`In relation to the proceedings before the Regional Court of Mannheim
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`I am the Vice President of Research and Development for Aspen Aerogels, Inc. I have been
`employed with Aspen Aerogels and its predecessor company, Aspen Systems, since 1999. Prior to
`joining Aspen, I was a chemistry professor at the University of Illinois at Chicago. I hold a B.A. in
`Chemistry from the College of Wooster, a Ph.D. in Inorganic Chemistry from Yale University, and I
`completed post‐doctoral training at Brookhaven National Laboratory.
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`I am an inventor of the subject matter presented and claimed in European Patent EP 1,638,750 B1
`[“the ‘750 patent”] (German PTO File No. 60 2004 039 041.0 T2). The filing date of this European
`Patent was June 23, 2004; the priority date is June 24, 2003 (based on US Provisional Application
`60/482,359); the European Patent was granted on August 22, 2012. I have an intimate knowledge
`of the subject matter presented and claimed in this patent. This patent describes a process for
`producing long continuous sheets of reinforced aerogel material using a continuous, conveyer‐
`belt‐based casting process.
`
`In 2001, Aspen Aerogels began work to improve the commercial availability of aerogel products by
`scaling‐up the commercial production of reinforced aerogel sheets. I was one of the primary
`technicians and scientists working on this project, and I have an intimate knowledge of the
`processes and equipment used in this early production system. The procedures used in Aspen’s
`initial scaled‐up production system were based on a general process known in the art as “batch
`casting” (see paragraph 4, infra).
`
`In general, a batch casting process comprises the following steps:
`i) a sol comprising gel precursors suspended in a solvent is prepared within a tank (for example,
`a silica gel precursor such as tetraethoxysilane is combined sequentially with water and a
`hydrolysis catalyst), followed by the addition of a gel‐inducing agent (such as ammonia), thus
`forming a batch of catalyzed sol in which the entire volume of catalyzed sol will be subject to
`simultaneous gelation;
`ii) a reinforcement material (such as a lofty fibrous batting sheet) is placed within an elongated
`molding tank of limited volume (sometimes referred to as a “static casting table”);
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`iii) the entire batch of catalyzed sol is poured over the reinforcement material, and the catalyzed
`sol is then manually manipulated to ensure complete infiltration of the sol into the
`reinforcement material;
`iv) the gel precursor materials within the batch of catalyzed sol are allowed to gel and age for a
`predetermined time to form a reinforced gel material; and
`vi) the reinforced gel material is dried using supercritical solvent extraction techniques to
`produce a reinforced aerogel material.
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`5. From 2001 to 2003, Aspen Aerogels used a batch casting process to produce reinforced aerogel
`sheets which were up to 4.88 meters (16 feet) in length. According to my recollection (including a
`review of sales records and production travelers available from that period), Aspen Aerogels did
`not produce any reinforced aerogel sheets longer than 4.88 meters (16 feet) using the batch
`casting process.
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`I am unaware of any reinforced aerogel sheets longer than 4.88 meters which were available to
`the public prior to the invention of the subject matter presented and claimed in the ‘750 patent.
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`7. Aspen Aerogels began producing fiber‐reinforced aerogel sheets longer than 5 meters in length
`using the conveyer‐belt‐based casting process described in the ‘750 patent. This process has since
`allowed Aspen Aerogels to produce continuous, fiber‐reinforced aerogel sheets as long as 160
`meters long; a length which is entirely inconceivable using any other known casting process.
`
`I have extensive knowledge and experience related to producing fiber‐reinforced aerogel sheets
`through both small‐scale and large‐scale production. I also have extensive knowledge and
`experience specifically related to processing reinforced aerogel sheets using a batch casting
`process. According to my knowledge and experience, the batch casting processes known in the art
`prior to the invention of the conveyer‐belt‐based casting process described in the ‘750 patent
`could not have been used to produce rolls of reinforced aerogel sheets longer than 5 meters, for
`the following reasons:
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`8.
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`Long Gel Sheets Must Be Rolled To Allow For Processing Into Long Aerogel Sheets
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`9. An important consideration in processing particularly long sheets of gel material (i.e. reinforced
`gel sheets longer than 5 meters) into long sheets of aerogel material is the ability of the gel sheets
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`to be rolled. For a gel material to be processed into an aerogel material, the gel material must
`dried under controlled solvent extraction conditions (such as supercritical extraction conditions).
`This can be accomplished by placing the gel material into an enclosed extraction tank, which
`facilitates processing the gel material under the controlled solvent extraction conditions.
`
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`10. For particularly long sheets of gel material to be placed in an enclosed extraction tank, the long gel
`sheets must be rolled. The rolled sheets of gel material can then be processed and dried within the
`enclosed extraction tanks under the controlled solvent extraction conditions, thereby producing
`rolled sheets of aerogel material.
`
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`11. Thus, to produce reinforced aerogel sheets longer than 5 meters in length using a batch casting
`process, the long gel sheets formed on the static casting table must have been able to be rolled
`into a form which could be placed into an enclosed extraction tank for supercritical solvent
`extraction. This rolling processes would need to comprise one of two processes: 1) pulling the
`entire gel sheet across the length of the static casting table to a roll at one end of the table; or 2)
`rolling the gel material over itself from one end of the static casting table to the other end.
`However, neither of these rolling process would have been possible for long sheets of reinforced
`gel material which are batch cast on a static casting table because of physical limitations related
`to tensile strength (see paragraphs 12‐18, infra), compression strength (see paragraphs 23‐26,
`infra), and gel time (see paragraphs 28‐32, infra)
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`The Length of a Reinforced Gel Sheet Is Limited by Tensile Strength
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`12. One significant factor limiting the length of aerogel sheets produced by a batch casting process is
`the limited tensile strength of a reinforced gel material. The tensile strength of a material is the
`ability of that material to withstand structural failures when exposed to tension along the length
`of the material. In the specific context of a batch casting process, a reinforced gel sheet must have
`enough tensile strength to withstand the tensile stresses associated with adhesion and friction if
`the sheet of gel material is being pulled across the surface of the static casting table to be rolled
`at the end of the surface (see option 1 in paragraph 11, supra).
`
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`13. Reinforced gel materials do not have sufficient tensile strength to withstand the dragging‐and‐
`rolling process associated with producing particularly long sheets of reinforced gel material in a
`batch casting process. As a sheet of gel material is pulled across the surface of a static casting table,
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`the significant tensile stresses associated with adhesion and friction will result in fracturing and
`other significant structural failures within the long gel sheet. These fractures and structural failures
`will render the long sheet of gel material inoperable for processing into a long sheet of aerogel
`material. These statements are supported by experimental observations related to frictional forces
`and adhesive forces, as described in paragraphs 14‐18, infra.
`
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`14. When long sheets of gel material are cast onto a surface, the gel material will have a certain level
`of natural adhesion to that casting surface. Aspen Aerogels conducted experiments to examine the
`extent of this natural gel adhesion, as well as the effect of gel adhesion on the ability of a reinforced
`gel sheet to be pulled over a static batch casting surface and rolled at the end of the surface. The
`procedures and results of these Gel Adhesion Experiments are presented in Appendix A.
`
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`15. According to the gel adhesion experiments and results presented in Appendix A, the natural
`adhesion of a gel material onto a static casting surface presents a significant limit to the size of gel
`sheets which can be cast and rolled in a batch casting process. Specifically, the results presented
`in Appendix A show that any reinforced gel sheet longer than 5 meters in length which is cast using
`a batch casting process cannot be pulled along the length of the casting table without catastrophic
`tearing and structural failure due to gel adhesion forces. The force required to overcome the
`adhesion force of a reinforced gel sheet 5 meters in length on a casting surface would be more
`than 25 times the tensile strength of the reinforced gel material.
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`16. Long sheets of reinforced gel materials can be very heavy and can have a large surface areas. The
`weight and large surface area of a long gel sheet will result a significant frictional counter‐force
`against the gel sheet as it is pulled across the surface of a static casting table to be rolled at the
`end of the surface. Aspen Aerogels conducted experiments to examine the extent of this frictional
`force on gel sheets, as well as the effect of frictional forces on the ability of a reinforced gel sheet
`to be pulled over a static casting surface and rolled at the end of the surface. The procedures and
`results of these Frictional Force Experiments are presented in Appendix B.
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`17. According to the frictional force experiments and results presented in Appendix B, the frictional
`forces exerted on a long gel sheet as it is dragged over a static casting surface presents a significant
`limit to the size of gel sheets which can be cast and rolled in a batch casting process Specifically,
`the results presented in Appendix B show that any reinforced gel sheet longer than 5 meters in
`length which is cast using a batch casting process cannot be pulled along the length of the casting
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`table without catastrophic tearing and structural failure due to frictional forces. The force required
`to overcome the frictional force of a reinforced gel sheet 5 meters in length on a casting surface
`would be nearly 4 times the tensile strength of the reinforced gel material.
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`18. Thus, the length of a reinforced aerogel sheet produced by a batch casting process is limited by
`the tensile strength of reinforced gel sheets. Specifically, reinforced gel sheets longer than 5
`meters in length do not have sufficient tensile strength to withstand the significant tensile stresses
`from adhesion and friction as the long reinforced gel sheet is pulled over a static casting surface to
`be rolled at the end of the surface.
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`19. Aspen Aerogels overcame the tensile strength limitations associated with a batch casting process
`by developing a conveyer‐belt‐based casting process, as described in the ‘750 patent. This
`innovative system included: a molding surface in the form of a moving belt; a mechanism for
`introducing long, continuous sheets of reinforcement material onto the moving belt; a mechanism
`for dispensing the catalyzed pre‐gel solution onto the moving belt in combination with the sheet
`of reinforcement material; and a mechanism for rolling the reinforced gel sheet as it comes off of
`the moving belt. This novel system for producing long sheets of reinforced gel material did not
`exist in the industry or in the known literature at the time its invention. This novel system allows
`for the production of long reinforced gel sheets of an indeterminate length, including reinforced
`gel sheets longer than 5 meters in length.
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`20. The conveyer‐belt system described in the ‘750 patent removes the tensile strength limitations on
`the production of long reinforced gel sheets.
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`21. First, the conveyer‐belt system allows the entire length of a long reinforced gel sheet to be rolled
`without significant tensile stress from adhesion forces. The moving belt and the rolling mechanism
`can be synchronized such that every portion of the gel sheet is delaminated from the belt surface
`at the exact end of the moving belt, thereby minimizing any tensile forces from adhesion placed
`on the gel sheet as it is delaminated from the belt surface. This conveyer‐belt system thus allows
`a long gel sheet to be cast, gelled, and rolled without being subjected to destructive amounts of
`tensile stress from adhesive forces.
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`22. Second, the conveyer‐belt system described in the ‘750 patent allows the entire length of a long
`reinforced gel sheet to be rolled without any tensile stress from frictional forces. The moving belt
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`provides a stable molding surface which carries the reinforced gel material from the gel‐casting
`system at one end of the belt to the rolling system at the other end of the belt without requiring
`any dragging of the gel sheet along the surface of the belt. This conveyer‐belt system thus allows
`a long gel sheet to be cast, gelled, and rolled without being subjected to destructive amounts of
`tensile stress from frictional forces.
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`The Length of a Reinforced Gel Sheet Is Limited by Compressive Strength
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`23. Another significant factor limiting the length of aerogel sheets produced by a batch casting process
`is the limited compression strength of a reinforced gel material. The compression strength of a
`material is the ability of that material to withstand structural failures when exposed to
`compressive stress or forces. In the specific context of a batch casting process, a reinforced gel
`sheet must have enough compression strength to withstand significant compression from a heavy
`roll of gel material as the gel sheet is rolled upon itself from one end of the gel sheet to the other
`end (see option 2 in paragraph 12, supra).
`
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`24. According to my knowledge and experience, reinforced gel materials do not have sufficient
`compression strength to withstand the process of rolling a long, heavy gel sheet along its own
`length from one end to the other. As a long sheet of gel material is rolled upon itself, the significant
`compression stress from the growing roll of heavy gel material will result in fracturing and other
`significant structural failures as portions of the gel framework are crushed or torn by the
`combination of compressing and rolling the gel material. These fractures and structural failures
`will render the long sheet of gel material inoperable for processing into a long sheet of aerogel
`material. The compression stress from rolling a long reinforced gel sheet upon itself will also
`compress the gel layers together, resulting in gel layers fusing together or in separator materials
`between the gel layers being compressed into the framework of the gel sheet. This compression
`will result in damaged gel layers which have insufficient flow between roll layers for effective aging
`or for effective processing into aerogels by supercritical solvent extraction.
`
`25. The conveyer‐belt system described in the ‘750 patent (see paragraph 19, supra) removes the
`compression strength limitations on the production of long reinforced gel sheets. Specifically, the
`conveyer‐belt system allows the entire length of a long reinforced gel sheet to be rolled without
`any significant compressive forces being placed on the surface of the reinforced gel sheet. The
`moving belt and the rolling mechanism can be synchronized such that entire length of the heavy
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`gel sheet can be collected on the gel sheet roll at the exact end of the casting belt without requiring
`the gel material to be rolled upon itself. This conveyer‐belt thus system allows a long gel sheet to
`be cast, gelled, and rolled without being subjected to destructive amounts of compressive force
`from the heavy gel sheet being rolled upon itself.
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`The Length of a Reinforced Gel Sheet Is Limited by Gel Strength and Flexibility
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`26. Yet another significant factor limiting the length of aerogel sheets produced by a batch casting
`process is the narrow window of gel strength and flexibility at which a gel material can be
`effectively rolled.
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`27. As mentioned earlier, a batch casting process requires that an entire volume of a catalyzed pre‐gel
`solution (i.e., gel‐precursor particles + solvent + gel‐inducing agent) is dispensed onto a casting
`surface at the same time (see paragraph 4, supra), with the gel‐inducing agent inducing gelation
`simultaneously throughout the entire volume of the catalyzed pre‐gel solution. The gel material is
`formed as collections of gel‐precursor particles suspended in the liquid solvent polymerize to form
`a complex, three‐dimensional gel framework with a corresponding network of pores that grows to
`encompass the solvent. The resulting gel framework is initially fragile and unable to withstand
`bending or other physical stress (even with a fiber reinforcement); the gel framework must be
`strengthened through an aging process called “synerisis” before it is strong enough to be bent or
`rolled. As the gel ages, the molecular bonds within the gel framework are gradually strengthened
`until a more robust gel framework is produced around the reinforcing fibers. The strengthened gel
`framework can then withstand the industrially‐demanding processes of bending, flexing, and
`rolling (with the aid of a reinforcing material). If aging is allowed to continue too long, the gel
`framework will continue to strengthen and stiffen until the gel framework is no longer flexible.
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`28. There is therefore a narrow window of time within the production of a long, reinforced gel sheet
`in which each portion of the reinforced gel sheet can be rolled. If a portion of the gel material is
`rolled before it reaches a sufficient gel strength, then the gel framework will collapse and fracture,
`resulting in tears and other significant structural failures within the gel framework of the reinforced
`gel sheet. Likewise, if a portion of the gel material is allowed to age too long, then the gel
`framework becomes overly‐stiff and loses necessary flexibility. As the rigid portion of the gel sheet
`is rolled, the gel framework will fracture and crack, resulting in tears and other significant structural
`failures within the gel framework of the reinforced gel sheet.
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`29. In the specific context of a batch casting process, it is important to remember that the entire
`volume of catalyzed pre‐gel solution will transition into a gel simultaneously, such that the entire
`length of the resulting gel sheet will be subject to the same aging progression of gel strength and
`flexibility. Rolling the sheet of reinforced gel material cannot begin at the leading end of the gel
`sheet until the reinforced gel framework is strong enough to withstand the industrially‐demanding
`processes of bending, flexing, and rolling. The entire length of the gel sheet must then be dragged
`along the static casting table or rolled upon itself without breaking or crushing the fragile gel
`material. Rolling the entire gel sheet must be completed before the lagging end of the gel sheet
`becomes too stiff or rigid to withstand the flexural forces of rolling. As the length of a reinforced
`gel sheet becomes particularly long, the window of gel strength and flexibility for rolling the long
`gel sheets eventually becomes too narrow to roll the entire sheet. Either the leading end of the gel
`sheet would collapse because the gel sheet was being rolled too early, or the lagging end of the
`gel sheet would fracture and crack because the gel sheet was being rolled too late.
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`30. Aspen Aerogels overcame the limitations associated with this narrow gel processing window by
`developing a system for controlling the gelation and aging of gel sheets as they are continuously
`dispensed onto a conveyer‐belt casting system, as described in the ‘750 patent.
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`31. First, the conveyer‐belt casting system does not dispense a single volume of catalyzed pre‐gel
`solution which will simultaneously transition into a gel material (as in a batch casting system).
`Instead, the conveyer‐belt casting system dispenses catalyzed pre‐gel solutions which have
`staggered or graded gelation windows. By controlling gelation factors (such as catalyst
`concentration and the speed of the moving element), the conveyer‐belt casting system allows for
`every portion of the gel material to individually transition to a gel at a controlled point along the
`moving element (commonly referred to as the “gel front”).
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`32. Second, the conveyer‐belt casting system ensures that each portion of the reinforced gel sheet is
`subjected to flexing and rolling at an optimized point within the gel processing window of gel
`strength and flexibility. By controlling the speed of the moving element, the conveyer‐belt casting
`system allows for every portion of the gel material to age under the same aging conditions and for
`the same amount of time from the gel front to the end of the casting belt. Thus, by controlling the
`speed of the moving element and the aging conditions of the gel sheet, each portion of the gel
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`sheet can reach the exact same optimized level of gel strength and flexibility when being wound
`onto the roll at the end of the moving belt.
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`33. The conveyer‐belt casting system described in the ‘750 patent thus allows for long, continuous
`sheets of fiber‐reinforced gel material to be produced by ensuring that each portion of a gel sheet
`reaches the exact same optimized level of gel strength and flexibility when being wound onto the
`roll at the end of the moving belt. The conveyer‐belt casting system dispenses catalyzed pre‐gel
`solutions which have staggered or graded gelation windows, thus allowing for each portion of the
`gel material to individually transition to a gel at the controlled gel front on the moving element.
`The conveyer‐belt casting system also allows for every portion of the gel sheet to age under the
`same aging conditions and for the same amount of time from the gel front to the end of the casting
`belt.
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`Conclusion
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`34. The novel production process and conveyer‐belt casting system described in the ‘750 patent
`allowed for the production of an entirely new product comprising rolls of more than five meters in
`length of continuous aerogel sheets reinforced with fibrous batting or mat material. According to
`my recollection, Aspen Aerogels did not produce any reinforced aerogel sheets longer than 4.88
`meters (16 feet) using a batch casting process. I am also unaware of any reinforced aerogel sheets
`longer than 4.88 meters which were available to the public prior to the invention of the subject
`matter presented and claimed in the ‘750 patent. Furthermore, I do not believe that a batch casting
`system could have been used to produce rolls of reinforced aerogel sheets longer than 5 meters,
`for the reasons set forth in paragraphs 9‐33, infra.
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`SIGNATURE
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`I, Dr. George L. Gould, Vice President of Research and Development for Aspen Aerogels, lnc.,
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`declare that I have read the foregoing Declaration in relation to the proceedings before the Regional
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`Court of Mannheim, and I know its contents. To the best of my knowiedge, information and belief
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`founded upon reasonable inquiry, the statements contained in the Declaration and accompanying
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`Appendices are true and correct.
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`«7
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`Place, Date
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`Signature
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`Appendix A ‐ Gel Adhesion Experiments
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`EXPERIMENTAL PROCEDURES
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`Fiber‐reinforced gel sheets were cast using a batch casting process. Sheets of polyester Thinsulate G80
`fiber (10 mm thickness, varying width and length) were placed in a molding surface. Silbond H‐5 was used
`as a silica precursor with a H2O:Si molar ratio of 6, and a target silica density of 0.055 g/cc. Concentrated
`NH4OH was used as the gel‐inducing agent. Concentrated NH4OH was added to the silica precursor
`solution until the NH4OH comprised 0.3% of the total volume of the solution. The entire volume of the
`catalyzed silica precursor solution was poured into the polyester fiber sheet. The resulting material had a
`gel time of 5 min. The gel was allowed to age under syneresis conditions for 20 min.
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`To prepare each gel sheet for testing, a small section of the reinforced wet‐gel sheet was peeled away
`from the casting surface, and then rolled twice around a mandrel with a 3.5” outer diameter. A wire was
`attached to each end of the mandrel near the casting surface. A force gauge was clipped to the center of
`the wire for pulling. See Figure 1 for testing configuration as described.
`
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`Figure 1. Testing configuration for reinforced wet‐gel sheet
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`Multiple reinforced gel sheets of 6 inches (15.24 cm) in width and 3 inches (7.62 cm) in width were
`produced and tested. Tensile stress was applied in‐plane with the casting surface until the blanket was
`pulled along the casting surface or suffered catastrophic structural failure, such as tearing.
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`RESULTS
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`Tensile strength for the reinforced gel sheets was measured using a manual force gauge. Tensile strengths
`up to about 2.0 psi (140 gf/cm2) were observed.
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`Tensile stress was applied to reinforced gel sheets of 6 inches (15.24 cm) in width, which had
`approximately 10 inches (25.4 cm) in length of gel sheet material remaining adhered to the casting
`surface. Tensile stress was applied in‐plane with the casting surface, with intent to peel the reinforced gel
`sheet away from the casting surface and then advance the reinforced gel sheet along the casting surface.
`The reinforced gel sheet suffered catastrophic tearing and structural failure before the 10 inches (25.4
`cm) of reinforced gel sheet could be peeled away from the casting surface (See Figures 1a and 1b).
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`Figure 1a (above) ‐ Result of tensile stress applied to a reinforced gel sheets of 6 inches (15.24
`cm) in width and having approximately 9 inches (22.86 cm) in length of gel sheet material
`remaining adhered to the casting surface; Figure 1b (below)‐ Showing a portion of the reinforced
`gel sheet unrolled from the mandrel to show tearing.
`
`Tensile stress was applied to additional reinforced gel sheets of 6 inches (15.24 cm) in width with gradually
`reduced lengths of gel sheet material remaining adhered to the casting surface. It was observed that the
`adhesion forces between the reinforced gel sheet and the molding surface were sufficient to cause
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`catastrophic tearing and structural failure if the adhered length of reinforced gel sheet exceeded 5.6
`inches (14.224 cm). Similar testing was conducted on reinforced gel sheets of 3 inches (15.24 cm) in width,
`with similar results (See Figures 2a and 2b).
`
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`Figure 2a (above) ‐ Result of tensile stress applied to a reinforced gel sheets of 3 inches (7.62 cm)
`in width and having approximately 10 inches (25.4 cm) in length of gel sheet material remaining
`adhered to the casting surface; Figure 2b (below)‐ Showing a portion of the reinforced gel sheet
`unrolled from the mandrel to show tearing.
`
`Based on the testing of reinforced gel sheets of various sizes, the force required to overcome gel adhesion
`to the casting surface was calculated to be no less than 0.11 pounds for each square inch of blanket
`adhered to the surface (7.73 gf/cm2).
`
`For a gel sheet 16.4 feet (5 meters) in length and 3.28 feet (1 meter) in width, a force of 852 pounds (386
`kg) would be required to overcome the adhesive force for the entire blanket. The resulting tensile stress
`(applied across the cross section of the gel sheet) would be about 55 psi (3.866 kgf/cm2). Thus, the force
`required to overcome the adhesive force of a reinforced gel sheet 5 meters in length on a casting surface
`would be more than 25 times the tensile strength of the reinforced gel material.
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`Appendix B – Friction Force Experiments
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`EXPERIMENTAL PROCEDURES
`
`Fiber‐reinforced gel sheets were cast using a batch casting process. Sheets of polyester Thinsulate G80
`fiber (10 mm thickness, varying width and length) were placed in a molding surface. Silbond H‐5 was used
`as a silica precursor with a H2O:Si molar ratio of 6, and a target silica density of 0.055 g/cc. Concentrated
`NH4OH was used as the gel‐inducing agent.
`
` A
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` first group of gel sheets were produced with concentrated NH4OH being added to the silica precursor
`solution until the NH4OH comprised 0.3% of the total volume of the solution. The entire volume of the
`catalyzed silica precursor solution was poured into the polyester fiber sheet. The resulting material had a
`gel time of 5 min. The gel was allowed to age under syneresis conditions for 20 min. Tensile strength for
`the first group of gel sheets was measured using a manual force gauge.
`
` A
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` second group of gel sheets were produced using similar procedures, and using a range of NH4OH
`concentrations from 0.2 volume percent to 1.5 volume percent, with target gel times from 45 seconds to
`10 minutes. Each reinforced gel was allowed to age under syneresis conditions for 10 min. Tensile strength
`for the second group of gel sheets was measured using an Instron universal testing instrument (cross head
`speed of 0.05 inch/min).
`
`To prepare the first group of gel sheets for testing, the entire length of each reinforced wet‐gel sheet
`was peeled away from the casting surface and replaced on the casting surface. A small section of each
`gel sheet was then rolled twice around a mandrel with a 3.5” outer diameter. A wire was attached to
`each end of the mandrel near the casting surface. A force gauge was clipped to the center of the wire
`for pulling. See Figure 1 for testing configuration as described.
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`
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`14
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`Figure 1. Testing configuration for reinforced wet‐gel sheet
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`Tensile stress was applied in‐plane with the casting surface until the blanket was pulled along the casting
`surface or suffered catastrophic structural failure, such as tearing.
`
`RESULTS
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`Tensile strength for the first group of gel sheets was measured using a manual force gauge. Tensile
`strengths up to about 2.0 psi (140 gf/cm2) were observed. Tensile strength for the second group of gel
`sheets was measured using an Instron universal testing instrument. Tensile strengths ranging from 0.30
`psi (21 gf/cm2) up to 1.93 psi (135.7 gf/cm2) were observed. All observed tensile strength measurements
`were below 2.0 psi (140 gf/cm2).
`
`Tensile stress was applied in‐plane with the casting surface to the first group of reinforced gel sheets, with
`the intent of advancing the reinforced gel sheet along the casting surface. The average in‐plane force
`required to overcome friction for the reinforced gel sheet was 0.016 pounds for each square inch of
`blanket in contact with the surface (1.125 gf/cm2).
`
` A
`
` reinforced gel sheet 16.4 feet (5 meters) in length and 3.28 feet (1 meter) in width would thus requir