U.S. patent application number 12/975478 was filed with the patent office on 2011-06-30 for epoxy compositions and surfacing films therefrom.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to David T. Amos, Scott A. Boyd, Dmitriy Salnikov.
Application Number | 20110159266 12/975478 |
Document ID | / |
Family ID | 44168313 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110159266 |
Kind Code |
A1 |
Boyd; Scott A. ; et
al. |
June 30, 2011 |
EPOXY COMPOSITIONS AND SURFACING FILMS THEREFROM
Abstract
A composition is provided comprising: a) a curable epoxy resin;
and b) 0.01-30% by weight of a polycarbodiimide according to
Formula I: ##STR00001## wherein n is an integer between 0 and 100,
and wherein each R is independently selected from aromatic and
aliphatic groups which contain between 1 and 24 carbons and which
are optionally substituted, typically comprising 0.1-20% by weight
of the polycarbodiimide. In some embodiments the present disclosure
provides sheet materials made of such cured, uncured or partially
cured materials. In some embodiments these compositions may be
useful in making surfacing films for composite parts and may
demonstrate good paint stripper resistance and microcrack
resistance.
Inventors: |
Boyd; Scott A.; (White Bear
Lake, MN) ; Salnikov; Dmitriy; (Woodbury, MN)
; Amos; David T.; (St. Paul, MN) |
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
44168313 |
Appl. No.: |
12/975478 |
Filed: |
December 22, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61290719 |
Dec 29, 2009 |
|
|
|
Current U.S.
Class: |
428/220 ;
525/452 |
Current CPC
Class: |
C08L 63/00 20130101;
C08G 59/4021 20130101; C08L 79/00 20130101; C08G 59/4042 20130101;
C08L 63/00 20130101; C08L 2666/20 20130101 |
Class at
Publication: |
428/220 ;
525/452 |
International
Class: |
C08L 63/00 20060101
C08L063/00; B32B 27/38 20060101 B32B027/38 |
Claims
1. A composition comprising: a) a curable epoxy resin; and b)
0.01-30% by weight of a polycarbodiimide according to Formula I:
##STR00006## wherein n is an integer between 0 and 100, and wherein
each R is independently selected from aromatic and aliphatic groups
which contain between 1 and 24 carbons and which are optionally
substituted.
2. The composition according to claim 1 comprising 0.1-20% by
weight of said polycarbodiimide.
3. The composition according to claim 1 comprising 0.1-10% by
weight of said polycarbodiimide.
4. The composition according to claim 1 comprising 0.5-5% by weight
of said polycarbodiimide.
5. The composition according to claim 1 comprising 1-3% by weight
of said polycarbodiimide.
6. The composition according to claim 1 wherein n is at least
1.
7. The composition according to claim 1 wherein n is at least
2.
8. The composition according to claim 1 wherein R contains between
3 and 12 carbons.
9. The composition according to claim 1 wherein all R groups are
aromatic.
10. The composition according to claim 1 wherein all R groups are
selected from the group consisting of phenyl, toluoyl, phenylene
and methyl-phenylene.
11. The composition according to claim 1 which is partially
cured.
12. A cured composition obtained by curing the composition
according to claim 1.
13. A composite part comprising the cured composition of claim
12.
14. A composite part having an outermost surface comprising the
cured composition of claim 12.
15. The composition according to claim 1 which is a sheet having a
thickness of less than 0.5 mm.
16. The composition according to claim 11 which is a sheet having a
thickness of less than 0.5 mm.
17. The composition according to claim 1 which is a solution or
suspension in solvent.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/290,719, filed Dec. 29, 2009, the disclosure of
which is incorporated by reference herein in its entirety.
FIELD OF THE DISCLOSURE
[0002] This disclosure relates to epoxy compositions including
polycarbodiimide species, in particular epoxy compositions useful
in making surfacing films with good paint stripper resistance and
micro crack resistance.
SUMMARY OF THE DISCLOSURE
[0003] Briefly, the present disclosure provides a composition
comprising: a) a curable epoxy resin; and b) 0.01-30% by weight of
a polycarbodiimide according to Formula I:
##STR00002##
wherein n is an integer between 0 and 100, and wherein each R is
independently selected from aromatic and aliphatic groups which
contain between 1 and 24 carbons and which are optionally
substituted. The composition typically comprises 0.1-20% by weight
of the polycarbodiimide and may in some embodiments comprise
0.1-10% by weight of the polycarbodiimide, in some embodiments
0.5-5% by weight of the polycarbodiimide, and in some embodiments
1-3% by weight of the polycarbodiimide. In some embodiments n is at
least 1. In some embodiments n is at least 2. In some embodiments,
R contains between 3 and 12 carbons. In some embodiments all R
groups are aromatic. In some embodiments all R groups are phenyl or
phenylene. In some embodiments the present disclosure provides
compositions which are the composition described above being
partially cured or fully cured. In some embodiments the present
disclosure provides sheet materials made of such cured, uncured or
partially cured materials. In some embodiments the present
disclosure provides composite parts comprising the cured
composition. In some embodiments the present disclosure provides
composite parts having an outermost surface comprising the cured
composition.
[0004] In this application, "substituted" means, for a chemical
species, group or moiety, substituted by conventional substituents
which do not interfere with the desired product or process, e.g.,
substituents can be alkyl, alkoxy, aryl, phenyl, halo (F, Cl, Br,
I), cyano, nitro, etc.
DETAILED DESCRIPTION
[0005] The present disclosure provides epoxy compositions which, in
some embodiments, may be used to form surfacing films demonstrating
increased resistance to paint strippers.
[0006] The present disclosure provides uncured epoxy compositions
and cured epoxy compositions that resulting from the cure of the
uncured epoxy compositions provided herein. The uncured epoxy
composition may include any suitable epoxide resin, including
epoxide monomers or epoxide prepolymers, and any suitable hardener,
typically an amine hardener. In some embodiments, the uncured epoxy
composition may include any suitable crosslinker, in addition to
those described below. In some embodiments, the uncured epoxy
composition includes no crosslinker other than those described
below.
[0007] In some embodiments, the uncured epoxy composition includes
a carbodiimide species, which is typically a polycarbodiimide
species. Typically, the polycarbodiimide species is isocyanate
capped, more typically, the isocyanate capped polycarbodiimide
species is according to Formula I:
##STR00003##
wherein n is an integer, typically between 0 and 100, more
typically between 1 and 20, which may vary or may be a single
value; and where each R is independently selected from aromatic and
aliphatic groups which may optionally be substituted and which
typically contain between 1 and 24 carbons, more typically between
3 and 12 carbons. In some embodiments, all R groups are aromatic.
In some embodiments, all R groups are phenyl or phenylene. In some
embodiments, the isocyanate capped polycarbodiimide species is a
phenyl isocyanate capped toluene diisocyanate polycarbodiimide.
[0008] In some embodiments, the uncured epoxy composition includes
an oxazolidone ring-containing epoxy resin. In some embodiments,
the uncured epoxy composition includes both an oxazolidone
ring-containing epoxy resin and a polycarbodiimide species as
described above.
[0009] In some embodiments, uncured or cured epoxy compositions
according to the present disclosure may additionally comprise
fillers, pigments, carbon particles, or carbon nanotube
materials.
[0010] In some embodiments, uncured epoxy compositions according to
the present invention may be formed into films by any suitable
method. In some embodiments, such films may be used as surfacing
films. In some embodiments, such films may be used as surfacing
films in the manufacture of fiber-matrix composite parts.
Typically, such a surfacing film is cured during cure of the
composite matrix, and becomes a cured-in component of the composite
part forming the outer surface of the composite part.
[0011] In some embodiments, such films may be used to form a
multi-layered construct with polyvinylidene fluoride (PVDF) films,
which may in some embodiments be used as surfacing films. In some
embodiments, such films may be used in applications such as and
including those described in U.S. patent application Ser. Nos.
12/761,162, 12/761,212, 12/625,002, 12/637,879 and 12/637,915, the
disclosures of which are incorporated herein by reference.
[0012] In some embodiments, epoxy compositions according to the
present invention may be used as curable adhesives.
[0013] In some embodiments, epoxy compositions according to the
present invention may be used as matrix materials in prepregs or in
fiber-matrix composite parts
[0014] Objects and advantages of this disclosure are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this disclosure.
EXAMPLES
[0015] Unless otherwise noted, all reagents were obtained or are
available from Aldrich Chemical Co., Milwaukee, Wis., or may be
synthesized by known methods.
The following abbreviations are used to describe the examples:
[0016] .degree. F.: Degrees Fahrenheit
[0017] .degree. C.: Degrees Centigrade
[0018] rpm: Revolutions per minute
[0019] mil: 10.sup.-3 inches
[0020] .mu.-inch: 10.sup.-6 inches
[0021] .mu.m: micrometers
[0022] mm: millimeters
[0023] cm: centimeters
[0024] kPa: kilopascals
[0025] psi: pounds per square inch
[0026] mg: milligrams
Test Methods:
[0027] Pencil Hardness. Gouge hardness of the test surface was
measured according to ASTM D3363-05. Hardness was reported for the
hardest pencil that left the test surface uncut for a stroke length
of at least 3 mm, using pencils obtained from General Pencil
Company, Redwood City, Calif. Surface Roughness. Surface roughness
was measured with a portable surface profile gauge, model
"POCKETSURF", obtained from Mahr Federal, Inc., Providence, R.I.
The reported results were the average of 5 readings. Paint Stripper
Uptake. The test panel was weighed and an area of 4 cm by 5 cm was
marked. Four grams of a benzyl alcohol-based paint stripper, type
"CEE BEE E2012A", obtained from Cee Bee Aviation Products,
McGean-Rohco, Inc. Cleveland, Ohio, was brushed onto the test area.
After 24 hours at 70.degree. F. (21.1.degree. C.) the paint
stripper was manually scraped off the test area, and the panel then
rinsed with iso-propyl alcohol. After drying the panel for 60
minutes at 70.degree. F. (21.1.degree. C.) it was reweighed. The
increased weight of the test panel was reported as paint stripper
uptake. Panel Mark Off. The test panel was visually inspected
following the paint stripper uptake test. Any deterioration in
appearance was recorded accordingly. Micro Crack Testing. Micro
crack testing was performed on primed and painted test panels. The
primer was CA 7501 two part fluid resistance gray applied as a
single light coat. The paint was 8800 three part white topcoat,
applied to the primed panel in two coats. The paint and primer are
available from PRC Desoto, Sylmar, Calif. Mixing and drying were
performed as per manufacturer's instructions. Micro crack testing
was conducted in a thermal shock chamber, a two chamber oven with a
shuttle that can be moved between the two chambers. One chamber was
set at -54.degree. C. (-65.degree. F.) and the other at 49.degree.
C. (120.degree. F.). The shuttle is programmed to sit in each
chamber for 10 minutes before moving back to the other chamber.
Samples were placed on a rack which was loaded onto the shuttle.
The samples were cycled between the two chambers between 3000 and
4000 cycles. The panels were inspected for micro cracks using an
optical microscope at a magnification of 16.times.. A known area is
inspected and the cracks per linear cm were calculated. Zero cracks
observed after all cycles were complete was rated a "pass", less
than or equal to 0.25 cracks per linear cm was rated a "marginal
pass", and greater than 0.25 cracks per linear cm was rated a
"fail".
Materials Used:
[0028] C-150 HP: Agglomerates of multi-walled carbon nanotubes,
available under the trade designation "BAYTUBES C-150 HP", from
Bayer MaterialScience AG, Leverkusen, Germany. CG-1400: A
micronized dicyandiamide, having an approximate amine equivalent
weight of 21 grams/equivalent, available under the trade
designation "AMICURE CG-1400", from Air Products and Chemicals
Incorporated, Allentown, Pa. DER 6508: A 2-functional epoxy resin
which has been chemically modified to allow the formulation of
highly crosslinked, heat-resistant systems having an approximate
epoxy equivalent weight of 400 grams/equivalent, available under
the trade designation "D.E.R. 6508" from Dow Chemical Company,
Midland, Mich. DEH-85: An unmodified phenolic hardener having an
active hydrogen equivalent weight of approximately 265
grams/equivalent, available under the trade designation "DEH-85",
from Dow Chemical Company, Midland, Mich. EP 7200: A modified
bisphenol-A epoxy resin with an approximate equivalent weight of
approximately 207.5 grams/equivalent, available under the trade
designation "EPALOY 7200", from CVC Specialty Chemicals Inc.,
Moorestown, N.J. Epon 826: A low viscosity liquid bisphenol A based
epoxy resin having an approximate equivalent weight of 182 650
grams/equivalent, available under the trade designation "EPON 826",
from Hexion Specialty Chemicals, Columbus, Ohio. EPON 1002F: A
bisphenol-A polyepoxide resin having a functionality of 2 and an
approximate epoxy equivalent weight of 650 grams/equivalent,
available under the trade designation "EPON 1002F", from Hexion
Specialty Chemicals, Columbus, Ohio. EPON 1004F: A bisphenol-A
polyepoxide resin having a functionality of 2 and an approximate
epoxide equivalent weight of 875 grams/equivalent, available under
the trade designation "EPON 1004F", from Hexion Specialty
Chemicals. F-1. A polyester anti-crater and flow additive,
available under the trade designation "Dynoadd F-1", from Dynea,
Helsinki, Finland. MEK: Methyl ethyl ketone. MX-120: A diglycidyl
ether of Bisphenol-A epoxy resin butadiene-acrylic co-polymer core
shell rubber having an approximate epoxy equivalent weight of 243
grams/equivalent, available under the trade designation "KANE ACE
MX-120", from Kaneka Texas Corporation, Pasadena, Tex. MY-720: A
tetra-functional liquid epoxy, having an approximate epoxy
equivalent weight of 125.5 grams/equivalent, available under the
trade designation "ARALDITE MY-720", from Huntsman Advanced
Materials America Incorporated, The Woodlands, Tex. PCDI 77.5%: A
phenyl isocyanate capped toluene diisocyanate polycarbodiimide,
having a 2:1 ratio by weight toluene diisocyanate:phenyl
isocyanate, at approximately 77.5% by weight in toluene, prepared
as follows: To a clean dry 3-liter flask under a nitrogen
atmosphere, 600 g of toluene diisocyanate, 205 g of phenyl
isocyanate, and 184 g of toluene were charged. The solution was
mixed, to which a catalyst premix of 7.7 grams of
3-methyl-1-phenyl-2-phospholene-1-oxide in 11.6 grams of toluene,
was then added. The batch slowly heated, for approximately 60
minutes, to 230.degree. F., then held at this temperature for 4
hours. Using infrared spectroscopy to confirm the isocyanate had
been consumed, the mixture was then cooled 75.degree. F.
##STR00004##
PCDI 40%: A phenyl isocyanate capped toluene diisocyanate
polycarbodiimide, having a 2:1 ratio by weight toluene
diisocyanate:phenyl isocyanate, at approximately 40% by weight in
toluene, prepared as follows: To a clean dry 2-liter flask under a
nitrogen atmosphere, 320 g of toluene diisocyanate, 109.4 g of
phenyl isocyanate, and 480 g of toluene were charged. The solution
was mixed, to which a catalyst premix of 1.84 grams of
3-methyl-1-phenyl-2-phospholene-1-oxide in 12.5 grams of toluene,
was then added. The batch was slowly heated, for approximately 60
minutes, to 230.degree. F., then held at this temperature for 3
hours. Using infrared spectroscopy to confirm the isocyanate had
been consumed, the mixture was then cooled 75.degree. F. PKHP: A
micronized phenoxy resin, having a number average molecular weight
(MN) 10,000-16,000, and a hydroxy equivalent weight 284
grams/equivalent, available under the trade designation "PAPHEN
PKHP-200", from Phenoxy Associates, Rock Hill, S.C. USA. R-960: A
rutile titanium dioxide pigment, available under the trade
designation "TI-PUR R-960", from E.I. du Pont de Nemours &
Company, Wilmington, Del. RA95: A high viscosity, Bisphenol A epoxy
resin modified butadeine-acrylonitrile elastomer having an
approximate epoxy equivalent weight of 202.5 grams/equivalent,
available under the trade designation "Hypox RA95" from CVC
Specialty Chemicals Inc., Moorestown, N.J. SU-2.5: A bisphenol-A
polyepoxide resin having a functionality of 2.5 and an approximate
epoxy equivalent weight of 190 grams/equivalent, available under
the trade designation "EPON SU-2.5", from Hexion Specialty
Chemicals. SU-8: A bisphenol-A polyepoxide resin having a
functionality of 8 and an approximate epoxy equivalent weight of
212.5 grams/equivalent, available under the trade designation "EPON
SU-8", from Hexion Specialty Chemicals. U-52: An aromatic
substituted urea (4,4'-methylene bis(phenyl dimethyl urea), having
an approximate amine equivalent weight of 170 grams/equivalent,
available under the trade designation "OMICURE U-52", from CVC
Specialty Chemicals Incorporated. VYG: A copper-phthalocyanine
pigment, available under the trade designation "VYNAMON GREEN
600734", from Heucotech Ltd., Fairless Hills, Pa. XAC-4151: An
oxazolidone ring containing epoxy, having an approximate epoxy
equivalent weight of 420 grams/equivalent, available under the
trade designation "XAC-4151", from Asahi Kasei, Kanto, Japan.
##STR00005##
AF 191U: A thermosetting modified epoxy structural adhesive film,
having a base weight of approximately 0.05 pounds per square foot
(lbs/ft.sup.2) (244.2 grams per square centimeter (g/cm.sup.2)),
available under the trade designation "SCOTCH-WELD STRUCTURAL
ADHESIVE FILM, 0.05", from 3M Company, St. Paul, Minn. SM 905M: A
composite surfacing film, having a base weight of 0.020
lbs/ft.sup.2 (171 g/cm.sup.2), available under the trade
designation "SURFACE MASTER 905M", from Cytec Engineered Materials,
Inc., Tempe, Ariz.
Preparation of Resin Compositions:
[0029] Comparatives and Examples were prepared as described below,
according to the compositions listed in Tables 1 and 2.
TABLE-US-00001 TABLE 1 Compo- Comparative Example Example Example
Example nent A 1 2 3 4 XAC- 19.15 0 18.05 16.60 16.16 4151 MX-120
19.15 18.05 18.05 16.60 16.16 SU-2.5 19.15 18.05 18.05 16.60 16.16
MY-720 15.32 2.89 2.89 2.66 2.59 CG-1400 6.85 3.77 3.77 3.47 3.38
U-52 0.38 0.20 0.20 0.18 0.18 EPON 0 18.05 0 0 0 1002F PCDI 0 24.4
24.40 22.45 21.85 77.5% VYG 0 0 0 1.53 0 R-960 0 0 0 4.78 7.69
C-150 HP 0 0 0 0 0.58 MEK 17.0 14.59 14.59 15.13 15.25 Toluene 3.0
0 0 0 0
TABLE-US-00002 TABLE 2 Component Example 5 Example 6 XAC4151 14.81
DER6508 19.41 SU-8 5.82 7.63 MX-120 16.05 21.25 MY-720 2.57 3.37
PCDI 77.5% 21.69 PCDI 40% 5.51 Epon 826 Milling 8.02 7.35 CG-1400
3.36 4.4 U-52 0.18 0.23 VYG 0.49 0.47 R-960 2.46 2.33 RA95 9.22
9.55 Epon 826 Letdown 1.06 F-1 0.69 0.75 MEK 14.65 16.46 Toluene
0.23
Comparative A
[0030] XAC-4151 was manually crushed with a pestle and mortar and
charged into a 200 gram capacity plastic cup designed for use in a
planetary mill, model "SPEED MIXER Model DA 400 FV", available from
Synergy Devices Limited, Buckinghamshire, United Kingdom. 85:15
MEK/toluene was added to the cup, which was then secured to the
mill and rotated at 2,200 rpm until the mixture was dissolved,
approximately 5 minutes. The cup was removed from the mill, to
which MX-120, SU-2.5 and MY-720 were added, and the mixing
continued for another 2 minutes at 2,200 rpm. The cup was again
removed from the mill and CG-1400 and U-52 were added. The mixture
was manually stirred to wet out the curatives and the cup returned
to the mill for another 2 minutes at 2,200 rpm, until all
components were homogeneously dispersed.
Example 1
[0031] Epon 1002F was manually crushed with a pestle and mortar and
charged into a 200 gram capacity plastic cup, to which MEK was
added. The cup was placed in the planetary mill, and mixed at 2,200
rpm until dissolved, approximately 5 minutes. The cup was removed
from the mill, to which MX-120, SU-2.5, MY-720 and PCDI were added,
and the mixing continued for another 2 minutes at 2,200 rpm. The
cup was again removed from the mill and CG-1400 and U-52 were
added. The mixture was manually stirred to wet out the curatives
and the cup returned to the mill for another 2 minutes at 2,200
rpm, until all components were homogeneously dispersed.
Example 2
[0032] The process as described in Example 1 was repeated according
to the composition listed in Table 1, wherein the Epon 1002F was
replaced with XAC-4151.
Example 3
[0033] R-960, VYG and SU-2.5 were charged into a 200 gram capacity
plastic cup. The cup was placed in the planetary mill, and mixed at
2,200 rpm for 2 minutes. The mixture was then milled in a
three-roll paint mill for three passes and set aside. XAC-4151 was
manually crushed with a pestle and mortar and added to a planetary
mill cup, followed by MEK, and mixed in the planetary mill at 2,200
rpm until dissolved, approximately 5 minutes. The cup was removed
from the mill, to which the R-960, VYG and SU-2.5 from the
three-roll paint mill, followed by MX-120, MY-720 and PCDI were
added. The mixture was returned to the planetary mill, and the
mixing continued for another 2 minutes at 2,200 rpm. The cup was
removed from the planetary mill and CG-1400 and U-52 were added.
The mixture was manually stirred to wet out the curatives and the
cup returned to the planetary mill for another 2 minutes at 2,200
rpm, until all components were homogeneously dispersed.
Example 4
[0034] Example 3 was repeated, wherein the VYG was replaced with
CNT.
Example 5
[0035] R-960, VYG, CG-1400, U-52 and Epon 826 were charged into a
200 gram capacity plastic cup. The cup was placed in the planetary
mill, and mixed at 2,200 rpm for 2 minutes. The mixture was then
milled in a three-roll paint mill for three passes and set aside.
XAC4151 and SU-8 were manually crushed with a pestle and mortar and
added to a planetary mill cup, followed by MEK, and mixed in the
planetary mill at 2,200 rpm until dissolved, approximately 10
minutes. The cup was removed from the mill, to which the R-960,
VYG, CG-1400, U-52 and Epon 826 from the three-roll paint mill,
followed by MX-120, MY-720, F-1, RA-95 and PCDI 77.5% were added.
The mixture was returned to the planetary mill, and the mixing
continued for another 2 minutes at 2,200 rpm. The mixture was
manually stirred to scrape the sides of the cup and returned to the
planetary mill for another 2 minutes at 2,200 rpm, until all
components were homogeneously dispersed.
Example 6
[0036] R-960, VYG, CG-1400, U-52 and Epon 826 were charged into a
200 gram capacity plastic cup. The cup was placed in the planetary
mill, and mixed at 2,200 rpm for 2 minutes. The mixture was then
milled in a three-roll paint mill for three passes and set aside.
DER 6508 and SU-8 were manually crushed with a pestle and mortar
and added to a planetary mill cup, followed by MEK, and mixed in
the planetary mill at 2,200 rpm until dissolved, approximately 10
minutes. The cup was removed from the mill, to which the R-960,
VYG, CG-1400, U-52 and Epon 826 from the three-roll paint mill,
followed by MX-120, MY-720, F-1, RA-95, remaining Epon 826, toluene
and PCDI 40% were added. The mixture was returned to the planetary
mill, and the mixing continued for another 2 minutes at 2,200 rpm.
The mixture was manually stirred to scrape the sides of the cup and
returned to the planetary mill for another 2 minutes at 2,200 rpm,
until all components were homogeneously dispersed.
Preparation of Composite Panels:
[0037] Within one hour of preparation the resin compositions were
notch bar coated onto a bleached silicone coated release liner,
product #"23210 76# BL KFT H/HP 4D/6 MH" Loparex, Inc., Iowa City,
Iowa, at a bar gap of 6 mil (152.4 .mu.m). The coated liner was
then allowed to dry for at least 1 hour at about 70.degree. F.
(21.1.degree. C.).
[0038] Coupons of the dried polymeric composites Comparative A,
Examples 1-7, plus adhesive structural film 905M (designated
Comparative B), and composite surfacing film AF 191U (designated
Comparative C), were prepared as follows. Each surfacing film was
trimmed to 12-inch by 12-inch (30.4 by 30.4 cm) sections and
applied to a layup tool.
[0039] One ply of pre-impregnated graphite fabric, followed by
additional plies of unidirectional pre-impregnated grade 190
graphite tape, orientated at 0/+45/+90/-45/0/0/-45/90/+45/0
degrees. The layup was placed in a vacuum bag with surfacing film
directly against the tool surface which was then positioned in an
autoclave. A full vacuum of about 28 inches mercury (94.8 kPa) was
applied at approximately 72.degree. F. (22.degree. C.) for 10 to 15
minutes after which the external pressure was gradually increased
to 55 psi (397 kPa). The vacuum bag was kept under full vacuum (28
inches of Hg) for the duration of the cure cycle, and the
temperature was raised at 5.degree. F. per minute (2.8.degree. C.
per minute) up to 350.degree. F. (177.degree. C.) and held at this
temperature for 2 hours. The cured polymeric composite article with
surfacing approximately 72.degree. F. (22.degree. C.) temperature,
at which point the pressure was released, and the cured article
having an approximate thickness of 0.045 inches (0.114 mm) was
removed from the autoclave and vacuum bag.
[0040] Each coupon was measured for pencil hardness, gloss, surface
roughness, panel mark off and paint stripper uptake. In addition,
coupons corresponding to Examples 5 and 6 were tested for
microcrack resistance. Results are listed in Table 3.
TABLE-US-00003 TABLE 3 Test Data Pencil Hardness Surface Paint 24
Hours, Roughness Panel Stripper .DELTA. Change .mu.-inch (.mu.m)
Mark Uptake in pencil 24 Off (mg/cm.sup.2) Micro Sample Initial
hardness Initial Hours 24 Hours 24 Hours Crack Comparative A 4H B6
15.3 39.7 No 1.98 (0.39) (1.01) Comparative B 6H H5 30.6 90.0 Yes
2.46 (0.78) (2.29) Example 1 4H 3H1 19.5 26.8 No 1.53 (0.50) (0.68)
Example 2 4H 4H0 15.7 15.0 No 1.97 (0.40) (0.38) Example 3 4H 4H0
15.0 18.3 No 0.44 (0.38) (0.47) Example 4 4H 4H0 15.8 17.2 No 0.96
(0.40) (0.44) Example 5 6H 6H0 38 39.6 No 0.23 Fail (0.97) (1.01)
Example 6 6H 6H0 29.2 32.4 No 0325 Pass (0.74) (0.82)
[0041] The Examples according to the present disclosure showed
better resistance to degradation in various tests when challenged
with paint stripper. Example 6 additionally demonstrated good micro
crack resistance. This additional characteristic is believed to be
result from limiting the amount of PCDI to an amount in the range
of 0.5-5% or more specifically between 1% and 3%.
[0042] Various modifications and alterations of this disclosure
will become apparent to those skilled in the art without departing
from the scope and principles of this disclosure, and it should be
understood that this disclosure is not to be unduly limited to the
illustrative embodiments set forth hereinabove.
* * * * *