Development of a model for the fast analysis of polymer mixtures based on cellulose, hemicellulose (xylan), lignin using thermogravimetric analysis and application of the model to poplar wood

The storage of wood chips is associated with high dry matter losses and changes in raw material properties due to microbiological-chemical degradation processes. For a better understanding of degradation processes and their effect on wood components, very labor intensive chemical analysis of a large number of wood samples over a storage period of 6 to 9 months is necessary. The thermogravimetric analysis (TGA) of wood samples offers the possibility to considerably reduce the analysis effort while at the same time achieving a high repeat accuracy. For this purpose, a method was first developed in which the determination of characteristic values for wood analysis is possible in a staged TGA setup in a combined nitrogen and oxygen atmosphere. Based on these characteristic values, a model for the quantification of cellulose, xylan and lignin in polymer blends was developed and three polymer blends representing a broad spectrum of naturally occurring compositions in wood were analyzed to validate the model. The deviation between the polymer fractions determined by the model and used in the experiment was max. 1.37%. The developed model was then transferred to the analysis of extract-free poplar wood samples. The model results were validated by comparison with chemical analysis (NREL) and literature values. This comparison has shown that the wood constituents under consideration can be determined with sufficient accuracy using the new method. The developed method can thus serve as a basis for the development of a method for the continuous monitoring of degradation processes in wood chip storage.