U.S. patent application number 15/174860 was filed with the patent office on 2016-09-29 for fiber reinforced composites made with coupling-activator treated fibers and activator containing reactive resin.
The applicant listed for this patent is JOHNS MANVILLE. Invention is credited to Jawed Asrar, Michael John Block, Klaus Friedrich Gleich, Asheber Yohannes, Mingfu Zhang.
Application Number | 20160280868 15/174860 |
Document ID | / |
Family ID | 50230846 |
Filed Date | 2016-09-29 |
United States Patent
Application |
20160280868 |
Kind Code |
A1 |
Zhang; Mingfu ; et
al. |
September 29, 2016 |
FIBER REINFORCED COMPOSITES MADE WITH COUPLING-ACTIVATOR TREATED
FIBERS AND ACTIVATOR CONTAINING REACTIVE RESIN
Abstract
This invention relates to a process of making a fiber-reinforced
composite. Glass fibers may be provided. These glass fibers may be
treated with a sizing composition that has a coupling-activator
compound with the formula: S--X-(A).sub.n, where S represents a
silicon-containing coupling moiety capable of bonding to the
surface of glass fibers, X represents a linking moiety, and
(A).sub.n represents one or more polymerization activator moieties.
The treated glass fibers may be combined with a resin to make a
fiber-resin mixture. The resin may have a monomer, a catalyst, and
an activator compound capable of initiating a polymerization of the
monomer. The monomer may be a lactam or lactone having 3-12 carbon
atoms in the main ring. The fiber-resin mixture may then be cured
so that the monomer polymerizes to form a thermoplastic polymer
matrix of the fiber-reinforced composite. The thermoplastic polymer
matrix may be formed by in situ polymerization initiated from both
the surface of the glass fibers and the resin. The fiber-reinforced
composite formed may be at least 70 wt. % glass fiber.
Inventors: |
Zhang; Mingfu; (Highlands
Ranch, CO) ; Gleich; Klaus Friedrich; (Nuremberg,
DE) ; Yohannes; Asheber; (Littleton, CO) ;
Block; Michael John; (Centennial, CO) ; Asrar;
Jawed; (Englewood, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JOHNS MANVILLE |
Denver |
CO |
US |
|
|
Family ID: |
50230846 |
Appl. No.: |
15/174860 |
Filed: |
June 6, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13788857 |
Mar 7, 2013 |
9387626 |
|
|
15174860 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 7/14 20130101; Y10T
442/30 20150401; B29C 70/16 20130101; B29C 67/246 20130101; C08J
2367/04 20130101; C08J 5/08 20130101; B29C 70/48 20130101; B29C
70/18 20130101; C08L 77/02 20130101; Y10T 428/249921 20150401; B29C
70/06 20130101; B29C 39/18 20130101; B29C 45/02 20130101; C08J
2377/02 20130101; B29C 48/022 20190201; B29K 2077/00 20130101; C08G
69/18 20130101; B29C 53/56 20130101; C08J 5/043 20130101; B29K
2309/08 20130101 |
International
Class: |
C08J 5/08 20060101
C08J005/08; B29C 53/56 20060101 B29C053/56; B29C 47/00 20060101
B29C047/00; B29C 39/18 20060101 B29C039/18; C08K 7/14 20060101
C08K007/14; B29C 45/02 20060101 B29C045/02 |
Claims
1. A continuous fiber-reinforced thermoplastic composite, the
composite comprising a thermoplastic matrix and continuous glass
fibers, wherein the thermoplastic matrix is formed by in situ
polymerization initiated from both (i) the surface of the
continuous glass fibers and (ii) a resin that forms the
thermoplastic matrix.
2. The composite of claim 1, wherein the continuous glass fibers
are arranged into woven fabrics, multi-axial fabrics, continuous
strand mats, or combinations thereof.
3. The composite of claim 1, wherein the composite is produced in a
process selected from the group consisting of resin transfer
molding (RTM), reaction injection molding (RIM), pultrusion,
filament winding, casting, and prepreg processes.
4. A fiber-reinforced composite comprising: glass fibers; and a
polymer matrix formed from monomers in a resin composition, wherein
at least some of the monomers are polymerized using an activator
compound present in the resin composition, and wherein the glass
fibers and the polymer matrix are bonded together in part through a
coupling-activator compound applied to the glass fibers before
forming the fiber-reinforced composite, wherein the
coupling-activator compound included 1 to 5 activator moieties,
each of which is capable of initiating a polymerization of the
monomers in the resin composition, and wherein a molar ratio of (i)
the activator moieties in the coupling-activator compound to (ii)
the activator compound present in the resin composition ranges from
0.02:1 to 20:1.
5. The fiber-reinforced composite of claim 4, wherein the glass
fibers comprise continuous glass fibers.
6. The fiber-reinforced composite of claim 4, wherein the monomers
in the resin composition comprise a lactam or a lactone, and
wherein the lactam or the lactone have a ring with 3 to 12 carbon
atoms.
7. The fiber-reinforced composite of claim 4, wherein the polymer
matrix comprises at least one polyamide polymer selected from the
group consisting of nylon 6, nylon 6:12, and nylon 12.
8. The fiber-reinforced composite of claim 4, wherein the
coupling-activator compound applied to the glass fibers has a
formula: S--X-(A).sub.n wherein n is an integer with a value from 1
to 5; S comprises a silicon-containing coupling moiety through
which the coupling-activator compound bonds to a surface of the
glass fibers; X comprises a linking moiety to link the S moiety
with one or more A moieties; and (A).sub.n comprises the 1 to 5
activator moieties, each of which is capable of initiating a
polymerization of the monomers in the resin composition.
9. The fiber-reinforced composite of claim 8, wherein the X group
is a selected from an alkyl group, an aryl group, and an alkyl-aryl
group.
10. The fiber-reinforced composite of claim 8, wherein the X group
is an atom that is not nitrogen.
11. The fiber-reinforced composite of claim 8, wherein n has a
value from 2 to 5 and each of the activator moieties A is the same
or different.
12. The fiber-reinforced composite of claim 8, wherein at least one
of the A groups comprises a substituted or unsubstituted
organo-cyclic ring.
13. The fiber-reinforced composite of claim 12, wherein the
organo-cyclic ring comprises at least one heteroatom selected from
the group consisting of nitrogen and oxygen.
14. The fiber-reinforced composite of claim 12, wherein the
organo-cyclic ring has the formula: ##STR00014## wherein
##STR00015## represents a C.sub.3 to C.sub.12, subsitituted or
unsubstituted cyclic hydrocarbon chain.
15. The fiber-reinforced composite of claim 12, wherein the
organo-cyclic ring has the formula: ##STR00016##
16. The fiber-reinforced composite of claim 8, wherein the S group
has the formula: ##STR00017## wherein R.sub.1, R.sub.2, and R.sub.3
are the same or different and each represent a moiety selected from
the group consisting of an alkyl group, an aryl group, an alkoxy
group, a halogen, and a hydroxyl group.
17. The fiber-reinforced composite of claim 4, wherein the
activator compound present in the resin composition comprises a
blocked isocyanate compound.
18. The fiber-reinforced composite of claim 4, wherein the
activator compound present in the resin composition comprises
caprolactam hexane di-isocyanate.
19. The fiber-reinforced composite of claim 4, wherein the resin
composition further comprises a polymerization catalyst.
20. The fiber-reinforced composite of claim 19, wherein the
polymerization catalyst comprises a salt of a lactam.
21. The fiber-reinforced composite of claim 20, wherein the
polymerization catalyst comprises an alkali metal caprolactam.
22. The fiber-reinforced composite of claim 4, wherein the glass
fibers are at least 60 wt. % of the fiber-reinforced composite.
23. The fiber-reinforced composite of claim 22, wherein the glass
fibers are 60 wt. % to 90 wt. % of the fiber-reinforced
composite.
24. The fiber-reinforced composite of claim 4, wherein the glass
fibers are ordered into at least one arrangement selected from the
group consisting of a woven fabric, a multi-axial fabric, a
continuous strand mat, and a chopped strand mat.
25. The fiber-reinforced composite of claim 4, wherein the
thermoplastic polymer matrix comprises polymers that are not
directly bonded to the glass fibers.
26. A fiber-reinforced composite article made by a process
comprising: providing treated glass fibers treated with a sizing
composition that has a coupling-activator compound with the
formula: S--X-(A).sub.n wherein n is an integer having a value
between 1 and 5; S comprises a silicon-containing coupling moiety
through which the coupling-activator compound bonds to a surface of
the glass fibers; X comprises a linking moiety to link the S moiety
with one or more A moieties; and A comprises a polymerization
activator moiety; combining the treated glass fibers with a resin
composition to make a fiber-resin mixture, wherein the resin
composition comprises a monomer and an activator compound capable
of initiating a polymerization of the monomer, and wherein a molar
ratio of (i) the A moieties to (ii) the activator compound present
in the resin composition ranges from 0.02:1 to 20:1; and curing the
fiber-resin mixture to form the fiber-reinforced composite article,
wherein the treated glass fibers are at least 60 wt. % of the
fiber-reinforced composite article.
27. The fiber-reinforced composite article of claim 26, wherein n
has a value from 2 to 5 and each of the A moieties is the same or
different.
28. The fiber-reinforced composite article of claim 26, wherein the
monomers in the resin composition comprise a lactam or a lactone,
and wherein the lactam or the lactone have a ring with 3 to 12
carbon atoms.
29. The fiber-reinforced composite article of claim 26, wherein the
treated glass fibers range from 60 wt. % to 90 wt. % of the
fiber-reinforced composite article.
30. The fiber-reinforced composite article of claim 26, wherein the
resin composition further comprises a polymerization catalyst.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a division of prior pending U.S.
application Ser. No. 13/788,857 filed Mar. 7, 2013. The entire
contents of the above-identified application is herein incorporated
by reference for all purposes.
[0002] The technology disclosed herein is related to the following:
U.S. patent application Ser. No. 12/008,041(filed Jan. 8, 2008,
published Nov. 11, 2010, now abandoned); Ser. No. 12/724,024 (filed
Mar. 15, 2010, now U.S. Pat. No. 8,378,094, issued Feb. 19, 2013);
Ser. No. 12/881,736 (filed Sep. 14, 2010, now U.S. Pat. No.
8,852,732 issued Oct. 7, 2014); Ser. No. 12/913,326 (filed Oct. 27,
2010, published Feb. 24, 2011); Ser. No. 13/083,331(filed Apr. 8,
2011, now U.S. Pat. No. 8,293,322, issued Oct. 23, 2012); Ser. No.
13/335,813 (filed Dec. 22, 2011, now U.S. Pat. No. 9,169,351,
issued Oct. 27, 2015); Ser. No. 13/335,690 (filed Dec. 22, 2011,
now U.S. Pat. No. 8,962,735, issued Feb. 24, 2015); Ser. No.
13/335,761 (filed Dec. 22, 2011, now U.S. Pat. No. 8,791,203,
issued Jul. 29, 2014); and 13/335,793 (filed Dec. 22, 2011, now
U.S. Pat. No. 9,340,454, issued May 17, 2016). All of which are
herein incorporated by reference for all purposes.
BACKGROUND OF THE INVENTION
[0003] Inorganic materials are often incorporated in composite
articles to affect physical properties. In addition to increased
dimensional stability, the inorganic material may improve the
physical and mechanical properties of polymer composites. As one
example, glass fibers may be placed into a polymer matrix to affect
the strength of the composite. The high tensile strength of glass
fibers may cause the composite to become more rigid. In order to
improve the interfacial adhesion between glass fibers and the
polymer matrix, glass fibers may be treated with a sizing
composition after they are drawn from a bushing. Chemical bonding
between glass fibers and the polymer matrix affects the mechanical
properties and the aging performance of composite materials.
However, the degree of chemical bonding at the glass-polymer
interface may need to be adjusted to balance between various
composite properties, including mechanical strength and fracture
toughness. This and other needs are addressed in the present
application.
BRIEF SUMMARY OF THE INVENTION
[0004] Fiber-reinforced composites are suitable for a variety of
applications. Such applications may prefer fiber-reinforced
composites with properties such as high tensile strength,
interlaminar shear strength, and flexural strength. These stronger
composites may be achieved through increasing the weight percentage
of glass fibers in the composite. Chopped fiber-reinforced
composites, however, typically contain less than 50 wt. % glass
fiber. This limit is partly a result of the difficulty in mixing
highly viscous resins with a high amount of chopped fibers. Another
way to affect the strength properties of a fiber-reinforced
composite is through the covalent bonding between the fibers and
the polymer matrix. Coupling-activator (C-A) compounds may aid in
binding polymers, such as polyamide-6, to the fibers and increase
the strength of the final composite. However, the concentration of
these C-A compounds should balance the positive effects of binding
the polymers to the fibers with potentially negative effects of
creating too many initiation points on the fiber surface and also
reducing fracture toughness. The present application recognizes
that increasing the strength of a composite by loading in more
chopped fibers or further increasing the C-A compounds in the
binder resin eventually faces technical obstacles.
[0005] Novel methods that increase the fiber content and enable
tuning the fiber-matrix interfacial strength allow for more
flexibility in affecting the strength properties of
fiber-reinforced composites. Replacing some or all of the chopped
fibers with continuous fibers improves composite mechanical
properties. Reactive resin systems, such as polyamide-6 formed by
the anionic ring-opening polymerization of caprolactam, overcome
limitations in mixing highly viscous resins by starting with
low-viscosity monomers and then forming a polymer matrix through in
situ polymerization in the presence of fiber reinforcement.
Reactive resins may then enable higher fiber content in the
composite, resulting in improved mechanical properties of the
composite articles. The use of reactive resins permits glass fiber
concentrations in the composite of about 70 wt. % or more. The use
of continuous fibers may increase the strength of the composite
above the practical limits that can be achieved in composites that
exclusively use chopped fibers.
[0006] For reactive resin systems, such as polyamide-6 formed by
anionic polymerization of caprolactam, the activator compounds may
be added to both the resin and the fibers in a proportion adjusted
to affect the mechanical properties in the fiber-reinforced
composite. The activator compound added to the resin may be
different from that added to the fibers. For example, the activator
compound on glass fibers may be a coupling-activator, which may
covalently bond to glass fibers through its coupling moiety. The
activator compound in the resin may be an activator without a
coupling moiety or may be a different type of activator. Fracture
toughness may be increased by decreasing the amount of
coupling-activator compound applied to the fiber, and this decrease
in the amount of activator may be offset by increasing activator in
the resin. The ratio of the activator in the resin to the activator
on the fiber may be tuned for a desired strength and fracture
toughness of the final fiber-reinforced composite.
[0007] Embodiments of the invention that may include processes of
making a fiber-reinforced composite are described. Exemplary fibers
used in the composites may include glass fibers. These glass fibers
may be treated with a sizing composition that has a
coupling-activator compound with the formula:
S--X-(A).sub.n, (I)
where S represents a silicon-containing coupling moiety capable of
bonding to the surface of glass fibers, X represents a linking
moiety, and (A).sub.n represents one or more polymerization
activator moieties. The treated glass fibers may be combined with a
reactive resin to make a fiber-resin mixture. The resin may have a
monomer, a catalyst, and an activator compound capable of
initiating a polymerization of the monomer. The monomer may be a
lactam or lactone having 3-12 carbon atoms in the main ring. The
catalyst in the resin may include a salt of lactam, and the salt
may be an alkali metal salt or an alkali-earth metal salt. The
fiber-resin mixture may then be cured so that the monomer
polymerizes to form a polymer matrix of the fiber-reinforced
composite. The fiber-reinforced composite formed may contain at
least 70 wt. % glass fiber.
[0008] The glass fibers in the fiber reinforced composite may range
from about 70 wt. % to 90 wt. %. These glass fibers may include
continuous glass fibers. The ratio of the moles of the activator
moiety on treated fiber to the moles of the activator moiety in the
resin may be between 0.02 to 20.
[0009] The activator moiety (A).sub.n may include a C.sub.1 to
C.sub.9, substituted or unsubstituted, organo-cyclic ring. The
organo-cyclic ring may have at least one heteroatom that is a
nitrogen or oxygen atom. The organo-cyclic ring may have the
following formula:
##STR00001##
where
##STR00002##
represents a C.sub.3, to C.sub.12, substituted or unsubstituted
cyclic hydrocarbon chain. For example, R may be a C.sub.6
hydrocarbon chain, so that the activator moiety has the
formula:
##STR00003##
The linking moiety X may include an atom that connects X to one or
more activator moieties (A).sub.n, where the atom is not a nitrogen
atom.
[0010] The fibers may be arranged as a mono-axial and/or
multi-axial, woven and/or non-woven, continuous and/or chopped
strand mat. The mats may have multiple sections with different
weave styles, as well as combinations of woven and non-woven,
continuous and/or chopped sections.
[0011] This technology may be used in a variety of processes such
as resin transfer molding (RTM), reaction injection molding (RIM),
reactive extrusion, filament winding, pultrusion, casting
(including rotational casting), prepreg processes (including double
belt press), rotational molding, blow molding, D-LFT processes,
D-SMC processes, processes to produce organo sheets, and other
types of prepregs (reactive and already reacted ones).
[0012] Embodiments of the invention may also include glass fibers
treated with a sizing composition that has a coupling-activator
compound having the formula: S--X-(A).sub.n, where S represents a
silicon-containing coupling moiety capable of bonding to the
surface of glass fibers, X represents a linking moiety, and
(A).sub.n represents one or more polymerization activator moieties.
The treated glass fibers may be combined with a resin to make a
fiber-resin mixture. The resin may have a monomer and a catalyst.
The monomer may be a lactam or lactone having 3-12 carbon atoms in
the main ring. The catalyst in the resin may include a salt of
lactam, and the salt may be an alkali metal salt or an alkali-earth
metal salt. The fiber-resin mixture may then be cured so that the
monomer polymerizes to form a polymer matrix of the
fiber-reinforced composite.
[0013] At least one of the activator moiety, (A).sub.n may comprise
a C.sub.1 to C.sub.9 substituted or unsubstituted, organo-cyclic
ring. The organo-cyclic ring may include at least one heteroatom
that is a nitrogen or oxygen atom. The organo-cyclic ring may have
the following formula:
##STR00004##
where
##STR00005##
represents a C.sub.3, to C.sub.12, substituted or unsubstituted
cyclic hydrocarbon chain. For example, R may be a C.sub.6
hydrocarbon chain, so that activator moiety with an organo-cyclic
ring has the formula:
##STR00006##
The linking moiety X may include an atom that connects X to one or
more activator moieties (A).sub.n, where the atom is not a nitrogen
atom.
[0014] The fiber-reinforced composite formed may be at least 60 wt.
% glass fiber. The glass fiber content in the fiber-reinforced
composite may range from about 60 wt. % to 90 wt. %. The glass
fibers may comprise continuous glass fibers.
[0015] The fibers may be arranged as a mono-axial and/or
multi-axial, woven and/or non-woven, continuous and/or chopped
strand mat. The mats may have multiple sections with different
weave styles, as well as combinations of woven and non-woven
sections.
[0016] This technology may be used in a variety of processes such
as resin transfer molding (RTM), reaction injection molding (RIM),
reactive extrusion, filament winding, pultrusion, casting
(including rotational casting), prepreg processes (including double
belt press), rotational molding, blow molding, D-LFT processes,
D-SMC processes, processes to produce organo sheets, and other
types of prepregs (reactive and already reacted ones).
[0017] Additional embodiments and features are set forth in part in
the description that follows, and in part will become apparent to
those skilled in the art upon examination of the specification or
may be learned by the practice of the invention. The features and
advantages of the invention may be realized and attained by means
of the instrumentalities, combinations, and methods described in
the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] A further understanding of the nature and advantages of the
present invention may be realized by reference to the remaining
portions of the specification and the drawings where like reference
numerals are used throughout the several drawings to refer to
similar components. In some instances, a sublabel is associated
with a reference numeral and follows a hyphen to denote one of
multiple similar components. When reference is made to a reference
numeral without specification to an existing sublabel, it is
intended to refer to all such multiple similar components.
[0019] FIG. 1 shows a flowchart with selected steps in methods of
making fiber-reinforced composite articles according to embodiments
of the invention;
[0020] FIG. 2 shows a flowchart with selected steps in additional
methods of making fiber-reinforced composite articles according to
embodiments of the invention;
DETAILED DESCRIPTION OF THE INVENTION
[0021] Embodiments of the invention that may include processes of
making a fiber-reinforced composite are described. Methods
described may help to increase the fiber weight percentage in
composites. Continuous fibers may be used instead of chopped fibers
at a high fiber content in the composite. The activator compounds
may be added to both the resin and the fibers in a proportion
adjusted to affect the mechanical properties in the
fiber-reinforced composite. FIG. 1 shows selected operations in an
exemplary method. Exemplary fibers used in the composites may
include glass fibers, as shown in operation 102. These glass fibers
may be treated with a sizing composition that has a
coupling-activator compound with the formula: S--X-(A).sub.n, where
S represents a silicon-containing coupling moiety capable of
bonding to the surface of glass fibers, X represents a linking
moiety, and (A).sub.n represents one or more polymerization
activator moieties. The treated glass fibers may be combined with a
resin to make a fiber-resin mixture, as denoted by operation 104 in
FIG. 1. The coupling-activator compound may start the
polymerization of the surrounding monomer in close proximity to the
fiber surface. The fiber-resin mixture may then be cured so that
the monomer polymerizes to form a polymer matrix of the
fiber-reinforced composite, as shown by operation 106 in FIG. 1.
The fiber-reinforced composite formed may be at least 70 wt. %
glass fiber.
[0022] The present technology is suitable for a variety of
structural applications. The fiber-reinforced composite has high
tensile strength and interlaminar shear strength. Such properties
may make the fiber-reinforced composite suitable for wind turbine
blades, for automotive applications, as well as for other
applications in which shear stresses may overcome conventional
composite structures.
[0023] This technology may be used in a variety of processes such
as resin transfer molding (RTM), reaction injection molding (RIM),
reactive extrusion, filament winding, pultrusion, casting
(including rotational casting), prepreg processes (including double
belt press), rotational molding, blow molding, D-LFT processes,
D-SMC processes, processes to produce organo sheets, and other
types of prepregs (reactive and already reacted ones).
[0024] Suitable X moieties may include any number of organic,
semi-organic, or inorganic functional groups, and may include, for
example, alkyl, aryl, and/or alkyl-aryl groups. The linking group X
may be of any length, including null, in which case the activator
(A).sub.n would be directly attached to silicon-containing coupling
moiety S. The linking moiety X may include an atom that connects X
to one or more activator moieties (A).sub.n, where the atom is not
a nitrogen atom. With the atom directly adjacent to the activator
moiety (A).sub.n not a nitrogen atom, the coupling-activator
compound may be formed by a synthesis not using a precursor having
an isocyanate functional group. The coupling-activator compound may
be formed in a synthesis route that includes an ester group instead
of an isocyanate group.
[0025] The silicon-coupling moiety S may have any of the known
functional groups that react with the surface of an inorganic
substrate (e.g., an organosilane group). Compounds containing
organosilane groups as coupling agents in material systems may
include an inorganic or organic phase, such as, for example, glass
or polymer, respectively, and may serve to covalently bond the
organic groups in the compound to groups on the inorganic surface.
As one example, S may comprise an organosilane group of the
following Formula II:
##STR00007##
where X may be similar to X in Formula I above; and R.sup.1,
R.sup.2, and R.sup.3 may be the same or different and each may
represent alkyl, aryl, alkoxy, halogen, hydroxy, or a cyclic
structure where X is connected with one or more of R.sup.1,
R.sup.2, and R.sup.3.
[0026] The ring-opening polymerization activator moiety A may be
any known organic reactive group that participates in a
ring-opening polymerization reaction, which includes anionic
ring-opening polymerization, cationic ring-opening polymerization,
or ring-opening metathesis polymerization (ROMP). For example, such
reactive group may participate in the polymerization by forming a
reactive center where further cyclic monomers can join after
opening to provide a larger polymer chain through ionic
propagation.
[0027] The activator moiety (A).sub.n may include a C.sub.1 to
C.sub.9, substituted or unsubstituted, organo-cyclic ring. The
organo-cyclic ring may have at least one heteroatom that is a
nitrogen or oxygen atom. The organo-cyclic ring may have the
following formula:
##STR00008##
where
##STR00009##
represents a C.sub.3, to C.sub.12, substituted or unsubstituted
cyclic hydrocarbon chain. For example, R may be a C.sub.6
hydrocarbon chain, so that activator moiety with an organo-cyclic
ring has the formula:
##STR00010##
[0028] In another embodiment, the invention encompasses an
inorganic substrate bonded to a coupling-activator compound of
Formula I above. The inorganic substrate may include a plurality of
glass fibers where at least one glass fiber is at least partially
coated with the residue of a sizing composition comprising the
coupling-activator compound. As previously described, the
silicon-containing coupling moiety S of the coupling-activator
compound that is included in the coated sizing composition may
covalently bond to the glass fiber when the composition is coated
and dried on the glass substrate, thereby securely attaching the
coupling-activator compound to the glass substrate.
[0029] The ratio of the moles of the activator moiety on treated
fibers to the moles of activator moiety in the resin may be between
0.02 and 20. This ratio may be adjusted to affect the mechanical
properties in the fiber-reinforced composite. If too little
coupling-activator compound is used on treated fibers, a low degree
of covalent bonding between the fibers and the polymer matrix may
result, leading to decreased strength of the composite. Strong
covalent bonding between fibers and the polymer matrix created by
the coupling-activator compound enhances the overall strength of
the composite. However, if too much coupling-activator compound is
used on treated fibers, too much bonding between the fibers and the
polymer may reduce fracture toughness of the composite. In order to
increase fracture toughness, less coupling-activator compound may
be applied to the fibers. However, this decrease in the amount of
coupling-activator on treated fibers may be offset by adding more
activator in the resin. Thus, the ratio of the activator in the
resin to the coupling-activator on the fiber may be adjusted to
target a desired strength and fracture toughness of the final
fiber-reinforced composite.
[0030] After the sizing has been applied, fibers may be collected
in rovings. Glass fibers may include continuous glass fibers.
Rovings of continuous sized strands may be used in some
applications (e.g., in long-fiber thermoplastics) or the rovings
may be commingled and may be later chopped to a desired length.
Fiber-reinforced composites using continuous glass fibers may have
higher mechanical strength in the final composite than with chopped
fibers. Composites using continuous fibers and reactive resins can
reach glass fiber weight percentages of around 90 wt. %.
[0031] Some embodiments of glass fibers according to the present
invention may be particularly suited for reinforcing polyamide
resins. Polyamide resins reinforced with glass fibers in accordance
with the invention may include Nylon 6, Nylon 6:6, Nylon 6:12,
Nylon 4:6, Nylon 6:10, Nylon 12, polyamide 6T (polyhexamethylene
terephthalamide), polyamide 6I (polyhexamethylene isophthalamide)
or mixtures thereof. In one embodiment, the A moiety of the
coupling activator compound in formula I above may include a
blocked precursor of the active activator moiety, e.g., a blocked
isocyanate. In this embodiment, the precursor compound may be
coated on the glass substrate and the active form of the activator
may be generated in situ on the surface of a glass substrate when
exposed to unblocking conditions. Non-limiting examples of glass
fibers suitable for use in the present invention can include those
prepared from fibersable glass compositions, such as "E-glass`,
"A-glass", "C-glass", "S-glass", "ECR-glass" (corrosion resistant
glass), "T-glass", and fluorine and/or boron-free derivatives
thereof.
[0032] Examples of other fibers include ceramic fibers (e.g.,
aluminum oxide, silicon carbide, silicon nitride, silicon carbide,
basalt), carbon fibers (e.g., graphite, semi-crystalline carbon,
carbon nanotubes), metal fibers (e.g., aluminum, steel, tungsten),
and polymer fibers (e.g., aramid). The fibers may be arranged as a
mono-axial and/or multi-axial, woven and/or non-woven, continuous
and/or chopped strand mat. The mats may have multiple sections with
different weave styles, as well as combinations of woven and
non-woven sections. In addition, the mats may have regions where
fibers are incorporated, for example to allow better wet out and
resin penetration in a preselected part or parts of the composite
article.
[0033] The resin may have a monomer, a catalyst, and an activator
compound capable of initiating a polymerization of the monomer. The
monomer may be a lactam or lactone having 3-12 carbon atoms in the
main ring, such as caprolactam and caprolactone. The catalyst in
the resin may include a salt of lactam, and the salt may be an
alkali metal salt or an alkali-earth metal salt. The polymerization
catalyst may be an alkali metal salt of the lactam or lactone
monomer, such as sodium caprolactam and sodium caprolactone.
[0034] The fiber-resin mixture may then be cured to form a polymer
matrix of the fiber-reinforced composite. The fiber-reinforced
composite formed may be at least 70 wt. % glass fiber. The glass
fibers in the fiber reinforced composite may range from about 70
wt. % to 90 wt. %, as compared to conventional composites limited
to about 60 wt. % glass fiber. Higher weight percents of glass
fiber result in a stronger composite.
[0035] There may also be other known auxiliary components in the
polymerization mixture (e.g., co-activators, catalysts,
co-catalysts, electron donors, accelerators, sensitizers,
processing aids, release agents). The pre-polymerized mixture may
also include partially polymerized compounds such as dimers,
trimers, and/or oligomers.
[0036] When the combination of the pre-polymer lactam mixture and
fibers is raised to the polymerization temperature, the ring
structure may open or be otherwise activated to initiate a linear
or branched polymerized chain from the activator moiety. The chain
is coupled directly to the fiber through the coupling moiety and
linking moiety trunk of the coupling-activator compound.
[0037] In an example where caprolactam is the monomer, the
temperature of the pre-polymerized mixture may be raised from a
melting temperature of between about 80.degree. C. and 120.degree.
C., to a polymerization temperature of about 120.degree. C. or more
(e.g., about 120.degree. C. to about 220.degree. C.). In additional
examples, the pre-polymerized mixture may have a melting
temperature of about 80.degree. C. to about 200.degree. C. (e.g.,
about 100.degree. C. to about 160.degree. C.), and may have a
polymerization temperature of about 120.degree. C. to about
220.degree. C. (e.g., about 180.degree. C. to about 220.degree.
C.).
[0038] At least a portion of the polymer matrix formed by the
polymerization of the lactam monomers is initiated by the activator
moieties on the coupling-activator compounds bound to the treated
fibers. These moieties may also start the formation of linear
and/or branched polyamide polymers, the formation of which may also
be aided by the one or more catalysts present. The
coupling-activator compounds create covalent bonding between the
surface of the fibers and the surrounding polymers that is
significantly stronger than the bonding formed by simply curing a
polyamide resin in the presence of untreated fibers.
[0039] The present polymer matrices may also include polymers that
are not directly bonded to the treated fibers. These polymers may
have been formed, for example, through polymerizations that were
initiated from the activator compound in the resin or polymers that
have fragmented or decoupled after polymerization was initiated at
the fibers. Although these polymers may not be directly bonded to
the fibers, their coulombic and physical interactions with the
fiber surface-bonded polymers may further strengthen the bonding
between the treated fibers and the surrounding polymer matrix.
[0040] FIG. 2 illustrates the operations of forming
fiber-reinforced composites according to the present technology. In
operation 202, glass fibers may be treated with a sizing
composition that has a coupling-activator compound with the
formula: S--X-(A).sub.n, where S represents a silicon-containing
coupling moiety capable of bonding to the surface of glass fibers,
X represents a linking moiety, and (A).sub.n represents one or more
polymerization activator moieties. The S, X, and (A).sub.n moieties
may be any of the moieties discussed previously.
[0041] At least one of the activator moiety, (A).sub.n may comprise
a C.sub.1 to C.sub.9 substituted or unsubstituted, organo-cyclic
ring. The organo-cyclic ring may include at least one heteroatom
that is a nitrogen or oxygen atom. The organo-cyclic ring may have
the following formula:
##STR00011##
where
##STR00012##
represents a C.sub.3, to C.sub.12, substituted or unsubstituted
cyclic hydrocarbon chain. The organo-cyclic ring may include a
C.sub.6 hydrocarbon chain, such that the activator moiety has the
formula:
##STR00013##
[0042] In operation 204 of FIG. 2, the treated glass fibers may be
combined with a resin to make a fiber-resin mixture. The resin may
have a monomer and a catalyst. The monomer may be a lactam or
lactone having 3-12 carbon atoms in the main ring. The catalyst may
be any of the catalysts previously disclosed above.
[0043] The fiber-resin mixture may then be cured so that the
monomer polymerizes to form a polymer matrix of the
fiber-reinforced composite, as in operation 206 of FIG. 2.
Conditions for curing may include those disclosed above. The
mechanisms for polymerization may include those previously
discussed above.
[0044] The fiber-reinforced composite formed may be at least 60 wt.
% glass fiber. The glass fibers in the fiber reinforced composite
may range from about 60 wt. % to 90 wt. %. The glass fibers may
comprise unchopped glass fibers or continuous glass fibers. The
fibers may be any of the fibers previously discussed.
[0045] There may also be other known auxiliary components in the
polymerization mixture (e.g., co-activators, catalysts,
co-catalysts, electron donors, accelerators, sensitizers,
processing aids, release agents). The pre-polymerized mixture may
also include partially polymerized compounds such as dimers,
trimers, and/or oligomers.
EXAMPLES
Example 1
Preparation of Woven Fabric Reinforcement
[0046] 1,200 tex fiber glass rovings, which were treated with a
sizing formulation containing a coupling-activator,
2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide, were
weaved to form a unidirectional fabric with the area weight of 670
g/m.sup.2. A 6-layer 0/90.degree. stack of the unidirectional woven
fabric was then cut to 400 mm.times.400 mm and placed into the mold
as reinforcement for the composite panel.
Example 2
Preparation of Woven Fabric-Reinforced Polyamide-6 Composite
Panels
[0047] Two heated tanks were used for melting caprolactam-catalyst
and caprolactam-activator separately. An amount of 1,000 grams of
caprolactam (Bruggemann, AP Nylon grade) and 82.4 grams of
Bruggolen C10 (Bruggemann, contains 17-19% sodium caprolactamate)
were added to the first tank. This mixture of caprolactam and C10
was melted at 100.degree. C. Separately, 1,000 grams of caprolactam
(Bruggemann, AP Nylon grade) and 9.0 grams of Bruggolen C20
(Bruggemann, contains 80% caprolactam hexane di-isocyanate) were
added to the second tank. This mixture of caprolactam and C20 was
melted at 100.degree. C.
[0048] The melts from the two tanks were then mixed at a 1:1 ratio
in a static mixer, before the reactive mixture was injected into
the mold. The reactive mixture in this example contains 0.6 mol% of
active catalyst (sodium caprolactamate) and 0.1% mol of active
activator (caprolactam hexane di-isocyanate).
[0049] After the reactive mixture was injected into the mold, the
mold temperature was raised to 160.degree. C. to form polyamide-6
in the presence of woven fabric reinforcement. The resulting panels
have a glass content of 65% by weight and a thickness of 3.5
mm.
Test Methods
1. Tensile Strength
[0050] Tensile strength of the composite samples was tested based
on ISO 527-3 standard (Type 2 sample). A gauge length of 150 mm and
a testing speed of 2 mm/min were used for testing. For each
composite panel, eight samples of 250 mm in length and 25 mm in
width were cut for tensile tests.
2. Interlaminar Shear Strength (ILSS)
[0051] ILSS tests were conducted based on ASTM 2344 standard. A
span length of 12 mm and a testing speed of 1 mm/min were used for
testing. For each composite panel, 10 samples of 40 mm in length
and 6 mm in width were cut for ILSS tests.
3. Flexural Strength
[0052] Flexural strength tests were conducted based on ISO 178
standard. A span length of 48 mm and a testing speed of 1 mm/min
were used for testing. For each composite panel, 10 samples of 60
mm in length and 25 mm in width were cut for flexural strength
tests.
Test Results
TABLE-US-00001 [0053] TABLE 1 Tensile Interlaminar Flexural C20 C10
Strength Shear Strength Strength Panel (mol (mol (MPa) (MPa) (MPa)
# %)* %)* Ave STDev Ave STDev Ave STDev 1 0.10 0.60 271.8 31.6 63.4
13.2 202.0 28.3 2 0.15 0.60 274.2 25.1 71.3 10.1 377.7 44.3 3 0.21
0.60 316.7 21.6 82.8 10.6 441.9 23.4 4 0.30 0.60 299.5 38.8 71.5
14.9 434.5 37.2 *mole percent relative to caprolactam
[0054] Table 1 shows the mechanical properties of the composite
panels, produced with the same woven fabric reinforcement but
different reactive resins containing various amount of unbonded
activator (C20) in the resin. By adjusting the amount of activator
(C20) in the resin, the ratio of the glass surface-bonded activator
to the unbonded activator in the resin can be optimized to maximize
the composite mechanical properties. For example, the mechanical
properties, including tensile, ILSS, and flexural strengths of the
composite panel #3 are the highest among all four panels,
indicating an optimal ratio of glass surface-bonded activator to
unbonded activator in the resin.
[0055] Having described several embodiments, it will be recognized
by those of skill in the art that various modifications,
alternative constructions, and equivalents may be used without
departing from the spirit of the invention. Additionally, a number
of well-known processes and elements have not been described in
order to avoid unnecessarily obscuring the present invention.
Accordingly, the above description should not be taken as limiting
the scope of the invention.
[0056] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limits of that range is also specifically disclosed. Each
smaller range between any stated value or intervening value in a
stated range and any other stated or intervening value in that
stated range is encompassed. The upper and lower limits of these
smaller ranges may independently be included or excluded in the
range, and each range where either, neither, or both limits are
included in the smaller ranges is also encompassed within the
invention, subject to any specifically excluded limit in the stated
range. Where the stated range includes one or both of the limits,
ranges excluding either or both of those included limits are also
included.
[0057] As used herein and in the appended claims, the singular
forms "a", "an", and "the" include plural referents unless the
context clearly dictates otherwise. Thus, for example, reference to
"a process" includes a plurality of such processes and reference to
"the fiber" includes reference to one or more fibers and
equivalents thereof known to those skilled in the art, and so
forth.
* * * * *