Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 11, pp. 1726−1731.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © N.K. Luneva, E.A. Tel’puk, A.V. Onufreichuk, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 11, pp. 1818−1824.
AND POLYMERIC MATERIALS
Esteriﬁ cation with Orthophosphoric Acid of Cellulose Samples
with Different Extents of Structural Heterogeneity
N. K. Luneva, E. A. Tel’puk, and A. V. Onufreichuk
Institute of General and Inorganic Chemistry, National Academy of Sciences of Belarus, Minsk, Belarus
Received May 12, 2012
Abstract—Modiﬁ cation of cellulose samples with different extents of structural heterogeneity by esteriﬁ ca-
tion with orthophosphoric acid in the temperature range 140–160°С was studied. The reaction yielded cellulose
phosphates containing 3.2–6.0 wt % P, with the ion-exchange capacity of 2.2–3.0 mg-equiv g
. Introduction of
phosphorus into cellulose leads to a slight decrease in the structural heterogeneity. The polymer with the lower
ordering index is characterized by the higher phosphorus content, which suggests that the reaction mainly occurs
in the amorphous part of the polymer.
Cellulose phosphorylation is a route to materials
characterized by decreased combustibility and by
cation-exchange properties. In preparation of cellulose
phosphate by both direct and indirect phosphorylation
procedures, even with triple repetition of the process,
the phosphorus content of the fabric usually does not
exceed 4.0 wt % .
Introduction of phosphorus into cellulose requires
heating of cellulose ﬁ bers impregnated with phosphoric
acid solutions containing nitrogen compounds to no less
than 100°С. Heating above 100°С leads to a decrease
in the strength characteristics of the polymer taken for
modiﬁ cation. It was shown previously that the intensity
of cellulose esteriﬁ cation also depends on the modiﬁ er
composition, namely, on the degree of condensation of
phosphoric acid [2, 3].
As found in [4, 5], cellulose phosphorylation occurs
in the presence of nitrogen-containing compounds (urea,
pyridine, cyanurates, etc.). Some authors believe that
nitrogen-containing compounds prevent the polymer
degradation via partial neutralization of phosphoric acid
with the ammonia formed in the course of modiﬁ cation.
Other authors suggest that the nitrogen-containing
compound forms a complex with phosphoric acid, with
this complex being an active species in the reaction with
the cellulose-containing material. Also, participation
of urea, pyridine, and cyanurates in cellulose swelling,
making the reactive hydroxy groups of the polymer
more accessible to the phosphorylating agent, cannot be
It was shown  that, in synthesis of inorganic
phosphates by heating of orthophosphoric acid in an
ammonia medium, the acid undergoes low-temperature
condensation (170–200°С) with the formation of
stronger polyphosphoric acids or their salts.
Cellulose phosphates are prepared by treatment
of fabric, yarns, ﬁ bers, or paper. Because cellulose
is insoluble in dilute phosphoric acid, the process is
a heterogeneous reaction, and its rate and extent are
determined by diffusion of the modifying reagents
inside the ﬁ ber.
It is known that cellulose exists in several crystal
modiﬁ cations and is characterized by different extents
of structural heterogeneity. Cellulose modiﬁ cation is
accompanied in some cases by its transition from one
structural form into another . Some modiﬁ cation
reactions occur only in amorphous regions of natural
cellulose, and other reactions can also involve crystalline
regions of cellulose. Hence, with the modiﬁ cation
conditions being the same, the amount of the phosphorus
introduced and the product properties can differ
depending on the extent of structural heterogeneity of