WOOD RESEARCH Volume 67, Number 1, 2022
Yinluan Qin and Longhai Chen

Effects of modification with melamine–urea–formaldehyde resin on the properties of urea pretreated eucalyptus

Eucalyptus urophylla was treated with melamine-urea-formaldehyde resin (MUF) after pretreatment with urea solution. The properties of the wood were then determined. The weight percent gain (WPG) and, antiswelling efficiencies (ASE) of the wood treated with urea+MUF were 14% and, 45% higher than those of untreated wood, respectively. The water absorption (WA) of the wood treated with urea+MUF was decreased approximately 50% lower than that of the untreated wood. However, the mechanical properties of the wood treated with urea+MUF were weakened due to the destruction of the structure of wood. An X-ray photoelectron spectroscopy (XPS) analysis revealed that the atomic concentration ratio of O/C was increased. The ratio of C1 was decreased as the lignin and extractives contents were decreased, while the ratios of C2 and C3 were increased. The urea solution pretreatment was conducive to the impregnation of wood functional modifiers.

WOOD RESEARCH Volume 61, Number 5, 2016
Chu Jie, Ma Li, and Zhong Yang

Comparison of bamboo fibers in sulfuric acid, sodium hydroxide and glycerin pretreatments

The chemical compositions and structural characterizations of bamboo samples with three pretreatments using sand bath to heat were comparatively studied with Fourier infrared spectrum (FTIR). The results showed that the holocellulose and cellulose yields increased significantly and the dilute alkali (NaOH) pretreatment performed better lignin removal rate than that of dilute acid (H2SO4) and glycerin pretreatments.Furthermore, when the same solutions were used, the compositional changes were more remarkable at 135 than at 117°C, and the similar degradation of hemicelluloses was observed for the different pretreatments. With sodium hydroxide at 135°C, compared to un-treated bamboo, cellulose increased by 14.21 % and hemicellulose decreased to 13.98 %, counting the removal of lignin to 20.29 %. In which, the bamboo expressed the betterdelignification with sand bath and higher temperature and combinations with other methods of glycerin pretreatment should be evaluated in the future work.

WOOD RESEARCH Volume 65, Number 6, 2020
Boháček Štefan, Pažitný Andrej, Halaj Michal, Balberčák Jozef, and Kuňa Vladimír

Freeze-thaw pretreatment of poplar sapwood dust

The paper is focused on the effect of freezing and cyclic freezing-thawing pretreatment of poplar sapwood (Populus alba L.). The experimental comparison was carried out by the sawdust fraction 0.7 mm as (a) water-saturated and (b) dry. Monosaccharide yields, as well as an amount of acetic acid, were measured after 6, 24, 48, 72, and 96 hours of enzymatic hydrolysis with 15% load of the enzyme measured to total cellulose content. The influence of freezing rate on total yields was observed on equally prepared samples with different weights (31 g, 25 g, 62.5 g, 125 g, 250 g, 500 g, and 1000 g) by “cubic” tests. To increase the efficiency of pretreatment, a cyclic freezing-thawing experiment at temperatures -20°C and +25°C was performed. The results show that single freezing of grounded poplar sapwood impregnated by water or dry in its matter is not a sufficient pretreatment method, so cyclic freeze-thaw is needed to enhance the yield of monosaccharides. Analysis of cubic test showed that slower freezing process has a positive effect on enzyme accessibility.

WOOD RESEARCH Volume 65, Number 4, 2020
Pažitný Andrej, Albert Russ, Boháček Štefan, Monika Stankovská, Vladimír Ihnát, and Štefan Šutý

Effect of steam explosion on enzymatic hydrolysis of various parts of poplar tree

The effect of steam explosion on enzymatic hydrolysis of various parts of poplar tree (heartwood, sapwood and 1-year coppice) was investigated. These parts were milled, the obtained sawdust was chemically analysed and then steam explosion of 0.7 mm poplar particles at temperature of 205°C was performed. Concentration of monomers obtained after enzymatic hydrolysis was considered as the main indicator for cellulose accessibility. Analysis of high performance liquid chromatography showed that non-treated poplar sawdust does not enable sufficient cellulose accessibility, while excessively high temperature and rapid pressure release resulted in substantial breakdown of polysaccharides and lignin and formation of inhibitors. The concentration of monomers increased gradually in the order of coppice, sapwood and heartwood. Steam exploded heartwood gave the maximum monosaccharides concentration of 90.0 g.L-1 after 72 hours of enzymatic hydrolysis. However, glucose concentration culminated after 48 hours of this hydrolysis. This corresponds to the best holocellulose accessibility for enzymes. The maximum concentration of inhibitors (9.3 g.L-1) was determined for poplar coppice after 24 hours of enzymatic hydrolysis.