Cellulose degradation during hydrothermal treatment of birch wood (Betula pubescens Ehrh.)

• Study of cellulose degradation during wood's heat treatment showed a considerable degradation in both commercially and laboratory heat-treated wood samples, probably due to the low pH induced by the heat treatment. Experimental series were performed for investigating cellulose degradation in birch wood, at different pH levels and times, during heat treatments performed at pH values of 4, 7 and 10, for 3 and 6 hours at 180°C. The results show that the selected span of pH and time of treatment clearly affects the size of the cellulose molecules. Study of cellulose degradation involved intrinsic viscosity measurements on α-cellulose from the samples. As a result of heat treatment, viscosity drops from 1430 mL/g (untreated wood) to less than or equal 700 mL/g and less than or equal 350 mL/g, for durations of 3 and 6 hours, respectively. The wood buffered in an aqueous solution at pH 4 showed a drop in intrinsic viscosity around 880 mL/g, while a sample of commercial "thermowood" yielded an intrinsic viscosity of 732 mL/g. For neutral and alkaline pH values, the drop in viscosity is considerably lower. At pH values of 7 and 10, a 3 hr treatment had almost no effect on the degree of polymerisation, while a 6 hr treatment gave intrinsic viscosities around 1000 mL/g and 1216 mL/g, respectively. There is a distinct relation between cellulose's molecular size and wood's strength properties. The decrease in cellulose length in unbuffered systems may affect the strength properties of the treated wood. The experiments show that pH is an important factor to consider.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Industriell bioteknik -- Biomaterial (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Industrial Biotechnology -- Bio Materials (hsv//eng)

Keyword

Träfysik

Wood Physics

Publication and Content Type

ref (subject category)

art (subject category)