1070-4272/05/7805-0824C2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 5, 2005, pp. 824 !829. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5,
2005, pp. 840!845.
Original Russian Text Copyright C 2005 by Galimzyanova, Bakirova, Valuev, Zenitova.
AND POLYMERIC MATERIALS
Mechanism and Relationships of Chemical Degradation
of Rigid Polyurethane Foam
A. R. Galimzyanova, I. N. Bakirova, V. I. Valuev, and L. A. Zenitova
Kazan State Technological University, Kazan, Republic Tatarstan, Russia
Lebedev Research Institute of Synthetic Rubber, Federal State Unitary Enterprise, St. Petersburg, Russia
Received July 9, 2004; in final for, February 2005
Abstract-The regular trends in chemical degradation of rigid polyurethane foam under the action of oxy-
propylated hydroxy compounds were studied. The molecular-weight characteristics, functionality with respect
to 4,4`-diphenylmethane diisocyanate and OH groups, viscosity, and the content of terminal OH groups
of alcoholysis products at temperatures from 150 to 220oC were determined. A mechanism of degradation
of the network structure of rigid polyurethane foam was suggested.
Owing to a unique combination of low thermal
conductivity, low density, and high manufacturability
rigid polyurethane foams (PUFs) are widely used in
various branches of industry. An increase in their
production volume estimated in 2003 at 2000000 tons
results in accumulation of large amounts of wastes
which are environmental pollutants. At the same time,
a decrease in the natural resources and, as a result, rise
of their price dictates the need of using secondary
raw materials. The most promising solution of the
above environmental and economic problem is chemi-
cal degradation of wastes from PUF production by
The aim of this study was to reveal regular trends
in the alcoholysis of rigid PUFs and to establish the
mechanism of their chemical degradation.
Experiments were performed with wastes from
production of rigid PUF assigned for thermal insula-
tion of refrigerating equipment. Foam plastic was
prepared by the reaction of a hydroxy component with
polyisocyanate (PIC) derived from 4,4`-diphenylmeth-
ane diisocyanate (MDI).
As a degradation agent (DA) we used oxyprop-
ylated hydroxy compound Laprol-564
polyether based on propylene oxide with a molecular
weight M of approximately 500 and f
= 4. The
weight ratio PUF : DA was 40 : 60 and was chosen
Produced by the Nizhnekamskneftekhim Joint-Stock Co.
experimentally based on evaluation of the maximum
amount of wastes and minimum amount of DA.
Alcoholysis was carried out in the range 1503
220oC. The instant of addition of PUF crumb was
considered as the onset of degradation. Preliminary
milled PUF was continuously added into DA at a stir-
ring rate of 300 rpm. With increasing degradation
, the monitored time interval decreased
from 30 to 7 h. The alcoholysis products were ana-
lyzed starting from the instant of system homogeni-
The molecular-weight parameters were determined
by gel permeation chromatography (GPC) with a
chromatographic modular high-performance system
designed from units produced by Waters-244. Chro-
matographing was carried out with Styrogel columns
with the pore size of 10
, 500, and 100 A; the solvent
was freshly distilled tetrahydrofuran (THF) prepuri-
fied to remove peroxy compounds; the concentration
of sample solutions at the inlet of the chromatograph
was 0.130.3 wt %. Detection was carried out with a
refractometer and a photometer in parallel, which al-
lowed determination of the polymer concentration at
the outlet (refractometer) and the concentration of
aromatic rings (photometer). The operating UV wave-
length of the photometer was 255 nm.
The content of hydroxy groups c
in the alcohol-
ysis products was determined by the acetylation meth-
od according to GOST (State Standard) 25261-82.
The dynamic viscosity of the alcoholysis products
(Pa s) was determined on a Hoeppler rheovis-