A series of oxygen plasma resistant imide/arylene ether copolymers were prepared by reacting anhydride-terminated poly(amide acids) and amine-terminated polyarylene ethers containing phosphine oxide units. Inherent viscosities for these copolymers ranged from 0.42 to 0.80 dL/g. After curing, the resulting copolymers had glass transition temperatures ranging from 224 C to 228 C. Solution cast films of the block copolymers were tough and flexible with tensile strength, tensile moduli, and elongation at break up to 16.1 ksi, 439 ksi, and 23 percent, respectively at 25 C and 9.1 ksi, 308 ksi and 97 percent, respectively at 150 C. The copolymers show a significant improvement in resistance to oxygen plasma when compared to the commercial polyimide Kapton. The imide/arylene ether copolymers containing phosphine oxide units are suitable as coatings, films, adhesives, and composite matrices

Jensen, Brian J.

English

NASA Technical Reports Server

NASA Technical Memorandum 107712 /._ _ 7f_
Oxygen Plasma Resistant
Phosphine Oxide Containing
Imide/Arylene Ether Copolymers
Brian J. Jensen
January 1993
I¢/W 
National Aeronautics and
Space Adminstration
Langley Research Center
Hampton, Virginia 23681-0001
(NASA-TM-107712) OXYGEN PLASMA
RESISTANT PHOSPHINE OXIDE
CONTAINING IMIDE/ARYLENE COPOLYMERS
(NASA) 12 p
N93-20300
Unclas
03/27 01k6076
https://ntrs.nasa.gov/search.jsp?R=19930011111 2020-03-17T07:57:28+00:00Z

OXYGEN PLASMA RESISTANT PHOSPHINE OXIDE CONTAINING
IMIDE/ARYLENE ETHER COPOLYMERS
by
Brian J. Jensen
NASA Langley Research Center,
Hampton, VA 23665-5225
INTRODUCTION
As part of an effort to develop high performance structural resins for aerospace
applications, work has continued on block copolymers containing imide and arylene
ether segments. The copolymers reported herein represent an extension of previous
work 1-5 on these materials. The arylene ether block used in this study contains a
phosphine oxide unit in the polymer backbone while the imide block is a known
crystalline imide with excellent properties named LaRCTM-cPI 6 for Langley Research
Center Crystalline Polyimide.
A few copolymers containing an imide block and some other blocks have been
reported. Most notably, the copolymers containing imide and siloxane blocks have
received considerable attention 7-10 and more recently, polyimide-polyformal block
copoly.mers 11, triblock copolymers containing imide-aryl ether phenylquinoxaline
blocks 12 and imide-aryl ether ketone block copolymers 13 have been reported. The
preparation of amine-terminated sulfones by a method similar to that used herein has
been reported. 14 The incorporation of phosphorus into polymers is known to improve
fire resistance 15 and atomic oxygen resistance. 16 Recently poly(arylene ethers)
containing phenyl phosphine oxide (PPO) were shown to exhibit good weight retention
after exposure to simulated atomic oxygen.17,18
EXPERIMENTAL
Monomers - Bis(4-fluorophenyl)phenyl phosphine oxide (FPPO), (m.p. 123 °C) was
prepared following a known procedure. 19 2,2-Bis(4-hydroxyphenyl)hexafluoro-
propane (6AF) was obtained commercially and recrystallized twice from toluene to
yield a white solid (m.p.160-161 °C). 1,3-Bis(4-aminophenoxy-4'-benzoyl)benzene
(BABB) (m.p. 161.5-164 °C) was obtained from DayChem Laboratories, Inc. 3,3',4,4'-
Benzophenonetetracarboxylic dianhydride (BTDA) was obtained commercially and
vacuum sublimed to yield a white crystalline solid (m.p. 224-226 °C). 4- Aminophenol
was obtained commercially and vacuum sublimed to yield a white crystalline solid
(m.p. 185-187 °C).
Oligomers - The amine-terminated poly(arylene ethers) (ATAE) were synthesized as
shown in Eq. 1 by aromatic nucleophilic substitution of FPPO with 6AF and
4-aminophenol in N,N-dimethylacetamide (DMAc) using potassium carbonate. The
oligomers were prepared at two different calculated molecular weights (_n) by
adjusting the monomer ratio (6AF/DFBP) to 0.7825 and 0.8582 to provide I_ns of
2500 and 4000 g/mole, respectively. The anhydride-terminated polyamide acids
(ATAA) were prepared in DMAc as shown in Eq. 2 by adjusting the monomer ratio
(BABB/BTDA) to 0.821 and 0.906 to provide calculated Mns of 4000 and 8000 g/mole,
respectively.
- The copolymers were prepared by adding a solution of the ATAE in
DMAc to the ATAA solution and stirring overnight under nitrogen. For example, to
prepare ATAE 2500/ATAA 4000 block copolymer, BTDA (0.8056 g, 2.500 mmol) was
added to a solution of BABB (1.0273 g, 2.0524 mmol) and DMAc (10.4 g). The mixture
was stirred for 6 h to form a clear solution. A solution of ATPAE 2500 (1.1456 g,
0.4582 mmol) in DMAc (6.5 g) was added to the polyamide acid solution prepared
above to form a clear, viscous solution which was stirred overnight. These block
copolymers were then cast as a film on plate glass and dried lh each at 100, 200 and
300 °C to form a tough, creasible cyclodehydrated copolyimide film, ATAE 2500/ATI
4000. Alternatively, the copolymers were solution imidized by adding toluene to the
reaction mixture and heating to 155 °C overnight to collect a toluene/water azeotropic
mixture, providing an insoluble powder.
Characterization - Inherent viscosities (l]inh) were obtained on 0.5% solutions in
chloroform (CHCI3) at 25 °C for FPPO/6AF and in DMAc at 25 °C for the other
polymers and copolymers. Differential scanning calorimetry (DSC) was performed at a
heating rate of 20 °C/min with the apparent Tg taken at the inflection point of the AT
versus temperature curve.
Films - DMAc solutions (15% solids) of the polymers were centrifuged, the decantate
doctored onto plate glass and dried at room temperature to a tack-free form in a low
humidity chamber. The films on glass were dried 1 h each at 100, 200 and 300 °C.
Mechanical tests were performed as recommended in ASTM D882 on at least four
specimens per test condition.
Oxygen Plasma Asher ExDos_re- Simulated atomic oxygen exposures were preformed
on thin films (0.5 in x 0.5 in, ~2 mils thick) in a Tegal Plasmod Asher. The Asher was
operated at 500 millitorr, 100 Watts of radio frequency, 02 pressure of 3 psi and a flow
rate of 50 cm3/min. Since the Asher was not calibrated, simultaneous exposures of
Kapton® were preformed. Exposures were preformed for up to 15 h and the weight
loss of the films monitored as a function of exposure time.
RESULTS AND DISCUSSION
ATAEs with calculated Mns of 2500 and 4000 g/mole were prepared by
offsetting monomer stoichiometry. These oligomers had 1]inhSof 0.082 and 0.124 dL/g
and Tgs of 173 and 186 °C, respectively. When the oligomers were reacted with a
stoichiometric amount of BTDA, the TlinhSincreased to 0.95 and 0.87 dL/g and the Tgs
increased to 218 and 216 °C for the ATAE 2500/BTDA and ATAE 4000/BTDA,
respectively. The high 1]inhS obtained indicated that the calculated _nS were
essentially correct. The FPPO/6AF was prepared with an 1]inh of 0.86 dL/g and a Tg
of 213 °C while LaRC_-CPi has a Tg of 222 °C and a Tm of 350 °C.
Four different block copolymers were prepared as shown in Table I from the
ATAE and ATAA oligomers. The copolymers were prepared by reacting a
stoichiometric ratio of oligomers (using calculated Mns) producing polyamide acids
with l"iinhS ranging from 0.42 to 0.80 dL/g in DMAc. The cured copolyimide films were
characterized by DSC and results are shown in Table 1. Tgs range from 224 to 228
°C, slightly higher than the Tgs of either homopolymer. The ATAE 2500/ATI 8000 also
displayed a small endotherm in the DSC curve at 335 °C indicating the presence of
some crystallinity.
Tensile properties of the clear yellow-orange films of the copolymers and
homopolymers are shown in Table 2. The polyimide has higher strength and modulus
than the arylene ether as expected. The tensile strength and modulus of the
copolymers varied widely with tensile strength as high as 16.1 ksi and tensile modulus
as high as 439 ksi. Each of the films displayed properties intermediate to those of
FBB/BPF and LaRCTM-cPI homopolymers.
Results from the oxygen plasma exposure are shown in Fig. 1 which plots
weight loss of the films versus time of exposure. Each of the phosphine oxide
containing copolymers displays higher weight retention than the Kapton® for the same
exposure times and films with higher concentration of phosphine oxide display better
weight retention than films with lower concentrations.
CONCLUSIONS
A series of imide/arylene ether block copolymers were prepared containing
phosphine oxide. These copolymers displayed a relatively high modulus and high
resistance to oxygen plasma etching, a combination of properties needed for matrix
materials for certain applications of composites in space.
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REFERENCES
B. J. Jensen, P. M. Hergenrother and R. G. Bass, Proc. Polvm. Matl. Sci. and
_]g.., 60, 294 (1989).
B. J. Jensen, P. M. Hergenrother and R. G. Bass, _, 30(2), 132
(1989).
B. J. Jensen, P. M. Hergenrother and R. G. Bass, Ibid., 31(1), 618 (1990).
B. J. Jensen and D. C. Working, Ibid., 33(1), 1082 (1992).
B. J. Jensen and S. J. Havens, Ibid., 33(1), 1084 (1992).
P. M. Hergenrother, N. T. Wakelyn and S. J. Havens, J. Polym. Sci.. Polym.
Chem. Ed., 25, 1093 (1987).
F. F. Holub, U. S. Patent 3,325,450 (1967) (To General Electric).
W. A. Fessler, U. S. Patent 3,736,290 (1973) (To General Electric).
J. T. Hoback and F. F. Holub, U. S. Patent 3,740,305 (1973) (To General
Electric).
I. Yilgor, E. Yilgor, B. C. Johnson, J. Eberle, G. L. Wilkes and J. E. McGrath,
Polym. PreDr.. 24(2), 78 (1983).
M. M. Grade and J. W. Verbicky, Jr., J, Polym. Sci., Polym. Chem. Ed., 27, 1467
(1989).
12. J.L. Hedrick and J. W. Labadie, High Performance Pol,vmers, 2(1), 3 (1990).
13. J.L. Hedrick, W. Volksen and D. K. Mohanty, J, Polym. Sci.. Pol'vm. Chem. Ed.,
30, 2085 (1992).
14. J.H. Kawakami, G. T. Kwiatkowski, G. L. Brode and A. W. Debroin,
Polvm. Chem. Ed., 12, 565 (1974).
15. E. Weil in "Concise Encycl. of Polym. Sci. and Eng.," John Wiley & Sons, Inc.,
New York, 1990, p. 720.
16. L. L. Fewell, _ A.DDI. Polvm. Sci., 41,391 (1990).
17. C.D. Smith, H. J. Grubbs, H. F. Webster, J. P. Wightman and J. E. McGrath,
Polym. Matls. Sci. Eng. PreDr., 65,108 (1991).
18. J.G. Smith, J. W. Connell and P. M. Hergenrother, .P_..gJ.E]!_T..P,_L,33(2), 241
(1992).
19. C. D. Smith, A. Gungor, K. M. Keister, H. A. Marand and J. E. McGrath, Polym,
r.C.L_.P.L,32(1), 93 (1991).
TABLE 1. CHARACTERIZATION OF COPOLYMERS
Copolymer
ATAE 2500/ATI 4000
ATAE 2500/ATI 8000
ATAE 4000/ATI 4000
ATAE 4000/ATI 8000
Tlinh, dL/g,
(Polyamic acid)
0.80
0.42
0.42
0.58
Tg, °C,
by DSC
228
228
224
225
TABLE 2. THIN FILM PROPERTIES OF POLYMERS
AND COPOLYMERS.
POLYMER
ATAE 25OO/
ATI 4OOO
ATAE 2500/
ATI 8000
ATAE 4OOO/
ATI 4000
ATAE 4000/
ATI 8O0O
Imide
Homopolymer
Arylene Ether
Homopolymer
1Tested at 177°C.
TENSILE STRENGTH, KSI (TENSILE MODULUS,
KSI) [ELONGATION, %]
RT
14.7 (375)[23]
16.1 (439) [8.5]
10.8 (379)[3.7]
15 (412)[11.1]
22.0 (630)[8.3]
9.9 (280)[36]
150°C
8.8 (287)[43]
9.1 (299) [22]
6.4 (308)[2.5]
8.0 (250)[97]
15.2 (540) [2111
6.4 (260)[80]
E1 5 A Kapton®
m ATAE 2500 / ATI 8000
, ATAE 4000/AT! 8000
• ATAE 2500 1 AT, 4000 /_# ATAE 4000 AT! 4000
0 5 10 15
Time, Hours
Figure 1. Oxygen Plasma Etching of Phosphine
Oxide Containing Copolymers.
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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
January 1993 Technical Memorandum
,.,m
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
Oxygen Plasma Resistant Phosphine Oxide Containing
Imide/Arylene Ether Copolymers
6. AUTHOR(S)
Brian J. Jensen
7. PERFORMINGORGANIZATIONAME(S)AND ADDRESS(ES)
NASA Langley Research Center
Hampton, VA 23681-0001
9. SPONSORING / MONITORING AGENCY NAME(S)' A_ILD ADDRESS(ES) .
National Aeronautics and Space Administration
Washington, DC 20546-0001
506-43-11
8. PERFORMING ORGANIZATION
REPORT NUMBER
10. SPONSORING / MONITORING
AGENCY REPORT NUMBER
NASA TM-107712
11. SUPPLEMENTARY NOTES
Use of trade names or names of manufacturers in this report does not constitute an official
endorsement of such products or manufacturers either expressed or implied by the National
Aeronautics and Space Administration, Brian J. Jensen, or NASA Langley Research Center.
12a.DISTRIBUTION/ AVAILABILITYSTATEMENT
Unclassified-Unlimited
Subject Category 27
12b. DISTRIBUTION CODE
13. ABSTRACT (Maximum 200words)
A series of oxygen plasma resistant imide/arylene ether copolymers were prepared by reacting
anhydride-terminated poly(amide acids) and amine-terminated polyarylene ethers containing
phosphine oxide units. Inherent viscosities for these copolymers ranged from 0.42 to 0.80 dL/g.
After curing, the resulting copolymers had glass transition temperatures ranging from 224°C to
228°C. Solution cast films of the block copolymers were tough and flexible with tensile strength,
tensile moduli and elongation at break up to 16.1 ksi, 439 ksi and 23%, respectively at 25°C and
9.1 ksi, 308 ksi and 97%, respectively at 150°C. The copolymers show a significant improvement
in resistance to oxygen plasma when compared to the commercial polyimide Kapton ®. The
imide/arylene ether copolymers containing phosphine oxide units are suitable as coatings, films,
adhesives and composite matrices.
14. SUBJECT TERMS
Polyimides; Poly(arylene ether)s, Copolymers,
Phosphine oxide, Oxygen plasma
17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION
OF REPORT OF THIS PAGE
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OF ABSTRACT
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12
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Oxygen plasma resistant phosphine oxide containing imide/arylene copolymers

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