Abstract: Microcrystalline cellulose was cyanoethylated by using acrylonitrile as etherifying agent. Effects of reaction time and reaction temperature on degree of substitution (D_S) of the product were studied. It was indicated that D_S of microcrystalline cellulose increases with prolonging of reaction time or increment of reaction temperature under 50℃. The peak of hydroxyl group of the cyanoethylated microcrystalline cellulose obviously became weaker and shaped cyano absorption peak was observed by FT-IR. It was concluded that part of hydrogens of hydroxyl group were substituted by cyanoethyls. X-Ray diffration pattern showed that the original crystal structure of microcrystalline cellulose was broken. With increase of D_S of cyanoethylated microcrystalline cellulose, thermoplasticity increased before D_S reach 1.43, then receded with increase of D_S, as shown by X4 microscopic melting-point and Vicat softening-point measurements. It was concluded in this study that the rate constant of cyanoethylation of microcrystalline cellulose was ordered by 1.30,1.61,1.94 and 2.26 s^-1 under reaction temperature of 30,35,40 and 45℃ respectively. Activation energy of cellulose cyanoethylation was 29.8 kJ/mol.

Key words: microcrystalline cellulose, degree of substitution, cyanoethylation, kinetics, thermoplasticity