988 resultados para Chemistry, Organic.


Relevância:

80.00% 80.00%

Publicador:

Resumo:

The effects of alkali treatment on the structural characteristics of cotton linters and sisal cellulose samples have been studied. Mercerization results in a decrease in the indices of crystallinity and the degrees of polymerization, and an increase in the alpha-cellulose contents of the samples. The relevance of the structural properties of cellulose to its dissolution is probed by studying the kinetics of cellulose decrystallization, prior to its solubilization in LiCl/N,N-dimethylacetamide (DMAc). Our data show that the decrystallization rate constants and activation parameters are only slightly dependent on the physico-chemical properties of the starting celluloses. This multi-step reaction is accompanied by a small enthalpy and large, negative, entropy of activation. These results are analyzed in terms of the interactions within the biopolymer chains during decrystallization, as well as those between the two ions of the electrolyte and both DMAc and cellulose.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Includes bibliography.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Includes bibliographical references and indexes.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Pt. 1.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

"List of books consulted": p. 207-208.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Supplements to v. 14 issued 1951-69 (8 v.)

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Includes bibliographical references.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Mode of access: Internet.