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Polymer International
Polym Int 48:1065±1067 (1999)
Rapid Report
Preparation of polyetherimide/carbon fibre
composites by a cataphoresis process
Houssain Qariouh, Rossitza Schué, Nabil Raklaoui and François Schué*
Université Montpellier II, Laboratoire de Chimie Macromoléculaire CC 009, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
Abstract: Preliminary results in this study show that it is possible to achieve a good Ultem 1000/carbon
®bres covering by means of electrophoretical deposition. The expected amount of deposited polymer is
well controlled and the deposited ®lms have a good appearance. In this way a variety of carbon ®bre
composite materials can be manufactured.
# 1999 Society of Chemical Industry
Keywords: polyimide; carbon ®bre; cataphoresis process; composites
INTRODUCTION
Cataphoretic electrodeposition is an excellent coating
technique, enabling the coating of an object of any
shape with a high quality ®lm in a single processing
step.1 The technique also obviates the need for organic
solvents, making it environmentally benign. The
application of this method to polyimides could
increase their utility considerably.2±5 In a previous
paper we described an optimized cataphoretic process
of deposition of polyetherimide on to aluminium and
steel surfaces.6 Because this process is suitable for all
conductive substrates, it can be applied to the
preparation of polyetherimide/carbon ®bre composites. Such materials may be produced as prepregs by electrodeposition followed by stacking a
number of them together to obtain thick pieces. This
publication reports the results of our initial investigations.
EXPERIMENTAL
80 g of polyetherimide Ultem 1000 (product of GEC
Plastics), 165.3 g of N-methylpyrrolidone and 20.6 g
acetophenone were charged in a reaction ¯ask. The
polymer was dissolved with stirring at approximately
85±90 °C under a blanket of nitrogen. When the
polymer was completely dissolved, a mixture of 18.9 g
N-methylpiperazine and 61.8 g acetophenone was
added over a period of 2 h. Vigourous stirring was
maintained throughout. The temperature was kept at
85±90 °C during the addition. After the addition was
complete, the mixture was stirred and warmed to
110 °C and held at that temperature for 2 h 30 min.
The resulting solution of modi®ed polymer was then
used to prepare the electrophoretic deposition emulsion as detailed below.
5.98 g of acetophenone and 1.48 g of 50% aqueous
lactic acid were added to 30 g of the modi®ed polymer
solution. The mixture was stirred vigorously while 78 g
of deionized water was added slowly. The stirred
mixture became quite viscous and then thinned out as
the addition of water was completed.
Solvents (N-methylpyrrolidinone, acetophenone)
and reagents (1-methylpiperazine, lactic acid) were
purchased from Aldrich Chemical Co without additional puri®cation. The ®laments used to braid the
carbon ®bre fabrics had a diameter of about 8 mm. All
electrodeposition experiments were carried out at
constant applied voltages using a Consort E425
apparatus. A multimeter with a data storage option
(Metrix) was used to monitor current decay.
The emulsion was placed in a constant temperature
bath at room temperature equipped with a Te¯on
stirbar and submersible magnetic stirrer. Carbon ®bre
fabric test pieces (60 mm 60 mm) were pretreated in
N-methylpyrrolidone and placed in the emulsion
together with an aluminium anode measuring
15 mm 15 mm. The distance between the cathode
and the anode was about 40 mm. The test piece was
removed, rinsed rapidly in deionized water and placed
in a warm (60 °C) dry chamber to evaporate solvents
from the ®lm. The coated fabrics were baked in several
steps in an oven (Eurotherm818P, Thermolyte) to
effect the reimidization reaction.
* Correspondence to: François Schué, Université Montpellier II, Laboratoire de Chimie Macromoléculaire CC 009, Place Eugène Bataillon,
34095 Montpellier Cedex 5, France
(Received 6 August 1999; accepted 12 August 1999)
# 1999 Society of Chemical Industry. Polym Int 0959±8103/99/$17.50
1065
H Qariouh et al
Anode:
2H2 O ! O"2 ‡ 4H‡ ‡ 4eÿ
4RCOOÿ ‡ 4H‡ ! 4RCOOH
Cathode:
4H2 O ‡ 4eÿ ! 2H"2 ‡ 4OHÿ
Figure 1. Current density and polymer yield at different voltages plotted
versus deposition time.
DEPOSITION MECHANISM
In aqueous emulsions, the passage of an electric
current results in the electrolysis of water and the
discharge of the various ionic species. The following
scheme shows such processes relevant to the system
under study:6
Because gas formation occurs during the coating
process, the coagulated (so called `wet') ®lm contains
some hydrogen which leads to bubbles and pinholes.
The successful use of this process depends on
Figure 2. SEM of the surface (a, c) and the cross-section (b, d) of non-coated carbon fibre fabric and coated carbon fibre fabric, respectively, at 68V and 240 s
deposition time.
1066
Polym Int 48:1065±1067 (1999)
Preparation of polyetherimide/carbon ®bre composites
minimizing both the amount and the effects of this
gassing.
®bre surface recovering due to a large number of
assembled ®laments in each ®bre.
SEM study
RESULTS AND DISCUSSION
Electrodeposition process
Clearly, it is important to verify that electrodeposition
occurs effectively with carbon ®bre. Thus, different
applied voltages (45, 68 and 80 V) and deposition
times were used. Figure 1 shows the evolution of the
current density and the polymer yield with deposition
time.
The current decay curves at various voltages can be
attributed to the insulating effect of the coating.
During deposition, a coherent layer of material is
formed on the cathode, the ®lm resistance leading to a
decrease in current to a limiting value (residual current
density) depending on the applied voltage. For
example, for voltages of 45 and 68 V, the residual
current was recorded to be 1 and 2.5 mA cmÿ2,
respectively. One may observe that the decrease is
very similar compared to E-coating systems previously
studied.6
Figure 1 shows also the yield of polymer deposited
on the cathode as a function of deposition time and
voltage (45, 68 and 80 V); electrodeposition of polyetherimide on carbon ®bres obeys Faraday's law. The
yield of polymer increases with increasing voltage and
grows linearly, even for very long deposition times.
The rate of deposition increases with increasing
voltage and takes values of 0.048, 0.066 and
0.098 mg cmÿ2 sÿ1 at 45, 68 and 80 V, respectively.
Usually, with classical E-coating systems, the deposition yield grows linearly for a given period before
tending towards a maximum. Here, with this system,
the saturation effect is observed after a longer deposition time than we expected (more than 15 min). This
difference could be attributed to a highly developed
Polym Int 48:1065±1067 (1999)
The deposited layer was studied in terms of its ability
to form a ®lm homogeneous in thickness and density
(hole free). Figure 2 shows the surfaces and crosssections of carbon ®bres before and after deposition.
Figure 2(c, d) shows perfect coverage of the surface by
the polymer and good penetration of the polymer
between the ®bres and ®laments. The imperfections,
such as craters, seen in the ®lm surface could mostly be
avoided by adjusting the electrical parameters. The
desired ®lm thickness could be obtained by choosing
the appropriate electrodeposition conditions; for
example, in Fig 2(d) the ®lm thickness is 55 mm which
was obtained at 68 V and 240 s deposition time.
CONCLUSIONS
The preliminary results in this study show that it is
possible to achieve a good Ultem 1000/carbon ®bre
covering by electrophoretic deposition. The expected
amount of deposited polymer is well controlled and
the deposited ®lms have a good appearance. In this
way a variety of carbon ®bre composite materials can
be manufactured.
REFERENCES
1 Mark HF, Bikales NM, Overberger CG, Menges G and
Kroschwitz JI, Encyclopedia of Polymer Science and Engineering,
2nd Edn, John Wiley and Sons, New York. Vol 3 p 675 (1985).
2 Buchwalter SL, Polym Mater Sci Eng, 59:61 (1988).
3 Uebner M and Ng K, J Appl Polym Sci 36:1525 (1988).
4 Alvino WM, Fuller TJ and Scala LC, J Appl Polym Sci 28:267
(1983).
5 Alvino WM and Scala LC, J Appl Polym Sci 27:341 (1982).
6 Qariouh H, Raklaoui N, Schue R, Schue F and Bailly C, Polym Int
48(11): (1999) (accepted).
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