Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 11, pp. 1920−1923.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © I.N. Burmistrov, A.S. Leshchenko, L.G. Panova, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 11, pp. 1834−1837.
AND POLYMERIC MATERIALS
Study of Cross-Linking Parameters
of Polyacrylic Acid Hydrogels
I. N. Burmistrov, A. S. Leshchenko, and L. G. Panova
Engels Technological Institute, Branch of Saratov State Technical University, Engels, Saratov oblast, Russia
Received February 18, 2011
Abstract—Swelling of modiﬁ ed polyacrylic acid hydrogels under conditions of a photoinitiated polymerization
of acrylic acid to give a sealing hydrogel for ﬁ reproof multiple glazing units was studied. Mechanisms by which
crosslinks are formed in the gel are suggested and the possibility of controlling the degrees of swelling and cross-
linking is discussed.
Polyacrylic acid (PAA) hydrogels attract particular
researchers’ attention because of having an extremely
broad range of applications, including that as ﬁ re-
protecting layers in ﬁ reproof multiple glazing units [1,
2]. Effective application of PAA hydrogels in various
ﬁ elds requires knowledge of the structure of these gels.
There have been studies devoted to synthesis of PA
cross-linked with various cross-linking agents [3, 4]. It
has been shown that a chemical hydrogel is formed in
the course of a photoinitiated polymerization of acrylic
acid in aqueous solutions [2, 5].
The goal of this study was to examine the main
synthesis parameters and structural properties of PAA
hydrogels used as sealing formulations in ﬁ reproof
multiple glazing units.
The gels under study were produced by photoinitiated
polymerization of acrylic acid in an aqueous solution
with addition of polyvinyl alcohol (PVA), phosphoric
acid (PA), and acid magnesium phosphates obtained
by dissolution of magnesium in PA. The formulation
was polymerized with UV light from TUFT80 lamps
in the presence of a photoinitiator (2,2-dimethyloxy-
2-phenylacetophenone) in a multiple glazing unit with
inner size of 40 × 60 × 1 mm, fabricated from 4-mm-
thick silicate glass.
The average power density of the UV irradiation
installation is 400 ± 25 mW m
; inside the multiple
glazing unit it decreases to 290 ± 25 mW m
resulting gel has a high elasticity, and, therefore, it can
be suggested that macromolecules in the polymers are
packed comparatively loosely and the degree of cross-
linking is low. The swelling of the gel under study was
regarded as one-way diffusion of solvent molecules into
the PAA+PVA copolymer. The swelling was evaluated
by the degree of swelling, α, and swelling constant k.
The degree of swelling was determined as follows:
a 30 × 20 × 1 mm sample of a gel polymerizate was
weighed on a balance (with an accuracy of 0.01 g) and
placed in a weighing bottle ﬁ lled with distilled water. At
certain intervals of time, a sample was extracted from
the weighing bottle with pincers and, after its surface
was dried, was weighed. This procedure was repeated
to constant mass, which corresponds to the maximum
equilibrium degree of swelling. The degree of swelling
(%) was found using the formula :
m – m
α = –——— × 100, (1)
where m is the mass of the swollen gel (g), and m
before swelling (g).
The swelling constant for an interval of time t, k
was calculated by the formula