KINETICS OF NON-CATATALYZED HYDROLYSIS OF POLYACRYLONITRILE IN NEAR-CRITICAL WATER

In order to explore new applications of near-critical water (NCW) and develop a green technology of polyacrylonitrile (PAN) hydrolysis, kinetics of non-catatalyzed hydrolysis of PAN in NCW was investigated. After examining the repeatability of experiment data and studying the effect of the ratio of PAN to water on hydrolysis reaction,the non-catalyzed hydrolysis kinetics of PAN in NCW was systematically determined in the temperature range from 210 degrees C to 250 degrees C, and hydrolysis products were characterized by IR, TG, GPC and element analysis. The results reveal that non-catatalyzed hydrolysis of polyacrylonitrile in NCW is feasible. The acid concentration initially increases rapidly and then reaches a constant level of around 55% similar to 60% of the total amount of functional groups. The amide concentration passes through a shallow maximum and then remains constant at approximately 40% similar to 45% of the total amount of functional groups. Amide and acid groups obviously reach equilibrium concentrations, in which reaction temperature and the ratio of water to PAN are the two key factors influencing the hydrolysis reaction. Binary or ternary copolymers with different contents of functional groups could be obtained by altering the reaction conditions. Using the assumption of a series of first-order kinetics equations, the activation energies evaluated are 53.37 kJ.mol(-1) for PAN hydrolysis and 120.55 kJ.mol(-1) for polyacrylamide hydrolysis. A new methodology of non-catalyzed modification of PAN in NCW is established,which is environmentally-benign and reaction controllable.