Annals of Warsaw University of Life Sciences - SGGW

Annals of Warsaw University of Life Sciences – SGGW
Forestry and Wood Technology No 71, 2010: 14-19
(Ann. WULS-SGGW, For and Wood Technol. 71, 2010)
The study of thermal degradation of softwood cellulose in the presence of
antioxidants – SEC analysis
ANDRZEJ ANTCZAK
Department of Wood Science and Wood Protection, Warsaw University of Life Sciences – SGGW
Abstract: The study of thermal degradation of softwood cellulose in the presence of antioxidants – SEC
analysis. The purpose of the study was examination antioxidants influence on degradation of cellulose during
thermal ageing in 130°C. Size-exclusion chromatography was used to evaluate cellulose depolymerization. On
the basis of these results, it was observed, that higher decrease of the polymerization degree of cellulose is in the
air than in nitrogen atmosphere. Antioxidant addition – 0.2% (EQ, PG, THBP) to cellulose matrix considerably
reduces the weight average polymerization degree of cellulose during thermal aging (130ºC) in air atmosphere.
Also the presence of low molecular substances (extractives) accelerates thermo oxidative degradation of
cellulose. On the other hand, in nitrogen atmosphere, the presence of antioxidants does not cause significant
changes in degradation of cellulose.
Keywords: thermal degradation, antioxidants, cellulose aging, SEC
INTRODUCTION
Studies of cellulose degradation met with great interest in last years. This subject area
is very important in many different industries (electrical, paper and textile) or in archives and
libraries. It is generally known that cellulose degradation in natural conditions runs very slow.
In order to model long-term changes in a shorter time scale, accelerated tests are used. In
these tests samples are artificially aged by exposing them to elevated temperatures, specified
humidity and atmosphere conditions.
Size exclusion chromatography (SEC) is modern analytical technique which can be
used to study cellulose degradation. This method gives information about the weight average
molar mass (Mw), the number average molar mass (Mn) and also, what is the most important,
the molar mass distribution (MMD) of polymeric sample. Moreover, the degree of
polymerization (DP) of cellulose can be obtained.
The aim of the study was examination antioxidant’s influence on cellulose degradation
during thermal ageing in 130°C. Natural antioxidants (extractives, lignin) and synthetic
(especially phenolic compounds) are widely applied in a number of manufactured products to
prevent oxidative degradation. However their effectiveness in thermal conditions still remains
poorly understood.
MATERIALS AND METHODS
Research material
- non extracted sawdust of pinewood (Pinus sylvestris L.) from sapwood zone
- extracted sawdust of pinewood (Pinus sylvestris L.) from sapwood zone (without
extractives) extracted by ethanol:chloroform (3:97)w mixture according to own method
[Antczak et al. 2006]
- cellulose – separated from above-mentioned extracted pinewood (Pinus sylvestris L.)
by Kürschner-Hoffer method [Krutul 2002]
- above-mentioned pinewood cellulose with antioxidant – propyl gallate (PG), 2,4,5trihydroxyphenone
(THBP) and ethoxyquin (EQ) which were coated on cellulose fibre
by method with stirring [Antczak et al. 2007]. The method consisted in immersing a
sample of cellulose in 0.2% antioxidant solution in methanol and then total
evaporation of solvent under vacuum while stirring.
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