneficial. Multiple such layers are created, staked and prepared for curing/cross-linking of the resin system to produce a final product, such as a composite laminate. This step may vary in duration but may take about 2 hours to complete.
In step (D), the prepared layers of the resin impregnated substrate are cured in a static press or a combination of two or more static presses. At the end of the press cycle, the materials are removed from the press. This is followed by removal of the plastic film and any additional layer or layers of materials that may have been used in step (C). A cured composite laminated is therefore yielded. This step may vary in duration but may take about 2 hours to complete.
As will be discussed below in greater detail, an improved process according to aspects of this invention can further improve upon the first process. For example, the improved process can be less labor intensive, requiring less physical manpower, number of process steps, and number of operators in the production of panels/laminates. Additionally, the improved process can result in a reduced amount of wasted raw materials, thus increasing the overall process yield. Furthermore, the improved process eliminates the need for special freezer or refrigeration storage of materials, and also, offers an overall set-up with a significantly reduced operational footprint.
In order to further improve upon such systems, this invention also makes it possible to produce fiber or fabric or substrate reinforced composite panels impregnated with polymer or resin systems in a semi-continuous process. The semi-continuous process can provide significantly improved control, a reduction in Volatile Organic Compounds (VOCs) emitted from the polymer or resin system, as well as other benefits.
Referring generally to the figures, the system 100 is one embodiment of an improved system for impregnating substrates with resin and makes it possible to avoid use of the resin injection concept. By doing so, the system 100 reduces or eliminates the radial flow path of the polymer across the substrate as well as the resulting non-uniform surface appearance caused by different levels of resin distribution across the composite laminate or fabric pattern distortion. The system 100 also makes it possible to avoid use of the metallic tool dies that can make the laminate curing process cumbersome. As an alternative to the tool die concept, the improved system 100 makes it possible to use a set of disposable films as a die according to one aspect of the invention.
The improved process (such as the embodiment of system 100) also includes improvements to the first process described above. For example, the improved process can be less labor intensive, requiring less physical manpower, a reduced number of process steps, and a reduced number of operators in the production of panels/laminates. Also, the improved process can be semi-continuous or continuous. Additionally, the improved process can result in a reduced amount of wasted raw materials, thus increasing the overall process yield. Other benefits of the improved process are described elsewhere herein.
While the process pathway of
Referring generally to the figures, a system 100 for producing composite products including a substrate, such as substrate 14, and a resin, such as resin 106, integrated with the substrate 14, is disclosed. A lower film supply, such as lower film supply 12, is located at an upstream end portion 102 of the system 100, which is configured to receive the substrate 14 into the system 100. The lower film supply 12 is configured to introduce a lower film, such as lower film 316, into the system 100 and in a downstream direction toward a downstream end portion 104 of the system, which is configured to deliver the composite products, such as final laminates 108, from the system 100. A substrate supply, such as substrate supply 13, is located at the upstream end portion 102 of the system 100 and configured to introduce the substrate 14 into the system 100 and onto the lower film 316 and in the downstream direction toward a downstream end portion 104 of the system.
In step (A) illustrated in
In step (B), a resin dispenser, such as resin dispenser 15 (
In step (C), as the resin-substrate combination 16 exits the resin dispenser 15 and moves in a downstream direction to a next station, such as a soaking station 1 (item 37 in
In step (D), the resin-substrate combination 16 moves in a downstream direction toward a press, such as press 11, the press being positioned to apply pressure to the resin-substrate combination through the upper film 317 and the lower film 316 when the resin-substrate combination 16 is co-located with the press 11. According to one embodiment of the invention, the curing process comprises a resin temperature and viscosity control step, which is performed for crosslinking control and to build up molecular weight. A temperature and viscosity control step may be configured to occur at one or more soaking stations having a preheating station, which is configured to initiate or accelerate polymer reaction. In yet another embodiment, the curing process comprises one or more of the soaking stations applying a vacuum to remove any undesired trapped air, contaminants, and/or particulates from the resin-substrate combination 16.
In step (E), a film removal station, such as film removal station 18, is located at a downstream end portion 104 of the system and configured to remove the lower film 33b and the upper film 35b from the resin-substrate combination 16. At a downstream end portion 104 of the system, reinforced composite product 108 is delivered from the system 100. In one example, reinforced composite product 108 comprises a substrate, such as substrate 14, and a resin 106 integrated with the substrate 14, and has an exterior surface characterized by uniformity of at least one of color, weave pattern, and surface veil appearance. In another example, reinforced composite product 108 comprises a substrate, such as substrate 14, and a resin 106 integrated with the substrate 14, and has an exterior surface characterized by uniformity of at least one of thickness, fiber content, resin content, thickness after secondary pressing, noise generation in ultrasonic C-scan, and cross-section.
As explained in greater detail elsewhere, the improved process according to embodiments of this invention makes it possible to achieve, for example, improved consistency in color, reduced surface deformities, and improved thickness uniformity, among other improved properties. Accordingly, the process makes it possible to produce panels that can be utilized for downstream processing into final products and components with greater quality and predictability.
Generally, the improved panel production assembly 200 disclosed herein uses two films creating a die, a continuous or semi-continuous transport system, and a press to produce composite panels. Embodiments of the panel production assembly are illustrated in the figures and described below.
In one embodiment, as illustrated by
The substrate 31a can be cut from a larger substrate at a substrate indexing station, such as a fabric index and cutting station 32, located at an upstream end portion 102 of the system and configured to index a position 320 of the substrate relative to a position of the lower film 316. The fabric index and cutting station 32 comprises a cutter 32b having a vacuum to collect loose fiber from substrate 31a and a roller 32c configured to facilitate movement of the substrate 31a along a continuous or semi-continuous transport system. As seen in
A lower film supply, such as a lower polyethylene terephthalate (PET) un-wind 33, is located at the upstream end portion 102 of the system and configured to introduce a lower film 316 into the system and in a downstream direction toward the press 39. The lower PET un-wind 33 supplies lower film, such as lower film 33b including polyethylene terephthalate. The lower PET-unwind 33 also includes brakes 33a to supply back tension.
The substrate 31a is disposed onto the lower film and in the downstream direction toward an enclosure, such as a resin dispensing system 34, which is located upstream of the press 39 and downstream of the fabric let-off station 31 and configured to apply the resin 106 to the substrate 31a to form a resin-substrate combination 16. The resin dispensing system 34 includes a resin reservoir, such as a resin tank 34a having a pumping system including a pump configured to advance resin 106 for application to the substrate 31a. The resin dispensing system 34 further comprises an enclosure, such as a gantry system 34b, configured to spray the resin 106 onto the substrate 31a, the enclosure including (i) a spray box 321, as seen in
The resin dispensing system 34 further comprises an exhaust, such as emission tube 34d, which is configured to reduce pressure within resin dispensing system 34 and is positioned to purge VOCs from the resin dispensing system 34 and into a filter, such as filter 41a of
The resin dispensing system 34 also includes a downstream gate, or exit gate 318, such as for example the pneumatic pass thru gate (back) 34e, that opens to allow the resin-substrate combination 16 to exit the resin dispensing system 34.
An upper film supply 17, such as upper PET unwind 35, is located downstream of, or aligned with, the resin dispensing system 34. The upper PET un-wind 35 supplies upper film 317, such as upper film 35b including polyethylene terephthalate. The upper PET-unwind 35 also includes brakes 35a to supply back tension.
The upper PET unwind 35 is configured to introduce an upper film 317 into the system, in a downstream direction toward an upstream gate, such as pneumatic pass thru gate (front) 34e of the resin dispensing system 34, and onto the resin-substrate combination, the upper film 317 providing a barrier against the escape of VOCs from the resin-substrate combination as the resin-substrate combination exits the downstream gate of the resin dispensing system 34. The upper film 317 can be introduced through a gate in the top of the enclosure at a location downstream of the spray head(s) applying resin to the substrate. In this configuration, the upper film 317 travels downwardly onto the surface of the resin-wetted substrate and then exits the enclosure through a downstream gate of the enclosure.
A sensor or an encoder attached, for example, to a rotating object such as a wheel is part of system automation. The encoder wheel, such as encoder wheel 36, is programmed to measure the distance of material movement in the process flow direction for ensuring consistent and accurate positioning of the material in each process step. The encoder wheel can also be programmed for dynamic behavior such that the rate of movement of the material is smooth and free of abrupt starts and stops to ensure good process flow and continuity.
The resin-substrate combination is pulled to one or more wet-out stations, such as soaking station 1 (37) and a soaking station 2 (38), each including an edge sealer including one or more brushes (37a, 38a) configured to seal edges of the upper film 317 to edges of the lower film 316, thereby reducing VOC emissions as the resin-substrate combination exits the downstream gate 34e of the resin dispensing system 34.
In one embodiment of the present invention, at least one wet-out station includes a heater, which is configured to maintain an elevated temperature of the resin-substrate combination as it moves in a downstream direction towards the press 39. Maintaining an elevated temperature of the resin-substrate combination may be achieved by means of at least one of ultraviolet light, heat lamps, or other temperature sources as would be understood by persons skilled in the art.
The press 39 is located downstream of the upper film supply 35 and upstream of a film removal station 18, such as stripping station 313. Furthermore, the press 39 is positioned to apply pressure to the resin-substrate combination through the upper film 317 and the lower film 316 when the resin-substrate combination is co-located with the press 39. In addition, as seen in
The press 39 is configured to close on the lower film 316 and the upper film 317 with the resin-substrate combination between the lower film 316 and the upper film 317 until a seal is formed to enclose at least a portion of the lower film 316, the upper film 317, and the resin-substrate combination. When the top platen 51 and the bottom platen 52 are moved away from one another by movement of at least one of the top platen 51 and the bottom platen 52, the press 39 opens and the seal is released and the resin-substrate combination is pulled to a cooling station 311, which is located upstream from a film removal station 18, such as stripping station 313.
System 300 also includes a pulling station, such as station 312 having a nip puller 312a, configured to pull the lower film 316 and the upper film 317, with the resin-substrate combination between the lower film 316 and the upper film 317, in a downstream direction. Nip puller 312a is located downstream of the press upstream of a film removal station, such as stripping station 313. Stripping station 313 is configured to remove the lower film 316 and the upper film 317 from the resin-substrate combination. Stripping station 313 includes an unwinder, such as winder 313a, configured to roll the lower film 316 and the upper film 317 onto respective rolls (313b, 313c) of the lower film 316 and the upper film 317, the winder 313a including drive motors, a gear box, and clutches as appropriate.
At a downstream end portion 104 of the system, reinforced composite product 314 is delivered from the system 300. In one example, reinforced composite product 314 comprises a substrate, such as substrate 31a, a resin 106 integrated with the substrate 31a, and has an exterior surface characterized by uniformity of at least one of color, weave pattern, and surface veil appearance. In another example, reinforced composite product 314 comprises a substrate, such as substrate 31a, a resin 106 integrated with the substrate 31a, and has an exterior surface characterized by uniformity of at least one of thickness, fiber content, thickness after secondary pressing, noise generation in ultrasonic C-scan, resin content, and cross-section.
Press
Referring now to
The press 11 is also configured to apply pressure for a pre-determined duration. For example, press 11 can be configured to apply pressure for 4 min to 60 min, preferably 5 min to 30 min, or more preferably 5 min to 10 min. In one embodiment, the press 11 is configured to apply pressure being selected as a function of time. As illustrated in
As seen in
The bottom platen 52 is mounted on a press bed 53, which is configured for movement relative to press crown 54. The press bed 53 and press crown 54 are separated by a fixed distance D defined by a plurality of vertical guide posts 55. When the top platen 51 and the bottom platen 52 are moved toward one another by movement of at least one of the top platen 51 and the bottom platen 52, the distance between top platen 51 and bottom platen 52 decreases. The press 39 further comprises an oil tank 56 configured to supply the working fluid and includes a pressure release valve.
In one embodiment, as seen in
Heater
In one embodiment, as shown in
Substrate Supply
In one embodiment, as shown in
Substrate
The substrate 14 can include fibrous material, non-fibrous material, or a combination thereof. Also, the substrate 14 can include metallic material, non-metallic material, or a combination thereof. For example, the substrate 14 can include one or more of glass, carbon, ceramic, basalt, steel, and cellulosic fiber materials, and combinations thereof. Also, the substrate 14 can include one or more of continuous, discontinuous, woven, non-woven, crimped, uncrimped, uni-directional, multi-directional, porous, and non-porous materials and hybrids or combinations thereof.
In certain embodiments, the substrate 14 is substantially planar and has an outer periphery. Further, as illustrated in
As illustrated in
Resin Dispenser
The resin dispenser 15 may be configured to apply resin, such as resin 106, including a thermoplastic polymer or a thermoset polymer having a viscosity up to 5000 cps. In another example, the resin dispenser 15 may be configured to apply resin 106 including a thermoplastic polymer or a thermoset polymer having a lower viscosity up to 500 cps, preferably up to 250 cps, or more preferably about 100 cps or less. The resin dispenser 15 may also be configured to apply resin 106 including a polymer, monomer, or combination thereof that can be cross-linked for polymerization. Further, the resin dispenser 15 may be configured to apply resin 106 including one or more of a color package, a reaction initiator, a reaction inhibitor, an impact modifier, a flame retardant, a lubricant, a light stabilizer, an electrical or thermal conductor additive, and an anti-oxidant.
In another embodiment, the resin dispenser 15 may be configured to apply resin 106 including a thermoplastic polymer that is dissolvable into solvent to reduce viscosity. In one example, the resin dispenser 15 may be configured to apply resin 106 including polycarbonate dissolved in a suitable solvent such as dichloromethane (DCM). As illustrated in
Referring now more closely to
In one example, the spray head 921 is moveable in a first direction and is configured to spray the resin 106 onto the substrate 14 in a single pass. In another example, the spray head 921 is immoveable and is configured to spray the resin 106 on the substrate 14 as the substrate 14 is moved towards the downstream direction of the system. In one embodiment, the resin dispenser 91 includes a plurality of spray heads 921 configured in a series, each spray head being configured to move in a first direction for spraying the resin 106 onto substrate 14 in at least one pass. In yet another embodiment, the resin dispenser 91 includes a plurality of spray heads 921 configured to be immoveable, such that the spray heads 921 apply resin 106 onto substrate 14 as the substrate 14 is moved towards the downstream direction of the system. Additionally, each spray head may be configured to spray a distinct formulation of resin 106 in a predetermined pattern. In other words, different resin formulations can be applied, concurrently or simultaneously, by different spray heads or spray nozzles.
An upper film supply 17 (not shown in
Finally, the resin dispenser also includes an exhaust, such as emission collection tube 920, configured to reduce pressure within gantry system 919 and positioned to purge VOCs from the gantry system 919 and into a filter, such as filter 41a of
As illustrated in
Referring now to
As illustrated in
As shown in
Lower Film Supply
Referring now to
Upper Film Supply
Referring now to
Referring now to
Film Removal Station
In one embodiment, as seen in
At a downstream end portion 104 of the system, a reinforced composite product, such as laminate 1005, is delivered from the system. In one example, reinforced composite product 1005 has an exterior surface characterized by uniformity of at least one of color, weave pattern, and surface veil appearance. In another example, reinforced composite product 1005 has an exterior surface characterized by uniformity of at least one of thickness, fiber content, thickness after secondary pressing, noise generation in ultrasonic C-scan, resin content, and cross-section.
Pulling Station
In yet another embodiment, as seen in
Wet-Out Stations
In one embodiment, the system includes at least one wet-out station configured to promote integration of the resin 106 into the substrate in the resin-substrate combination. The system, such as system 300, optionally includes plural wet-out stations. In one embodiment of the present invention, at least one wet-out station includes a preheating station, which is configured to initiate polymer reaction and maintain an elevated temperature of the resin-substrate combination as it moves in a downstream direction of the system. Maintaining an elevated temperature of the resin-substrate combination may be achieved by means of ultraviolet light, heat lamps, or other heating methods as would be understood by persons skilled in the art. In yet another embodiment, at least one wet-out station is configured to apply a vacuum to remove any undesired trapped air, contaminants, and/or particulates.
Further, as see in
Index Station
In yet another embodiment, as seen in
Referring now to
Cooling Station
As illustrated in
Resin Dispenser With Pump
As seen in
In one embodiment, as illustrated in
As generally described above and illustrated in the figures, the panel production system makes it possible to use a carrier film (316, 317) of plastic underneath a cut fabric or substrate 31a, with the film (316, 317) extending at least partially or all the way to the other end of the production line from the upstream end portion 102 to the downstream end portion 104. Nip pullers, such as nip pullers 312a, at the downstream end of the line pull the carrier film (316, 317) and the fabric or substrate 31a above it.
Resin
In exemplary embodiments, a substrate in the form of a dry fabric, such as substrate 31a, is pulled into an enclosure, such as gantry box 321, where a resin, such as resin 106, includes premixed MMA/PMMA formulation, along with ingredients such as reaction initiator (peroxide), reaction inhibitor, color package, filler (such as fine clay), surfactant (to reduce surface tension), impact modifier, and additional optional additives, is sprayed onto the fabric or substrate 31a. Referring to
The low viscosity of the resin mix 106 (<500 cps, or more preferably up to 250 cps, or most preferably about 100 cps or less, for example) results in rapid impregnation of the fabric or substrate material 31a as it driven by forces of capillarity. Although viscous forces can be used, the lower viscosity resin 106 makes it possible to decrease the soak time required for good wetting of the fabric or substrate 31a.
The substrate-resin combination 16 is pulled out of the enclosure, such as gantry box 321, by the nip pullers 312a. As it is being pulled, another layer of plastic film 317 is added above the wet fabric or substrate 16. This film 317, much like the bottom film 316 described above, is pulled with the same nip pullers 312a.
The top film layer 317, wet fabric/substrate 316, and bottom film layer 316 form a closed system limiting or eliminating escape of VOCs. Accordingly, the top and bottom films (317, 316) form a die, such as die 1101 of
Tool-Less Die Assembly
Referring now to
The die 1101 also includes an upper film 1102 configured for movement relative to the press 39 in the downstream direction extending from the upstream end of the press 39 toward the downstream end of the press 39. The upper film 1102 has a lower surface, such as 1102a, positioned and configured to contact the combination 1104 of the substrate and the resin. Like the lower film 1103, the upper film 1102 also has a continuous length selected to extend beyond the upstream end of the press 39 in the upstream direction and beyond the downstream end of the press 39 in the downstream direction.
In the die 1101, a seal is formed by contact between the upper surface 1103a of the lower film 1103 and the lower surface 1102a of the upper film 1102. The thus-formed seal is positioned to at least partially surround the substrate. The seal extends along portions of the continuous lengths of the lower film 1103 and the upper film 1102. The seal also extends lateral to the continuous lengths of the lower film 1103 and the upper film 1102. The lower film 1103, the upper film 1102, and the seal together define a die interior configured to enclose the combination 1104 of the substrate and the resin 106.
In one embodiment, the seal forms a perimeter to at least partially surround the substrate 31a. The perimeter has a shape generally corresponding to a shape of the substrate 31a, thereby reducing the amount of resin 106 squeezed out of the substrate 31a upon application of pressure.
The lower film can include polyethylene terephthalate or polycarbonate, such as lower PET unwind 33. In one embodiment, the lower film can include polyethylene or polyetherimide or other suitable polymeric materials. In one example, the lower film 1103 is 0.01 inch or less in thickness. In another example, the lower film 1103 has a 0.075 mm nominal thickness.
Similarly, the upper film optionally includes polyethylene terephthalate or polycarbonate, such as upper PET unwind 35. In one embodiment, the upper film 1102 is 0.01 inch or less in thickness. Additionally, the upper film 1102 may have a nominal thickness. The upper film 1102 and the lower film 1103 may be the same in terms of at least one of dimensions, composition, and source.
The film substrate (1102, 1103) according to one example is formed from polyethylene terephthalate, being 60 to 63 inches in width, and a thickness of 0.075 mm. The thickness may be up to 0.254 mm thick (0.01 in) or thicker. The width of the film (1102, 1103) is dictated by process size and could be up to 5 meters in width dependent on the substrate, such as substrate 31a, and finished product size, such as laminate 1005.
Although it is contemplated to use the same films for top and bottom films (1102, 1103), different materials can be used for the top and bottom films (1102, 1103). Also, other film materials can be used dependent on the polymers and resin types to be used for a particular product and the release properties for a selected resin matrix. Other films and or release films may also be needed for thermoset resin systems.
As described above, systems according to aspects and embodiments of this invention make it possible to make a closed “mold,” such as die 1101, without the need for a mold into which resin, such as resin 106, is injected or otherwise introduced. In other words, the top and bottom films (1102, 1103) become the mold, and seals between the top and bottom films formed by the press 39 (to prevent out-flow of the liquid resin under pressure) become part of that mold.
Panel Production Process
Referring now to
In step (A), lower film 316 is supplied to introduce the lower film 316 in a downstream direction.
In step (B), a substrate 31a is supplied to introduce the substrate 31a in the downstream direction and onto the lower film 316.
In step (C), a resin 106 is dispensed to apply the resin 106 to the substrate 31a to form a resin-substrate combination 16.
In step (D), an upper film 317 is supplied to introduce an upper film 317 onto the resin-substrate combination 16.
In step (E), pressure is applied to the resin-substrate combination 16 through the upper film 317 and the lower film 316.
Finally, in step (F), the lower film 316 and the upper film 317 are removed from the resin-substrate combination 16.
Referring now to
In step (A), a lower film supply, such as lower film supply 33, is configured to introduce a lower film, such as lower film 33b, for introduction into the system in a downstream direction towards the press 39.
In step (B), an upper film supply, such as upper film supply 35, is configured to introduce an upper film, such as upper film 35b, for introduction into the resin dispenser, such as resin dispensing system 34, in a downstream direction towards the resin dispenser 34.
In step (C), a substrate, such as substrate or fabric 31a, is supplied to introduce the substrate 31a in the downstream direction.
In step (D), resin, such as resin 106, is prepared for application onto the substrate 31a.
In step (E), the substrate 31a is cut from a larger substrate.
In step (F), a substrate supply, such as station 31, supplies substrate 31a onto lower film 33b and in the downstream direction toward a resin dispenser 34.
In step (G), resin dispenser 34 dispenses resin 106 to apply resin 106 onto the substrate 31a to form a resin-substrate combination, such as combination 16.
In step (H), an upper film, such as upper film 35b, is applied onto the resin-substrate combination 16, the upper film 35b providing a barrier against the escape of VOCs from the resin-substrate combination as the resin-substrate combination 16 exits the resin dispenser 34 and moves in a downstream direction to a next station, such as soaking station 1 (37) and a soaking station 2 (38), each including an edge sealer including one or more brushes (37a, 38a) configured to seal edges of the upper film 35b to edges of the lower film 33b, thereby reducing VOC emissions. Additionally, resin temperature and viscosity control, including the control of temperature at one or more soaking or wet-out stations, can be performed for crosslinking control and to build up molecular weight.
In step (I), the resin substrate combination moves in a downstream direction toward a press, such as press 39.
In step (J), press 39 is configured to apply pressure to the resin-substrate combination 16 through the upper film 35b and the lower film 33b when the resin-substrate combination 16 is co-located with the press 39.
In step (K), when the press 39 opens and the resin-substrate combination 16 is pulled to a cooling station 311, which is located upstream from a film removal station 18, such as stripping station 313.
In step (L), a pulling station, such as station 312 having a nip puller 312a, configured to pull the lower film 33b and the upper film 35b, with the resin-substrate combination 16 between the lower film 33b and the upper film 35b, in a downstream direction. At a downstream end portion 104 of the system, reinforced composite product 314 is delivered.
In one example, reinforced composite product 314 comprises a substrate, such as substrate 31a, a resin 106 integrated with the substrate 31a, and has an exterior surface characterized by uniformity of at least one of color, weave pattern, and surface veil appearance. In another example, reinforced composite product 314 comprises a substrate, such as substrate 31a, a resin 106 integrated with the substrate 31a, and has an exterior surface characterized by uniformity of at least one of thickness, fiber content, thickness after secondary pressing, noise generation in ultrasonic C-scan, fiber content, and cross-section.
Referring now to
Referring now to
In one embodiment, the process pathways of any one of 12A-12D includes heating the resin-substrate combination 16 to an elevated temperature above an ambient temperature. The elevated temperature is selected to accelerate curing or polymerization of the resin of the resin-substrate combination.
In yet another embodiment, the process pathways of any one of 12A-12D further comprises sealing a perimeter of the lower film 316 and the upper film 317 to at least partially surround the substrate 31a. The perimeter can have a shape generally corresponding to a shape of the substrate 31a, thereby reducing the amount of resin squeezed out of the substrate upon application of pressure.
In one example, the process pathways of any one of 12A-12D includes applying pressure to the resin-substrate combination 16 for a predetermined period of time. The process may include varying the amount of pressure applied to the resin-substrate combination 16 as a function of time during the predetermined period of time.
Process improvements are beneficial and needed because the release of Volatile Organic Compounds (VOCs) is regulated by different national and local governments, resulting in the quantity of methyl methacrylate (MMA) that can used during manufacturing being restricted. In order to reduce the quantity of VOCs released, the processes and systems described herein are designed to reduce emissions and maximize possible manufacturing output.
In order to capture VOCs, composite products in the form of panels are cured in between two pieces of film (316, 317), such as a polyester release liner. A substrate such as fabric 31a is carried on the film 316 as it is moved from a resin application zone such as a spray-box 321 to a heat-press 39 and out from the heat-press 39. To monitor VOC emissions, fabric and release liner weights are recorded throughout the process so that they can be subtracted from the weights of the cured panels, such as laminate 1005, at the end of the process line. Final resin weight can be calculated by this method. Initial weights of carbon-filter drums, such as containers 41a, can also be recorded, and initial weights can be subtracted from final weights to obtain the net weight of VOCs captured.
Compared to other manufacturing methods such as the first process described herein, methods according to aspects of this invention surprisingly provide an improvement of more than 50% in terms of the reduction of VOC emissions, more preferably more than 60%, and even more preferably more than 70%. This improvement over other manufacturing processes makes the improved process an important step in the direction to reduce VOCs and at the same time increase manufacturing capacity.
With the release of Volatile Organic Compounds (VOCs) monitored closely and regulatory restrictions on the quantity of material such as methyl methacrylate (MMA) that can be used, the process improvements have been made to mitigate release of VOCs during manufacturing. The reduction of VOCs released will consequently allow an increase in the amount of MMA that can be used for processing.
Processes described herein utilize a resin infusion method for creating thermoplastic composite panels. These processes have been designed to run as a substantially or completely closed system, allowing the full polymerization of MMA and the capture of any VOCs that may otherwise escape during processing.
According to one embodiment, as illustrated by
In step (A), a substrate, such as substrate 31a, is introduced into an enclosure, such as gantry box 321, of a resin dispenser, such as resin dispensing system 34.
In step (B), resin, such as resin 106, is applied onto the substrate 31a to form a resin-substrate combination, such as combination 16.
In step (C), the gantry box 321 is configured to contain VOCs emitted in the gantry box 321 when the gantry box 321 is closed.
In step (D), an exhaust, such as fan 1406 is configured to reduce pressure within the gantry box 321, as well as purge the VOCs from the gantry box 321 and into the filter, such as carbon filters 1404, 1405.
In step (E), one or more filters, such as carbon filters 1404 and 1405, is/are configured to receive VOCs from the gantry box 321.
As explained generally above, VOC capture is accomplished using one or more activated carbon drum filters, such as filters 1404 and 1405. In one embodiment, as seen in
Gross losses from a substantially closed system may in some cases be greater than one percent. Such losses may result from one or more of three sources, or a combination of any. One source is overspray of resins. Another source is leaks of VOCs during processing. Yet another source is less than full polymerization of the resin formulation caused by either the formulation and/or heating duration. Accordingly, any losses of VOC capture can be controlled by reducing or eliminating overspray of resins, reducing or eliminating leaks of VOCs during processing, and/or promoting increased or full polymerization of the resin formulation. As illustrated in
Using VOC detection systems, such as the RAE System's MiniRAE 300 PGM7320 VOC meter, VOCs escaping from the processing system can be detected at various locations in the system. For example, monitoring for VOC escape can be made at the exit gate, such as exit gate 318 of
VOC Capture Assembly (Equipment Assembly and Subassemblies)
According to one embodiment of the present invention, as illustrated in
As illustrated in
In one embodiment, the system includes an upper film supply 17 located upstream of the downstream gate, such as exit gate 318, of the enclosure 34 and configured to introduce an upper film 317 into the system, in a downstream direction toward the downstream gate 318 of the enclosure 34, and onto the resin-substrate combination 314. The upper film 317 provides a barrier against the escape of VOCs from the resin-substrate combination 314 as the resin-substrate combination 314 exits the downstream gate 318 of the enclosure 34. The enclosure 34 of the resin dispenser 91 may also include an upper film gate, such as gate 916, positioned to allow entry of the upper film 317 into the enclosure 34. In one example, the upper film gate 916 is positioned in a top portion of the enclosure 34 to allow passage of the upper film 317 toward an upper surface of the substrate 31a.
As shown in
Referring to
In step (A), the process includes opening an upstream gate, such as entry gate 319, of an enclosure 34, and actuating an exhaust, such as fan 1406, to reduce pressure within the enclosure 34 when the upstream gate 319 of the enclosure 34 is opened to receive substrate 31a in the enclosure 34 and when the upstream gate 319 of the enclosure 34 is closed upon entry of the substrate 31a.
In step (B), resin is applied to the substrate 31a to form the resin-substrate combination 314 in the enclosure 34, and VOCs are exhausted from the enclosure 34 and into a filter (1404, 1405).
In step (C), the process includes actuating the exhaust 1406 to reduce pressure within the enclosure 34, opening a downstream gate, such as exit gate 318, of the enclosure 34, and delivering the resin-substrate combination 314 from the enclosure 34 through the downstream gate 318 of the enclosure 34.
In one embodiment, the process can also include introducing an upper film 317 in a downstream direction toward the downstream gate 318 of the enclosure 34 and onto the resin-substrate combination 314, the upper film 317 providing a barrier against the escape of VOCs from the resin-substrate combination 314 as the resin-substrate combination 314 exits the downstream gate 318 of the enclosure 34.
In yet another embodiment, the process can also include sealing the downstream gate 318 of the enclosure 34 against the upper film 317. Such sealing can be provided in various ways such as by using a sealing surface. Such a sealing surface can, for example, include a gasket or a contact blade or other structure capable of reducing or preventing the passage of gases from within the enclosure.
Also, the process may include actuating the exhaust 1406 when the upstream gate 319 of the enclosure and the downstream gate 318 of the enclosure 34 are closed. The resin can be applied while the exhaust 1406 is actuated and while the upstream gate 319 of the enclosure 34 and the downstream gate 318 of the enclosure 34 are closed. At least one of the upstream gate 319 of the enclosure 34 and the downstream gate 318 of the enclosure 34 can be opened while the exhaust 1406 is actuated, and the resin-substrate combination 314 can be delivered from the enclosure 34 through the downstream gate 318 of the enclosure while the exhaust 1406 is actuated. The exhaust can be de-actuated when the upstream gate 319 of the enclosure 34 and the downstream gate 318 of the enclosure 34 are both closed.
In addition to the improvements noted above, the system and processes according to embodiments of this invention produce reinforced composite panels with improved properties. Among other improvements, the reinforced composite panels have improved surface properties and reduced variation of properties across the panel.
According to an embodiment of the present invention, a reinforced composite product 1501 includes a substrate 31 and a resin integrated with the substrate 31a. The reinforced composite product 1501 has an exterior surface 1502 characterized by uniformity of at least one of color, weave pattern, and surface veil appearance.
The substrate, such as substrate 31a, may include fibrous material, non-fibrous material, or a combination thereof. In one example, the substrate includes metallic material, non-metallic material, or a combination thereof. In another example, the substrate includes one or more of glass, carbon, ceramic, basalt, steel, and cellulosic fiber materials. In yet another embodiment, the substrate includes one or more of continuous, discontinuous, woven, non-woven, crimped, uncrimped, uni-directional, multi-directional, porous, and non-porous materials and hybrids or combinations thereof.
The substrate 31a may be substantially planar and having an outer periphery. In one example, the outer periphery of the substrate 31a is a geometric shape, a predetermined shape, or an arbitrary shape. For example, the geometric shape can be rectangular or square.
In one embodiment, the substrate 31a is cut from a larger substrate. The substrate 31a may be cut using a CNC or nesting operation. It can be provided with any regular or irregular shape by programming the CNC to cut the substrate 31a. The substrate 31a may be cut or otherwise formed into a desired shape in line with the composite production line, such that the process can be continuous or semi-continuous. Alternatively, the substrate 31a can be pre-cut or pre-formed for subsequent processing in the composite production line.
In one example, the substrate 31a has a thickness (T) not exceeding about 5 mm. However, the substrate 31a may be thicker or thinner than 5 mm depending on the final product to be produced.
The resin, such as resin 106, can include a thermoplastic polymer or a thermoset polymer having a viscosity up to 5000 cps. In another example, the resin 106 includes a thermoplastic polymer or a thermoset polymer having a viscosity up to 500 cps, or more preferably up to 250 cps, or most preferably about 100 cps or less.
In addition, the resin 106 may include a polymer, monomer, or combination thereof that can be cross-linked for polymerization. Further, the resin 106 can include one or more of a color package, a reaction initiator, a reaction inhibitor, an impact modifier, a flame retardant, a lubricant, a light stabilizer, an electrical or thermal conductor additive, and an anti-oxidant, or combinations thereof.
Further, the resin 106 may include a thermoplastic polymer that is dissolvable into solvent to reduce viscosity. In one example, the resin 106 includes polycarbonate dissolved in dichloromethane (DCM). Finally, the resin 106 can be configured to be applied by spraying as noted above.
According to another aspect of the invention, a panel 314 produced according to the processes described herein can have a narrower distribution of properties in terms of at least one of color, mechanical properties, thickness, and c-scan. Also, the properties can have a narrower distribution on a bell curve and the position of that narrower distribution can be increased (moved to the right on the bell curve) or decreased (moved to the left on the bell curve) as compared to prior processes.
Referring now to
A mass-balance experiment was performed in triplicate to determine the VOC emissions from the composite panel production system. The mass-balance experiment was done in triplicate over three days at ambient conditions. Intermediates of a resin included monomer (MMA) and initiator (BP-75). The weight of the resin that was added into a reservoir tank was recorded as the initial weight.
Panels were cured in between two pieces of polyester release liner that the fabric rode on as it was moved from a spray-box to a heat-press and out. Fabric and release liner weights were recorded throughout the process so that they could be subtracted from the weights of the cured panels at the end of the process line. Final resin weight was calculated by this method.
Initial weights of the carbon-filter drums were recorded before each of three trials. Initial weights were subtracted from final weights at the end of each trial to obtain the net weight of volatiles captured.
Compared to the first process described herein, the composite panel production system and improved process provided an improvement of 70.6% in terms of the reduction of VOCs. The improvement over the first process makes the composite panel production system an important step in the direction to reduce VOCs and increase manufacturing capacity.
In each trial, resin was weighed and added to the composite panel production machine and run through the system. Losses were accounted for by subtracting the output quantity of resin from the input quantity. Activated carbon filters were used in series with an exhaust fan to pull fumes out of a closed dispensing gantry box of the improved process at all times the system was open, whether during normal operation or troubleshooting. The emissions generated from the composite panel production system and improved process are assumed here to be the gross (not accounting for carbon filter collection) and net losses (accounting for carbon filter collection) associated with the difference from resin-in to resin-out. The following equipment was used in the trials:
Three trials were performed. Trial 1 yielded the highest ‘resin lost’ and ‘collected in filter drum’ quantities, as seen in Table 2 and graphically depicted in
Trial 1 also yielded the highest gross and net loss percentages as seen in Table 3 below. Gross loss was calculated to indicate loss of VOCs before any collection process was used. This result represents what is lost during processing due to process and equipment limitations. The resin used is cured to levels in accordance with the resin's product data sheet. Net loss values are representative of the process and equipment loss after utilizing the carbon-filter collection drums.
Referencing Tables 2 and 3, the carbon-filter collection drums on average collected 32% of the gross loss. Variation between trials can be attributed to resolution of the drum scale used to measure relatively small quantities. Measuring hundreds of grams in drums that weigh close to 100 kilograms with a precision limited to 45 grams lends itself to an inevitable error that equates to roughly +/−10% on the drum collection percentage. All trials were performed with as few adjustable variables as possible. The difference between Trial 1 from Trials 2 and 3 was the spray nozzle used in the resin dispensing system. Spray nozzle comparisons can be seen in
The spray nozzle used in Trial 1 caused overspray within the spray gantry box. The overspray stayed within the box throughout the processing of the panels. It is likely that the overspray that was left in the gantry box resulted in the higher than normal loss quantities as the resin did not make it onto the fabric and into the press for curing. For trials 2 and 3, a cleaner-applying spray nozzle was used.
The three trials that were conducted resulted in net loss of VOCs from our reduced emissions manufacturing process in the range of one to three percent, with the mean gross loss of resin being 2.52% by weight of the initial quantity added to the system. After accounting for the carbon collection, the final mean net loss of resin and/or volatiles to the environment was 1.76%. On average, the carbon filter system collected 32% of the lost resin/volatiles that made the difference between initial and final weights of the resin that was put into the system. Compared to the first process that allows for a loss of 6% to the environment, the composite panel production system and improved process is an improvement of 70.6%. This number is effectively higher if Trial 1 is omitted from the data. Trial 1 resulted in higher loss values because of the spray nozzle design as discussed above.
Embodiments of the systems and methods described herein provide a semi-continuous process to produce fabric reinforced panels where the resin is sprayed on the fabric using a programmable robotic head that travels over the fabric surface. The resin system primarily is Methyl Methacrylate (MMA)/Poly-Methyl Methacrylate (PMMA), which is a thermoplastic that can be considered to behave in some ways like a thermoset. The substrate can be in the form of woven fabric, non-woven/non-crimp fabric, different surface veils—all produced from various types of fibers or their combination.
Like thermoset resins, there is a chemical cross-linking reaction involved accompanied by an exotherm. However, according to embodiments of the resin system, post-curing the laminates can be thermoformed into a 3-D shape using heat and pressure.
According to exemplary embodiments of the disclosed process, benefits of the invention can include one or more of the following:
An experiment was performed to compare the thickness of composite panels produced in accordance with the first process (
Referring to
To determine thickness measurements of each sample obtained from composite panels produced in accordance with the first process and the improved process according to aspects of the invention, five (5) samples, each 10″×10″ size, were cut from the large panel. Samples 1, 2, 4, and 5 (
The mean thickness (measured in mm), standard deviation, and coefficient of variance of each sample was calculated. Compared to the first process, the improved process according to aspects of the invention provided an improvement in terms of the thickness of applied resin on the composite panels. For example, as seen in Tables 6 and 7 below, the present invention results in a smaller range of differences in resin thickness. In Table 8 below, the following properties are reported and are defined as follows:
“Average Thickness” is the average thickness of all thickness measurements; specifically, it is the average of Measurements 1-12 for Samples 1-5. In other words, it is the average thickness based on all 60 thickness measurements.
“Thickness Standard Deviation” is the standard deviation of all thickness measurements; specifically, it is the standard deviation of Measurements 1-12 for Samples 1-5. In other words, it is the standard deviation based on all 60 thickness measurements.
“Thickness Covariance” is the Thickness Standard Deviation (defined above) divided by the Average Thickness (defined above) times 100. By dividing the thickness standard deviation by the average thickness, the standard deviation value is normalized to account for various nominal thicknesses of panels being evaluated.
“Maximum Thickness” is the maximum thickness from Measurements 1-12 for Samples 1-5. In other words, it is the maximum thickness of all 60 measurements.
“Minimum Thickness” is the minimum thickness from Measurements 1-12 for Samples 1-5. In other words, it is the minimum thickness of all 60 measurements.
“Thickness Uniformity” is the number one minus the difference between “Maximum Thickness” minus “Minimum Thickness” divided by “Average Thickness,” then multiplied by 100. Again, by dividing the difference by the average thickness, the value is normalized to account for various nominal thicknesses of panels being evaluated.
“Thickness Uniformity Index” is “Thickness Uniformity” divided by “Thickness Covariance.”
Referring generally to
The present invention improves upon the uniformity of thickness. For example, as seen in
Referring specifically to
Further, as seen more clearly in
Looking at
An experiment was performed to compare the content of resin on the composite panels produced in accordance with a first process and with the improved process. The first process, as described above, includes steps of wrapping, stacking, and cooling of pre-pressed sections of material for subsequent unwrapping and pressing.
The experiment was performed according to the following conditions. Referring to
The mean resin content (measured wt %), standard deviation, and coefficient of variance of each sample was calculated. Compared to the first process, the present invention provided an improvement in terms of the content of applied resin on the composite panels. For example, as seen in Tables 9-11 below, the present invention results in an improved resin content uniformity based on the low level of covariance indicated by the new process. In Table 11 below, the following properties are reported and are defined as follows:
“Average Resin Content” is the average resin content of all resin content measurements; specifically, it is the average of resin contents for Samples 1-9. In other words, it is the average resin content based on all 9 resin content measurements.
“Resin Content Standard Deviation” is the standard deviation of all resin content measurements; specifically, it is the standard deviation of resin contents for Samples 1-9. In other words, it is the standard deviation based on all 9 resin content measurements.
“Resin Content Covariance” is the Resin Content Standard Deviation (defined above) divided by the Average Resin Content (defined above) times 100. By dividing the resin content standard deviation by the average resin content, the standard deviation value is normalized to account for various nominal resin contents of panels being evaluated.
“Maximum Resin Content” is the maximum resin content from Samples 1-9. In other words, it is the maximum resin content of all 9 measurements.
“Minimum Resin Content” is the minimum resin content from Samples 1-9. In other words, it is the minimum resin content of all 9 measurements.
“Resin Content Uniformity” is the number one minus the difference between “Maximum Resin Content” minus “Minimum Resin Content” divided by “Average Resin Content,” then multiplied by 100. Again, by dividing the difference by the average resin content, the value is normalized to account for various nominal resin contents of panels being evaluated.
“Resin Content Uniformity Index” is “Resin Content Uniformity” divided by “Resin Content Covariance.”
The foregoing properties relating to thickness uniformity and resin content uniformity are enhanced by the improved process. It is believed that these enhanced properties result from the conditions and steps of the improved process and their impact on the uniformity of the thickness of produced panels and the uniformity of the resin content of the produced panel. For example, and without being tethered to any particular theory, when resin viscosity is very high, e.g. measuring few 10 thousand cps, viscous forces are dominant. The dominant viscous forces limit the resin's ability to achieve optimum wet-out/impregnation of a given substrate material. This is especially true when the resin is allowed to impregnate the substrate at ambient/normal atmospheric pressure conditions. In the case of reactive systems, the problem is further exacerbated because the resin-coated substrate is stored at refrigerated/freezer conditions in order to increase the materials' shelf life and prevent a premature initiation of the cross-linking reaction.
Because the degree of wet-out/impregnation is a function of the resin viscosity and the substrate permeability, lower viscosity and higher permeability would be desired for maximum substrate wet-out/impregnation by the resin system. This relationship is based on the concepts of flow through porous media as explained by Darcy's law.
When the substrate impregnated with highly viscous resin is introduced in a press of the first process for composite laminate/part production, the resin is pushed out/flashed along the perimeter of the substrate. It is desired for the substrate to be ideally or optimally impregnated by the resin, but the chances of a relatively excessive amount of resin being squeezed out along the perimeter is higher with the use of a highly viscous resin. Further, the resin can be pushed and evened out in the central region of the substrate, but depending on the size of the substrate, and for relatively larger substrates, the resin could be highly concentrated in the center portion of the material system relative to the peripheral regions in the first process described above. This can result in a resin content gradient in the composite panel with the central or core region having a higher amount of resin as compared to the peripheral region where the resin is pushed out.
Accordingly, the material systems with higher viscosity resins can have drawbacks in some circumstances, including that the composites produced by the first process can result in greater variability in certain composite panel properties such as thickness and fiber/resin content. Variability in these properties can further have implications on variability in material, mechanical, and potentially other properties.
In contrast, the improved process contemplates use of resin with reduced viscosity (as low as ˜100 cps for example), such that capillarity forces are more dominant than viscosity forces. As a result, the resin wets-out/impregnates the substrate much faster and the resin is evenly driven by concepts of capillarity and wicking effects. When the resin-coated substrate is introduced in a press for composite laminate/part production, the amount of resin pushed out/flashed along the perimeter of the substrate is relatively lower because it is easier for the low viscosity resin to pack and move within the substrate to fill in any voids or regions that might be resin starved. Accordingly, the materials system with lower viscosity resin has the advantage of producing composite panels with more uniform thickness and more uniform resin/fiber content, and hence, may be expected to have better consistency in mechanical and other properties.
As illustrated in
In addition to the viscosity of the resin used in the process, the improved process differs from the first process in other ways that are believed to impact the uniformity of thickness and/or uniformity of resin content. For example, the improved process embodiment illustrated herein utilizes spray application of resin onto a substrate, a resin-substrate combination interposed or “sandwiched” between two elongated film layers to form a continuous or semi-continuous die, an enclosure within which the resin is applied in a controlled way, a press positioned to press the resin-substrate combination through the film layers, the continuous or semi-continuous nature of the process that advances the resin-substrate combination from a resin-application station to a press and to the film removal.
It is believed that these features of the improved process, individually or in combination, contribute to improved uniformity of the produced panel. This uniformity is especially beneficial with respect to thickness and resin content.
Thickness
Improved uniformity of the thickness of the produced panels can be quantified in terms of Thickness Covariance, Thickness Uniformity, and Thickness Uniformity Index. Specifically, a reduction in Thickness Covariance is desired as is an increase in Thickness Uniformity and an increase in Thickness Uniformity Index.
The Thickness Uniformity Index of the reinforced composite product is preferably 8 or greater, or more preferably 10 or greater. The Thickness Covariance of the reinforced composite product is preferably 7% or less, or more preferably 6% or less. The Thickness Uniformity of the reinforced composite product is preferably 61% or greater, or more preferably 70% or greater. The reinforced composite product can have at least one of a Thickness Uniformity Index of 8 or greater, a Thickness Covariance of 7% or less, and/or a Thickness Uniformity of 61% or greater, or any combination of these.
Resin Content
Improved uniformity of the resin content of the produced panels can be quantified in terms of Resin Content Covariance, Resin Content Uniformity, and Resin Content Uniformity Index. Specifically, a reduction in Resin Content Covariance is desired as is an increase in Resin Content Uniformity and an increase in Resin Content Uniformity Index.
The Resin Content Uniformity Index of the reinforced composite product is preferably 16 or greater, or more preferably 20 or greater. The Resin Content Covariance of the reinforced composite product is preferably 5% or less, or more preferably 4% or less. The Resin Content Uniformity of the reinforced composite product is preferably 83% or greater, or more preferably 85% or greater. The reinforced composite product can have at least one of a Resin Content Uniformity Index of 16 or greater, a Resin Content Covariance of 5% or less, and/or a Resin Content Uniformity of 83% or greater, or any combination of these.
While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.
This application claims priority to U.S. Provisional Application No. 63/073,284, titled “COMPOSITE PRODUCT, COMPOSITE PRODUCT PRODUCTION SYSTEM, COMPOSITE PRODUCT PRODUCTION PROCESS, AND SYSTEM AND METHOD FOR REDUCING VOC EMISSIONS ASSOCIATED WITH COMPOSITE PRODUCT PRODUCTION”, filed Sep. 1, 2020, the contents of which are incorporated herein by reference in its entirety for all purposes.
Filing Document | Filing Date | Country | Kind |
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PCT/US2021/048500 | 8/31/2021 | WO |