Transformations of polymers and copolymers of acrylonitrile during heterogeneous saponification

Abstract

The kinetic and thermodynamic specific features of the process of heterogeneous alkaline saponification of the copolymer of acrylonitrile (92.2%), methyl acrylate (6.3%), and sodium monoithaconate (1.5%) were investigated. Chemical and infrared spectroscopic methods reveal that the saponification of the nitrile groups of copolymer of acrylonitrile proceeds faster to yield amide groups and then slower to yield carboxylate groups. The order of both stages of the process with respect to the accumulation of the respective groups was evaluated. The dependence of the rate of saponification on the packing density of the structural units was demonstrated. With increasing conversion, the fiber structure becomes looser, as demonstrated by density and sorption investigations. If acrylonitrile copolymer is treated with alkali, the carboxylate groups in the polymer substrate accumulate as a result of saponification of the ester groups of the copolymer, while the nitrile groups are predominantly transformed into the amide groups. If the degree of conversion (with respect to the CN groups) is higher than 62.7%, the copolymer abruptly suffers a marked change in its mechanical properties and gradually dissolves. The products of partial saponification of copolymer were investigated by thermomechanical methods and DTA. The polycyclization of the polymer substrate was found to proceed at a temperatures which decreases as the content of the amide groups increases.

Thermal and rheological behavior of acrylonitrile–carboxylic acid copolymers and their metal salt complexes

“…180°C). Acidic reagents 3 such as acetic acid, benzene sulphonic acid, at 85°C, 75% sulphuric acid of 5°C, and at room temperature to 60°C, and alkaline reagents [5][6][7][8][9] such as sodium carbonate, sodium hydroxide, and potassium hydroxide at room temperature to 85°C and sodium metasilicate 10 have been used for the hydrolysis of nitrile groups in PAN.…”

“…The study revealed that the rate of saponification is greater for the terpolymer than for the homopolymer due to loose packing of the molecular chains in the terpolymer. Geller et al 7 found that during alkaline hydrolysis of ANmethylacrylate-itaconic acid terpolymer fibers, the nitrile groups that are sufficiently remote from the carboxylic acid units are saponified more quickly.…”