Technologies of liquefaction of bamboo and preparation of adhesive

The technology of liquefying processed-waste bamboo with phenol is investigated by single factor trials and an orthogonal design. We studied the preparation technology and properties of adhesives from this phenol-liquefied bamboo with formaldehyde (BPF). The results show that temperature has a significant effect on liquefaction. The effect of the mass ratio of phenol to bamboo comes second and the catalyst dosage within the range of 2%–4% is the least effective. The optimum conditions of liquefaction are as follows: a mass ratio of phenol to bamboo 3.5, a catalyst dosage of 4%, liquefying temperature 145°C and liquefying time 60 min. The liquefaction rate of bamboo reached 99.1%. For the preparation of the adhesive, a mass ratio of liquefied bamboo products to formaldehyde (37%) is 100 to 164.8–199.5, while the ratio 100 to 108.2 is the best. This adhesive has a lower curing temperature than that of normal PF resin. At a hot-press temperature of 130 or 140°C, this new adhesive provides excellent bonding strength of plywood. The most favorable temperature for hot-pressing is 140°C. __________ Translated from Chemistry and Industry of Forest Products, 2007, 27(6): 65–70 [译自: 林产化学与工业]     

Dynamic viscoelastic behavior of wood under drying conditions

In this study heartwood from a Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] plantation was treated using a high-temperature drying (HTD) method at 115°C, a low-temperature drying (LTD) method at 65°C, and freeze vacuum drying (FVD), respectively. The dynamic viscoelastic properties of dried wood specimens were investigated. The measurements were carried out at a temperature range of −120 to 250°C at four different frequencies (1, 2, 5, and 10 Hz) using dynamic mechanical analysis (DMA). We have drawn the following conclusions: 1) the storage modulus E′ and loss modulus E″ are the highest for HTD wood and the lowest for FVD wood; 2) three relaxation processes were detected in HTD and LTD wood, attributed to the micro-Brownian motion of cell wall polymers in the non-crystalline region, the oscillations of the torso of cell wall polymers, and the motions of the methyl groups of cell wall polymers in the non-crystalline region in a decreasing order of temperatures at which they occurred; and 3) in FVD wood, four relaxation processes were observed. A newly added relaxation is attributed to the micro-Brownian motions of lignin molecules. This study suggests that both the HTD and the LTD methods restrict the micro-Brownian motion of lignin molecules somewhat by the cross-linking of chains due to their heating history. __________ Translated from Journal of Beijing Forestry University, 2008, 30(3): 96–100 [译自: 北京林业大学学报]     

Liquefaction of bamboo, preparation of liquefied bamboo adhesives, and properties of the adhesives

This study investigated the liquefaction of bamboo in phenol, which involved the effects of weight ratios of phenol to bamboo, amount of catalyst, temperature, etc. The study showed that liquefaction could be accomplished with a phenol to bamboo weight ratio of 2–1: 1, a 5% catalyst of HCl or BF₃, and a temperature of 115°C. Liquefied bamboo formaldehyde (BLF) resin adhesive for exterior use could be obtained with a phenol to formaldehyde molar ratio of 1:1.6–2.0. The curing behavior of BLF resin adhesive, studied by TG-DSC and IR analyses, showed that BLF resin adhesives had a lower curing temperature than PF adhesives but had the same characteristic trough in IR spectra as PF adhesives. __________ Translated from Chemistry and Industry of Forest Products, 2004, 24(3) [译自: 林产化学与工业, 2004, 24(3)]     

Heat-transfer process during hot-pressing of flakeboard

Hot-pressing is the main process in flakeboard manufacture. Studies in this field also emphasize the effect on the heat-transfer process of the following factors: hot-pressing temperature, original moisture content (MC), target thickness and target density. In this experiment, dynamic data of changes in temperature in mats can be logged through temperature transducers and a computer data log system. The results of the experiment indicate that the core temperature-time curve can be divided into three stages: a stage of a rapidly rising temperature, a stage of moisture vaporizing and a stage of a slowly increasing temperature. If the hot-pressing temperature or the original MC increases during the first stage, the temperature will increase at an accelerated rate. This rate of acceleration in thin or low-density boards is very high. During the second stage, increasing the hot-pressing temperature or decreasing the original MC can shorten the time used to vaporize moisture. In thin or low-density board, this time period is short. In the third stage the original MC does not affect the rate of temperature increase, while the effect of the other factors is the same as that at the first stage. Given different conditions, vaporization temperature in the mat changes. __________ Translated from Journal of Beijing Forestry University, 2005, 27(2): 92–95 [译自: 北京林业大学学报, 2005, 27(2): 92–95]     

Microscopic structure and properties of wood-based foaming composites

In order to reduce the density of wood-based composites without causing a deterioration of their mechanical properties, we studied the process of manufacturing wood-based composites. A combination of polymer foaming technology and flat hot-pressing technology was used. The microscopic structure of the various wood-based composites was analyzed with a scanning electron microscope (SEM). Modulus of rupture (MOR), modulus of elasticity (MOE), impact strength, and thickness expansion rate of water sorption (TS) were all measured. The results showed that fibers loosely interweave, and fibers had been connected by micropore. They also showed that spaces between fibers had big micropore structure. MOR, MOE and impact strength were the highest among three levels of ratio. When the total content of resin and foaming agent were 20% by weight, TS was higher. A hot-pressing temperature of 120°C was optimal. At the low temperatures of 80°C, the foaming process was uncompleted. At a higher temperature, micropores burst at a certain pressure. Based on the variance analysis and maximum difference analysis, a significance test shows that the optimum conditions for the total content of resin and foaming agent is 20% by weight, with a hot pressing temperature of 120°C for 15 min. Under these conditions, the properties of wood-based foaming composites all achieved the industry standard. __________ Translated from Journal of Beijing Forestry University, 2007, 29(3): 154–158 [译自: 北京林业大学学报]     

Pyrolytic characteristics of burning residue of fire-retardant wood

In order to investigate the pyrolytic characteristics of the burning residue of fire-retardant wood, a multifunctional fire-resistance test oven aimed at simulating the course of a fire was used to burn fire-retardant wood and untreated wood. Samples at different distances from the combustion surface were obtained and a thermogravimetric analysis (TG) was applied to test the prrolytic process of the burning residue in an atmosphere of nitrogen. The results showed that: 1) there was little difference between fire-retardant wood and its residue in the initial temperature of thermal degradation. The initial temperature of thermal degradation of the combustion layer in untreated wood was higher than that in the no burning wood sample; 2) the temperature of the flame retardant in fire-retardant wood was 200°C in the differential thermogravimetry (DTG). The peak belonging to the flame retardant tended to dissipate during the time of burning; 3) for the burning residue of fire-retardant wood, the peak belonging to hemicellulose near 230°C in the DTG disappeared and there was a gentle shoulder from 210 to 240°C; 4) the temperature of the main peaks of the fire-retardant wood and its burning residue in DTG was 100°C lower than that of the untreated wood and its burning residue. The rate of weight loss also decreased sharply; 5) the residual weight of fire-retardant wood at 600°C clearly increased compared with that of untreated wood. Residual weight of the burning residue increased markedly as the heating temperature increased when burning; 6) there was a considerable difference with respect to the thermal degradation temperature of the no burning sample and the burning residue between fire-retardant wood and untreated wood. __________ Translated from Journal of Beijing Forestry University, 2006, 28(3): 133–138 [译自: 北京林业大学学报]     

Hydrolysis of bamboo fiber cellulose in formic acid

Bamboo fiber dissolution and hydrolysis in formic acid were studied. After hydrolysis, formic acid can be recovered in a clean state and reused. Solid water-soluble sugars were obtained. After being dipped into the formic acid solution for 30 min, the bamboo fibers started to swell. After one hour, the bamboo fibers gradually started to dissolve in the formic acid solution. The color of the liquor/solution turned green and dark. In the end, the bamboo fibers became thoroughly dissolved in the liquor after four hours. There was a clear hierarchical tissue structure on the fiber surface, as observed by AFM before treatment. The differential structure disappeared after 30 min of treatment. The fiber surface became plump and glossy. After six hours reaction at 60°C, the solid sugar mixture recovered contained glucose, cellobiose, cellotriose, cellotetrose, cellopentose and cellohexaose. A significant fraction of the sugar products consisted of monomeric glucose. More than 54.5% of the bamboo fiber mass had been transformed into monomeric glucose. __________ Translated from Biomass Chemical Engineering, 2007, 41(2): 5–10 [译自: 生物质化学工程]     

Plant community characteristics and their relationships with climate in the Hexi Corridor region of northwestern China

Species, coverage, density, appearance, important values and above ground biomass of desert plant communities in the Hexi Corridor region in northwestern China were investigated. Data on the meteorological factors at the investigation sites were collected. Their relationships were statistically analyzed. The results show that the composition of plant species and total density in the Hexi Corridor region are positively correlated with elevation and longitude, but negatively with latitude. The relation decreases from the southeast to the northwest in this region. In the desert regions with an accumulated temperature of >10°C greater than 3200°C, the shrubs, including semi-shrubs, occupy dominant positions in the communities. Their importance values reach 100. When the accumulated temperature is about 3000°C, the communities are often in some type of transition, either with herbage being the dominant species, with some semishrubs or shrubs as companion species, or the dominant species being semi-shrubs with some perennial herbage as companion species. In desert communities with an annual precipitation of over 110 mm, the main life forms of plants are semi-shrubs or perennial herbs. When precipitation is less than 110 mm, the main life forms of the vegetation are dwarf shrub or annual herbs. In the extreme arid regions with annual precipitation of around 50 mm in the northwestern part of the Hexi Corridor, barely some annual herbage come to life during the rainy season. Desert ecosystems consist of sparse vegetation with small biomass. They change with climate factors and are especially sensitive to precipitation, which is particularly important for their conservation. __________ Translated from Acta Botanica Boreali-Occidentalia Sinica, 2007, 27(5): 859–863 [译自: 西北植物学报]     

Investigation of changes in compressed moso bamboo (<Emphasis Type="Italic">Phyllostachys pubescens</Emphasis>) after hot-press molding

In this study, molding moso bamboo strips to a curved shape using hot-press molding operation was explored. Bamboo strips with different thickness and moisture content (MC) were subjected to press molding under 120–210 °C for different time. Changes in the chemical components of bamboo were analyzed by Fourier-transform infrared spectroscopy (FTIR). Effect of MC on thermal mechanical behavior of bamboo was investigated using dynamic mechanical analysis (DMA). Results showed that the influencing degree of four variables on compression and recovery ratios decreased as: temperature?>?time?>?thickness?>?MC. Compression ratio increased and recovery ratio decreased dramatically when pressing temperature exceeded 180 °C. FTIR analysis indicated that polysaccharide (especially hemicelluloses) underwent a progressive thermal degradation during compression at 180 and 210 °C for 40 min, whereas relative content of lignin increased. DMA results showed that bamboo samples with a higher MC had a lower storage modulus value, confirmed water had a plasticizing effect. The loss factor of bamboo with higher MC (12 and 16%) exhibited two major transitions centred around 100 °C (α₁) and 50 °C (α₂), respectively. The temperature of these α transitions kept almost unchanged as moisture level increased from 12 to 16%. These findings provide fundamental information for the future preparation of curved bamboo as profiled components in engineered products.     

Effects of surface performance on bamboo by microwave plasma treatment

Abstract Surface treatment of bamboo was carried out by microwave plasma (MWP), surface contact angle of the sample was measured using glycerin and urea-formaldehyde resin (UFR) liquid, and the effects on the surface performance of the bamboo sample was evaluated. The results show that the surface contact angle of the sample presented a generally decreasing trend when prolonging the MWP treatment time and shortening the distance between the sample and the resonance cavity. The surface contact angle of the sample decreased by 49%–59% under the following conditions: MWP treatment for 30 s, the distance between the sample and resonance cavity at 40 mm, and measurement at 15 s after dripping with glycerin. The surface contact angle of the sample measured with the glycerin was lower than that with UFR. No matter whether we used glycerin or UFR, the contact angle of the sample at 15 s after dripping was lower than that at 5 s after dripping. The grinding treatment had little effect on the surface contact angle of the sample after MWP treatment, and the modification effect ofMWP treatment after grinding was better than that of sole MWP treatment. __________ Translated from Journal of Nanjing Forestry University (Natural Sciences Edition), 2007, 31(4): 33–36 [译自: 南京林业大学学报(自 然科学版)]     

Division of afforestation site type in the watershed of Wangjiagou, West Shanxi through GIS

Using quantification theory I, an analysis of the relation of soil water and qualitative factors, such as, slope degree, slope aspect, slope position, and soil in Wangjiagou watershed area has been done. The study aims to quantify the factors influencing soil water, the descending order of the factors being the slope aspect, soil, slope degree, and slope position, thereby scientifically facilitating division of afforestation site types and afforestation site products digitally on geographical information system (GIS). __________ Translated from Journal of Northwest Forestry University, 2006, 21(3): 184–188 [译自: 西北林学院学报, 2006, 21(3): 184–188]     

Aspirated pits in wetwood and micromorphology of microbial degradation in subalpine fir

Differentiating from normal wood, pit membranes in wetwood of subalpine fir contain bacteria of water drop shape or orbicular shape, and flaky shape, as observed using Scanning Electronic Microscope. Not only are ray parenchyma cells in wetwood partially degraded but also margo strands in pit membranes are somewhat degraded by bacterial activities. Most of the bordered-pit membranes in normal wood are unaspirated in green conditions and the proportions of aspirated pits in earlywood and latewood account for only 6.8% and 13.4%, respectively. Nevertheless, most of the bordered-pit membranes in wetwood are aspirated in green conditions and the proportions of aspirated pits account for 77.7% and 72.1%, respectively. The problem of hard-to-dry for subalpine fir could be reasoned from the considerable amount of aspirated pit membranes in wetwood. __________ Translated from Journal of Nanjing Forestry University (National Science Edition), 2006, 30(1): 53–56 [译自: 南京林业大学学报 (自然科学版), 2006, 30(1): 53–56]     

Characteristics of thermal decomposition of bamboo with different chemical additives

By means of the analysis of TG-DSC curves, we studied the effect of temperature and several additives, i.e., H₂SO₄, HCl, NaOH, H₂O₂ and H₃PO₄ on the performance of the thermal decomposition of bamboo. The results indicated that the weightlessness of pure bamboo powder may be divided into three stages, up to 700°C. At each stage, the effect of each chemical additive on the weightlessness rate of bamboo was different. In the end, we analyzed the function of additives in practical applications of the thermal decomposition of bamboo. __________ Translated from Journal of Bamboo Research, 2007, 26(1): 42–45 [译自: 竹子研究汇刊]     

Nonisothermal moisture movement in wood

In order to analyze the effect of temperature gradient on moisture movement during highly intensive drying, such as microwave-vacuum drying, the profile of the temperature and moisture content in sealed wood whose opposite faces were subjected to temperature gradient for a short time was measured. The ratio of the moisture content (MC) gradient to the temperature gradient (dM/dT) was calculated and the factors influencing moisture movement under nonisothermal conditions were discussed. The results indicate that moisture moved in wood from the warm surface to the cold one even if opposite faces of the sealed wood assembly were exposed continuously to different but constant temperatures for a short period. The moisture content on the cold surface was higher than that on the warm surface. The moisture content gradient opposite to the temperature gradient was established, and the dM/dT was below 0.9%/°C. The temperature in the sample and the distance from the hot surface of the sample was strongly linearly correlated. With an increase in temperature, initial moisture content and experimental time, the dM/dT was significantly increased. __________ Translated from Journal of Beijing Forestry University, 2005, 27(2): 96–100 [译自: 北京林业大学学报, 2005, 27(2): 96–100]     

Spatial fluctuation of forest fires and their regional behaviors

Historical forest fire records from Alaska State (1950–2000), California State (1895-2001), USA and Heilongjiang Province (1980–1999), China were used to calculate the longitude and latitude of the annual burned area’s centroids for these regions. Fluctuation phenomena by year were analyzed using spectrum analysis. The results show that centroids of burned areas in these three regions are in a fluctuating condition that encircles the distribution center. The distribution centers are 151.11°W, 64.96°N in Alaska State, 120.02°W, 37.11°N in California State and 127.07°E, 49.59°N in Heilongjiang Province, respectively. The fluctuation of the burned area’s centroids in Alaska State and California State in longitude has obvious periodicity, and the periodicities are 4.2 years, 6.25 years in Alaska State and 6.24 years, 106 years in California State. The fluctuation of the burned area’s centroids in Heilongjiang Province has a periodicity both in longitude and latitude, and the periodicities are both 3.3 years, 6.67 years. Fluctuation of the burned area’s centroids in Alaska State and California State in latitude does not have periodicity, and big forest fires with low frequencies predominate. __________ Translated from Scientia Silvae Sinicae, 2006, 42(5): 89–103 [译自: 林业科学]     

Variation in tensile properties and relationship between tensile properties and air-dried density for moso bamboo

This research investigated the variation in tensile properties and the relationship between the tensile properties and the air-dried density for the moso bamboo (Phyllostachys pubescens) by sampling at different heights and radial positions. Results showed that the variation of the longitudinal tensile properties in the radial direction was greater than that in the longitudinal direction. The longitudinal tensile modules of elasticity (MOE) ranged from 8.49 to 32.49 GPa. MOE for the outermost layer was 3–4 times as high as that for the innermost layer. The longitudinal tensile strength (MOR) ranged from 115.94 to 328.15 MPa. MOR for the outermost layer is 2–3 times as high as that for the innermost layer. Linear and curvilinear regressions were done from tested data of MOE, MOR and air-dried density in this paper. The linear equation worked a little better than the curvilinear one to predict the longitudinal MOR and MOE from air-dried density. __________ Translated from Scientia Silvae Sinicae, 2006, 42(3): 72–76 [译自: 林业科学]     

Nutrient dynamics of foliar litter in reciprocal decomposition in tropical and subtropical forests

In order to explore the release of nutrients and the effects of global warming on the decomposition rate of forest litter, an experiment is designed to reciprocally decompose forest foliar litter in two sites across climatic zones: Mt. Jianfengling in Hainan Province in the tropics and Mt. Dinghushan in Guangdong Province in the subtropics. The two sites have similar altitudes, soil types, annual mean rainfall and seasonality of dry and wet. The main difference between these two sites is the annual mean temperature with the difference of 3.7°C. Foliar litters of 10 native dominant tree species have been collected respectively from the two sites and divided into single-species litter and mixed litter. They are decomposed reciprocally in the two sites. The results indicate that litter decomposes in the tropical site 1.36–3.06 times more rapidly than in the subtropical site. Apparent Q ₁₀, calculated on the basis of the temperature difference between the two sites, ranges from 3.7 to 7.5. The return amount of N, P and C will increase by 32.42, 1.033 and 741.1 kg/hm², respectively in Mt. Dinghushan in the first year’s litter decomposition under the prevailing temperature condition. Only in Mt. Dinghushan is the correlation between decomposition rate constant and initial litter quality high and significant in the ratio of lignin to N, lignin, the ratio of lignin to P, HLQ and C. This is not the case at Mt. Jianfengling. __________ Translated from Journal of Beijing Forestry University, 2005, 27(1): 24–32 [译自: 北京林业大学学报, 2005, 27(1): 24–32]     

Improvement in compatibility and mechanical properties of modified wood fiber/polypropylene composites

To improve the interfacial compatibility between wood fibers and polypropylene and the toughness of wood-fiber/polypropylene composites, maleic anhydride grafted polypropylene (PP-g-MAH) and maleic anhydride grafted styrene-ethylene-butadiene-styrene copolymers (SEBS-g-MAH) were used as modifiers. Mechanical properties of wood-fiber/polypropylene (WF/PP) composites were improved when PP-g-MAH or SEBS-g-MAH was added. When either of these copolymers was added, the composites had better interfacial compatibility than the unmodified composite. This was verified by scanning electron microscope (SEM) observations and dynamic mechanical analysis (DMA). The mechanical properties of the composites were significantly improved because of the good interfacial bonding between wood fibers and polypropylene when PP-g-MAH and SEBS-g-MAH were added. __________ Translated from Journal of Beijing Forestry University, 2007, 29(2): 133–137 [译自: 北京林业大学学报]     

Programmed cell death of Ulmus pumila L. seeds during aging

The programmed cell death (PCD) characteristics of Ulmus pumila L. seeds were investigated. The seeds were treated at a high temperature of 37°C and 100% relative humidity for six days. DAPI (4′6-diamidino-2-phenylindole) staining revealed that the aging treatment induced condensation and margination of chromatin, as well as the formation of apoptotic bodies. DNA electrophoresis results of U. pumila seeds on an agarose gel showed a characteristic “ladder” pattern. Levels of electrolyte leakage of seed cells showed that membranes retained their integral form during almost the entire aging time. There was an immediate increase in the production rate of superoxide anion (O₂ ⁻) and in the amount of hydrogen peroxide (H₂O₂), which remained at a μmol level. All of these common characteristics indicate that seed aging can be classified as PCD. __________ Translated from Journal of Beijing Forestry University, 2007, 29(3): 8–14 [译自: 北京林业大学学报]     

Impact of coupling agent on properties of wood-plastic composite

The impact of two coupling agents, maleic anhydride (coupling agent 1) and isocyanate (coupling agent 2) on the properties of wood-plastic composites (WPC) was studied. Wood-plastic composites were made with coupling agents 1 and 2 and properties were tested under the condition that the ratio of wood fiber to thermoplastic polymer was 7:3, target density was 0.7 g/cm³, press temperature was 175°C, press time was 8 min, and adding amount of coupling agent 2%. Results show that coupling agent 2 was superior to coupling agent 1 and had great effect on the physical and mechanical properties of WPC. When using the same coupling agent, the impact on their properties varied with different thermoplastic polymers. Translated from China Forest Products Industry, 2006, 33(4): 30–32 [译自: 林产工业]