1
HIGH TEMPERATURE POLYIMIDE MATRIX
COMPOSITES
Tsuyoshi Ozaki, Composites Research and Development
Koji Moriuchi and Shinichi Sakane, IST Corporation
Satoshi Uehara and Takashi Yokoyama, Super Resin Inc.
2
Fiber reinforced plastic matrix composites
Very attractive materials
＊ Light-weight structures
＊ Especially for aerospace applications
Some of the aerospace parts such as engine components
require high heat resistance of more than 200 ℃.
3
Polyimide resin as high temperature matrix
Epoxy
Bismaleimide
5250-4, 5270-1 Less than 230 ℃
SKYBONDⓇⓇ 700, 703, 705
PMR-15 More than 300 ℃
Very attractive matrix for high temperature composites
High heat resistance
Polyimide
Less than 200 ℃
4
Major disadvantage of polyimide matrix resin
＊ The difficulty in polyimide curing process
＊ Imidization and curing happened simultaneously.
⇒ High voids of more than 3 %
⇒ Derade the mechanical and thermal performance
SolventSolvent
ImpregnationImpregnation LaminationLaminationHeatHeat
DryingDrying CuringCuring
HeatHeat
WaterWaterSolventSolvent
ImpregnationImpregnation LaminationLaminationHeatHeat
DryingDrying CuringCuring
HeatHeat
WaterWater
(Imidization)
5
IST’ｓ SKYBONDⓇⓇ 8000 and SKYBONDⓇⓇ 800
IST has developed new polyimide resins to solve the problem.
2 solutions are proposed.
（１） SKYBONDⓇⓇ 8000 for RTM (Resin Transfer Molding)
Citraconic endcapped imide oligomer
（２） SKYBONDⓇⓇ 800 for two stage autoclave process
Citraconic endcapped amic acid oligomer
N NR’ RR
OO
n
O O
N N
O OO O
N NR’ RR
OO
n
O O
N N
OO OOO O
N NR’ RR
O
O
O
O
OH
OO
HO
n
O O
OH
N N
HO
N NR’ RR
O
O
O
O
OH
OO
HO
n
O O
OH
N N
HO
SKYBONDⓇⓇ 8000 for RTM
6
7
Resin Transfer Molding (SKYBONDⓇⓇ 8000)
SKYBONDⓇⓇ 8000 (Citraconic endcapped imide oligomer )
(1) Solvent free (imidized powder)
(3) Can be cured at >300 C
without volatiles
(2) Low melt viscosity (of less than 1.0 Pa･s)
N NR’ RR
OO
n
O O
N N
O OO O
m
N NR’ RR
OO
n
O O
N N
OO OOO O
m
N NR’ RR
OO
n
O O
N N
O OO O
N NR’ RR
OO
n
O O
N N
OO OOO O
0 100 200 300 400
1E+1
1E+2
1E+3
1E+4
1E+5
1E+6
Temperature (℃)
Vi
sc
os
ity
(
P)
0 100 200 300 400
1E+1
1E+2
1E+3
1E+4
1E+5
1E+6
Temperature (℃)
0 100 200 300 400
1E+1
1E+2
1E+3
1E+4
1E+5
1E+6
0 100 200 300 400
1E+1
1E+2
1E+3
1E+4
1E+5
1E+6
0 100 200 300 400
1E+1
1E+2
1E+3
1E+4
1E+5
1E+6
Temperature (℃)
Vi
sc
os
ity
(
P)
Temperature Scan with 10℃/minFig.1
1.0 Pa･s
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SKYBONDⓇⓇ 8000 molding & cure condition
Carbon Fabric 1) G30(0/90)n
Volume Fraction 48-50 %
Injection Temp. 240 ℃
Cure Temp. 335 ℃
200
250
300
350
0 100 200 300 400
335 ℃ x 4 h cure
Ramp Step 1 C/min
Injection & Hold Step
Time (min)
Te
m
p.
(℃
)
Table 1. Molding condition
Fig.1 Cure cycle
1) Desized at 400 C for 1hr
1.40 (0.29)48.5 (0.45)50.1 (0.38)40.7 (0.39)1.50 (0.00)Ave. (Std. Dev.)
1.648.849.741.01.503
1.648.050.440.31.502
1.148.850.240.81.51Sample1
Voids (%)Resin Volume (%)Vf (%)Resin (wt%)Density (g/cc)
1.40 (0.29)48.5 (0.45)50.1 (0.38)40.7 (0.39)1.50 (0.00)Ave. (Std. Dev.)
1.648.849.741.01.503
1.648.050.440.31.502
1.148.850.240.81.51Sample1
Voids (%)Resin Volume (%)Vf (%)Resin (wt%)Density (g/cc)
Fig.4 Microscopy of Cross Section
Fig.3 Ultrasonic C-scan-
Poor
Good
Small amount of voids
compared with conventional polyimide composites
ASTM D3171
Table 2. Summary of the Acid Digestion
Void content of SKYBONDⓇⓇ 8000 RTM FRP
9
Calculated void content by digestion method
10
Flexural Strength of SKYBONDⓇⓇ 8000 FRP
0
20
40
60
80
100
120
Stress
Modulus
R
et
en
tio
n
R
at
e
(%
)
23℃ 180℃ 200℃ 220℃ 230℃ 240℃ 250℃
Stress 856.4 MPa
Modulus 48.1 MPa
n = 5 error bar = σ
Test Temp. (℃)
0
20
40
60
80
100
120
Stress
Modulus
R
et
en
tio
n
R
at
e
(%
)
23℃ 180℃ 200℃ 220℃ 230℃ 240℃ 250℃
Stress 856.4 MPa
Modulus 48.1 GPa
n = 5 error bar = σ
Fig.5 Flexural strength of SKYBONDⓇⓇ 8000
Test Temp. (℃)
> 60 %
Only a small reduction
Good retention
SKYBONDⓇⓇ 800 for two stage autoclave process
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12
Two stage cure autoclave process
Conventional
Imidization stage and curing stage would overlap.
Imidization stage Curing stage
1st 1st -- StageStage 2nd 2nd -- StageStage
Cure laminatesCure laminatesRemove volatiles Remove volatiles
(solvent/water)(solvent/water)
Two stage cure for autoclave process
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SKYBONDⓇⓇ 800 for two stage autoclave process
SkybondⓇⓇ 800 (Citraconic endcapped amic acid oligomer)
N NR’ RR
O
O
O
O
OH
OO
HO
n
O O
OH
N N
HO
N NR’ RR
O
O
O
O
OH
OO
HO
n
O O
OH
N N
HO
150 ℃ to 220 ℃
1st :Imidization stage
Imidization was completely
separated from curing stage
Laminates can be cured
without influence of water
N NR’ RR
OO
n
O O
N N
O OO O
N NR’ RR
OO
n
O O
N N
OO OOO O
N NR’ RR
OO
n
O O
N N
O OO O
m
N NR’ RR
OO
n
O O
N N
OO OOO O
m
> 300 ℃
2nd : Curing stage
Very unique resin for molding of composite laminates
having such a ‘two-stage’ cure cycle.
with NMP solvent
DSC (Differential scanning calorimetric analysis) of SKYBONDⓇⓇ 800
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Fig.6 DSC thermograms of SKYBONDⓇⓇ 800 powder after it is dried
Metho d: imidization
dt 1 .0 0 s
30 .0 -40 0 .0°C 3 .00 °C/min
Synchro nizatio n enabled
Sa mple: SK8 00 PAA powder.., 9 .0 4 00 mg
Co ntent 12 .0 8e+0 3 %
no rma lized -12 0 .76 J g^-1
Onset 13 4 .17 °C
Pea k 16 2 .63 °C
Left L imit 11 0 .34 °C
Rig ht L imit 23 2 .81 °C
m W
0
5
10
m in
°C50 100 150 200 250 300 350
0 20 40 60 80 100
^ e x o
S T A R e S W 9 . 2 0L a b : M E T T L E R
Imidization
Crosslink
Endothermic
220 ℃
335 ℃165 ℃
Temperature
H
ea
t f
lo
w
Exothermic
Imidization ratio of SKYBONDⓇⓇ 800
15
Table 3 Imidization ratio of SKYBONDⓇ 800
Conditions 1)
Ratio 2)
1376 cm-1
/1500 cm-1
Imidization
ratio
(%)
150 ℃ -1 hr 0.740 0
150 ℃ -1 hr, 220 ℃ -30 min 1.000 71
150 ℃ -1 hr, 220℃ -1 hr 1.036 81
150 ℃ -1 hr, 220℃ -2 hrs 1.080 93
150 ℃ -1 hr, 220 ℃ -1 hr and 335 ℃ -4hr 1.106 100
1) Atmospheric pressure
2) 1376 cm-1: C-N streching of imide group
2) 1500 cm-1: C-N streching of para-benzene group
Tg of SKYBONDⓇⓇ 800 neat resin
16
Fig.7 DMA of SKYBONDⓇⓇ 800 neat resin
2 stage cured film
296 ℃
Tensile properties of SKYBONDⓇⓇ 800 neat resin
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Table 4 Tensile properties of SKYBONDⓇ 800 neat resin
Properties 23 ℃ 250 ℃ Measurement
Tensile strength 96 MPa 52 MPa ASTM D638
Tensile modulus 2.6 GPa 1.5 GPa ASTM D638
Elongation 5.6% 4.8% ASTM D638
Help to make the composite tougher than other brittle resin matrix like BMI.
About 5% elongation
SKYBONDⓇⓇ 800 FRP with two stage cure process
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0
100
200
300
400
500
600
0 2 4 6 8 10 12
Time (hrs)
Te
m
pe
ra
tu
re
(
℃
)
-12
-8
-4
0
4
8
12
P
re
ss
ur
e
(k
gf
/c
m
2 )
Pressure : 1
