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We report here on some aspects of the acetylation in LiCl/N,N-dimethylacetamide, DMAc, of untreated and mercerized sisal cellulose, hereafter designated as sisal and M-sisal, respectively. Fiber mercerization by NaOH solution has resulted in the following changes: 29.9% decrease in the index of crystallinity; 16.2% decrease in the degree of polymerization and 9.3% increase in &#945;-cellulose content. A light scattering study of solutions of sisal, M-sisal, microcrystalline and cotton celluloses in LiCl/DMAc has shown that they are present as aggregates, with (an apparent) average aggregation numbers of 5.2, 3.2, 9.8, and 35.3, respectively. The presence of these aggregates affects the accessibility of cellulose during its functionalization. A study of the evolution of the degree of substitution, DS, of cellulose acetate as a function of reaction time showed an increase up to 5 h, followed by a decrease at 7 h. Possible reasons for this decrease are discussed. As expected, M-sisal gave a higher DS that its untreated counterpart.Este trabalho apresenta alguns aspectos da acetilação em LiCl/N,N-dimethylacetamida, DMAc de celulose de sisal nativa e mercerizada (sisal e M-sisal). A mercerização da fibra em solução de NaOH resulta nas seguintes alterações: decréscimo de 29.9 % no índice de cristalinidade; diminuição de 16.2% no grau de polimerização e aumento de 9.3% no conteúdo de &#945;-celulose. Estudo com espalhamento de luz de soluções de sisal, M-sisal, celulose microcristalina e algodão mostrou que elas se apresentam na forma de agregados, com números médios de agregação de 5.2, 3.2, 9.8 e 35.3, respectivamente. A presença destes agregados afeta a acessibilidade à celulose durante sua funcionalização. Acompanhamento do grau de substituição, DS, de acetato de celulose em função do tempo, mostrou que o mesmo aumenta por um intervalo de tempo de 5 h, seguido por um decréscimo após 7 h. Possíveis razões para este decréscimo são discutidas. Como esperado, M-sisal apresenta um DS maior que a sisal nativa.(FAPESP) São Paulo Research Foundatio

Some aspects of acetylation of untreated and mercerized sisal cellulose