Green systhesis of carboxymethyl cellulose
Date
2018
Authors
Bannerman, Natasha
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Abstract
Contemporary production of Carboxymethyl Cellulose (CMC) is carried out
almost exclusively by the solvent slurry process which utilises large quantities of
solvents such as isopropyl alcohol, ethanol and methanol. This study has focused
on reducing the environmental impact of the CMC production by evaluating water
as an alternative solvent and microwave energy as an alternative heating source.
Due to poor reaction efficiency and product quality the historical dry/aqueous
CMC manufacturing process was abandoned in the late 1950’s. To address
these short comings the reaction conditions were optimised and the best reaction
products then compared to those produced by the conventional solvent slurry
process. Current investigations into the use of microwave technology for the
carboxymethylation of cellulose focus mainly on solvent based reactions. The
application of microwave technology for the dry/aqueous reaction was evaluated
by comparing reactions where microwave and conventional heating were used
respectively.
X-ray diffraction (XRD) was used to evaluate the degree to which the cellulose
was swelled during mercerisation, while the product quality and molecular
characteristics of the CMC products were used to evaluate the results of the
etherification reactions. By comparing the change in slope of the conformational
plot, as determined by size exclusion chromatography with multi-angle light
scattering (SEC-MALS), to the degree of thixotropy of the polymer solutions it
was found that the slope could be used as new and novel method for estimating
the uniformity of the substituent distribution along the cellulose backbone. This is
a parameter which has a significant impact on the solubility and rheology of the
CMC.
This investigation concluded that water could be used as a viable alternative
solvent for the industrial production of technical grade CMC’s. Comparable
reaction efficiencies of 74.8% to the solvent slurry process were achieved for the
low DS products and the use of microwave heating was found to significantly
reduce the reaction time.
Description
A dissertation submitted in fulfilment of the requirements for the
degree of Master of Science to the Faculty of Science, University of the
Witwatersrand, Johannesburg, 2018
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Citation
Bannerman, Natasha (2018) Green synthesis of carboxymethyl cellulose, University of the Witwatersrand, Johannesburg, <http://hdl.handle.net/10539/31530>