Intensification of the freeze-thaw pretreatment of disintegrated poplar wood

This research was focused on the effect of water content in the cells of disintegrated Populus nigra L. on a freeze-thaw pretreatment method before an enzymatic hydrolysis. Two chipped and sieved fractions 2.5 mm and 0.7 mm and two milled fractions, characterized as 18°SR (Shopper–Riegler index) and 37°SR, of the disintegrated 5 years old poplar tree were used for our experiment. Glucose and xylose yields were measured after 24 and 48 hours of enzymatic hydrolysis with a 15% load of the enzyme measured to a total cellulose content. The influence of nine freeze-thaw cycles under -20°C and +20°C was considered. The results showed that an increase in moisture content positively affects yields in all fractions but a desirable result was achieved mainly for the 0.7 mm fraction where the total yield increased by about 16%. More effective way is a finer wet beating of wood mass, while wood fibre receives moisture already in the technological process. The highest glucan conversion 51,74% and the total hemicelluloses conversion 47,72% was achieved for the finest fraction 37°SR. The higher moisture content has a positive effect on the increase in the conversion of oligosaccharides, especially glucan, in chipped fractions.

Study on machining properties and surface coating properties of heat treated densified poplar wood

In this study, a modification combining densification and heat treatment of poplar wood (Populus tomentosa Carr.) was carried out, and the machining properties of the unmodified poplar wood (control) and the heat treated densified wood (HTD) were tested and evaluated. In addition, the water-based UV paint was covered on the control and HTD respectively, and the surface coating properties of them were evaluated. The results showed that: (1) The machining properties of poplar wood were improved after the heat treatmentdensification modification. The score of comprehensive machining properties of the HTD was 45 (excellent grade), while the score of the control was 36 (good grade). (2) The abrasion resistance, hydrophobicity and adhesion were improved after heat treatment-densification modification. Therefore, the modification combining densification and heat treatment played a significant role in enhancing the value of wood.

Decay resistance of preservative injected poplar and its process of preventing white rot fungi infection

This study initially investigated decay resistance of preservative injected poplar and its infection mechanism of preventing white rot fungi. The living poplar was injected with different concentrations (0.0, 0.5, 1.0 and 1.5 wt.%) of alkaline copper quaternary (ACQ). Using the scanning electron microscopy, the process of preservative injected poplar wood preventing white rot fungi infection at different tree heights were examined. The decay resistance test results showed that the decay resistance of preservative injected poplar at different tree heights was significantly different. With the increase in tree height, the decay resistance decreased, and the higher the ACQ concentration, the better the decay resistance. The white rot fungi infested the poplar wood with the vessels as the breakthrough point, being spread to other cells through pits. The white rot fungi degraded wood cell walls by secreting enzymes and preferentially degraded the parenchyma cells.

Effect of water leaching on photodegraded poplar wood monitored by IR spectroscopy

Poplar (Populus x euramericana cv. pannonia) samples were irradiated using ultraviolet light emitter mercury lamp. Other series of specimens were treated with the combination of UV radiation and water leaching. The total duration of UV radiation for both series of specimens was 20 days. The total duration of water leaching was 10 days. One cycle of the combined treatment consisted of 2-day UV radiation followed by one day water leaching. The IR measurement was carried out after both UV radiation and water leaching to monitor both effects separately. Lignin degradation of water leached samples was found to be greater than that of the solely UV treated samples. The guaiacyl and the syringyl lignin showed similar degradation properties. The unconjugated carbonyl groups generated by the photodegradation proved to be the most sensitive chemical components to leaching. As a consequence of photodegradation, two absorption bands of unconjugated carbonyl groups were grown up at 1715 and 1759 cm-1 wavenumbers. The band at 1759 cm-1 was much more sensitive to water leaching than the band at 1715 cm-1. Ten days of water leaching was long enough to remove all unconjugated carbonyls generated by the photodegradation. The water was able to leach out carbonyl groups (absorbing at 1745 cm-1) originally presented in poplar wood as well.