Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 1, pp. 76−82.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © I.A. Novakov, D.V. Pyl’nov, M.A. Vaniev, A.V. Nistratov, V.P. Medvedev, E.V. Petrosyan, 2013, published in Zhurnal Prikladnoi
Khimii, 2013, Vol. 86, No. 1, pp. 82−88.
AND POLYMERIC MATERIALS
Rheokinetic Features of the Initial Steps of Curing
of Oligodiene–Urethane Prepolymer with a Hydroxyl-Containing
Curing Agent at Equimolecular Ratio of the Reactive Groups
I. A. Novakov, D. V. Pyl’nov, M. A. Vaniev, A. V. Nistratov, V. P. Medvedev, and E. V. Petrosyan
Volgograd State Technical University, Volgograd, Russia
“Limited Liability Company LKM-Group,” Lipetsk, Russia
Received August 29, 2012
Abstract—Rheokinetic studies of curing of oligodiene–urethane prepolymer with a hydroxyl-containing cur-
ing agent at the molar ratio NCO/OH = 1.0 were performed. In the initial step of curing, catalyltic formation of
polydiene–urethane follows a second-order equation, whereas the urethane formation step is adequately described
by a kinetic equation with an autoacceleration effect.
Polyurethanes based on cold-curable oligomeric
compounds are widely used for production of sealing
materials and of sports, rooﬁ ng, and waterprooﬁ ng
coatings [1, 2]. Formation of the 3D structure in
polyurethane curing is a complex multistep process
[1–5]. The chemistry of polyurethane formation was
examined in numerous studies [2–4]. At the same
time, changes in rheological properties in the course
of polyurethane formation are studied poorly. The
initial steps can be reliably monitored by rotation
viscometry, with measuring variation of the viscosity in
time at a given temperature. Rheokinetic studies allow
determination of characteristic steps and periods of
formation of the 3D structure in the course of curing
of polyurethane compounds and, correspondingly,
evaluation of the process parameters.
Formation of 3D network structure in synthesis of
polyurethanes (PUs) from oligomers occurs in two steps.
First, the viscosity slightly increases owing to chain
lengthening and formation of branching points, with the
reaction mass remaining ﬂ uid; then, in the critical point
(gel point) when a continuous 3D network of chemical
bonds is formed, the ﬂ uidity is lost. From the viewpoint
of processability evaluation, the ﬁ rst step when the
compound remains processable is of most interest [6–9].
In this study we examined the rheokinetic features of
the initial steps of catalytic (“cold”) curing of polydiene–
urethane compounds at various temperatures.
The experiments were performed with Krasol NN23
isocyanate polybutadiene prepolymer, a macrodiisocya-
nate derived from Krasol LBH-3000 oligobutadienediol
and 4,4'-diphenylmethane diisocyanate with terminal
NCO groups (4.5 wt % content). The prepolymer con-
tained oil viscosity modiﬁ er [10, 11]. The structural for-
mula of the prepolymer is as follows: