INFLUENCE OF EXPLOSIVE AUTOHYDROLYSIS ON DYNAMIC MECHANICAL CHARACTERISTICS OF WOOD OAK QUERCUS ROBUR
Abstract
The dynamic dependencies of the dynamic shear modulus and the loss modulus of Quercus Robur L. oak wood, subjected to pretreatment by explosive autohydrolysis, were obtained by dynamic mechanical analysis. It is shown that, as a result of an increase in the degree of hydrolysis stiffness, the glass transition temperature of the complex of amorphous wood components decreases. The maximum decrease in the glass transition temperature in comparison with the initial wood, determined from the positions of the minimum temperature derivative of the dynamic shear modulus and the peak at the temperature dependence of the dynamic loss modulus, is 75 °C and 45 °C, respectively. With increasing rigidity of the conditions of barothermal processing, the value of the dynamic shear modulus tends to decrease at room temperature. It was found that the temperatures of the maxima position on the temperature dependences of the dynamic loss modulus do not correspond to the temperatures of the minima on the temperature derivative, and with the increase in the degree of hydrolysis stiffness this discrepancy is significantly increased. Assumptions are made about the nature of the processes occurring in the wood tissue and causing these effects. It is most likely that the decrease in the glass transition temperature of the amorphous component in the samples of the hydrolyzed wood substance compared to the original wood is a consequence of the increase in the flexibility of the molecular chains of the lignocarbon complex. Reducing substances and fragments of low molecular weight lignin, formed during hydrolysis, act as a plasticizer and facilitate the mobility of the kinetic components of the wood substance.
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