AND POLYMERIC MATERIALS
Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 2, pp. 301−306.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © D.A. Belov, S.Yu. Stefanovich, M.Yu. Yablokova, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 2, pp. 305−310.
Curing of a Network Polyimide Modiﬁ ed
with a Linear Component
D. A. Belov, S. Yu. Stefanovich, and M. Yu. Yablokova
Lomonosov Moscow State University, Moscow, Russia
Received August 6, 2010
Abstract—The curing and relaxation processes in polymeric composites based on blends of network and linear
polyimides applied onto a ﬁ ller were studied by dielectric spectroscopy. The sensitivity of dielectric spectroscopy
to processes occurring in the course of curing was examined.
Heat-resistant polymeric composite materials
(PCMs) based on polyimides are widely used in various
branches of engineering and technology, in particular,
as advanced structural materials exhibiting enhanced
heat resistance and high strength. The matrices of
such PCMs are, as a rule, network polyimides .
Modiﬁ cation of the rigid polyimide matrix of PCM with
a linear polyimide allows the required mechanical and
electrophysical characteristics of PCMs to be attained
without deterioration of the heat resistance [1–3].
Thermal, mechanical, and dielectric characteristics of
such compounds are often nonmonotonic functions
of their composition, which was attributed in  by
changes in the composite material nanostructure.
Because PCM curing is accompanied by changes
in both amount and mobility of various polar groups,
dielectric spectroscopy allows real-time monitoring of
changes that occur in the polymeric matrix in the course
of curing. Such approach is widely used in studying
curing of epoxy resins [4–6].
In this study we examined by dielectric spectroscopy
the curing of PCMs based on a network polyimide I
modiﬁ ed with a linear polyimide II.
As monomers for preparing a network polyimide
we used 3,3',4,4'-benzophenonetetracarboxylic acid
dianhydride (mp 224–226°C, Aldrich), endic anhydride
(5-norbornene-2,3-dixarboxylic acid anhydride, mp
165–167°C, Aldrich), and 4,4'-diaminodiphenylmethane
(mp 92°C, Aldrich). The network polyimide I was
synthesized by the known procedure [7–9] with
preparation of di- and monoethyl esters, followed by
application onto the ﬁ ller (Scheme 1).
As linear component we used polyamido acid
derived from 4,4'-oxydiphthalic dianhydride and
4,4'-(1,3-phenylenedioxy)dianiline as 20% solution
in dimethylformamide of PILK grade, TU (Technical
Speciﬁ cation) 6-05-211–1992 (Scheme 2).
PCM samples were prepared by vacuum
forming of prepregs based on KT 11-30 glass
fabric [TURB (Technical Speciﬁ cation of Belarus
Republic) 05780 349-040–2000] impregnated with
the preliminarily prepared mixtures of solutions of
3,3',4,4'-benzophenonetetracarboxylic acid mono- and
diesters, endic anhydride, and diaminodiphenylmethane
with polyamido acid II (linear component content 0, 3,
5, 10, and 15 wt %).
The real and imaginary parts of the complex
dielectric permittivity and the dielectric loss angle were
measured for all the PCM samples in the temperature
range 80–400°С and frequency range from 0.1 Hz to
3 MHz with a Novocontrol Beta-N impedance analyzer