U.S. patent application number 11/287475 was filed with the patent office on 2006-11-23 for high strength aerogel panels.
Invention is credited to George L. Gould, Duan Li Ou.
Application Number | 20060263587 11/287475 |
Document ID | / |
Family ID | 38309620 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060263587 |
Kind Code |
A1 |
Ou; Duan Li ; et
al. |
November 23, 2006 |
High strength aerogel panels
Abstract
Embodiments of the present invention describe a structure
comprising at least one fiber-reinforced aerogel layer and at least
one binder layer, said binder layer comprising a silicon-containing
organic material and where the binder layer is bonded to at least
one surface of a fiber-reinforced aerogel layer.
Inventors: |
Ou; Duan Li; (Northborough,
MA) ; Gould; George L.; (Mendon, MA) |
Correspondence
Address: |
Aspen Aerogels, Inc.;IP Department
Building B
30 Forbes Rd
Northborough
MA
01532
US
|
Family ID: |
38309620 |
Appl. No.: |
11/287475 |
Filed: |
November 23, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60631217 |
Nov 24, 2004 |
|
|
|
Current U.S.
Class: |
428/292.1 |
Current CPC
Class: |
Y10T 428/249924
20150401; B32B 2264/104 20130101; B32B 27/283 20130101; B32B 27/20
20130101; B32B 5/02 20130101; B32B 27/308 20130101; B32B 5/32
20130101; B32B 27/18 20130101; B32B 27/16 20130101; B32B 2262/0276
20130101; B32B 2250/24 20130101; B32B 2262/0269 20130101; B32B
2307/102 20130101; B32B 2419/00 20130101; B32B 7/12 20130101; B32B
2264/102 20130101; B32B 2307/558 20130101; B32B 2307/304 20130101;
B32B 2262/0253 20130101; B32B 27/28 20130101; B32B 2262/0246
20130101 |
Class at
Publication: |
428/292.1 |
International
Class: |
D04H 1/00 20060101
D04H001/00 |
Claims
1. A structure comprising: at least one fiber-reinforced aerogel
layer and at least one binder layer, said binder layer comprising a
silicon-containing organic material and wherein the binder layer is
bonded to at least one surface of a fiber-reinforced aerogel
layer.
2. The structure of claim 1 further comprising at least two
fiber-reinforced aerogel layers wherein said binder layer is
positioned between said two fiber-reinforced aerogel layers and
bonded to at least one surface of each.
3. The structure of claim 1 wherein said structure is bonded to a
non-aerogel surface such that the binder layer is simultaneously
boded to the aerogel layer and the non-aerogel surface.
4. The structure of claim 1 wherein the silicon-containing organic
material comprises at least one acrylic moiety.
5. The structure of claim 1 wherein the silicon-containing organic
material comprises siloxane linkages.
6. The structure of claim 1 wherein the fiber reinforced aerogel
layer is reinforced with a batting, a matt or a felt or a
combination thereof.
7. The structure of claim 1 wherein the fiber reinforced aerogel
layer comprises an inorganic component.
8. The structure of claim 7 wherein the fiber reinforced aerogel
layer comprises silica.
9. The structure of claim 1 wherein the fiber reinforced aerogel
layer comprises an organic component.
10. The structure of claim 9 wherein the aerogel material comprises
an acrylic.
11. The structure of claim 1 wherein a chemical bond is formed
between the binder layer and the fiber-reinforced aerogel
layer.
12. The structure of claim 11 wherein the chemical bond is a
siloxane bond.
13. The structure of claim 11 further comprising biocide compounds,
anti-fungal compounds, flame retardant compounds, 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 any combination
thereof.
14. A method of preparing a structure comprising: providing at
least one layer of a fiber-reinforced aerogel material; applying a
silicon-containing organic compound on at least one surface of the
aerogel layer; and directing an amount of energy onto said
silicon-containing organic layer, said energy sufficient to:
initiate polymerization of said silicon-containing organic compound
thereby resulting in a binder layer, and to initiate forming of
chemical bonds between the silicon-containing organic compound and
the aerogel layer.
15. The method of claim 14 wherein the binder layer comprises
oligomers.
16. The method of claim 14 wherein the silicon-containing organic
compound comprises at least one alkoxysilyl segment.
17. The method of claim 14 wherein the silicon-containing organic
compound comprises at least one acrylic moiety.
18. The method of claim 14 wherein the fiber-reinforced aerogel
layer comprises a batting, matt, felt or a combination thereof.
19. The method of claim 14 wherein the energy is. heat,
electromagnetic energy, infrared energy, an x-ray energy, a
microwave energy, a gamma ray energy, acoustic energy, ultrasound
energy, particle beam energy, electron beam energy, beta particle
energy, an alpha particle energy, or combinations thereof.
20. The method of claim 14 wherein at least one layer of
fiber-reinforced aerogel comprises a batting, felt, matt or a
combination thereof.
21. A structure according to any one of claims 14 to 20.
Description
PRIORITY DOCUMENTS
[0001] This application claims priority to U.S. provisional patent
application identified by serial No. 60/631,217 (filed Nov. 24,
2004) which is hereby incorporated by reference.
GOVERNMENT INTEREST
[0002] There is no government interest in this application.
FIELD OF INVENTION
[0003] The present invention relates in general to structures
formed from bonding fiber-reinforced aerogel layers to each other
and/or a non-aerogel surface with a binder layer. Said binder layer
can also be utilized as a coating.
[0004] Aerogels, first prepared by Kistler in 1931 [S. S. Kistler,
Nature, 1931, 127, 764], are a type of material structure rather
than a specific material, and can be prepared by replacing the
liquid solvent in a wet gel with air without substantially altering
the network structure (e.g., pore characteristics) or the volume of
the gel body. Supercritical and subcritical fluid extraction
technologies are commonly used to extract the fluid from the gel
without causing the collapse of the pores. "Aerogels" refers to
"gels containing air as a dispersion medium" in a broad sense and
include, xerogels and cryogels in a narrow sense. A variety of
different aerogel compositions are known and may be inorganic,
organic or organic-inorganic hybrids. Inorganic aerogels can be
based upon metal alkoxides such as silica [S. S. Kistler, Nature,
1931, 127, 764], alumina [S. J. Teichner et al, Adv. Colloid
Interface Sci. 1976, 5, 245], and various carbides [C. I.
Merzbacher et al, J. Non-Cryst. Solid, 2000, 285, 210-215]. Organic
aerogels include, but are not limited to, urethane aerogels [G.
Biesmans et al, 1998, 225, 36], resorcinol formaldehyde aerogels
[R. W. Pekala, U.S. Pat. No. 4,873,218], and polyimide aerogels [W
Rhine et al, U.S.2004132845].
[0005] Organic-inorganic hybrid aerogels are mainly ormosil
(organically modified silica) aerogels [D. A. Loy et al, J.
Non-Cryst. Solid, 1995, 186, 44]. The organic components in these
aerogels are either dispersed throughout or chemically bonded to
the silica network. It is usually preferred to have covalently
bound organic components in such structures to minimize the amount
of washout during solvent extraction from the wet gel.
[0006] Low to moderate density aerogel materials (typically in the
range of about 0.01 g/cm.sup.3 to about 0.3 g/cm.sup.3) are widely
considered to be the best solid thermal insulators, and have
thermal conductivities of about 12 mW/m-K and below at 37.8.degree.
C. and atmospheric pressure. Aerogels function as thermal
insulators primarily by minimizing conduction (low density,
tortuous path for heat transfer through the solid nanostructure),
convection (very small pore sizes minimize convection), and
radiation (IR absorbing or scattering dopants are readily dispersed
throughout the aerogel matrix). Aerogel materials also display many
other interesting acoustic, optical, and chemical properties that
make them useful in both consumer and industrial markets. Since
aerogels, particularly in low density form are fragile, they must
be handled or processed with great care. This presents a
significant limitation for the application of aerogels in certain
sectors of the insulation market.
[0007] In the past two decades, many investigators have attempted
to improve the mechanical properties of the aerogels materials. A
few notable improvements are as follows: N. Leventis, et al, claim
an increase in strength of silica aerogels by a factor over 100
through cross-linking the silanols of the silica hydrogels with
poly (hexamethylenediisocyanate) [Nano Letters, 2002, 2(9),
957-960, U.S. 2004/0132846]. In this approach, highly reactived
isocyanate substance was used as reinforcement agent, and was
introduced into the silica network in the post gelation stage.
Relatively large amounts of this toxic substance is needed for the
preparation of high strength aerogel presenting many problems in
large scale manufacturing. All of the examples taught in this
approach are performed on the bench scale, with typical example for
the aerogel dimension of less than 2 cm.
[0008] B. M. Fung et al developed a new class of high organic
cellulose aerogel [M. M. Fung et al, Adv. Mater. 2001, 13,
644-646]. Cellulose aerogels demonstrate relatively high impact
strength of up to 0.85 Newton meters, considerably greater than
typical metal oxide aerogel materials. Fung teaches preparative
examples on very small scales, and little data is provided on the
material properties. Further studies on cellulose aerogels made
according to Fund et al., shows that they have inferior thermal
insulation properties compared to other aerogels such as those
based on metal oxides like silica.
[0009] The development of fiber-reinforced aerogel composites such
as those described by Stepanian et al. (U.S.2002/094426) has opened
up many application areas for aerogel materials. The fiber
reinforcement adds considerable toughness and resilience,
particularly in high flexural strain applications. The flexibility
of thin sheets (typically between about 0.1 mm and about 25 mm)
allows for the manufacture of large sections of aerogel composites
while retaining most of the useful qualities such as low density
and low thermal conductivity. However, the flexural toughness of
the fiber-reinforced aerogel composites tends to lower the
effective stiffness of the composites such that large sections may
not support their own weight when standing on edge.
[0010] Embodiments of the present invention describe strengthened
fiber-reinforced aerogels without any of the aforementioned
drawbacks. Such structures provide increased mechanical stability,
ability to support more than their own weight when standing on
edge, and a host of other benefits while maintaining the
exceptional insulation properties of fiber-reinforced aerogels.
SUMMARY OF THE INVENTION
[0011] Embodiments of the present invention describe a structure
comprising at least one fiber-reinforced aerogel layer and at least
one binder layer, said binder layer comprising a silicon-containing
organic material and where the binder layer is bonded to at least
one surface of at least one fiber-reinforced aerogel layer.
DESCRIPTION
[0012] Embodiments of the present invention describe structures
comprising at least one fiber-reinforced aerogel layer and at least
one binder layer, said binder layer comprising a silicon-containing
organic material. Such structures are highly useful as thermal
insulators, acoustic insulators or both. The binder layer can be
used as a coating, an adhesive, or both for the fiber-reinforced
aerogel composites. The unique combination of at least one binder
layer and at least one fiber-reinforced aerogel layer, as described
herein allows a variety of useful configurations for fiber
reinforced aerogels such as but not limited to: adhesion to like
and/or dissimilar surfaces, high strength coatings, molded
fiber-reinforced aerogel forms, mechanically stable multi-ply
structures, and a host of others.
[0013] In one embodiment, "aerogel materials" or "aerogel material"
refers to aerogel particles and monoliths. Fiber-reinforced forms
of aerogel materials may additionally comprise chopped fibers,
mats, battings, felts or a combination thereof. Furthermore,
aerogel materials can be prepared from inorganic, organic or hybrid
organic-inorganic precursors, whereby the resultant chemical
structure will comprise the same or substances derived there from.
Density of aerogels is generally between about 0.03 g/cm.sup.3 and
about 0.3 g/cm.sup.3 with surface areas typically between about
300-1000 m.sup.2/g with greater than 90% porosity. Surface
treatment of aerogels with compounds such as silyalting agents
yields a hydrophobic surface.
[0014] The development of fiber-reinforced aerogel materials has
opened up many application areas for, and facilitated manufacture
of aerogel materials while retaining their exceptional insulating
properties thereof. As used herein, "blankets" or "aerogel
blankets" refers to fiber-reinforced aerogel materials which
comprise a batting. Aerogels reinforced with a batting is described
in published U.S. patent application U.S.2002/094426 (Stepanian et
al.) which hereby incorporated by reference. Of course
fiber-reinforced forms of organic, inorganic and hybrid
organic-inorganic aerogels can also be prepared. By way of a
non-limiting example, a fiber-reinforced form of inorganic aerogels
is described in Stepanian et al., the teachings of which can be
used in an analogous manner for preparing organic or
organic-inorganic hybrid forms of the same. A non-limiting example
of fiber reinforced form of hybrid organic-inorganic aerogels can
be obtained from U.S. patent applications 2005/0192367 and
2005/019366 (which is based on U.S. provisional application
60/594,359), all three which are hereby incorporated by reference.
Another non-limiting example involves, silica-organic polymer
hybrid aerogels with urea linkages, as described in U.S.
provisional patent application 60/692,100 which is hereby
incorporated by reference. Yet another non-limiting example
involving silica-chitosan hybrid aerogels and variation thereof is
described in U.S. provisional patent application 60/594,359 also
incorporated by reference.
[0015] The binder layer in embodiments of the present invention may
serve as a coating to coat at least one surface of at least one
fiber-reinforced aerogel material. The binder may also serve as an
adhesive to bind at least two layers of fiber-reinforced aerogels,
or at least one layer of a fiber-reinforced aerogel to another
surface, or any combination of the preceding. By "another surface"
it is intended to include a surface that is chemically or
structurally, dissimilar to that of said fiber-reinforced aerogels.
Examples of such surfaces include but are not limited to
non-aerogel forms of polymeric, ceramic or metallic surfaces.
[0016] In general, the binder layer is a silicon-containing organic
material. Of particular interest are silicon-containing polymeric
materials. This type of binder layer is formed from organic
compounds (i.e. precursors) which contain at least one silicon
atom, the polymerization and/or three-dimensional cross-linking of
said compound yields the silicon containing organic material.
Precursors can be in the form of monomers, oligomers or both and
comprise a silicon-containing segment and an organic segment. A
non-limiting example of the silicon-containing segment is an
alkoxysilyl or silanol group. Examples of alkoxysilanes include
mono-, di- or trialkoxysilanes where the alkoxy groups comprise 1
to 12 carbon atoms.
[0017] The organic segment can comprise acrylics such as but not
limited to methacrylates, methyl methacrylates, ethyl
methacrylates, propyl methacrylates, butyl methacrylates, and the
higher alkyl or aryl chain relatives in the methacrylate series.
Other polymerizable monomers may be reacted with the cross-linking
silicon containing reagent such as, but not limited to:
cyanoacrylate, styrene, and other activated olefinic monomers to
form the organic segment.
[0018] The binder layer is applied to at least one surface of at
least one fiber-reinforced aerogel and exposed to an energy flux
suitable for initiating polymerization, cross-linking or both in
said binder layer. Such energy forms include but are not limited to
heat, electromagnetic energy, an infrared energy, an x-ray energy,
a microwave energy, a gamma ray energy, acoustic energy, ultrasound
energy, particle beam energy, electron beam energy, beta particle
energy, an alpha particle energy, and combinations thereof.
[0019] Upon polymerization, cross-linking or both, the binder layer
adheres to the surface of the fiber-reinforced aerogel and further
strengthens itself. In the case of alkoxysilyl functionalized
organic compounds (precursor of the binder layer) and silica
fiber-reinforced aerogels layers, the application of a suitable
energy flux results in hydrolysis/condensation of alkoxy groups
thereby resulting in siloxane (Si--O--Si) linkages within the
binder layer and between the binder layer and the silica aerogel
material. Furthermore such bonding can also occur with another
surface, as previously described. Therefore the binder layer can
simultaneously bind, two or more surfaces, thereby acting in a
sense as an all purpose adhesive for fiber-reinforced aerogels.
[0020] In the case of silicon-containing organic compounds
comprising an alkoxysilyl segment and an acrylic moiety, both
hydrolysis/condensation and free radical polymerization can take
place. The free radical polymerization of acrylic moieties results
in cross-linkages within the binder layer and may also form
chemical bonds with at least one surface of an aerogel material
(such as silica aerogels), or another surface or both.
DESCRIPTION OF FIGURES
[0021] FIG. 1 illustrates the chemical structure of a
silicon-containing organic compound as a binder layer
(alkoxysilyl-containing methacrylate oligomer) before curing,
placed between two hybrid silica-PMA aerogel blankets.
[0022] FIG. 2 illustrates the structure of FIG. 1 after thermal
curing is carried out, indicating siloxane and other chemical bonds
formed.
[0023] FIG. 3 is a cylindrically shaped structure according to an
embodiment of the present invention.
STRUCTURES UTILIZING SILICA-POLYMER AEROGEL BLANKETS
[0024] The following is an example of a structure according to
embodiments of the present invention wherein hybrid silica-PMMA
blankets are utilized. This example is intended for further
illustration of embodiments of the present invention without
limiting the scope thereof in any way.
[0025] In this embodiment, trialkoxysilyl-containing
polymethacrylate oligomers are used as a binder layer to attach at
least two fiber-reinforced silica-PMMA aerogel blankets thereby
forming a rigid insulation panel with increased insulation value
(R-value), or to coat such hybrid aerogel blankets, or both. A
two-ply structure comprising two hybrid aerogel blankets and a
binder layer disposed there between can resist up to 4000 psi
compression stress and 200 psi flexural stress, before rupture. The
thermal conductivity values are typically below 16 mW/mK.
Accordingly, structures with dimensions of up to 100 square feet
and over 10 inch thick can be prepared. The binder layer, when used
as a coating for these hybrid aerogel blankets provides an
effective barrier to damage from contact with water or common
organic solvents (such as THF, ethanol, etc.)
[0026] In one embodiment, the polymer content in the silica-polymer
hybrid aerogel is less than about 90% or less that about 80% or
less than about 70% or less than about 60% or less than about 50%
or less than about 40% or less than about 30% or less than about
20% or less than about 10% or less than about 5% (wt).
[0027] Trialkoxysilyl-containing polymethacrylate oligomers can be
prepared by thermal (usually in the presence of a radial initiator)
or UV initiated polymerization between a methacrylate monomer and a
cross linker such as trimethoxylsilyl propylmethymethacrylate
(referred as TMSPM here after). Thermal initiated polymerization
was used in this embodiment, unless stated otherwise. Suitable
initiators include, but are not limited to: azobisisobutyronitrile,
tert-butylperoxy-2-ethyl hexanoate,
.alpha.,.alpha.-dimethoxy-.alpha.-phenyl acetophenone,
2-benzyl-2-(dimethylamino)-1-[4-4-morpholinyl)-butanone. The
methacrylate monomer includes, but not limited to
methylmethacrylate (referred as MMA there after), ethylmethacrylate
(referred as EMA thereafter), butylmethacrylate (referred as BMA
there after), hydroxyethylmethacrylate (referred as HEMA there
after), hexafluorobutyl methacrylate (referred as HFBMA there
after), etc.
[0028] The polymerization was carried out in lower alcohol
solutions at elevated temperatures between 40.degree. C. to
100.degree. C. and preferably 70.degree. C. to 80.degree. C. To
ensure a fast reaction the reactant concentration in alcohol
solution needs to be in the range between 5 and 95 weight percent,
and preferably from 40 to 70 weight percent. The mole ratio of
TMSPM/methacylate monomer is in the range between 1 and 10 and
preferably between 1 and 4. The resulting trimethoxysilyl
containing polymethacrylate oligomer has a molecular weight between
about 30,000 and about, 350,000 and is soluble in common organic
solvents.
[0029] Generally the principal route for the formation of fiber
reinforced silica-PMMA aerogel blankets can be followed according
to published U.S. patent application 2005/019366. Here,
trimethoxysilyl containing polymethacrylate oligomer was
co-condensed with a silicon alkoxide such as
tetraethylorthosilicate (TEOS), tetramethylorthosilicate (TMOS) or
partially hydrolyzed an oligomerized silicon alkoxide materials
(e.g. polyethylsilicates commercially available as Silbond 50,
Silbond 40, Silbond H-5 or Dynasil 40) in alcohol solution to form
a hybrid alcogel. A suitable fibrous batting material with the x-y
oriented tensile strengthening layers was added to the hybrid
alcogel prior to its gelation. The fiber reinforced PMA/silica
aerogel blanket is formed from this composite after surface
modification and CO.sub.2 supercritical extraction.
[0030] In preparation of a panel, according to an embodiment,
trimethoxysilyl containing polymethacrylate oligomer was coated
onto the surface of a fiber reinforced silica-PMA aerogel blanket,
before attaching to a second piece of the fiber reinforced
silica-PMA aerogel blanket. A unique characteristic of the
trimethoxysilyl-containing polymethacrylate oligomer (i.e. binder
layer) is that it does not penetrate into the matrix of the aerogel
thereby damaging the nanoporous structure, and/or significantly
increasing the thermal conductivity.
[0031] The surface of a silica-PMA hybrid aerogel blanket has
silanol (Si-OH) and methacrylate pendent groups.
Trimethoxysilyl-containing polymethacrylate oligomer also contains
methacrylate as well as alkoxysilyl pendant groups. The multiple
layers of PMMA/silica aerogel blanket glued together by
trimethoxysilyl-containing polymethacrylate oligomer (i.e. binder
layer) were placed in an oven for the final fixing step. The curing
temperature ranges between 40.degree. C. to 100.degree. C. and
preferably 70.degree. C. to 80.degree. C. At elevated temperatures,
and in the presence of a thermal initiator in the oligomer binder,
the methacrylate functions in the oligomer binder will react with
the similar functions on the surface of the hybrid aerogel blanket
to form covalent bonds; the alkoxysilyl functions in the binder
layer reacts with the silanol groups on the surface of the hybrid
aerogel to form a strong Si--O--Si covalent bond thereto, as
illustrated in FIG. 2. The multiple plies of aerogel blanket are
thus strongly affixed to each other. The trimethoxysilyl-containing
polymethacrylate oligomer coatings turn into a rigid layer
sandwiched between the aerogel blankets after curing, which will
add strength in the resulting structure (e.g. panel).
[0032] The following non-limiting examples are provided to further
illustrated how to carry out the methods of the present invention.
In the ensuing examples, weights are expressed as grams (g) unless
stated otherwise. The MMA Monomer was purchased from Aldrich;
cross-linker TMSPM was obtained from Ashland Chemicals as Dow
Corning Z6030 silane, catalyst tert-butylperoxy-2-ethyl hexanoate
was obtained from Degussa.
EXAMPLE 1
[0033] This example illustrates the formation of trimethoxysilyl
containing polymethymethacrylate oligomer binder. 35.4 g of
tert-butylperoxy-2-ethyl hexanoate were added to a mixture of 780 g
of MMA, 975.0 g of TMSPM and 422 g of methanol, following by
vigorous stirring at 68 to 78.degree. C. for 40 minutes. The
polymethymethacrylate oligomer binder was obtained as a viscous
liquid in concentrated methanol solution. GPC shows 70% of the
monomer was polymerized and the oligomer has Mw of 632570.
EXAMPLE 2
[0034] This example illustrates the formation of a rigid thermal
insulation panel. The binder of example 1 was coated as a layer
between three pieces of 1'.times.1' foot fiber-reinforced
PMA/silica hybrid aerogel blankets with a density of about 0.16
g/cm.sup.3. The three hybrid aerogel blankets were affixed to one
another with a binder layer between every two blankets. The
five-layer coupon was placed into an oven set at 75.degree. C. for
2 hours. The resultant structure, which is in the form of a panel
shows a density of about 0.17 g/cm.sup.3; thermal conductivity of
about 13.9 mW/mK under ambient conditions and flexural strength at
rupture of about 101 psi. The size of this rigid insulation panel
is 1'.times.1' foot and 2'' inches thick. This panel deforms lass
than 10% under 17.5 psi compression. For much higher compression
loading of 4000 psi, this panel recovery up to 90% of its original
thickness within 2 hours after compression.
EXAMPLE 3
[0035] Ultra large size rigid aerogel insulation panels with over
90 square feet dimension can be prepared. For example,
30.thrfore..times.3' dimension and 1/8'' thick silica-PMA aerogel
composite (two blankets and a binder layer as a glue) was prepared
according to this approach. In theory, there is no limitation on
the size of the composite prepared with the embodiments of the
present invention. It is only currently limited by the space
available for drying the composite sheet. Such high strength
aerogel panels show good compression resistant properties (<10%
under 17.5 psi, up to 98% recovery strain after 4000 psi loading).
The resulting high strength aerogel panels also exhibit good
flexural strength (resist 100 psi flexural pressure). The
improvement of mechanical properties in this hybrid aerogels
composite was achieved without sacrificing other inherent
properties of aerogel such as low density and low thermal
conductivity.
[0036] In one embodiment of the present invention, a shaped
structure is formed from at least one binder layer and at least one
fiber-reinforced aerogel layer. A fiber-reinforced aerogel layer
can be shaped to a desired geometry and subsequently coated with a
binder layer. Upon curing, the binder layer further rigidifies
permanently maintaining the aerogel layer in the desired geometry.
Of course the same can be practiced with two or more
fiber-reinforced aerogel layers where these layers sandwich a
binder layer, and/or are coated with a binder layer where again
upon curing, the desired shape of the aerogel layers is achieved.
Examples of such geometries include, but are not limited to:
spherical, hemispherical, cylindrical, hemi cylindrical, half-pipe,
annular, helical, navicular, corrugated, grooved, rippled, and
various others. Without limiting the scope of this embodiment an
example of a shaped structure using silica-PMMA hybrid aerogel
layer or layers is described, and also illustrated in FIG. 3. In
this example a Trimethoxysilyl-containing polymethacrylate oligomer
was coated onto a silica-PMMA blanket which was fixed on a
cylindrical template prior to thermal curing. The cylindrical
shaped structure (as illusrated in FIG. 2) was formed after curing
at 80.degree. C. for 2 hr.
[0037] In another embodiment, a structure comprises at least one
fibrous layer in addition to at least one fiber-reinforced aerogel
layer and at least one binder layer. The fibrous layer can comprise
energy absorbing ballistic fibers such as polyaramids (e.g.
Kevlar.RTM.) ultrahigh molecular weight polyethylene (e.g.
Specra.RTM.), PBO as well as others, and can be in the form of a
batting, a matt or a felt. The binder layer (such as a
trimethysilyl-containing polymethacrylate) is capable of
impregnating the fibrous layer thereby affixing the same to at
least one fiber-reinforced aerogel layer after curing. The benefits
of such structure include added reinforcement and insulation
capability.
[0038] In another embodiment, a fiber-reinforced aerogel layer is
adhered to another surface via the binder layer. For instance, if
another surface contains silanols or other suitable reactive
surface pendant groups, the binder layer can affix the aerogel
layer there to via chemical bonds. Exemplary surfaces include but
are not limited to polymeric, ceramic or metallic surfaces and
non-aerogel forms thereof. In a sense, the binder layer can act as
an all purpose glue for fiber-reinforce aerogel layers.
[0039] In another embodiment a protective layer is formed by
coating a fiber-reinforced aerogel layer with at least one binder
layer. A binder layer such as the trimethoxysilyl-containing
polymethacrylates, when cured is an effective barrier to damage
from contact with water or common organic solvents (such as THF,
ethanol, etc.) Furthermore, the cured binder layer can be useful as
an abrasion resistant, or corrosion resistant coating. The coatings
can be 0.1 mm in thickness or greater depending on the desired
application.
[0040] In one embodiment, additives are added to the
fiber-reinforced aerogel layer for added performance. Examples of
additives include, but are not limited to, biocide compounds,
anti-fungal compounds, flame retardant compounds, opacification
compounds or combinations thereof. Examples of opacification
compounds are 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.
[0041] In another embodiment the binder layer comprises a
polyacrylate, polymethacrylate, polybutylmethacrylate,
polyethylmethacrylate, polypropylmethacrylate, poly
(2-hydroxyethylmethacrylate), poly (2-hydroxypropylmethacrylate),
poly (hexafluorobutylmethacrylate), poly
(hexafluoroisopropylmethacrylate) and combinations thereof.
[0042] In another embodiment the fiber for the fiber-reinforced
aerogel is selected from Polyester based fibers, polyolefin
terephthalates, poly(ethylene) naphthalate, polycarbonates, Rayon,
Nylon, cotton based lycra.RTM. (manufactured by DuPont), Carbon
based fibers like graphite, precursors for carbon fibers like
polyacrylonitrile(PAN), oxidized PAN, uncarbonized heat treated PAN
such as the one manufactured by SGL carbon, fiberglass based
material like S-glass, 901 glass, 902 glass, 475 glass, E-glass,
silica based fibers like quartz, quartzel (manufactured by
Saint-Gobain), Q-felt (manufactured by Johns Manville), Saffil.RTM.
(manufactured by Saffil), Durablanket (manufactured by Unifrax) and
other silica fibers, Polyaramid fibers like Kevlar.RTM.,
Nomex.RTM., Sontera.RTM. (all manufactured by DuPont) Conex.RTM.
(manufactured by Taij in), polyolefins like Tyvek.RTM.
(manufactured by DuPont), Dyneema.RTM. (manufactured by DSM),
Spectra.RTM. (manufactured by Honeywell), other polypropylene
fibers like Typar.RTM., Xavan.RTM. (both manufactured by DuPont),
fluoropolymers like PTFE with trade names as Teflon.RTM.
(manufactured by DuPont), Goretex.RTM. (manufactured by GORE),
Silicon carbide fibers like Nicalon.RTM. ( manufactured by COI
Ceramics), ceramic fibers like Nextel.RTM. (manufactured by 3M),
Acrylic polymers, fibers of wool, silk, hemp, leather, suede,
PBO-Zylon fibers (manufactured by Tyobo), Liquid crystal material
like Vectan.RTM. (manufactured by Hoechst), Cambrelle.RTM. fiber
(manufactured by DuPont), Polyurethanes, polyamaides, Wood fibers,
Boron, Aluminum, Iron, Stainless Steel fibers and other
thermoplastics like PEEK, PES, PEI, PEK, PPS or any combination of
the preceding.
[0043] In another embodiment, the silicon-containing organic
compound is an organopolysiloxane or a non-organopolysiloxane.
[0044] In yet another embodiment, the binder layer is applied to
the surface of the aerogel layer with a brush, or a double roll in
a continuous or semi-continuous manner.
* * * * *