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Structural modifications of cellulose in heterogeneous acetylation process

Domenii publicaţii > Chimie + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Olaru, N.; Ciolacu, D.; Tampu, D.; Olaru, L.



Three cellulosic materials with crystalline structures of cellulose I, cellulose II and mixture of cellulose I and III, respectively,
are acetylated in a heterogeneous system consisting of a mixture of acetic acid and toluene in order to decrease their
hydrophilic character. Different degrees of acetylation are achieved by carrying out the process for various times of reaction.
The variation of water affinity of the acetylated fibres estimated from DSC thermograms is studied in relation with the extent
of acetylation and with the structural modification of cellulose fibres as revealed by X-ray and FTIR analyses. It was found
that two factors are involved in decreasing the hydrophilic character of the studied samples: the change in supramolecular
structure and the degree of chemical modification. At lower degrees of acetylation, the reducing of ordered regions in
cellulosic material increases the water affinity, while at higher extents of modification, though the decrystallization is more
pronounced, water affinity is reduced because of the lower number of free OH groups on the cellulose chain. It was also
established that although a decrease of crystallinity is produced for all the studied celluloses, the crystalline forms of the
starting celluloses are maintained.

Cuvinte cheie: Cellulose, Heterogeneous acetylation, Supramolecular structure, X-ray, DSC, FTIR