CA1082391A - Unsaturated epoxides as coupling agents for carbon fibers and unsaturated matrix resins - Google Patents
Unsaturated epoxides as coupling agents for carbon fibers and unsaturated matrix resinsInfo
- Publication number
- CA1082391A CA1082391A CA314,058A CA314058A CA1082391A CA 1082391 A CA1082391 A CA 1082391A CA 314058 A CA314058 A CA 314058A CA 1082391 A CA1082391 A CA 1082391A
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- unsaturated
- coupling agent
- composite structure
- radical
- matrix resin
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Abstract
Abstract of the Disclosure The adhesion between carbon fibers and unsaturated matrix resins used in the preparation of composite structures is improved by the use of an unsaturated epoxide bifunctional coupling agent.
The coupling agent can be applied to the carbon fibers or incorpo-rated into the matrix resin system.
The coupling agent can be applied to the carbon fibers or incorpo-rated into the matrix resin system.
Description
23~1 This invention relates to composite structures comprising carbon fibers and unsaturated matrix resins. More particularly it relates to such structures which incorporate an unsaturated epoxide compound as a bifunction-al coupling agent to improve adhesion between carbon ibers and unsaturated matrix resins. This application is divided out of our application Serial No.
252,762, filed on May 18, 1976.
The term "carbon fibers" is used in this application in its generic .~
sense and includes all fibers which consist essentially of carbon ranging from graphite fibers to amorphous carbon fibers. Graphite fibers are defined here-in as fibers which consist essentially of carbon and have a predominate x-ray diffraction pattern characteristic of graphite. Amorphous carbon fibers on the other hand are defined as fibers which consist essentially of carbon and which have an essentially amorphous x-ray diffraction pattern. Carbon fibers `can be prepared by known processes from polymeric fibrous material, such as po7yacrylonitrile, polyvinyl alcohol, pitch, natural and regenerated cellulose, which processes include the steps of carbonizing or graphitizing the fiber.
`;A major use of carbon fibers is in the preparation of composites using a variety of different matrix resins. However, it has been observed that adhesion between carbon fibers and unsaturated matrix resins is gener-ally lower than that desired.
. , : ~ ',:
Now, in accordance with this invention, it has been discovered that ~ . .
composites having improved adhesion between carbon fibers and unsaturated ma-trix resins can be obtained by use of certain unsaturated epoxide bifunction- -~
al-coupling agents.
Accordingly,~in one aspect this invention provides a composite structure which is a cured admixture comprising (a) carbon fibers, (b) an unsaturated matrix resin and (c) an unsaturated epoxide bifunctional coupl-ing agent having the general structural formula:
-~L~8~
~o\
252,762, filed on May 18, 1976.
The term "carbon fibers" is used in this application in its generic .~
sense and includes all fibers which consist essentially of carbon ranging from graphite fibers to amorphous carbon fibers. Graphite fibers are defined here-in as fibers which consist essentially of carbon and have a predominate x-ray diffraction pattern characteristic of graphite. Amorphous carbon fibers on the other hand are defined as fibers which consist essentially of carbon and which have an essentially amorphous x-ray diffraction pattern. Carbon fibers `can be prepared by known processes from polymeric fibrous material, such as po7yacrylonitrile, polyvinyl alcohol, pitch, natural and regenerated cellulose, which processes include the steps of carbonizing or graphitizing the fiber.
`;A major use of carbon fibers is in the preparation of composites using a variety of different matrix resins. However, it has been observed that adhesion between carbon fibers and unsaturated matrix resins is gener-ally lower than that desired.
. , : ~ ',:
Now, in accordance with this invention, it has been discovered that ~ . .
composites having improved adhesion between carbon fibers and unsaturated ma-trix resins can be obtained by use of certain unsaturated epoxide bifunction- -~
al-coupling agents.
Accordingly,~in one aspect this invention provides a composite structure which is a cured admixture comprising (a) carbon fibers, (b) an unsaturated matrix resin and (c) an unsaturated epoxide bifunctional coupl-ing agent having the general structural formula:
-~L~8~
~o\
2 CH - X - R
wherein X is a radical selected from the group consisting of (CH2)n - 0 - , - (CH2)n - 0 - I - where n = 1-10; and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon `( atoms~ cmd R is an unsaturated radical selected from the group consisting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an aryl radical containing an ethylenically unsaturated C2-C4 aliphatic substituent, (c) the alpha-terpinylradical,(d~the gamma-terpinyl radical and (e) the abietyl radical.
~` 10 In another aspect, this invention provides a process of improving the adhesion between carbon fibers and an ethylenically unsaturated matrix resin in a carbon fiber reinforced composite structure comprising incorporat-ing into a maxture of said matrix resin and carbon fibers, an unsaturated ;
epoxide bifunctional coupling agent having the general structural formula~
/0\
GH - CH X - R
wherein X is a radical selected from the group consisting of - (CH2) - o _ ~ (GH2)n 1l where n = 1-10, ,`,, O
~, and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 ' carbon atoms, and R is an unsaturated radical selected from the group con-`1 20 sisting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an , .
aryl radical containing an ethylenically unsaturated C2-C4 aliphatic substit-uent, (c) the alpha-terpinyl radical, (d) the gamma-terpinyl radical~
; (e) the abietyl radical, and curing the resulting mixture.
Yet another aspect of this invention provides a process of improv-ing the adhesion between carbon fibers and an ethylenically unsaturated matrix - 2a -. .
08~
resin in a carbon fiber reinforced composite structure comprising (1) modi-fying the surface of said carbon fibers by treatment thereof with an unsatur- ~:
ated epoxide bifunctional coupling agent having the general structural formula~
/ O\ , ~
C~2 CH X R
wherein X is a radical selected from the group consisting o-f ( 2~n ~ (CH2)n- - C - where n = 1-10;
.: O
:,:
and divalent aIkyl, aryl, aralkyl and alkaryl radicals eontaining up to 20 . carbon atoms, and R is an unsaturated radical selected from the group con-sisting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an . aryl radical containing an ethylenically unsaturated C2-C~ aliphatic substit- :
uent, (c) the alpha-terpinyl radieal, (d) gamma-terpinyl radical and (e) ~:
the abietyl radical~ (2) admixing the surface modified carbon fibers and an . . ~ .
ethylenically unsaturated matrix resin, and (3) curing the resulting admix- ~;?~
ture. ~.
, :,:
~ ", ' .
.
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When the coupling agent is used with carbon fiber and a poly-(arylacetylene)-based matrix system, R is any ethylenically unsaturated radi-cal. With other matrix systems, if R is ethylenically unsaturated then it has 2 to 4 carbon atoms.
Illustrative examples of unsaturated epoxides suitable for use with any unsaturated matrix resin are vinyl glycidyl ether, allyl glycidyl ether~ `
ortho-allyl phenyl glycidyl ether, 5,6-epoxy-n-hexyl allyl ether~ 2~,3~-epox~ypropyl 3-butenyl ether, 9,10-epoxy-n-decyl vinyl ether, glycidyl alpha- .
terpinyl ether, glycidyl gamma-terpinyl ether, l-allyl-4-(epoxyethyl)benzene, 1-vinyl-4-(epoxyethyl)benzene, 1,2-epoxy-3-butene, 1,2-epoxy-5-hexane, 1,2-epoxy-9-decene, 1,2-epoxy-17-octadecene~ glycidyl acrylate~ glycidyl methacrylate, glycidyl crotonate, 5~6-epoxy-n-~'.
~, .
, .j . .
.
., `;
, ~ .
wherein X is a radical selected from the group consisting of (CH2)n - 0 - , - (CH2)n - 0 - I - where n = 1-10; and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon `( atoms~ cmd R is an unsaturated radical selected from the group consisting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an aryl radical containing an ethylenically unsaturated C2-C4 aliphatic substituent, (c) the alpha-terpinylradical,(d~the gamma-terpinyl radical and (e) the abietyl radical.
~` 10 In another aspect, this invention provides a process of improving the adhesion between carbon fibers and an ethylenically unsaturated matrix resin in a carbon fiber reinforced composite structure comprising incorporat-ing into a maxture of said matrix resin and carbon fibers, an unsaturated ;
epoxide bifunctional coupling agent having the general structural formula~
/0\
GH - CH X - R
wherein X is a radical selected from the group consisting of - (CH2) - o _ ~ (GH2)n 1l where n = 1-10, ,`,, O
~, and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 ' carbon atoms, and R is an unsaturated radical selected from the group con-`1 20 sisting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an , .
aryl radical containing an ethylenically unsaturated C2-C4 aliphatic substit-uent, (c) the alpha-terpinyl radical, (d) the gamma-terpinyl radical~
; (e) the abietyl radical, and curing the resulting mixture.
Yet another aspect of this invention provides a process of improv-ing the adhesion between carbon fibers and an ethylenically unsaturated matrix - 2a -. .
08~
resin in a carbon fiber reinforced composite structure comprising (1) modi-fying the surface of said carbon fibers by treatment thereof with an unsatur- ~:
ated epoxide bifunctional coupling agent having the general structural formula~
/ O\ , ~
C~2 CH X R
wherein X is a radical selected from the group consisting o-f ( 2~n ~ (CH2)n- - C - where n = 1-10;
.: O
:,:
and divalent aIkyl, aryl, aralkyl and alkaryl radicals eontaining up to 20 . carbon atoms, and R is an unsaturated radical selected from the group con-sisting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an . aryl radical containing an ethylenically unsaturated C2-C~ aliphatic substit- :
uent, (c) the alpha-terpinyl radieal, (d) gamma-terpinyl radical and (e) ~:
the abietyl radical~ (2) admixing the surface modified carbon fibers and an . . ~ .
ethylenically unsaturated matrix resin, and (3) curing the resulting admix- ~;?~
ture. ~.
, :,:
~ ", ' .
.
,'' ~ ':' ~ - 2b - ~ -~'' , B23~
When the coupling agent is used with carbon fiber and a poly-(arylacetylene)-based matrix system, R is any ethylenically unsaturated radi-cal. With other matrix systems, if R is ethylenically unsaturated then it has 2 to 4 carbon atoms.
Illustrative examples of unsaturated epoxides suitable for use with any unsaturated matrix resin are vinyl glycidyl ether, allyl glycidyl ether~ `
ortho-allyl phenyl glycidyl ether, 5,6-epoxy-n-hexyl allyl ether~ 2~,3~-epox~ypropyl 3-butenyl ether, 9,10-epoxy-n-decyl vinyl ether, glycidyl alpha- .
terpinyl ether, glycidyl gamma-terpinyl ether, l-allyl-4-(epoxyethyl)benzene, 1-vinyl-4-(epoxyethyl)benzene, 1,2-epoxy-3-butene, 1,2-epoxy-5-hexane, 1,2-epoxy-9-decene, 1,2-epoxy-17-octadecene~ glycidyl acrylate~ glycidyl methacrylate, glycidyl crotonate, 5~6-epoxy-n-~'.
~, .
, .j . .
.
., `;
, ~ .
- 3 -. .
~z~
`3 hexyl methacrylatet 9,10-epoxy-n-decyl crotonate and glycidyl abietate.
Illustrative examples of unsaturated epoxides which in ad-dition to the above are suitable for use as a coupling agent be-tween carbon fibers and poly~arylacetylene) matrix systems are vinyl cyclohexyl glycidyl ether, glycidyl-4-hexenoate, glycidyl
~z~
`3 hexyl methacrylatet 9,10-epoxy-n-decyl crotonate and glycidyl abietate.
Illustrative examples of unsaturated epoxides which in ad-dition to the above are suitable for use as a coupling agent be-tween carbon fibers and poly~arylacetylene) matrix systems are vinyl cyclohexyl glycidyl ether, glycidyl-4-hexenoate, glycidyl
4-heptenoate, glycidyl 5-methyl-4-heptenoate, glycidyl sorbate, .~ ~
` glycidyl linoleate, glycidyl oleate, glycidyl 3-butenoate,glyci-.
dyl 3-pentenoate, glycidyl 4-methyl-3-pen~enoate, the glycidyl -~ lO ester of 2-cyclohexene carboxylic acid and the glycidyl ester o~
4-methyl-3-cyclohexene carboxylic acid.
The following examples serve to illustrate the various as- ~ -pects of this invention. In these examples parts and percentages - are by weight unless otherwise specified. ~ ?
Example 1 Carbon fiber which has been electrolytically surface treated is passed through a 2% by volume solution of -allyl glyci-dyl ether (AGE) in ethylene dichloride~ This coats the fiber ;i with AGE solution. The coated fiber is then heated to 200C.
~,i 20 for 2 minutes to evaporate the ethylene dichloride solvent. The .-: .
amount of allyl glycidyl ether deposited on the fiber is 0.8% by weight, based on the weight of fiber. The fiber is then heated ~ at 125C. for 1 hour to react the allyl glycidyl ether with ~he q carbon fiber surface. `
Example 2 The procedure of Example 1 was repeated using glycidyl acrylate in place of allyl glycidyl ether to modify the surface of carbon fiber.
Examples 3-lO
.
Carbon fibers, modlfied in accordance with Examples ~ and 2, unmodified, and optionally sized as indicated in Table I are ` used to prepare compositas. In these examples the matrix resin employed is a styrene modified unsaturated polyester prepared from isophthalic acid, maleic anhydride and propylene glycol in a ~ ;
4 ~
~8239~
ratio of 1:1:2 and modified wi~h 4~% by weight styrene. The cur-ing ~gent or hardener employed in this resin system is 1% by weight, based on the weight of the resin, of t-butyl-perbenzoate.
`` In Examples 5 and 6 the carbon fiber is coated with 1.3 by weight, based on the weight of the fiber, of the styrene-modi-fie~ unsaturated polyester resin as a protective size before for-mation of the composite.
; In Examples 8 and 9 allyl glycidyl ether is dissolved in the matrix resin system.
The composite specimens are made in the form of an NOL
ring containing about 60% by volume of treated graphite fiber.
~ In preparation of the composite, the graphite fiber is passed ; through the unsaturated polyester matrix resin system, through a tensioning device and onto a rotating mold. The whole system is enclosed in a vacuum chamber to provide a low void composlte specimen. The mold is removed from the NOL device and placed in a curing oven for one hour to harden the resin. A discussion of NOL ring specimens and their manufacture may be found in Plastics ~ Technology, November 1958, pp. 1017-24, and Proceedings of 21st 3 20 Annual Technical Conference SPI Reinforced Plastics Division, :, :
~- Section 8-D, February 1966.
; Composite samples prepared as described are tested for j short beam shear strength in accordance with ASTM-2344. The re-sults of short beam shear strength tests are shown in Table I.
Examples 11-14 Carbon fibers, unmodified or modified with allyl glycidyl ether in accordance with Example 1 are used to prepare composites -- using poly(arylacetylene) matrix resin system. The resin system contains a prepolymer and a fluidizer and is prepared as follows.
A polymerization vessel is charged with a mixture of 630 parts of meta-diethynylbenzene and 70 parts of para-diethynylben-zene dissolved in 307~7 parts of anhydrous benzene~ The solution is sparged with nitrogen and heated to reflux temperature. Then a catalyst mixture is added to the refluxing solution in four :. S
~ Z3~ f approximately equal increments prepared by mixing 4.4 par-ts of nickel ace-tylacctonate and 8.8 parts of triphenylphosphine in 50 parts of anhydrous benzene. A~ter addition of the initial incre-ment, the others are separately added one, two and three hours later The solution is held at reflux temperature for a total o six and one-quarter hours, at which time the monomer conversion is 85 . 5Po . The prepolymer then is precipitated by adding the solu-tion to seven times its volume of petroleum ether. The yellow powder, which is separated by filtration amounts to 406 parts.
~ 10 The prepolymer contains 11.8% acetylene groups.
-- A molding composition is prepared by dissolving in acetone the prepolymer and, as a fluidizer, a high boiling aromatic coal tar. The amount of coal tar used is 20~, by weight, based on the weight of the prepolymer. The acetone solvent is then removed in ~` a rotary evacuator. The compositions are dried under vacuum for -- 16 hours at room temperature, followed by one hour at 60C. The resulting molding compos~tion is used with unmodified and allyl - glycidyl modified carbon fibers to prepare composite NOL rings as described in Examples 3-10. The resulting composite ~O~ rings :-, 20 are tested for short beam shear strength. The results are shown -in Table I.
The results in Table I show the improved adhesion, as meas-ured by short beam shear s~trength, between carbon fibers and un-saturated matrix resins when allyl glycidyl ether or glycidyl~ ;~
acrylate is used as a coupling ayen-t.
", " -. "
''' ;' '' " '',:
~ :
: :.- .~ :. .
' ~
- .
~Z3~1 .
,~
Table I
Composite Short Beam Shear Ex. Carbon Fiber Matrix Resin System Stren,~th 3 Unmodified Unsaturated polyester 7~700 - 4 AGE modified (Ex. 1) ~ 11,870 Sized with unsaturated " 9,100 polyester 6 Sized with unsaturated ~' 11,200 polyester + AGE
7 AGE modified (Ex. 1) then " 10,600 ; sized with unsaturated -~ polyester ~-~
` 8 Unmodified Unsaturated polyester 10,300 containing 1% AGE
9 Unmodified Unsaturated polyester 10,600 containing 5% AGE
Glycidyl Acrylate Unsaturated polyester 10,715 Modified (Ex. 2) - , 11 Unmodified Poly(arylacetylene) ~ 6,070 fluidizer `''`' . .1 12 AGE modified (Ex. 1) " 9,400 ` 13 Unmodified " 6~620 j . .
14 AGE modified (Ex. 1) ~ 10,570 Carbon fibers employed in accordance with this invention must have a surface adhesionable or reactive with epoxide groups. To improve the ad-hesion between the carbon fiber surface and epoxide groups the carbon fiber .
, surface can be pretreated, for example, by electrolytic treatment or by I oxidation.
One method of employIng coupling agents is to apply the coupling agent onto the fiber prior to forming the composite. Processes for applica- -tion of coupling agent to carbon fiber, and carbon fibers modified with the coupling agent are the subject of our above-mentioned application Serial No.
-~ 252,762. The coupling agent is generally applied to the fiber in the form of ~ 7 ... ...
9239~
a solution in a sllitable solvent followed by removal of the solvent by air drying or by heating to effect evAporation. Examples of suitable solvents are benzene, polar solvents, such as halogenated hydrocarbons, for example, methylene chloride and ethylene dichloride~ diacetone alcohol, ketones and esters. However, if the coupling agent is liquid, no solvent is necessary and the coupling agent can be applied directly onto the fiber.
The concentration of the coupling agent in the solvent, if one is used, is usually in the range of about 0.5 to about 5.0~ preferably about 1.0 to about 3.0% by weight, based on the total weight of the solution. The `~
solution can be applied to the fiber by known methods, for example, by drawing the fiber ~hrough a bath containing the solution or by spraying the solution ontothefïber.
The amount of coupling agent applied to the fiber surface is~
from about 0.05 to about 10.0% by weight, based on the weight of the fiber, and is~*~ preferably from about 0.5 to about 3.0%.
~, ~
To protect the surface modified carbon fiber of this invention from abrasion during subsequent handling, a size can be applied to the carbon ~iber.
The size can be applied from the same solution as the coupling agent or it can be applied after the carbon fiber has been modified with the coupling agent.
The size selected for application to the carbon fiber will be one compatible with the unsaturated matrix resin to be used in preparing the finàl composite.
An alternate method of employing the coupling agent in accordance ;`~
with this invention is to incorporate the unsaturated epoxide into the un~
saturated matrix resin system to be used in preparing the composite. The coupling agent is ~ used in an amount from about 1 to about 5% by ;
weight, based on the weight of the matrix resin system.
Composites of carbon fibers and unsaturated matrix resins can be prepared by any of the known methods. For example, carbon fibers can be used to prepare filament wound composites. In another common method, the composite æ39~
is prepared by incorporating chopped carbon fibers into the matrix resin and then forming the composite, for example, by press molding.
Any type of unsaturated polymer can be used as the matrix resin to prepare composites in accordance with this invention. Illustrative examples of these polymers are polybutadiene-1,2; polybutadiene-1,4; styrene--~butadiene copolymers; butyl rubber ' , ' :`''~ ~
'~ :
'~
.' ~ ` ., ., '`', '` ', .
0~,..
:!
. ~, ~ .
,~,',.;; ~ ~', . :, . .
: , . :~
` - 8a -~38Z3~L f : (polyis~butylene--isoprene copolymers)i natural rubber; polyester resins such as, for example, maleate containing polyesters and polyacrylate esters; butadiene--acrylonitrile copolymers; ethylene--propylene--dicyclopentadiene terpolymers; polychloroprene; polyiso-prene; alkyd resins, such as for example, tall oil alkyd resins;
and polyether copolymers and terpolymers containing at least one - unsaturated epoxide constituent such as, for example, propylene oxide--allyl glycidyl ether copolymers and ethylene oxide--epi-chlorohydrin--allyl glycidyl ether terpolymers. Poly(arylacetyl-10 ene)-fluidizer thermosetting molding compositions are also suit-able matrix resin systems.
Illustrative examples of unsaturated polyesters are poly-esters prepared from polyhydric alcohols and unsaturated polycar-boxylic acids or their anhydrides, optionally along with saturated ;;
polycarboxylic acids by methods well known in the art. These polyesters generally have a molecular weight of 500 to 3000 and an acid number and a hydroxyl number in each case of 2~ to S0.
Examples of polyhydric alcohols which can be employed in preparation of unsaturated polyesters are ethylene glycol, pro-20 pane-1,2-diol, propane-1,3-diol, butane-1,4-diol, butene-1,4-diol, dimethylpropane-1,3-diol, diethyleneglycol, dipropyleneglycol, `~
dimethylolcyclohexane and bis-(hydroxyethyl)- or bis-~hydroxy-propyl)diphenylolmethane or -propane. Examples of unsaturated ~ ;~
carboxylic acids are maleic acid, fumaric acid, itaconic acid and the like. Examples of saturated (i.e., free from aliphatic multi-ple bonds) polycarboxylic acids are phthalic acid, isophthallc acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, aæelaic acid, suberic acid and cyclohexanedicarboxylic acid and their existing anhydrides~ The saturated dicarboxylic acids are 30 generally used in a proportion of 0 to 90; preferably 0 to 70 moI
percent.
The unsaturated polyesters are usually employed along with - copolymerizable monomers when used as a matrix resin for preparing ; ~ composites. The ratio of monomer to polyester is usually in the ` - 9_ .
~23~
r~nge of 30:70 to 90:10. Examples of suitable monomers include styrene~
vinyltoluene, alkylstyrenes, such as alpha-methyl- or tert-butylstyrene, diallyl phthalate, divinylbenzene~ and esters of methacrylic or acrylic acid.
In one embodiment of the invention the unsaturated matrix resin is a poly(arylacetylene) matrix resin system. A preferred poly(arylacetylene~
matrix resin system comprises (1) a prepolymer of at least one pol~vacetylen-ically substituted aromatic compound~ said prepolymer having a number average --. , ; molecular weight from about 900 to about 12~000~ a ratio of aromatic protons to olefinic protons greater than about 2.4 and containing from about 5 to about 20% acetylenic groups by weight of the prepolymer~ with (2) from about 2 to about 200~o by weight of the prepolymer of at least one aromatic organic compound containing at least two six-membered aromatic rings~ said rings being condensed with each other or coupled with each other directl~ or through a methylene, dimethylmethylene, ethylene or vinylene group, said compound or mixtures thereof containing no crystalline organic phase at 220 C., having a viscosity of less than 20 cen~ipoises at 220 C. and containing no more than
` glycidyl linoleate, glycidyl oleate, glycidyl 3-butenoate,glyci-.
dyl 3-pentenoate, glycidyl 4-methyl-3-pen~enoate, the glycidyl -~ lO ester of 2-cyclohexene carboxylic acid and the glycidyl ester o~
4-methyl-3-cyclohexene carboxylic acid.
The following examples serve to illustrate the various as- ~ -pects of this invention. In these examples parts and percentages - are by weight unless otherwise specified. ~ ?
Example 1 Carbon fiber which has been electrolytically surface treated is passed through a 2% by volume solution of -allyl glyci-dyl ether (AGE) in ethylene dichloride~ This coats the fiber ;i with AGE solution. The coated fiber is then heated to 200C.
~,i 20 for 2 minutes to evaporate the ethylene dichloride solvent. The .-: .
amount of allyl glycidyl ether deposited on the fiber is 0.8% by weight, based on the weight of fiber. The fiber is then heated ~ at 125C. for 1 hour to react the allyl glycidyl ether with ~he q carbon fiber surface. `
Example 2 The procedure of Example 1 was repeated using glycidyl acrylate in place of allyl glycidyl ether to modify the surface of carbon fiber.
Examples 3-lO
.
Carbon fibers, modlfied in accordance with Examples ~ and 2, unmodified, and optionally sized as indicated in Table I are ` used to prepare compositas. In these examples the matrix resin employed is a styrene modified unsaturated polyester prepared from isophthalic acid, maleic anhydride and propylene glycol in a ~ ;
4 ~
~8239~
ratio of 1:1:2 and modified wi~h 4~% by weight styrene. The cur-ing ~gent or hardener employed in this resin system is 1% by weight, based on the weight of the resin, of t-butyl-perbenzoate.
`` In Examples 5 and 6 the carbon fiber is coated with 1.3 by weight, based on the weight of the fiber, of the styrene-modi-fie~ unsaturated polyester resin as a protective size before for-mation of the composite.
; In Examples 8 and 9 allyl glycidyl ether is dissolved in the matrix resin system.
The composite specimens are made in the form of an NOL
ring containing about 60% by volume of treated graphite fiber.
~ In preparation of the composite, the graphite fiber is passed ; through the unsaturated polyester matrix resin system, through a tensioning device and onto a rotating mold. The whole system is enclosed in a vacuum chamber to provide a low void composlte specimen. The mold is removed from the NOL device and placed in a curing oven for one hour to harden the resin. A discussion of NOL ring specimens and their manufacture may be found in Plastics ~ Technology, November 1958, pp. 1017-24, and Proceedings of 21st 3 20 Annual Technical Conference SPI Reinforced Plastics Division, :, :
~- Section 8-D, February 1966.
; Composite samples prepared as described are tested for j short beam shear strength in accordance with ASTM-2344. The re-sults of short beam shear strength tests are shown in Table I.
Examples 11-14 Carbon fibers, unmodified or modified with allyl glycidyl ether in accordance with Example 1 are used to prepare composites -- using poly(arylacetylene) matrix resin system. The resin system contains a prepolymer and a fluidizer and is prepared as follows.
A polymerization vessel is charged with a mixture of 630 parts of meta-diethynylbenzene and 70 parts of para-diethynylben-zene dissolved in 307~7 parts of anhydrous benzene~ The solution is sparged with nitrogen and heated to reflux temperature. Then a catalyst mixture is added to the refluxing solution in four :. S
~ Z3~ f approximately equal increments prepared by mixing 4.4 par-ts of nickel ace-tylacctonate and 8.8 parts of triphenylphosphine in 50 parts of anhydrous benzene. A~ter addition of the initial incre-ment, the others are separately added one, two and three hours later The solution is held at reflux temperature for a total o six and one-quarter hours, at which time the monomer conversion is 85 . 5Po . The prepolymer then is precipitated by adding the solu-tion to seven times its volume of petroleum ether. The yellow powder, which is separated by filtration amounts to 406 parts.
~ 10 The prepolymer contains 11.8% acetylene groups.
-- A molding composition is prepared by dissolving in acetone the prepolymer and, as a fluidizer, a high boiling aromatic coal tar. The amount of coal tar used is 20~, by weight, based on the weight of the prepolymer. The acetone solvent is then removed in ~` a rotary evacuator. The compositions are dried under vacuum for -- 16 hours at room temperature, followed by one hour at 60C. The resulting molding compos~tion is used with unmodified and allyl - glycidyl modified carbon fibers to prepare composite NOL rings as described in Examples 3-10. The resulting composite ~O~ rings :-, 20 are tested for short beam shear strength. The results are shown -in Table I.
The results in Table I show the improved adhesion, as meas-ured by short beam shear s~trength, between carbon fibers and un-saturated matrix resins when allyl glycidyl ether or glycidyl~ ;~
acrylate is used as a coupling ayen-t.
", " -. "
''' ;' '' " '',:
~ :
: :.- .~ :. .
' ~
- .
~Z3~1 .
,~
Table I
Composite Short Beam Shear Ex. Carbon Fiber Matrix Resin System Stren,~th 3 Unmodified Unsaturated polyester 7~700 - 4 AGE modified (Ex. 1) ~ 11,870 Sized with unsaturated " 9,100 polyester 6 Sized with unsaturated ~' 11,200 polyester + AGE
7 AGE modified (Ex. 1) then " 10,600 ; sized with unsaturated -~ polyester ~-~
` 8 Unmodified Unsaturated polyester 10,300 containing 1% AGE
9 Unmodified Unsaturated polyester 10,600 containing 5% AGE
Glycidyl Acrylate Unsaturated polyester 10,715 Modified (Ex. 2) - , 11 Unmodified Poly(arylacetylene) ~ 6,070 fluidizer `''`' . .1 12 AGE modified (Ex. 1) " 9,400 ` 13 Unmodified " 6~620 j . .
14 AGE modified (Ex. 1) ~ 10,570 Carbon fibers employed in accordance with this invention must have a surface adhesionable or reactive with epoxide groups. To improve the ad-hesion between the carbon fiber surface and epoxide groups the carbon fiber .
, surface can be pretreated, for example, by electrolytic treatment or by I oxidation.
One method of employIng coupling agents is to apply the coupling agent onto the fiber prior to forming the composite. Processes for applica- -tion of coupling agent to carbon fiber, and carbon fibers modified with the coupling agent are the subject of our above-mentioned application Serial No.
-~ 252,762. The coupling agent is generally applied to the fiber in the form of ~ 7 ... ...
9239~
a solution in a sllitable solvent followed by removal of the solvent by air drying or by heating to effect evAporation. Examples of suitable solvents are benzene, polar solvents, such as halogenated hydrocarbons, for example, methylene chloride and ethylene dichloride~ diacetone alcohol, ketones and esters. However, if the coupling agent is liquid, no solvent is necessary and the coupling agent can be applied directly onto the fiber.
The concentration of the coupling agent in the solvent, if one is used, is usually in the range of about 0.5 to about 5.0~ preferably about 1.0 to about 3.0% by weight, based on the total weight of the solution. The `~
solution can be applied to the fiber by known methods, for example, by drawing the fiber ~hrough a bath containing the solution or by spraying the solution ontothefïber.
The amount of coupling agent applied to the fiber surface is~
from about 0.05 to about 10.0% by weight, based on the weight of the fiber, and is~*~ preferably from about 0.5 to about 3.0%.
~, ~
To protect the surface modified carbon fiber of this invention from abrasion during subsequent handling, a size can be applied to the carbon ~iber.
The size can be applied from the same solution as the coupling agent or it can be applied after the carbon fiber has been modified with the coupling agent.
The size selected for application to the carbon fiber will be one compatible with the unsaturated matrix resin to be used in preparing the finàl composite.
An alternate method of employing the coupling agent in accordance ;`~
with this invention is to incorporate the unsaturated epoxide into the un~
saturated matrix resin system to be used in preparing the composite. The coupling agent is ~ used in an amount from about 1 to about 5% by ;
weight, based on the weight of the matrix resin system.
Composites of carbon fibers and unsaturated matrix resins can be prepared by any of the known methods. For example, carbon fibers can be used to prepare filament wound composites. In another common method, the composite æ39~
is prepared by incorporating chopped carbon fibers into the matrix resin and then forming the composite, for example, by press molding.
Any type of unsaturated polymer can be used as the matrix resin to prepare composites in accordance with this invention. Illustrative examples of these polymers are polybutadiene-1,2; polybutadiene-1,4; styrene--~butadiene copolymers; butyl rubber ' , ' :`''~ ~
'~ :
'~
.' ~ ` ., ., '`', '` ', .
0~,..
:!
. ~, ~ .
,~,',.;; ~ ~', . :, . .
: , . :~
` - 8a -~38Z3~L f : (polyis~butylene--isoprene copolymers)i natural rubber; polyester resins such as, for example, maleate containing polyesters and polyacrylate esters; butadiene--acrylonitrile copolymers; ethylene--propylene--dicyclopentadiene terpolymers; polychloroprene; polyiso-prene; alkyd resins, such as for example, tall oil alkyd resins;
and polyether copolymers and terpolymers containing at least one - unsaturated epoxide constituent such as, for example, propylene oxide--allyl glycidyl ether copolymers and ethylene oxide--epi-chlorohydrin--allyl glycidyl ether terpolymers. Poly(arylacetyl-10 ene)-fluidizer thermosetting molding compositions are also suit-able matrix resin systems.
Illustrative examples of unsaturated polyesters are poly-esters prepared from polyhydric alcohols and unsaturated polycar-boxylic acids or their anhydrides, optionally along with saturated ;;
polycarboxylic acids by methods well known in the art. These polyesters generally have a molecular weight of 500 to 3000 and an acid number and a hydroxyl number in each case of 2~ to S0.
Examples of polyhydric alcohols which can be employed in preparation of unsaturated polyesters are ethylene glycol, pro-20 pane-1,2-diol, propane-1,3-diol, butane-1,4-diol, butene-1,4-diol, dimethylpropane-1,3-diol, diethyleneglycol, dipropyleneglycol, `~
dimethylolcyclohexane and bis-(hydroxyethyl)- or bis-~hydroxy-propyl)diphenylolmethane or -propane. Examples of unsaturated ~ ;~
carboxylic acids are maleic acid, fumaric acid, itaconic acid and the like. Examples of saturated (i.e., free from aliphatic multi-ple bonds) polycarboxylic acids are phthalic acid, isophthallc acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, aæelaic acid, suberic acid and cyclohexanedicarboxylic acid and their existing anhydrides~ The saturated dicarboxylic acids are 30 generally used in a proportion of 0 to 90; preferably 0 to 70 moI
percent.
The unsaturated polyesters are usually employed along with - copolymerizable monomers when used as a matrix resin for preparing ; ~ composites. The ratio of monomer to polyester is usually in the ` - 9_ .
~23~
r~nge of 30:70 to 90:10. Examples of suitable monomers include styrene~
vinyltoluene, alkylstyrenes, such as alpha-methyl- or tert-butylstyrene, diallyl phthalate, divinylbenzene~ and esters of methacrylic or acrylic acid.
In one embodiment of the invention the unsaturated matrix resin is a poly(arylacetylene) matrix resin system. A preferred poly(arylacetylene~
matrix resin system comprises (1) a prepolymer of at least one pol~vacetylen-ically substituted aromatic compound~ said prepolymer having a number average --. , ; molecular weight from about 900 to about 12~000~ a ratio of aromatic protons to olefinic protons greater than about 2.4 and containing from about 5 to about 20% acetylenic groups by weight of the prepolymer~ with (2) from about 2 to about 200~o by weight of the prepolymer of at least one aromatic organic compound containing at least two six-membered aromatic rings~ said rings being condensed with each other or coupled with each other directl~ or through a methylene, dimethylmethylene, ethylene or vinylene group, said compound or mixtures thereof containing no crystalline organic phase at 220 C., having a viscosity of less than 20 cen~ipoises at 220 C. and containing no more than
5% of material volatile at 240 C.l Preferably the prepolymer comprises a polymer~ a diethynylben=ene, for example a copolymer of a diethynylbenzene and diphenylbutadiyne or a copolymer of a diethynylbenzene and phenylacetylene.
A~preferred aromatic organic compound is anthracene. Another preferred aromatic organic compound is the complex miixture of high boiling aromatic compounds , ;:, . .
present in high boiling fractions of coal tar pitch. -Examples of poly(arylacetylene) matrix resin systems are the thermo- ~
- ~
- setting molding compositions described in U.S. patent 3,882,073, May 6, 1975, to L. C. Cessna.
, ,', ' - .
,-......................................................................... ..
,,., ' .-~-, '''
A~preferred aromatic organic compound is anthracene. Another preferred aromatic organic compound is the complex miixture of high boiling aromatic compounds , ;:, . .
present in high boiling fractions of coal tar pitch. -Examples of poly(arylacetylene) matrix resin systems are the thermo- ~
- ~
- setting molding compositions described in U.S. patent 3,882,073, May 6, 1975, to L. C. Cessna.
, ,', ' - .
,-......................................................................... ..
,,., ' .-~-, '''
Claims (34)
1. A composite structure which is a cured admixture compri-sing (a) carbon fibers, (b) an unsaturated matrix resin and (c) an unsaturated epoxide bifunctional coupling agent having the general structural formula:
wherein X is a radical selected from the group consisting of where n = 1-10; and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon atoms, and R is an unsaturated radical selected from the group consisting of (a) ethylenically unsaturated C2-C4 ali-phatic radicals, (b) an aryl radical containing an ethylenically unsaturated C2-C4 aliphatic substituent, (c) the alpha-terpinyl radical, (d) the gamma-terpinyl radical and (e) the abietyl radi-cal.
wherein X is a radical selected from the group consisting of where n = 1-10; and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon atoms, and R is an unsaturated radical selected from the group consisting of (a) ethylenically unsaturated C2-C4 ali-phatic radicals, (b) an aryl radical containing an ethylenically unsaturated C2-C4 aliphatic substituent, (c) the alpha-terpinyl radical, (d) the gamma-terpinyl radical and (e) the abietyl radi-cal.
2. The composite structure of claim 1 wherein said bifunc-tional coupling agent is an unsaturated glycidyl ether.
3. The composite structure of claim 2 wherein said bifunc-tional coupling agent is allyl glycidyl ether.
4. The composite structure of claim 1 wherein said bifunc-tional coupling agent is an unsaturated glycidyl ester.
5. The composite structure of claim 4 wherein said bifunc-tional coupling agent is glycidyl acrylate.
6. The composite structure of claim 1 wherein said unsatu-rated matrix resin is an unsaturated polyester resin.
7. The composite structure of claim 6 wherein said unsatu-rated polyester resin is a styrene modified unsaturated polyester derived from isophthalic acid, maleic anhydride and propylene glycol.
8. A composite structure which is a cured admixture compri-sing (a) carbon fibers, (b) poly(arylacetylene) matrix resin system and (c) an unsaturated epoxide bifunctional coupling agent having the general structural formula:
wherein X is a radical selected from the group consisting of -(CH2)n-O-, where n =1-10; and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon atoms, and R is an ethylenically unsaturated radical.
wherein X is a radical selected from the group consisting of -(CH2)n-O-, where n =1-10; and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon atoms, and R is an ethylenically unsaturated radical.
9. The composite structure of claim 8 wherein said poly-(arylacetylene) matrix resin system comprises (1) a prepolymer of at least one polyacetylenically substituted aromatic compound, said prepolymer having a number average molecular weight from about 900 to about 12,000, a ratio of aromatic protons to olefinic protons greater than about 2.4 and containing from about 5 to about 20% acetylenic groups by weight of the prepolymer, with (2) from about 2 to about 200% by weight of the prepolymer of at least one aromatic organic compound containing at least two six-membered axomatic rings, said rings being condensed with each other or coupled with each other directly or through a methylene, dimethylmethylene, ethylene or vinylene group, said compound or mixtures thereof containing no crystalline organic phase at 220°C., having a viscosity of less than 20 centipoises at 220°C. and con-taining no more than 5% of material volatile at 240°C.
10. The composite structure of claim 9 wherein the prepoly-mer comprises a polymer of a diethynylbenzene.
11. The composite structure ofclaim 10 wherein the polymer of a diethynylbenzene is a copolymer of a diethynylbenzene and diphenylbutadiyne.
12. The composite structure of claim 10 wherein the poly-mer of a diethynylbenzene is a copolymer of a diethynylbenzene and phenylacetylene.
13. The cornposite structure of claiin 10 wherein the aroma-tic organic compound is anthracene.
14. The composite structure of claim 10 wherein the aroma-tic organic compound is the complex mixture of high boiling aro-matic compounds present in high boiling fractions of coal tar pitch.
15. The composite structure of claim 8 wherein said bifunc-tional coupling agent is an unsaturated glycidyl ether.
16. The composite structure of claim 15 wherein said bi-functional coupling agent is allyl glycidyl ether.
17. The composite structure of claim 8 wherein said bi-functional coupling agent is an unsaturated glycidyl ester.
18. The composite structure of claim 17 wherein said bi-functional coupling agent is glycidyl acrylate.
19. A process of improving the adhesion between carbon fibers and an ethylenically unsaturated matrix resin in a carbon fiber reinforced composite structure comprising incorporating into a mix-ture of said matrix resin and carbon fibers, an unsatu-rated epoxide bifunctional coupling agent having the general structural formula:
wherein X is a radical selected from the group consisting of -(CH2)n- O - , where n =1-10;
and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon atoms, and R is an unsaturated radical selected from the group consisting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an aryl radical containing an ethyleni-cally unsaturated C2-C4 aliphatic substituent, (c) the alpha-terpinyl radical, (d) the gamma-terpinyl radical, (e) the abietyl radical, and curing the resulting mixture.
wherein X is a radical selected from the group consisting of -(CH2)n- O - , where n =1-10;
and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon atoms, and R is an unsaturated radical selected from the group consisting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an aryl radical containing an ethyleni-cally unsaturated C2-C4 aliphatic substituent, (c) the alpha-terpinyl radical, (d) the gamma-terpinyl radical, (e) the abietyl radical, and curing the resulting mixture.
20. The process of claim 19 wherein said coupling agent is incorporated in an amount of from about 1 to about 5% by weight based on the weight of the matrix resin.
21. The process of claim 20 wherein said bifunctional coupling agent is an unsaturated glycidyl ether.
22. The process of claim 21 wherein said bifunctional coupling agent is allyl glycidyl ether.
23. The process of claim 20 wherein said bifunctional coupling agent is an unsaturated glycidyl ester.
24. The process of claim 23 wherein said bifunctional coupling agent is glycidyl acrylate.
25. The process of claim 20 wherein said unsaturated matrix resin is an unsaturated polyester resin.
26. The process of claim 25 wherein said unsaturated polyester resin is a styrene modified unsaturated polyester derived from isophthalic acid, maleic anhydride and propylene glycol.
27. A process of improving the adhesion between carbon fibers and an ethylenically unsaturated matrix resin in a carbon fiber reinforced composite structure comprising (1) modifying the surface of said carbon fibers by treat-ment thereof with an unsaturated epoxide bifunctional coupling agent having the general structural formula:
wherein X is a radical selected from the group consisting of -(CH2)n-O-, where n = 1-10;
and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon atoms, and R is an unsaturated radical selected from the group consis-ting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an aryl radical containing an ethylenically unsaturated C2-C4 aliphatic substituent, (c) the alpha-terpinyl radical, (d) gamma-terpinyl radical and (e) the abietyl radical, (2) admixing the surface modified carbon fibers and an ethylenically unsaturated matrix resin, and (3) curing the resulting admix-ture.
wherein X is a radical selected from the group consisting of -(CH2)n-O-, where n = 1-10;
and divalent alkyl, aryl, aralkyl and alkaryl radicals containing up to 20 carbon atoms, and R is an unsaturated radical selected from the group consis-ting of (a) ethylenically unsaturated C2-C4 aliphatic radicals, (b) an aryl radical containing an ethylenically unsaturated C2-C4 aliphatic substituent, (c) the alpha-terpinyl radical, (d) gamma-terpinyl radical and (e) the abietyl radical, (2) admixing the surface modified carbon fibers and an ethylenically unsaturated matrix resin, and (3) curing the resulting admix-ture.
28. The process of claim 27 wherein said bifunctional coupling agent is an unsaturated glycidyl ether.
29. The process of claim 28 wherein said bifunctional coupling agent is allyl glycidyl ether.
30. The process of claim 27 wherein said bifunctional coupling agent is an unsaturated glycidyl ester.
31. The process of claim 30 wherein said bifunctional coupling agent is glycidyl acrylate.
32. The process of claim 27 wherein said unsaturated matrix resin is an unsaturated polyester resin.
33. The process of claim 32 wherein said unsaturated polyester resin is a styrene modified unsaturated polyester derived from isophthalic acid, maleic anhydride and propylene glycol.
34. The process of claim 27 wherein the amount of coupling agent modi-fying the carbon fiber is from 0.05 to 10.0% by weight based on the weight of the fiber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA314,058A CA1082391A (en) | 1975-05-23 | 1978-10-24 | Unsaturated epoxides as coupling agents for carbon fibers and unsaturated matrix resins |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/580,501 US4163003A (en) | 1975-05-23 | 1975-05-23 | Unsaturated epoxides as coupling agents for carbon fibers and unsaturated matrix resins |
| US580,501 | 1975-05-23 | ||
| CA252,762A CA1073282A (en) | 1975-05-23 | 1976-05-18 | Unsaturated epoxides as coupling agents for carbon fibers and unsaturated matrix resins |
| CA314,058A CA1082391A (en) | 1975-05-23 | 1978-10-24 | Unsaturated epoxides as coupling agents for carbon fibers and unsaturated matrix resins |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1082391A true CA1082391A (en) | 1980-07-22 |
Family
ID=27164486
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA314,058A Expired CA1082391A (en) | 1975-05-23 | 1978-10-24 | Unsaturated epoxides as coupling agents for carbon fibers and unsaturated matrix resins |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1082391A (en) |
-
1978
- 1978-10-24 CA CA314,058A patent/CA1082391A/en not_active Expired
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