Combined analysis of the microstructure of wood swollen by water and/or ethanol through dynamic mechanical analysis and small-angle X-ray scattering

Dynamic mechanical analysis and small-angle X-ray scattering (SAXS) measurements of hinoki wood swollen with water and/or ethanol in the temperature range of 20–78/95 °C were performed to clarify the relationship between swelling and microstructure in different swelling states. For the sample swollen in a water–ethanol mixture with an ethanol mole fraction of 0.2, a peak in tanδ, i.e., the ratio of the dynamic elastic modulus (E′) to the dynamic loss modulus (E″), was observed at around 50 °C. No clear peak was observed in the temperature range of the sample swollen with water or ethanol, but thermal softening behavior due to micro-Brownian motion of lignin was observed. The scattering behavior of the samples swollen with water and/or ethanol differed significantly from one solution to another. The SAXS intensity of samples swollen with water or mixture of water and ethanol increased with increasing temperature, while the SAXS intensity of samples swollen with ethanol changed little with increasing temperature. This suggested that the adsorption sites of ethanol were different. The position of the peak for the sample swollen with the water–ethanol mixture, observed in the Kratky plot, was shifted to the low-q side compared to the pure liquid. It was suggested that the aggregation state of the sample swollen with the mixture of water and ethanol was very different from those of the wood swollen with the pure liquid.