Papers by Author: Guo Feng Wu

Abstract: An environmental, biodegradable breeding container made from rice hull and starch adhesive was produced by a hot-press machine. The heat treatment was introduced to improve the properties of breeding container. The dry and wet strength, water absorption, FTIR, biodegradation, and thermal stability were tested and discussed. The results showed that curing temperature played a great influence of on the dry and wet strength of breeding container. The dry and wet strength was increased with the temperature rise. The water absorption decreased from 89.1% to 50.9%. Pattern of the peak at 3400 cm^-1, 2900 cm^-1, 1640 cm ^-1, 1500 cm^-1 and 1050 cm^-1 has changed after the heat treatment of specimens. The hydrogen bond was likely produced between straw and adhesive during the heat treatment process. The degradation rate of specimens after heat treatment was lower because the high temperature led to deeper cross-linked reaction. The TGA showed that heat treatment can improve the thermal stability, while the degradability was not changed.

Abstract: In this research, the urea-formaldehyde prepolymer and multilayer hot-press drying was used to obtain modified wood. The timbers were compressed and dried by the multilayer hot-press drying kiln. The combination of chemical modification and hot-press drying can improve the drying rate, which can also enhanced the physical and mechanical properties. Based on the findings, the basic density of modified wood improved 25.2 %, the bending strength and the bend elastic modulus improved 15.6 % and 25.0 % respectively. The dimensional stability of the treatment appeared to be slightly higher than that of untreated samples under the same conditions for processing temperatures and times. The improving dimensional stability of wood mainly was attributed to the prepolymer that changes wood cell wall components such as the degradation of the hemicelluloses and cellulose during hot-press drying treatment. The XRD results indicated that the degree of crystallinity increased to 35.45 %from 31.25 %. The TGA results show that the degradation of the samples can be divided into two step, both of the maximum weight loss velocity temperature of the two step increased to 266 °C, 355 °C from 244 °C and 341 °C.

Abstract: One best way to harness the petroleum-based solid wastes is to develop biodegradable materials. Among which, PLA is the most important one, because it is made from renewable plant. But Poly(lactic acid) (PLA) is brittle and low impact resistance. The cellulose nanowhiskers are about 5-40 nm in diameter and the length can be from 100 nm to several micrometers depending on the source of cellulose and the processing technology. The cellulose nanowhiskers can act as efficient reinforcement because of the high aspect ratios, important surface areas and high modulus. The celluloses nanowhiskers are hydrophilic because of the abundant exposed hydroxyl (-OH) groups and PLA is hydrophobic. So we added the low molecular weight polymeric-poly (ethylene glycol) (PEG) to improve compatibility between PLA matrix and the cellulose nanowhiskers. The PLA/cellulose nanowhiskers composites were prepared by casting solution. The tensile strength and the elongation rate of the composites improved 56.7% and 48% comparing with the PLA/cellulose whiskers composites. The thermo gravimetric analysis indicated that the thermal decomposition of PLA/cellulose nanowhiskers/PEG composites include only one stage. The pictures of SEM showed the fracture morphology of the different kind of the composites. The structure of the PLA/cellulose nanowhiskers/PEG composites were characterized by AFM, which showed that the cellulose nanowhiskers dispersed evenly in the PLA matrix.

Abstract: The aim of this work was to study the ability of NIR spectroscopy to determine holocellulose and alpha-cellulose contents in triploid clones of Populus tomentosa. For this purpose 90 trees with five families in different planting density grown in Shandong were analyzed. Calibration models were developed from wet chemical and NIR data using partial least squares (PLS) regression. High coefficients of determination (R2) and low root mean square errors of cross-validation (RMSECV) were obtained for holocellulose (R2 = 0.7805, RMSECV =0.652) and alpha-cellulose (R2 = 0.8702, RMSECV = 0.548) from wood meal. Prediction produced high correlation coefficients between laboratory and predicted values for holocellulose and alpha-cellulose contents, which R2 values are 0.7467 and 0.8505, and RMSEP are 0.993 and 0.553, respectively. This study showed that NIR analysis can be reliably used to predict holocellulose and alpha-cellulose contents in triploid clones of Populus tomentosa.

Abstract: A preparation method of Urea-formaldehyde performed polymer(UFP) with low molecular weight and high reactivity is presented. The UFP can impregnate into wood along trachea from the ends with pressurized impregnation method. In the following heating and pressing processes of the wood, the UFP polymerizes, and it enhances stability and strength of the wood. The impregnating-pressing-drying method avoiding the disadvantage of dealing with the large specimens using vaccum-pressing method is suitable for industrial production. Results from test showed the degree of crystallinity tested by XRD were 30%, 32% in different dosage of the modifier. Utilizing a combination of low molecular weight resin impregnation and pressing resulted in a density increase of UFP treated wood from 0.214 to 0.268g/cm3. At the same time, the Young’s modulus and bending strength increased from 1.407GPa to 1.759GPa and 64MPa to 74.5MPa, respectively. But the formaldehyde emission is great reduced from 0.5% to 0.008%. It can be concluded that the effective utilization of UFP impregnated in wood is a promising technique for the production of high-strength in the drying and pressing processing.

Abstract: The objective of this study was to determine the chemical and physical changes of chemical modified on poplar wood. The chemical modifier was impregnated into cell lumen space by pulse-dipping machine to improve the dimension stability and mechanical property of timber. The timbers were compressed and dried by the multilayer hot-press drying to produce the modified timber. The modified timber had better dimension stability than the natural wood when they were immerged water continuous eight-hour. Characteristics of Fourier Transform Infrared Spectroscopy (FTIR) for modified were studied by the FTIR spectrometer. The intensity of hydroxyl absorption peak in the infrared absorption spectrogram decreased significantly, and that of carbonyl decreased lightly, which due to the bond of the function groups of -NHCH2OH of urea-formaldehyde prepolymer react with the wood carboxyl (C=O) and hydroxyl(-OH). The morphologic models of chemical within wood were discovered by SEM.