Investigation on physical and mechanical properties of pulp–plastic composites from bagasse

High-density polyethylene (HDPE), bagasse fibers treated by four pulping processes (AS-AQ (alkaline sulfite anthraquinone), SODA-AQ (soda anthraquinone), MEA (monoethanolamine) and chemical–mechanical pulping (CMP)), three levels of nano-SiO₂ (0, 2, and 5?wt%), and maleic anhydride polyethylene as coupling agent were used to produce pulp–plastic composites (PPCs) by injection molding. The physical and mechanical properties of corresponding composites were evaluated according to ASTM standards. The results showed that compared to untreated bagasse/HDPE composite, the addition of bagasse pulp fibers increased significantly the mechanical properties such as tensile strength and modulus, flexural strength and modulus, and hardness. The chemical pulps-reinforced composites showed better mechanical strengths than that of CMP-reinforced composites, but in some properties, CMP pulp composites have comparable results to the chemical pulp-reinforced composites. Natural fibers (untreated and treated) increased water absorption and thickness swelling of composites compared to pure HDPE. The addition of nano-SiO₂ particles showed both increasing and decreasing trends on physical and mechanical properties ofPPCs.     

Comparison of water absorption and mechanical properties of wood–plastic composites made from polypropylene and polylactic acid

Abstract

This study focuses on the water absorption and mechanical properties of composites made from softwood sawdust and plastics, such as virgin and recycled polypropylene and polylactic acid (PLA). The composites were processed by extrusion, and their properties were investigated by a water immersion test, mechanical tests and a cyclic test for moisture resistance. Scanning electron microscopy was used to study the morphology of the fracture surfaces of the composites. The composites made with recycled polypropylene had the lowest water absorption and thickness swelling of the studied composites. The PLA composites made with heat-treated sawdust showed the highest flexural strength. Of the polypropylene based composites, virgin polypropylene resulted in composites with higher flexural strength. The Charpy impact strength of the composites was found to have an inverse trend compared to flexural strength. Cyclic treatment of the studied composites resulted in 20–60% loss of flexural strength, depending on type of composite.     

Manufacture and properties of Miscanthus–wood particle composite boards

Miscanthus sacchariflorus straw was used as a raw material for the manufacture of Miscanthus–wood particle composite board with Douglas-fir particles in ratios of 100/0, 80/20, 60/40, 40/60, 20/80, and 0/100. A commercial phenol–formaldehyde resin was used as a binder at 9 and 11 % for target densities of 0.50 and 0.65 g/cm³, respectively. The effects of the Miscanthus/wood particle ratio on the composite board properties were investigated. In addition, the density profile was also examined to improve the understanding of the composite board manufacturing process. Results indicate that the internal bonding value increased drastically in the board containing up to 50 % wood particles, providing a valuable parameter for subsequent research. The board properties were greatly improved with increasing density and binder addition level.     

Effect of organoclay platelets on the mechanical properties of wood–plastic composites formulated with virgin and recycled polypropylene

Abstract

This study investigated the effects of organoclay platelet contents (0, 3 and 5 wt%) and polypropylene type (virgin and recycled) on the mechanical properties of polypropylene/wood flour composites. Composite samples were made by melt compounding and consequent injection moulding. The tensile, flexural and impact properties of resultant composites were determined. X-ray diffraction (XRD) analysis of composites with 3 and 5% nanoclay content was also conducted. The results indicated that tensile and flexural properties of the composites increased with the addition of nanoclay particles up to 3 wt% and decreased thereafter. The impact strength of the composites, however, decreased with the incorporation of nanoclay. The mechanical properties of the recycled polypropylene-based nanocomposites were statistically comparable with those based on virgin polypropylene. XRD analysis revealed that the degree of intercalation in the nanocomposites containing 3% nanoclay was higher than in those containing 5%. Based on these results, it can be concluded that recycled polypropylene could be used instead of virgin polypropylene in the production of value-added products with no significant adverse effects on the mechanical properties.     

Effect of fatigue and annual rings’ orientation on mechanical properties of wood under cross-grain uniaxial compression

The mechanics of fresh wood with and without a fatigue pre-treatment that mimics a mechanical pulping process was experimentally studied. The mechanical properties of Norway spruce samples under compression are considered with the macroscopic stress–strain data and from local strain properties via digital image correlation technique. The results highlight the effects of the orientation of the wood annual rings compared to the loading direction and of the pre-fatigue. The wood presents a low yield point when the annual rings are tilted compared to the load axis, but the Young’s modulus and yield stress are higher when the annual rings are either parallel or perpendicular to the load direction. In the last case, buckling of softest layers occurs. The fatigue treatment makes the wood less stiff as deduced from the decreases of Young’s modulus and yield stress, whatever the orientation of annual rings. Secondly, it creates a thin and localized softened layer.     

Enhanced mechanical properties and water resistance of bamboo fiber–unsaturated polyester composites coupled by isocyanatoethyl methacrylate

Bamboo fibers were mechanically extracted from raw green bamboos by crushing, rolling, and combing techniques with 1,4-butanediol as a solvent. The morphology of the bamboo fibers thus obtained was analyzed. The bamboo fibers were treated with isocyanatoethyl methacrylate (IEM) in the presence of dibutyltin dilaurate as a catalyst, to improve the interfacial adhesion between the fibers and unsaturated polyester (UPE) resins. The bamboo fibers reinforced UPE composites were prepared by hand lay-up compression molding. FTIR, XPS, and NMR analyses indicated that the IEM was covalently bonded onto the bamboo fibers via carbamate linkages. The IEM treatments significantly increased the tensile strength, flexural strength, flexural modulus, and water resistance of the resulting composites and yet decreased the impact strength of the composites. The SEM images of the tensile-fractured surfaces of the IEM-treated bamboo fibers–UPE composites revealed that the fiber treatments markedly improved the interfacial adhesion between the bamboo fibers and UPE resins.     

Investigation on the compatibilizing effect of m-isopropenyl-α,α-dimethylbenzyl isocyanate grafted polypropylene on polypropylene and wood flour composites

Wood flour (WF) and polypropylene (PP) composites (WF/PP) were compatibilized by m-isopropenyl-α,α-dimethylbenzyl isocyanate grafted polypropylene (m-TMI-g-PP). The effect of wood flour, m-TMI-g-PP contents on the rheology, dynamic mechanical analysis (DMA), mechanical properties, as well as the morphology of the composites were investigated and discussed. Rheology, DMA results showed that m-TMI-g-PP was an effective compatibilizer for WF/PP composites. The shear modulus (G′) and complex viscosity (η*) of the composites were increased, which implied that the composites probably withstood pronounced shear forces, resulting from strong adhesion at the interface between the matrix PP and WF. The mechanical test indicated that the tensile strength and the flexural strength of the composites were improved with increasing content of m-TMI-g-PP. From the properties tests, the optimum loading of WF in WF/m-TMI-g-PP/PP was found to be 40%, and the optimum loading of m-TMI-g-PP was 6%. Property enhancement is attributed to improved wetting and interactions between the PP matrix and WF, which is supported by scanning electron microscopy analysis.     

Effects of wet–dry cycling on the mechanical properties of Arundo donax L. used for the vibrating reed in woodwind instruments

Wood Science and Technology - The effects of wet–dry and moist–dry cycling on the mechanical properties of reed (Arundo donax L.) were investigated. Because water-soluble extractives...     

Effects of habitat type, vegetation structure, and proximity to forests on bird species richness in a forest–agricultural landscape of West Java, Indonesia

To halt biodiversity loss in the humid tropics of developing countries, it is crucial to understand the roles and effects of human-modified landscapes with fragmented forest remnants in maintaining biodiversity while fulfilling the demands of local communities and reducing poverty. To implement appropriate landscape planning for conserving biodiversity and ecosystem functioning, appropriate information is required about parameters of habitat suitability among various anthropogenic habitats with a range of distances to forests and vegetation characteristics, but such information is limited. We examined differences in avian communities between a remnant forest and four types of man-made forest (two mature plantations and two agroforests) in a forest–agricultural landscape of West Java, and we analyzed the effects of both local and landscape factors on various types of species richness in this landscape. The results from non-metric multidimensional scaling revealed avifauna in the two types of agroforest was clustered separately from that in the remnant forest, mainly because drastic declines in the abundance of forest specialists (including IUCN red-listed species) and their replacement with open-habitat generalists. The mixed-tree agroforests were colonized by 30 % of forest specialists and forest-edge species found in the remnant forest, and maintained the highest richness of species endemic to Indonesia among man-made forests, implying that some forest specialists and endemics might have adapted to ancient landscape heterogeneity. High proportion of insectivorous birds was found in the remnant forest (more than 50 %) and drastically decline in man-made forests, although the species richness of insectivores did not decline significantly in broad-leaved plantations. We concluded that protection of remnant forests should be prioritized to conserve forest bird diversity. However, as different environmental factors affected the richness values of different ecological groups, appropriate landscape design and habitat management could improve functional diversity in forest–agricultural landscapes in the tropics.     

Influence of felling season,drying method and within-tree location on the brinell hardness and equilibrium moisture content of wood from 27–35-year-old Betula pendula

The Brinell hardness and equilibrium moisture content (EMC) were measured from thinning-aged silver birch wood. Wood material both from the trees harvested in the first commercial thinning and from trees remaining on site after the thinning was included. The average Brinell hardness was 19.40 MPa. It correlated significantly with the basic density of wood. With respect to the distance from the pith, the Brinell hardness of air-dried wood was higher than that of artificially dried wood. The average EMC of the conditioned (20°C, 65% relative humidity) wood was 12.0%. The EMC of the wood also varied, with the EMC being higher for air-dried wood than for kiln-dried wood. EMC was the highest at a distance of 30–40 mm from the pith, decreasing towards both pith and log surface. Seasonal variation in both the Brinell hardness and the EMC of the wood was found. It was presumed to be a consequence of season-dependent physiological changes in trees.     

The influence of silane coupling agent and poplar particles on the wet-tability,surface roughness,and hardness of UF-bonded wheat straw （Triticum aestivum L.）/poplar wood particleboard

We used silane coupling agents to improve the bonding ability between wheat straw particles and UF resin, and investigated surface properties （wettability and surface roughness） and hardness of parti-cleboard made from UF-bonded wheat straw （Triticum aestivum L.） combined with poplar wood as affected by silane coupling agent content and straw/poplar wood particle ratios. We manufactured one-layered particleboard panels at four different ratios of straw to poplar wood par-ticles （0%, 15%, 30% and 45% wheat straw） and silane coupling agent content at three levels of 0, 5% and 10%. Roughness measurements, average roughness （Ra）, mean peak-to-valley height （Rz）, and root mean square roughness （Rq） were measured on unsanded samples by using a fine stylus tracing technique. We obtained contact angle measurements by using a goniometer connected to a digital camera and computer sys-tem. Boards containing greater amounts of poplar particles had superior hardness compared to control samples and had lower wettability. Panels made with higher amounts of silane had lower Rq values.     

Effects of selection cutting on the forest structure and species diversity of evergreen broa-leaved forest in northern Fujian, southern China

The short-term effects of selection cutting of different intensities on the forest structure and species diversity of evergreen broad-leaved forest in northern Fujian Province were investigated and analyzed. The results showed that selection cutting of low and medium intensities caused little variation in the forest structure. After cutting, the dominant species retained their leading status in the community. However, the community structure changed significantly following selection cutting of high and extra-high intensities; the status of the dominant species of the community declined dramatically. Some tree species began to disappear from the sampling plots. Except for extra-high intensity cutting, the diversity of tree species did not change significantly for the other three cutting intensities. However, the evenness of the stands was very different among the four kinds of cutting plots. For low and medium intensity selection cutting, the evenness declined slightly. For extra-high intensity selection cutting, the evenness increased to some extent, which might be due to a more even distribution of tree species after cutting. Cutting operations resulted in some adverse reactions to development of arborous species diversity of evergreen broad-leaved forest, particularly serious damage to the forest canopy. But the rational selection cuttings, which may benefit the restoration and maintenance of species diversity over a long period and may come about from the variations in environmental factors such as sunlight, temperature and humidity.     

Effects of Public Financed Aid on Private Forest Investments: Some Evidence from Finland, 1963–2000

The relationship between private forest investments and public cost sharing (government financial aid to private investment projects) was first analysed with an economic optimization model. In the general case the model predicted that cost-sharing causes substitution between private funding of investments and public aid. However, in some special cases complementarities were not ruled out. Next, the model predictions were tested with a translog cost function specification of forest investment fund shares. Aggregate data from Finland in years 1963–2000 were used. The substitution and own price elasticities of purely private, subsidized individual and subsidized collective investments are derived from maximum likelihood estimates of translog system model, allowing for investment scale effects. Investments supported by public funding behave in a strongly complementary fashion to each other. Some substitution of subsidized private funding for non-subsidized private funding was found. Strong scale effects and forest investment incentives were found among forest owners in response to public investment aid.     

Effects of pocket gophers,bracken fern,and western coneflower on planted conifers in northern Idaho – an update and two more species

Grand Fir Mosaic forests innorthern Idaho are difficult to regenerate afternatural or human-caused disturbances. Sparseconifer regeneration appears to be associated withhigh populations of northern pocket gophers (Thomomys talpoides) plus expansion by bracken fern(Pteridium aquilinum (L.) Kuhn) and invasionof western coneflower (Rudbeckia occidentalisNutt.). This report updates an earlier study(Ferguson and Adams 1994) that quantified theeffects of four treatments on survival and growth ofplanted conifers: unweeded with gophers, weeded withgophers, unweeded without gophers, and weededwithout gophers. Weeding removed only bracken fernand western coneflower. Subalpine fir (Abieslasiocarpa (Hook.) Nutt.), grand fir (Abiesgrandis (Dougl.) Lindl.), and western larch (Larix occidentalis Nutt.) had over 80% mortalityfrom pocket gophers and other causes. Lodgepolepine (Pinus contorta var. latifoliaEngelm.) had 49.2% mortality from pocket gophersand 6.8% mortality from other causes, but snowdamage is a problem for lodgepole pine. Engelmannspruce (Picea engelmannii Parry ex Engelm.)had 42.2% gopher-caused mortality and 8.4%mortality from other causes. Spruce suffered littletop damage from snowpacks and was stout enough towithstand senescing bracken fern fronds. Westernwhite pine (Pinus monticola Dougl.) had only24.1% mortality from pocket gophers after 4 years,and only 11.8% of the white pine died from causesother than gophers. Of the mortality caused bypocket gophers, 76.8% occurred the first summer andnext two winters after planting. The recommendedspecies for reforestation are Engelmann spruce andwhite pine.     

Effects of Thidiazuron, basal medium and light quality on adventitious shoot regeneration from in vitro cultured stem of Populus alba×P. berolinensis

The effect of Thidiazuron (TDZ), basal media and light quality on adventitious shoot regeneration from in vitro cultured stem of Populus alba×P. berolinensis were determined to establish a high efficiency shoot regeneration system from stem explants of P. alba×P. berolinensis. Stems of Populus alba×P. berolinensis were collected from cultured shoots in vitro derived from dormancy buds of 3-year-old seedlings. The stem explants were cultured on MS medium containing 0.02-mg·L-1 NAA (naphthaleneacetic acid), and 0.1, 0.3, 0.5 and 1.0 mg·L-1 concentrations of TDZ to determine the effect of TDZ on shoot regeneration. Three basal media, i.e. MS, woody plant medium (WPM) and B5, were used to test their influences of different media on adventitious shoot regeneration. Green, red, blue and yellow plastic films in comparison with florescent light as control were used to observe their effects on shoot regeneration. The results showed that different concentrations of TDZ had an evident influence on shoot regeneration. Lower concentration of TDZ (0.1 mg·L-1) resulted in more adventitious shoot regeneration and higher concentration of TDZ (>0.1 mg·L-1) inhibited shoot regeneration. Among different media, MS medium exhibited a high efficiency for shoot regeneration, followed by WPM medium, while B5 medium inhibited shoot regeneration. Normal light and yellow light exhibited better effects on shoot regeneration, compared with other light.     

Effects of Thidiazuron,basal medium and light quality on adventitious shoot regeneration from <Emphasis Type="Italic">in vitro</Emphasis> cultured stem of <Emphasis Type="Italic">Populus alba</Emphasis>×<Emphasis Type="Italic">P. berolinensis</Emphasis>

The effect of Thidiazuron （TDZ）, basal media and light quality on adventitious shoot regeneration from in vitro cultured stem of Populus albaxP berolinensis were determined to establish a high efficiency shoot regeneration system from stem explants of P. alba~P berolinensis. Stems ofPopulus alba~P berolinensis were collected from cultured shoots in vitro derived from dormancy buds of 3-year-old seedlings. The stem explants were cultured on MS medium containing 0.02-mg·L-1NAA （naphthaleneacetic acid）, and 0.1, 0.3, 0.5 and 1.0 mg·L-1 concentrations of TDZ to determine the effect of TDZ on shoot regeneration. Three basal media, i.e. MS, woody plant medium （WPM） and B5, were used to test their influences of different media on adventitious shoot regeneration. Green, red, blue and yellow plastic films in comparison with florescent light as control were used to observe their effects on shoot regeneration. The results showed that differ- ent concentrations of TDZ had an evident influence on shoot regeneration. Lower concentration of TDZ （0.1 mg·L-1） resulted in more ad- ventitious shoot regeneration and higher concentration of TDZ （〉0.1 mg·L-1） inhibited shoot regeneration. Among different media, MS medium exhibited a high efficiency for shoot regeneration, followed by WPM medium, while B5 medium inhibited shoot regeneration. Normal light and yellow light exhibited better effects on shoot regeneration, compared with other light.