ISSN:
0323-7648
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
Despite the fact that graft copolymerization is a favored reaction for cellulose xanthate, a significant part of the cellulose and lignin component is subject to undesired degradation reaction. Exposure of thermomechanical pulp to ozone followed by grafting by the xanthation method further degrades the cellulose and decreases graft yield. Graft yield can be improved by introducing chemical crosslinks to the cellulose backbone before or after ozone exposure. It is suggested that crosslinking with formaldeyde recombines some of the degraded chains of hydroxylated cellulose after ozone exposure and also helps to prevent degradation of cellulose chain during grafting of cellulose xanthate. Sizing of pulp with dispersed and saponified rosin - Al complexes slows down the grafting reaction and decreases the polymer add-on percentage significantly. An exposure to ozone before or after the sizing process improves grafting efficiency and graft yield and the copolymer formation is the preferred reaction. The surface morphology of sized pulp has practically no influence on the grafting parameters. Unlike the sizing mechanism, the chemical nature of the sizing agent influences the grafting process. Sizing of pulp with an alkyl ketene dimer significantly decreased the copolymer formation by preventing reactive cellulose hydroxyl group from reacting.
Zusätzliches Material:
1 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/actp.1996.010470406
Permalink
