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Esterification of viscose fibres with aqueous solutions of orthophosphoric acid and urea at different ratios of components was investigated. It was shown that in phosphorylation of cellulose with these solutions, onesubstituted cellulose phosphates are formed and a side process of formation of cellulose carbamates takes place together with accumulation of phosphate groups. A decrease was found in the mechanical strength of the phosphorylated cellulose preparations and the degree was a function of the concentration of orthophosphoric acid and urea as the phosphorylating solution. Phosphorus-containing viscose fibres (up to 0.5 mmole/g of phosphate groups) obtained in solutions of orthophosphoric acid and urea with a 0.25-0.63 and 3.33-4.17 M concentration have the most satisfactory mechanical properties and stability in phosphate buffer with pH 7.5.Phosphorylation of cellulose in an aqueous solution of orthophosphoric acid in the presence of urea is the simplest and most industrially acceptable method of giving it additional biological activity [1]. Cellulose phosphate is biocompatible with human tissues, is resorbed with no inflammatory reaction, and neither it nor the products of biodegradation have any toxic effect on the body. The physicochemical properties of highly substituted cellulose phosphate are characterized relatively completely in the literature [1], which served as the basis for using it as a sorbent for stabilization of donor blood. At the same time, there is almost no information on the use of phosphorylated cellulose for obtaining resorbable surgical sutures. Moreover, the following are also necessary for successfully using cellulose phosphate in surgery in addition to these properties: sufficiently high dry and wet mechanical strength and knot strength; a rate of reduction in strength commensurate with wound healing times.The lack of a detailed study of the effect of the conditions of fabricating phosphorus-containing cellulose fibres on their physicomechanical properties and the shortage of quality resorbable materials make the study of esterification of cellulose by orthophosphoric acid pressing.We investigated the effect of the conditions of phosphorylation of viscose cord fibres on the physicochemical and mechanical properties of the cellulose phosphates obtained. Viscose cord fibre (Khimvolokno IA, Svetlogorsk) with a linear density of 184 tex was used as the initial material.Esterification of viscose fibre with orthophosphoric acid was conducted with the method in [1], improved to attain the maximum mechanical strength. Viscose fibres were placed in phosphorylating mixtures of different composition heated to 353±2 K (the bath ratio varied from 1:5 to 1:20 g/ml) and held in them for 30 min. The excess solution was then wrung out of the samples to 100% weight gain, dried to the air-dried state, and treated with heat in a thermostat at 418±2 K for 1

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