Browsing by Author "Van Groeningen, Trevor James"
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- ItemChemical properties of thermally degraded E. dunnii and E. macarthurii(Stellenbosch : Stellenbosch University, 2019-04) Van Groeningen, Trevor James; Meincken, Martina; Stellenbosch University. Faculty of Agrisciences. Dept of Forest and Wood Science.ENGLISH ABSTRACT: Wild fires in South Africa lead to the destruction of an average of 14 000ha of forest plantation annually. In order to reduce the loss of resources the possible recovery of wood after a wildfires was investigated. For this study two eucalyptus species - Eucalyptus dunnii and Eucalyptus macarthurii were selected, as plantations of these species are located in high risk fire regions. The main objective of this study was to determine, at which temperature wood degrades to such an extent that it is no longer suitable for the production of pulp and to find out if differences between different species exist. The aim was to determine whether wood that has been exposed to wildfires can still be used. The change in chemical composition of E. dunnii and E. macarthurii wood was determined before and after exposure to temperatures ranging from 150°C to 220°C. The cellulose, lignin and extractive content, as well as the molecular weight of cellulose were determined as a function of temperature to determine the change in chemical composition that can be expected after exposure to elevated temperatures. The acid insoluble lignin content decreased with increasing temperature, while the acid soluble lignin content increased. As a result, the total lignin content was only reduced by 2%, but the composition of the lignin has clearly changed. The ethanol extractive and water extractive content decreased with increasing temperature for both species. The cellulose content of E. dunnii showed a de facto increase due to the decrease of extractive and lignin content. The cellulose content of E. macarthurii remained relatively unchanged. The molecular weight of both species decreased after exposure to 150°C and reached a low of 160 000 after exposure to 160°C. However, after exposure to a temperature of 170°C the molecular weight began to increase, which was caused by the disintegration of low molecular weight amorphous cellulose. In order to utilise wood from fire damaged trees the wood exposed to a temperature of 160°C and higher must be removed to ensure the wood is suitable for pulp production.