U.S. patent application number 11/457504 was filed with the patent office on 2007-01-18 for secured aerogel composites and methods of manufacture thereof.
This patent application is currently assigned to ASPEN AEROGELS, INC.. Invention is credited to DanielE Bullock, Aaron R. Tomich.
Application Number | 20070014979 11/457504 |
Document ID | / |
Family ID | 37669407 |
Filed Date | 2007-01-18 |
United States Patent
Application |
20070014979 |
Kind Code |
A1 |
Bullock; DanielE ; et
al. |
January 18, 2007 |
Secured Aerogel Composites and Methods of Manufacture Thereof
Abstract
Embodiments of the present invention describe secured
fiber-reinforced aerogels and laminate structures formed therefrom.
In one embodiment a laminate comprises at least one
fiber-reinforced aerogel layer adjacent to at least one layer of
fiber-containing material wherein fibers from said at least one
fiber-reinforced aerogel layer are interlaced with fibers of said
at least one fiber-containing material. In another embodiment a
laminate comprises at least two adjacent fiber-reinforced aerogel
layers wherein fibers from at least one fiber-reinforced aerogel
layer are interlaced with fibers of an adjacent fiber-reinforced
aerogel layer.
Inventors: |
Bullock; DanielE; (North
Attleboro, MA) ; Tomich; Aaron R.; (Nashua,
NH) |
Correspondence
Address: |
ASPEN AEROGELS INC.;IP DEPARTMENT
30 FORBES ROAD
BLDG. B
NORTHBOROUGH
MA
01532
US
|
Assignee: |
ASPEN AEROGELS, INC.
Northborough
MA
|
Family ID: |
37669407 |
Appl. No.: |
11/457504 |
Filed: |
July 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60699840 |
Jul 15, 2005 |
|
|
|
Current U.S.
Class: |
428/292.1 |
Current CPC
Class: |
B32B 5/10 20130101; B32B
2266/0242 20130101; B32B 2250/02 20130101; B32B 2260/021 20130101;
B32B 2307/3065 20130101; B32B 2605/18 20130101; Y10T 442/3325
20150401; B32B 2307/202 20130101; Y10T 428/249955 20150401; Y10T
428/249969 20150401; B32B 2266/0278 20130101; Y10T 428/24996
20150401; B32B 5/06 20130101; B32B 2266/0285 20130101; B32B
2305/026 20130101; Y10T 428/249967 20150401; Y10T 442/647 20150401;
B32B 2307/302 20130101; B32B 5/024 20130101; B32B 5/32 20130101;
D04H 1/4374 20130101; B32B 5/245 20130101; D04H 1/498 20130101;
Y10T 442/50 20150401; B32B 2305/022 20130101; B32B 2266/057
20161101; B32B 2262/00 20130101; B32B 2305/08 20130101; Y10T
428/249953 20150401; B32B 2266/053 20161101; Y10T 428/249924
20150401; B32B 2605/12 20130101; B32B 5/26 20130101; B32B 2250/20
20130101; Y10T 428/24997 20150401; B32B 2266/126 20161101; B32B
2266/0214 20130101; B32B 5/022 20130101; Y10T 442/652 20150401 |
Class at
Publication: |
428/292.1 |
International
Class: |
D04H 13/00 20060101
D04H013/00 |
Claims
1. A laminate comprising at least one fiber-reinforced aerogel
layer adjacent to at least one layer of fiber-containing material
wherein fibers from said at least one fiber-reinforced aerogel
layer are interlaced with fibers of said at least one
fiber-containing material.
2. The laminate of claim 1 wherein the layer of fiber-containing
material comprises a fiber-reinforced foam composite or
fiber-reinforced polymeric composite.
3. The laminate of claim 1 wherein the layer of fiber-containing
material or fiber-reinforced aerogel comprises a felt, batting,
lofty batting, mat, woven fabric, non-woven fabric or a combination
thereof.
4. The laminate of claim 1 further comprising a functional layer
that is radiation absorbing, radiation reflecting, radar blocking,
thermally conductive or electrically conductive.
5. A laminate comprising at least two adjacent fiber-reinforced
aerogel layers wherein fibers from at least one fiber-reinforced
aerogel layer are interlaced with fibers of an adjacent
fiber-reinforced aerogel layer.
6. The laminate of claim 5 wherein the fiber-reinforced aerogel
layer comprises a felt, batting, lofty batting, mat, woven fabric,
non-woven fabric or a combination thereof.
7. The laminate of claim 5 further comprising a functional layer
that is radiation absorbing, radiation reflecting, radar blocking,
thermally conductive or electrically conductive.
8. A method of securing at least one fiber-reinforced aerogel layer
to at least one layer of a fiber-containing material comprising: a)
disposing a laminate comprising at least one layer of a
fiber-containing material adjacent to at least one fiber-reinforced
aerogel layer where at least one layer being a top layer that
defines an exposed surface; and b) penetrating said laminate
through said exposed surface with at least one felting needle
thereby interlacing fibers within the laminate.
9. A method of securing at least one fiber-reinforced gel composite
to at least one fibrous layer comprising: a) disposing a laminate
comprising at least two layers of adjacent fiber reinforced
aerogels where at least one layer being a top layer that defines an
exposed surface; and b) penetrating said laminate through said
exposed surface with at least one felting needle thereby
interlacing fibers within the laminate.
10. The method of claim 8 wherein the layer of fiber-containing
material or fiber-reinforced aerogel comprises a felt, batting,
lofty batting, mat, woven fabric, non-woven fabric or a combination
thereof.
11. The method of claim 8 further comprising a functional layer
that is radiation absorbing, radiation reflecting, radar blocking,
thermally conductive or electrically conductive.
12. A method of securing at least one fiber-reinforced gel
composite to at least one fibrous layer comprising: a) disposing a
laminate comprising at least two layers of adjacent fiber
reinforced aerogels where at least one layer being a top layer that
defines an exposed surface; and c) penetrating said laminate
through said exposed surface with at least one needle and at least
one yarn thereby quilting or stitch bonding the layers of the
laminate.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims benefit of priority from U.S.
Provisional Patent Application 60/699,840 filed on Jul. 15, 2006;
which is hereby incorporated by reference in its entirety as if
fully set forth.
SUMMARY OF THE INVENTION
[0002] Embodiments of the present invention describe secured
fiber-reinforced aerogels and laminate structures formed therefrom.
In one embodiment a laminate comprises at least one
fiber-reinforced aerogel layer adjacent to at least one layer of
fiber-containing material wherein fibers from said at least one
fiber-reinforced aerogel layer are interlaced with fibers of said
at least one fiber-containing material. The layer of
fiber-containing material can comprise a fiber-reinforced foam
composite or fiber-reinforced polymeric composite. Alternatively,
or in addition to, the layer of fiber-containing material can
comprise a felt, batting, lofty batting, mat, woven fabric,
non-woven fabric or a combination thereof. The aerogel layer can
comprise a felt, batting, lofty batting, mat, woven fabric,
non-woven fabric or a combination thereof. In some embodiments a
functional layer that is radiation absorbing, radiation reflecting,
thermally conductive or electrically conductive is used. In another
embodiment, a laminate comprises at least two adjacent
fiber-reinforced aerogel layers wherein fibers from at least one
fiber-reinforced aerogel layer are interlaced with fibers of an
adjacent fiber-reinforced aerogel layer. Again the fiber-reinforced
aerogel layer can comprise a felt, batting, lofty batting, mat,
woven fabric, non-woven fabric or a combination thereof. Also again
this laminate can comprise a functional layer that is radiation
absorbing, radiation reflecting, thermally conductive or
electrically conductive. One method of practicing an embodiment of
the present invention includes the steps of: [0003] a) disposing a
laminate comprising at least one layer of a fiber-containing
material adjacent to at least one fiber-reinforced aerogel layer
beneath at least one felting needle and where at least one layer
being a top layer that defines an exposed surface; and [0004] b)
penetrating said laminate through said exposed surface with said at
least one felting needle thereby transporting fibers within the
laminate. Another method comprises the steps of: [0005] a)
disposing a laminate comprising at least two layers of adjacent
fiber reinforced aerogels beneath at least one felting needle and
where at least one layer being a top layer that defines an exposed
surface; and [0006] b) penetrating said laminate through said
exposed surface with said at least one felting needle thereby
transporting fibers within the laminate.
DESCRIPTION
[0007] Manipulation of aerogels, one of the best known insulators,
can be very challenging given the fragility of this material form.
The development of fiber-reinforced aerogels has yielded a more
adaptable aerogel composite form with improved mechanical
properties such as conformability and flexibility without any
substantial loss of thermal insulation performance. However, few
methodologies have yet been developed for securing or attaching
these fiber reinforced forms. Moreover, securing mechanisms that do
not involve an extrinsic component such as stitches, tags, rivets,
adhesives, staples, tapes, and the like have remained virtually
unexplored. Extrinsic components are undesirable considering that
they can: add weight, fail under the adverse conditions (high
thermal loads, cryogenic temperatures, etc.) and can increase
production cost. For instance, most adhesives do not perform well
and ultimately fail at cryogenic temperatures such as those
encountered by insulation systems in liquid natural gas (LNG)
pipelines. At high operating temperatures, many adhesives tend to
burn off, plastic tags can melt and stitchings may fail. Such
tendencies are likely to be experienced by aerogel based
fireproofing systems, or other high temperature applications such
as the hot sections of aircraft engines and solid rocket
motors.
[0008] To date, typical mechanical tacking methods for fiber
reinforced aerogels require the introduction of an extrinsic
component, such as a metal rivet or a fiber stitch. As is the case
with chemical systems, the introduction of a foreign material to
the insulation system is likely to limit the acceptable operating
conditions of the system. In the case of a weight sensitive
product, such as insulation or fireproofing systems for marine or
space vehicles, the weight pick-up gained by adding metal rivets or
tags is undesirable. For this and various other reasons it is clear
that a need for securing methods which do not utilize extrinsic
components still persists for fiber-reinforced aerogels.
[0009] Embodiments of the present invention describe methods for
securing fiber-reinforced-aerogels and products derived therefrom.
In particular, current embodiments exploit the benefits of
needle-punching technology for manipulating fiber reinforced
aerogels. For instance a plurality of layers comprising aerogels
reinforced with a batting or felt can be tacked together using the
needle punching process. Also, aerogel blankets along with other
fibrous layers can be secured accordingly. This system minimizes
added weight, eliminates need for fallible external components and
without compromising thermal insulating performance.
[0010] One aspect of the present invention involves methods for
securing fiber-reinforced aerogels to: fiber-containing materials,
fiber-reinforced aerogels, or both. This can be accomplished by via
"needle-punching" technique; also sometimes known as "needling."
Another aspect relates to laminates or multiple layered structures
comprising at least one layer of fiber-reinforced aerogel secured
to a fiber-containing material, a fiber-reinforced aerogel or both.
"Fiber-containing material" as used herein denotes any material
with fibers conducive to needle-punching. In other words fibers in
the fiber-containing material can intermix, interpenetrate,
intertwined, interlaced, interwoven or entangle with fibers of
another material as a result of needle-punching. When the word
"interlaced" is used, it is meant to encompass one or more or all
of the preceding verbs to illustrate how fibers are in the
embodiments of the invention. Fiber-containing materials may be
exemplified by, but not limited to fibrous structures,
fiber-reinforced foam composites or fiber-reinforced polymeric
composites. Fibrous structures are further exemplified by, but not
limited to: felts, battings, lofty battings, mats, woven fabrics,
non-woven fabrics or combinations thereof. Suitable fiber
compositions include essentially all natural and synthetic fibers
which may be based on organic, inorganic or both compounds.
Examples of natural fibers include, but are not limited to: wool,
cotton, silk, linen, hemp, ramie, and jute. Examples of synthetic
fibers include, but are not limited to: acetate, acrylic, latex,
nylon, polyester, rayon, spandex. Other fibers may be based on
fiberglass, quartz, polyethylene, polypropylene, polybenzimidazole
(PBI), polyphenylenebenzo-bisoxasole (PBO), polyetheretherketone
(PEEK), polyarylate, polyacrylates, polytetrafluoroethylene (PTFE),
poly-metaphenylene diamide, poly-paraphenylene terephthalamide,
ultra high molecular weight polyethylene (UHMWPE), novoloid resins,
polyacryolintrile(PAN), polyacrylonitrile-carbon and carbon
fibers.
[0011] Needle-punching is a known technique for attaching or
orienting non-woven fiber-containing materials into stable, usable
forms. Needle-punched non-wovens are prepared via mechanical
orientation and interlocking of fibers such as those in a spun
bonded or carded web form. For instance, effective mechanical
interlocking between layers is achieved via a plurality of barbed
felting needles passing into and out of the fiber mass (at varying
locations) where the barbs on the needles carry fibers from one ply
through to another. The displaced fibers generated by the needling
process are often referred to as "Z-fibers" since they are
generally perpendicular to the plane of the fibrous layer. Examples
of needle-punched final products are: tennis court surfaces, space
shuttle tiles, boat hull composites, automotive carpeting,
automotive insulation, filtration media, geo textiles, vinyl
substrates, primary carpet backing, secondary carpet backing,
fiberglass matting, ballistic felts, tennis ball felts, aerospace
brake pads, oil absorbents, and many others.
[0012] FIG. 1 is an exemplary needle-punching process. Here, the
laminate 4 (containing fiber reinforced aerogel+fiber containing
material or two or more fiber reinforced aerogels) is fed into a
needle-loom 6 via feed rolls 2. A bed of needles 12 secured to a
beam board 8 is cyclically driven using a main drive 10 to
penetrate the layers in consecutive sections resulting in the
needle-punched products 14 which are subsequently wound using draw
off rolls 16. In the context of certain embodiments of the present
invention, said layers 4 comprise a layer of fiber-reinforced
aerogel and: at least one layer of a fiber-containing material, at
least one layer of another fiber reinforced aerogel, or both. Other
forms of needle punching that are applicable to embodiments of the
present invention involve needle punching via a structuring loom or
random velour loom. Furthermore needle-punching can be carried out
discontinuously for example where distinct sections are
needle-punched in one shot. Various other modifications can be used
for the needle punching process depending on the fabrication needs.
For instance, a needle punching device enabling measurement of
penetration depth is described in WO02070807A1 hereby incorporated
by reference. Hence it should be recognized that the
needle-punching concept as a whole is embraced by the embodiments
presented herein.
[0013] As noted earlier, aerogels describe material forms with
typically excellent thermal insulation, among other properties. As
used herein, "aerogel" and "aerogel materials" refer to gel
containing air as a dispersion medium in a broad sense and gels
dried via supercritical fluids in a narrow sense. The chemical
composition of aerogels can be inorganic, organic (including
polymers) or hybrid organic-inorganic. Inorganic aerogels may be
based on Silica, Titania, Zirconia, Alumina, Hafnia, Yttria, Ceria,
Carbides and Nitrides. Organic aerogels can be based on compounds
including but are not limited to: urethanes, resorcinol
formaldehydes, polyimide, polyacrylates, chitosan,
polymethylmethacrylate, members of the acrylate family of
oligomers, trialkoxysilyl terminated polydimethylsiloxane,
polyoxyalkylene, polyurethane, polybutadiane,
melamine-formaldehyde, phenol-furfural, a member of the polyether
family of materials or combinations thereof. Examples of
organic-inorganic hybrid aerogels include, but are not limited to:
silica-PMMA, silica-chitosan, silica-polyether or possibly a
combination of the aforementioned organic and inorganic compounds.
Published US patent applications 2005/0192367 and 2005/0192366
teach extensively of such hybrid organic-inorganic materials and
are hereby incorporated by reference in their entirety. In the
preferred embodiments of the present invention, silica aerogels are
discussed whereas the invention as a whole may be practiced with
other aerogel compositions as well. The preferred method of
preparing aerogels in the current embodiments is via drying of gels
derived the sol-gel process. Said process is described in great
detail in Brinker C. J., and Scherer G. W., Sol-Gel Science; New
York: Academic Press, 1990 which is hereby incorporated by
reference.
[0014] Gels may be additionally aged prior to drying to further
strengthen the network structure thereof by increasing the number
of cross-linkages. This procedure is potentially useful for
preventing potential volume loss during drying. Aging can involve:
maintaining the gel (prior to drying) at a quiescent state for an
extended period, maintaining the gel at elevated temperatures,
addition of cross-linkage promoting compounds or any combination
thereof. Aging time period typically requires between about 1 hr
and several days. The preferred temperatures are usually between
about 10.degree. C. and about 100.degree. C.
[0015] For optimal thermal insulation, aerogels can be opacified to
reduce the radiative component of heat transfer. At any point prior
to gel formation, opacifying compounds, radiation absorbing
compounds, radiation reflecting compounds, thermally conductive
components, electrically conductive components, radar blocking
components may be dispersed into the mixture comprising gel
precursors. Examples of opacifying compounds include and are not
limited to: B.sub.4C, Diatomite, Manganese ferrite, MnO, NiO, SnO,
Ag.sub.2O, Bi.sub.2O.sub.3 , TiC, WC, carbon black, titanium oxide,
iron titanium oxide, zirconium silicate, zirconium oxide, iron (I)
oxide, iron (III) oxide, manganese dioxide, iron titanium oxide
(ilmenite), chromium oxide, silicon carbide or mixtures
thereof.
[0016] Aerogels may be surface treated to impart or improve
hydrophobicity. The hydrophobic treatment is carried out by
reacting a hydroxy moiety of a silanol group present on a surface
of the wet-gel compound (silica gel) with a functional group of a
hydrophobing agent thereby converting the silanol group into a
hydrophobic group of the hydrophobicity-imparting agent. For
example, the hydrophobing treatment can be carried out by immersing
a gel in a hydrophobicity-imparting solution of a hydrophobing
agent in a solvent, and mixing the gel and the solution to allow
the hydrophobicity-imparting agent to permeate the gel, while if
necessary, heating such a gel mixture so that a
hydrophobicity-imparting reaction occurs. Examples of the solvent
for use in the hydrophobing treatment include methanol, ethanol,
isopropanol, xylene, toluene, benzene, N,N-dimethylformamide,
hexamethyldisiloxane and the like. There is no particular limit in
selection of the solvent, in so far as the solvent can easily
dissolve the hydrophobing agent and can replace the solvent
contained in the gel before the hydrophobing treatment. Where the
supercritical drying is carried out after the hydrophobing
treatment, the solvent to be used in the hydrophobing treatment is
preferably a medium that facilitates the supercritical drying
(e.g., methanol, ethanol, isopropanol, liquefied carbon dioxide or
the like), or a medium which can be replaced with the former
medium. Examples of the hydrophobing agent include
hexamethyldisilazane, hexamethyldisiloxane, trimethylmethoxysilane,
dimethyldimethoxysilane, methyltrimethoxysilane,
ethyltrimethoxysilane, trimethylethoxysilane,
dimethyldiethoxysilane, methyltriethoxysilane and the like.
Hydrophobing treatments are further described in U.S. Pat. No.
5,565,142 hereby incorporated by reference.
[0017] Drying plays an important role in engineering the properties
of aerogels, such as porosity and density which influence the
material thermal conductivity. To date, numerous drying methods
have been explored. U.S. Pat. No. 6,670,402 teaches drying via
rapid solvent exchange of solvent(s) inside wet gels using
supercritical CO.sub.2 by injecting supercritical, rather than
liquid, CO.sub.2 into an extractor that has been pre-heated and
pre-pressurized to substantially supercritical conditions or above
to produce aerogels. U.S. Pat. No. 5,962,539 describes a process
for obtaining an aerogel from a polymeric material that is in the
form a sol-gel in an organic solvent, by exchanging the organic
solvent for a fluid having a critical temperature below a
temperature of polymer decomposition, and supercritically drying
the fluid/sol-gel. U.S. Pat. No. 6,315,971 discloses processes for
producing gel compositions comprising: drying a wet gel comprising
gel solids and a drying agent to remove the drying agent under
drying conditions sufficient to minimize shrinkage of the gel
during drying. Also, U.S. Pat. No. 5,420,168 describes a process
whereby Resorcinol/Formaldehyde aerogels can be manufactured using
a simple air drying procedure. Finally, U.S. Pat. No. 5,565,142
herein incorporated by reference describes subcritical drying
techniques. The embodiments of the present invention can be
practiced with drying using any of the above techniques. In some
embodiments, it is preferred that the drying is performed at vacuum
to below super-critical pressures (pressures below the critical
pressure of the fluid present in the gel at some point) and
optionally using surface modifying agents.
[0018] Aerogels may be fiber-reinforced with various fibrous
structures to achieve a more conformable composite product.
Suitable fibrous structures include, but are not limited to wovens,
non-wovens, mats, felts, battings, lofty battings and combinations
thereof. Aerogel composites reinforced with a fibrous batting,
herein referred to as "blankets", are particularly useful for
applications requiring flexibility since they are highly
conformable and are excellent thermal insulators. Aerogel blankets
and similar fiber-reinforced aerogel composites are described in
published US patent application 2002/0094426A1 and U.S. Pat. Nos.
6,068,882; 5,789,075; 5,306,555; 6,887,563 and 6,080,475 all hereby
incorporated by reference, in their entirety. Fiber reinforced
aerogels of 2002/0094426 are particularly useful in the embodiments
herein where a continuous aerogel matrix or a "monolithic" aerogel
matrix is reinforced by a fiber component like a fibrous batting.
It is noted here that an aerogel blanket is a flexible aerogel
composite that can be used like a blanket to cover surfaces of
simple or complex geometry.
[0019] Applications involving aerogel blankets can benefit
tremendously from the needle punching technique. This novel method
for manipulating aerogel blankets can be used in a variety of
applications involving attachment of the blankets to any other
fibrous materials and/or creating a coherent lay up of insulating
plies. Although the aerogel matrix might be locally disrupted upon
needle penetration, the integrity of the needled end-product is
usually not compromised. In order to optimize needle punching of
fiber-reinforced aerogel composites the following factors are worth
considering: needle puncture density, needle penetration depth,
needle characteristics (crank, shank, blade, barb, point, etc.),
aerogel density, aerogel material (Organic, inorganic, hybrid
organic-inorganic), fiber/aerogel volume ratio, fiber forms
(batting, felt, mat, chopped fibers) and fiber compositions
(polyester, carbon, silica, etc.) Needles with the desired
attributes such as crank, shank, blade, barb, point properties,
aspect ratio or modulus can be obtained from a variety of vendors
such as Foster Needle inc. Examples of companies that currently
engage in manufacture of needle-punched products include Shoo Shyng
Machinery co., Ltd. and American Felt and Filter Company
(AFFCO.)
[0020] Insulation systems often require several inches in thickness
in order to achieve the overall required R-value (R=resistance to
heat flow.) Larger overall R values are achieved by stacking
multiple plies of an insulating material, since R values of
individual plies simply add up. Though not wishing to be bound by
theory, temporal considerations related to the kinetics of sol-gel
chemistry of gel preparation (and subsequent drying), suggests that
an upper limit on fiber-reinforced aerogel thickness often exists (
for example 1/2'') when manufactured in a cost-effective manner. As
such, requirements for certain insulation applications involving
fiber-reinforced aerogels must be met by constructing a laminate
(i.e. multiple ply) comprising secured insulation layers.
[0021] In one embodiment a laminate comprises at least one
fiber-reinforced aerogel layer adjacent to at least one layer of
fiber-containing material wherein fibers from said at least one
fiber-reinforced aerogel layer are interlaced with fibers of said
at least one fiber-containing material. The layer(s) of
fiber-containing material can comprise a felt, batting, lofty
batting, mat, woven fabric, non-woven fabric or combinations
thereof. Alternatively or in addition to, the layer(s) of
fiber-containing material can comprise a fiber-reinforced foam
composite or fiber-reinforced polymeric composite. The layers can
be needle-punched once to form the final laminate. Alternatively,
successive layers can be individually needle punched each time to
add to the stack. Potential applications include instances where an
aerogel blanket can is needled to a carpet as a backing, to an
apparel article as lining, or to a fibrous surface as a thermal
shield.
[0022] In another embodiment a laminate comprises at least two
adjacent fiber-reinforced aerogel layers wherein fibers from at
least one fiber-reinforced aerogel layer are interlaced with fibers
of an adjacent fiber-reinforced aerogel layer. The layers can be
needle-punched once to form the final laminate. Alternatively,
successive layers can be individually needle punched each time to
add to the stack.
[0023] In yet another embodiment, a laminate comprises at least two
layers of fiber-reinforced aerogels and a fiber-containing material
there between. Preferably the fiber containing material is selected
from felt, batting, lofty batting, mat, woven fabric, non-woven
fabric or combinations thereof. This arrangement may be
particularly useful for instances where fiber-reinforced aerogels
do not secure well to one another after needling wherein the in
between layer serves to better secure the layers to one
another.
[0024] In a special embodiment, at least one functional layer is
incorporated into the laminate structure comprising
fiber-reinforced aerogels via needle punching. The functional layer
may be radiation absorbing, radiation reflecting, thermally
conductive or electrically conductive. Metallic sheets, metallized
polymeric sheets and the like are few non limiting examples. Of
course it is desirable that the functional layer be compliant with
needle punching such that this process is not hindered.
[0025] In yet another embodiment, the thermal conductivity of the
fiber interlaced laminate is substantially same as that of the
fiber reinforced aerogel component. In other words, any mechanical
damage caused by needling process was surprisingly negligible and
hence interlacing using different embodiments of the present
invention prove to be very useful for securing fiber reinforced
aerogel to a fiber containing material or for securing more than
one layers of fiber reinforced aerogel layers.
[0026] In another special embodiment, a laminate is formed from
angular needling of the layers. In other words, at least one layer
of fiber reinforced aerogel is needled at an angle
non-perpendicular to the plane of said layer. More specifically,
the laminate is needled at least twice at different angles
preferably creating cross-entanglement of the drawn fibers.
[0027] In another embodiment, a blanket is needled to a fibrous
structure wherein said fibrous structure is subsequently permeated
with a polymeric material and which is cured therein. The result is
a polymeric coating on a fiber reinforced aerogel. Said coating can
be highly useful for instance, as an abrasion or chemical resistant
layer for the aerogel. Additionally, the fiber reinforced aerogel
can be molded to a shape and held in place with a hard coating. The
following is one exemplary mode: [0028] a) Fiber reinforced aerogel
needled to a fibrous structure such as felt, batting, lofty
batting, mat, woven fabric, non-woven fabric or combinations
thereof, thereby forming a laminate structure; [0029] b) The
laminate structure is bent or otherwise manipulated to a desired
shape, and held in place; and [0030] c) A polymeric material is
transferred into the fibrous structure and cured therein.
[0031] Various shapes might be achievable with this structure Such
as half-pipes, hemispheres, and various others. Thus preformed
shaped aerogel insulations are made possible via this method.
[0032] In another special embodiment, fiber reinforced wet gels are
needled prior to drying to form a laminate structure. A "wet gel"
may be understood as the un-dried gel comprising solvent and/or
diluent filled pores. The laminates prepared accordingly are
subsequently dried via techniques previously discussed. Methods for
producing such gel sheets is described in published US patent
application 2005/0167891A1 which is incorporated by reference in
its entirety. An advantage in needling wet gels is that less damage
to the overall aerogel matrix is sustained relative to needling
after the aerogel is dried. Furthermore, needling the
fiber-reinforced wet-gel to of fibrous layer, for instance a low
density lofty batting, can serve as a spacing layer, for enhancing
flow of the drying medium (e.g. supercritical fluid) once a wet
aerogel blanket is rolled and transferred to the drying, preferably
in a supercritical fluid drying.
[0033] The individual layers of the laminate can be of any
thickness but in a preferred embodiment, it is between about 1/16
in and about 1/2 in. The final product will have an R value that is
the sum or better than the sum of each individual aerogel blanket R
value thereby providing similar or improved thermal performance
relative to a single blanket layer of the same thickness. This
procedure can be repeated to add layers to an already needle
punched stack.
[0034] In yet another embodiment, external fibers or yarns are
introduced using needles through the layers of the laminate such
that the layers of the aerogel laminate are quilted together. There
are various art recognized quilting techniques that can be used.
The variables such as quilting patterns, needle size (length and
thickness), external (external to the layers of the laminate) fiber
type and thickness and frequency and movement of the laminates
through the quilting machine may be adjusted to provide the end
result such that the aerogel thermal performance is not
substantially changed from unquilted laminates of similar thickness
and type. Several types of yarns may be used for quilting or stitch
bonding as described below including polyester, carbon,
polyacrylonitrile, silica, glass, cotton, rayon, acrylics, Kevlar
type material, and Nomex type material.
[0035] In yet another embodiment, techniques such as stitch bonding
can also be used to accomplish the same purpose of joining more
than one layer in the laminate. Standard lock and chain stitches
may be used or modified lock stitch in which knots linking needle
and bobbin threads are formed at one surface of the laminate to
minimize in plane fiber distortion. Further information on Stitch
bonding is described in Potluri, P. et al, Composite Structures,
59, 251-259 (2003) which is incorporated in its entirety here. It
is important to point out that though aerogel type materials are
fragile, it was surprisingly found that quilting or stitch bonding
does not damage the aerogel composite material enough to have a
substantial impact on the thermal performance of the quilted or
stitch bonded laminates. This surprising result leads to very
simple way of attaching layers of aerogel composites or fiber
reinforced aerogel composites without any complex steps.
[0036] The needle punching art as a whole is integral to
embodiments of the present invention whereby needled products
comprising fiber-reinforced aerogels are prepared. The following
includes a few non-limiting modes for practicing certain specific
embodiments of the present invention, where one comprises the steps
of: [0037] a) disposing a laminate comprising at least one layer of
a fiber-containing material adjacent to at least one
fiber-reinforced aerogel layer beneath at least one felting needle
and where at least one layer being a top layer that defines an
exposed surface; and [0038] b) penetrating said laminate through
said exposed surface with said at least one felting needle thereby
transporting fibers within the laminate. Another method comprises
the steps of: [0039] a) disposing a laminate comprising at least
two layers of adjacent fiber reinforced aerogels beneath at least
one felting needle and where at least one layer being a top layer
that defines an exposed surface; and [0040] b) penetrating said
laminate through said exposed surface with said at least one
felting needle thereby transporting fibers within the laminate.
[0041] The foregoing description is considered as illustrative only
of the principles of the invention. Further, since numerous
modifications and changes will readily occur to those skilled in
the art, it is not desired to limit the invention to the exact
construction and process shown as described above. Accordingly, all
suitable modifications and equivalents may be resorted to falling
within the scope of the invention as defined by the claims that
follow. The words "comprise," "comprising," "include," "including,"
and "includes" when used in this specification and in the following
claims are intended to specify the presence of stated features,
integers, components, or steps, but they do not preclude the
presence or addition of one or more other features, integers,
components, steps, or groups thereof.
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