Thermogravimetric analysis is a common tool for identifying material composition of polymers and wood composites. A large variation in ash content was found when analyzing the composition of Scots pine sapwood sampled with an autosampler and analysed with a Perkin Elmer Thermogravimetric analyzer Pyris 1 TGA. An increase in ash content was found with increasing order of analysis. The TGA instrument has a hanging balance system, where the sample crucible hangs on a hook which is attached to the balance and placed above the furnace. Due to tar that depletes on the hook during pyrolysis and subsequent combustion in an oxidative atmosphere, the mass of the hook increases successively. This mass increase falsifies the individual ash content readings and therefore gives a biased composition of wood compounds. A method that enables the mathematical correction of the false ash contents and adjusts for a false initial mass of the sample is presented in this paper.
Keywords: correction method, false ash content, pyrolysis, TGA, wood combustion
Authors
Zimmer K.
Norwegian Forest and Landscape Institute, Ås, Norway
Fongen M.
Norwegian Forest and Landscape Institute, Ås, Norway
Grodås E.
Norwegian Forest and Landscape Institute, Ås, Norway
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