Sisal cellulose acetates obtained from heterogeneous reactions

Abstract

In the present work, cellulose obtained from sisal, which is a source of rapid growth, was used. Cellulose acetates were produced in heterogeneous medium, using acetic anhydride as esterifying agent and iodine as catalyst, to check if the procedure described in the literature for commercial cellulose also is adequate to sisal cellulose. The results indicated that iodine is an excellent catalyst to obtain sisal cellulose acetates, but the reaction is so fast as described in the literature when, instead of sisal, lower average molar weight cellulose (microcrystalline) is used. The crystallinity index (Ic) of sisal cellulose acetates diminished compared to sisal cellulose, but there was no direct correlation between their degree of substitution (DS) and Ic. Probably acetyl groups were introduced more homogeneously along the short chains of microcrystalline cellulose, when compared to sisal cellulose, and then for microcrystalline cellulose acetates the Ic decreases as DS increases. Using the linear correlation that was found between degree of substitution (DS) and time reaction is possible to control the DS of sisal cellulose acetates, considering a large interval of degrees of substitution (0.3–2.8)

Molecular iodine in monomer and polymer designing

“…Wood (cellulose, hemicelluloses, and lignin) underwent acetylation and butyrylation in order to improve its dimensional stability and UV resistance. [140] These modifications were run in a solvent-free conditions using acetic anhydride/butyric anhydride in the presence of catalytic amount of molecular iodine at temperatures of higher than 90-120°C for 2-6 h. Butyrylation was found to be slower and quantitatively lower than the acetylation counterpart. Dimensional stability of thus-esterified wood, estimated by anti-swelling efficiency (ASE), was observed to increase with the degree of esterification.…”

Biobased films prepared from NaOH/thiourea aqueous solution of chitosan and linter cellulose

“…The diffractogram patterns were obtained in a VEB CARL ZEISS-JENA URD-6 Universal Diffractometer operating with CuKa (k = 1.5406 Å ) generated at 40 kV and 20 mA (Ramos et al 2005;De Paula et al 2008;Ciacco et al 2008Ciacco et al , 2010Ass et al 2006). The crystallinity index (I c ) was calculated as previously described by Buschle-Diller and Zeronian (1992):…”

Functionalisation of bamboo and sisal fibres cellulose in ionic liquids

“…The chemical degradation occurs mainly by enzymatic, alkaline hydrolysis or oxidative methods. [11][12][13] Ionic liquids are the low melting salts that consist of organic cations and organic or inorganic anions (e.g. ethyl ammonium nitrate, tetra alkyl ammonium salts).…”