Qian Lang

Impregnation of poplar wood (Populus euramericana) with methylolurea and sodium silicate sol and induction of in-situ gel polymerization by heating

Abstract Poplar wood (Populus euramericana cv. “I-214”) has been impregnated by pulse dipping at 0.7–0.8 MPa for 30 min with a mixture of methylolurea and sodium silicate, and the sol modifier has been cured within the wood micropores by in situ gel polymerization by kiln drying, so that a Si-O-Si framework was formed. The treated wood acquired higher mechanical strength and its hygroscopicity was lowered. It was demonstrated by X-ray diffraction that sodium silicate crystallized within the interfibrillar region of the cell wall. Fourier transform infrared spectra showed that reactions occurred between the wood-OH, Si-OH, and N-CH2-OH from methylolurea to form C-O-Si and C-O-C bonds. As visible by scanning electron microscopy (SEM), the Si-O-Si framework was embedded in the pretreated wood. Moreover, SEM-energy-dispersive X-ray spectroscopy analysis revealed that the modifier formed layers from various thicknesses ranging from a thin layer on the cell walls up to big amounts filling the lumen.

Particulate reinforcement and formaldehyde adsorption of modified nanocrystalline cellulose in urea-formaldehyde resin adhesive

In this study, nanocrystalline cellulose (NCC) was used for reinforcement and formaldehyde (HCHO) adsorption of urea-formaldehyde (UF) resin adhesive in fiberboard. The original NCC was modified by 3-aminopropyltriethoxysilane for improving the wetting property with UF resin adhesive. The UF resin adhesive with modified NCC was analyzed by X-ray powder diffraction, thermogravimetric analysis, and Fourier transform infrared. The HCHO emission and bending and bonding strength of the UF resin adhesive with modified NCC were tested according to Chinese National Standard GB/T 17657-1999. Compared with the original UF resin adhesive, modified NCC led to limited effects on the crystal structure, thermal stability, and characteristic absorption peaks of UF resin adhesive. The HCHO emission of the UF resin adhesive with 1.0% modified NCC decreased by 13.0%, while the bending and bonding strength increased by 40.5 and 158.3%, respectively. The improvements of modified UF resin adhesive were destroyed by the reunion of NCC when the content was more than 1.5%.

The research of chemical modification on fast-growing wood

The aim of this study was to describe a chemical modification on fast-growing woods. After modification, it was found that the bending strength increased 42.7%, the compressive strength parallel to grain increased 37.8%. Moreover, the characteristics of the unmodified and modified samples were studied by X-Ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). The XRD analysis showed the degree of crystallinity changed from 35.49% to 37.31%, and the FTIR results revealed clear changes in the molecular structure. Finally, the SEM micrographs of modified and unmodified samples demonstrated strong and firm bonding between the inner wood cell and the wood modifier.

Characterization of hot-pressed poplar wood with chemical pretreatment

The aim of this research is to study the characterization of modified poplar wood. A chemical impregnation was utilized before the poplar wood was dried and compressed in a multilayer hot-press drying kiln. The results showed that with the compression rate of 31.7%, the basic density, the over dried density and air-dried density of treated wood increased 25%, 75% and 74%, respectively. The bending strength and compressive strength parallel to grain improved 72% and 47%. The water uptake rate of treated wood was lower compared with the untreated wood. The results of XRD curves indicated that the degree of crystallinity for treated wood increased from 37.88% to 39.01%. The FT-IR analysis showed that the intensity of hydroxyl (-OH) absorption decreased, which due to the reaction between the wood hydroxyl and the impegnated chemicals. The morphologic models of the poplar wood were examined by SEM.

Modification of NCC for Improving the Wetting Property with Polyurethane

In this study, different lipophilic groups from 3-aminpropyltriethoxysilane (APTES) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were used to alter the surface structure of nanocrystalline cellulose (NCC). The diversifications of NCC surface resulted from modifiers improved the wetting property between NCC and polyurethane significantly. The modified NCC was characterized by X-ray powder diffraction (XRD). And the wetting property was indicated by contact angle (CA). Epoxy groups from 6% GPTMS led to a 47.6% decline of CA, while the improvement of wetting property from APTES was inconspicuous.

Impregnation and Drying Schedule of Eucalyptus Wood

The aim of this research was to define a rapid and simple test that would indicate the probable performance of a pretreated wood species in a hot-press drying process and the kiln schedule. The drying rate (mass/time) and the remaining mass of water were measured at different moisture intervals. The moisture of timber decreased rapidly and the drying rate was 3.7% per day in the early five days. The timbers were B grade after drying used the hot-press drying kiln in 16 days. The moisture content of timber reached 9.20% after the drying process with the standard deviation of 0.92%. The gradient of the moisture content was 3.40%. The moisture content standard deviation in the thickness of timber was 2.70% and the residual stress was 1.38%. The mechanical properties of impregnation wood improve significantly compared to the untreated wood. The basic density of impregnation wood improved by 17.1%, the over-dried density increased to 0.55 g·cm-3 from 0.49 g·cm-3. The scanning electron microscopy explained the wood modifier has been permeated into the wood fiber which reacted with the wood composition.

Chemical Modification of Poplar Wood on the Mechanical Properties

In this research, the chemical and multilayer hot-press drying was used to modify poplar wood. The timbers were compressed and dried in the multilayer hot-press drying kiln. The combination of chemical modification and hot-press drying can improve the mechanical properties. The influence of chemical and hot-press drying on the compressive strength parallel to grain, the bending strength, the density, the water absorbent and the crystallinity of poplar wood have been investigated in this study. The chemical treated conditions close to real technological regimes selected. The samples were impregnated with three conditions. The samples were dried in a hot-press drying kiln for 130hrs. It was showed that the urea carbamate and hot-press drying treatment increase the properties. The density and mechanical properties increased with increasing urea carbamate, while the water absorption decreased. The crystallinity is 37.03%, 37.11%, 37.78%, separately, compared with the natural wood of 35.09%. The TAG showed the thermal stability increased.

Application of near-Infrared Spectroscopy to Predict Paper Properties of Acacia

First attempt to predicting physical properties of paper by Near Infrared Spectroscopy (abbreviated as NIRS) mathematical model, Acacia is a kind of fast-growing tree which is a potential resource in pulp and paper industry. The mathematical models of physical properties of Acacia unbleached kraft paper were established by software OPUS6.5 of Near Infrared Spectroscopy. Spectral data of Acacia unbleached kraft paper were acquired by Near-Infrared. Physical properties, which include quality, whiteness, tensile index, burst index and tear index, of the paper were measured by GB methods. NIRS mathematical models between the spectral data and the laboratory reference values were established and optimized by software OPUS6.5 partial least squares (abbreviated as PLS). The NIRS mathematical models were evaluated by its parameters, and used to predict the physical properties of unknown samples rapidly and accurately. Compared with NIRS mathematical model of physical properties of Acacia unbleached kraft pulp, the NIRS mathematical models of paper have a better prediction on unknown samples; Compared with traditional laboratory methods, predicting properties of paper by the NIRS mathematical models of paper is rapid, accurate and non-destructive.