High Wood Content Research Articles

Plasticizing cell walls as a strategy to produce wood-plastic composites with high wood content by extrusion processes

A challenge in producing wood-plastic composites (WPCs) with a high wood content using extrusion processes is the poor processability, which gives rise to inadequate properties of the resulting WPC. Plasticizing the stiff wood cell walls can be a strategic response to this challenge. Two thoughts are addressed herein on improving the plasticity of wood particle cell walls: use of ionic liquids or use of low molecular weight organic thermal conductors. An ionic liquid can dissolve the cell wall surface and therefore reduce the stiffness of cell wall during an extrusion process. Organic thermal conductors can be incorporated into the cell wall (bulking) to improve the thermal conductivity, thereby sufficiently softening the lignin, a native plasticizer embedded in the cell walls. The potential issues that may arise as a result of these approaches are also presented and discussed.

Extending Pine Bark Supplies with Wholetree and Clean Chip Residual Substrates

Abstract A limited supply of pine bark (PB) over the past several years has caused concern among many nursery producers. In continuing the search for alternative substrates and working to quantify the extent to which substrates can be amended with high wood content alternatives, this study was developed to evaluate substrate treatments comprised of PB with 25, 50, and 75% clean chip residual (CCR) or WholeTree substrate (WT), as well as 100% substrates of each high wood fiber substrate. By 180 and 365 DAT, pH and electrical conductivity (EC) values for all treatments were similar to those of the 100% PB control. Growth data at 365 days after planting (DAT) showed that with all nursery crops tested, nursery producers could use 75% CCR or 75% WT in their standard PB substrate with limited impact on crop growth. The purpose of this study was to allow nursery producers the opportunity to become comfortable using CCR or WT as amendments before switching completely to 100% alternative substrates.

Evaluation of Composted Poultry Litter as a Substrate Amendment for WholeTree, Clean Chip Residual, and Pinebark for Container Grown Woody Nursery Crops

Abstract WholeTree (WT) and clean chip residual (CCR) are potential new nursery substrates that are by-products of the forestry industry containing high wood content. Initial immobilization of nitrogen is one concern when using these new substrates; however the addition of composted poultry litter (CPL) to substrates containing high wood content could balance initial nitrogen immobilization and provide an inexpensive fertilizer source for growers. This study evaluated five woody nursery species being grown in WT, CCR, and pinebark (PB) with the addition of CPL or peat as a substrate amendment. Results indicate that these species can be grown successfully in WT and CCR substrates 6: 1 (by vol) with CPL. Use of CPL in WT and CCR substrates may provide an alternative to traditional PB plus peat based combinations in container plant production while providing poultry producers an environmentally sound means of waste disposal.

Moderation of Entrance Pressure Drop and Extrudate Swelling of Wood Fiber/Polypropylene Composites Melt in Rotating-Die Extrusion Process

A novel rotating-die system was proposed to moderate the elastic swelling for molten polypropylene (PP) and wood/polypropylene (WPP) composite. The results suggested that the neat PP and WPP melts followed the psuedoplastic non-Newtonian pattern. The rotation of the die could moderate the extrusion load and entrance pressure drop. The die rotation effect appeared to be very pronounced for the PP with high wood contents and high extrusion rates. The decreases in extrusion load and entrance pressure drop were related with reductions of melt viscosity due to shear heating effect. The results practically implied that use of the rotating die system could increase the productivity in the extrusion process. In terms of elastic swelling, in all cases, it was found that the swelling ratio of neat PP and WPP melt composite increased with increasing shear rate, but for any given shear rates, the addition of wood particles and the use of rotating die caused decreases in swell ratio of the melts, the wood content being more well-defined than the die rotating speed.

The impact of silane chemistry conditions on the properties of wood plastic composites with low density polyethylene and high wood content

AbstractSilane chemistry was implemented on various formulations of wood/thermoplastic polymer composites (WPCs) with low density polyethylene (LDPE) and high wood content (60 wt%). Taguchi analysis was used to evaluate the impact of vinyltrimethoxysilane content (VTMS), dicumyl peroxide content (DCP), and processing temperature on the rheological, morphological, and dynamic mechanic properties of WPCs. The torque power was measured by a Haake torque rheometer and indicated that the VTMS content and temperature most significantly impacted the rheological properties related to silane reactions. Differential scanning calorimetry also showed a larger depression in LDPE melting point and crystallinity index when a high VTMS content (35 phr), high DCP content (0.5 phr), and a high compounding temperature (200°C) were used. With dynamic mechanical analysis (DMA), it was shown that the compounded formulations had a higher storage modulus over a wide range of temperature whereas the β transition temperature increased with higher content in silane reactants. Interestingly, the high humidity/temperature conditioning step aimed at crosslinking resulted in a drop of dynamic moduli compared to the freshly compounded formulations. This was explained by the fact that during compounding of LDPE with high wood content and silane reactants, significant amounts of matrix and interfacial silane crosslinking already occurred. Subsequent conditioning in a high humidity and temperature environment was proposed to hydrolyze the interfacial siloxane bonds resulting in a degradation of mechanical properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Wood/Plastic Composite of High Filler Content

Preparation and properties of wood/plastic composite (WPC) with high content of wood filler around 80% are reported focusing at: effects of high filler content, preparation of all bio-based composite by using poly(lactic acid) (PLA) as plastic material and cellulose esters as compatibilizer, and method for improving weather resistance of wood/PP composite. Addition of about 2% of cellulose esters of C4-C6 aliphatic carboxylic acids was effective for improving the bending strength of high wood content WPC of PLA by slowing down the crystallization rate of plastic. For improving weather resistance of wood/PP composite, top-coating was found most effective.

THE PALEOBIOLOGICAL IMPLICATIONS OF HERBIVOROUS DINOSAUR COPROLITES FROM THE UPPER CRETACEOUS TWO MEDICINE FORMATION OF MONTANA: WHY EAT WOOD?

Rare assemblages of woody coprolites from different strata of the Two Medicine Formation provide surprising perspectives on the feeding behavior of Late Cretaceous ornithischian dinosaurs. Most of the irregularly shaped, calcareous specimens are largely composed of fragmented conifer wood (13%–85%) and can be identified as coprolites by the presence of distinctive backfilled dung beetle burrows. The large size (up to 7 L in volume), fibrous contents, and associated bones and eggshell strongly suggest that the source animals at one site were Maiasaura hadrosaurs. The wood-bearing coprolites occur in strata ranging in age from ∼74–80 Ma, revealing a recurring (possibly seasonal) habit of wood ingestion. The preponderance of wood in the specimens and the absence of recognizable small-diameter twig fragments suggest that wood ingestion was intentional—that the coprolite producers had not merely consumed wood inadvertently when feeding on the leaves and bark of terminal branches. Because undegraded wood provides inconsequential nutritive value for vertebrates, it is unlikely that ornithischians would have expended the energy to masticate intact wood for little benefit. Furthermore, patterns of tissue damage in the fecal wood fragments suggest fungal degradation. Thus, the most parsimonious explanation for the high fecal wood content is that the coprolite producers consumed decomposing wood to capitalize on resources released by fungal attack, along with the tissues of the decomposers and associated invertebrate detritivores. These multiple coprolite deposits provide direct fossil evidence of recurring dinosaur diets and suggest that some ornithischians at least occasionally tapped detrital resources. Although such feeding behavior is rare in large extant herbivores, utilization of rotting wood would have augmented the resource options of Cretaceous ecosystems that lacked fodder provided by grasses and other derived angiosperms.

Syntheses and properties of liquefied products of ozone treated wood/epoxy resins having high wood contents

Abstract Liquefied products with high wood content were prepared by pretreating wood with ozone before liquefaction. As a result, the ratio of wood to polyhydric alcohol (W/P ratio) used as solvent could be increased to 2:1. Resin blends were prepared by mixing liquefied products with ethylene glycol diglycidyl ether (EGDGE, water-soluble) and diglycidyl ether of bisphenol A (DGEBA, oily consistency). The wood content of the resin blend could be increased to 53%. The resins were cured by citric acid or triethylene tetramine (TETA), and their mechanical properties were evaluated. Dynamic mechanical measurements revealed that the former had higher glass transition temperatures than the latter. It was found that the resin with DGEBA cured by citric acid had almost the same level of tensile strength as commercial plastics.

Effect of wood powder on polymer foam nucleation

AbstractIt is usually reported that wood particles in wood/polymer composite foams can act as nucleating sites. Since high wood contents are used, it is difficult to determine exactly the effect of wood particles. In this study, LDPE was chemically foamed in a twin‐screw extruder, and small amounts of wood (0–5 phr) were added to determine their effect. Particle size was investigated by using three mesh sizes: 45–61, 104–125, and 180–210 μm. As expected, wood particles acted as nucleating agents that substantially reduced cell size and increased cell density. J. VINYL. ADDIT. TECHNOL., 12:19–24, 2006. © 2006 Society of Plastics Engineers

Wood/plastic ratio: Effect on performance of borate biocides against a brown rot fungus

Abstract The effect of wood/plastic ratio and the presence of a boron compound on resistance to biodegradation of wood plastic composites (WPC's) by the brown rot fungus Gloeophyllum trabeum was investigated in a soil block exposure. Weight losses of all WPC's were generally lower than those of solid wood, even when only the wood component of the WPC was used in calculating weight loss. Higher wood content was associated with greater weight losses, suggesting that the plastic encapsulated wood at lower wood levels. Borates markedly reduced weight losses at all wood/plastic ratios. Weight losses tended to be slightly lower with a Na/Ca borate than with similar levels of zinc borate. Mechanical properties did not correlate well with weight losses under the conditions evaluated, but these effects may have been masked by moisture sorption. The causes and implications of these differences are discussed.

Low-ash peat deposits from a dendritic, intermontane basin in the tropics: a new model for good quality coals

Many good quality, thick, low-ash Carboniferous, Cretaceous and Tertiary coal deposits have dulling-upward sequences that have been interpreted to be of ombrotrophic, lowland, coastal origin. Previous studies of potential modern analogues for thick, dulling-upward coal sequences have focused on tropical, ombrotrophic coastal peats. However, most modern coastal ombrotrophic deposits would yield “all bright” coal seams. New evidence from peat deposits of the southern intermontane Tasek Bera Basin, Western Malaysia, reveals that thick, low-ash, low-sulfur peat may originate in narrow tributary valleys with moderately steep flank gradients. These deposits may be favorable precursors to dulling-upward coals, in that they contain high wood and low-ash content at depth and medium wood and slightly increasing ash content in the upper parts. Peat accumulation in the Tasek Bera Basin began in Mid-Holocene time. During the past 4500 years, 500 cm of low-ash (<5 wt.%), low-sulfur (<0.4 wt.%) woody peat was deposited in narrow (400–700 m), elongate (3 km) tributary valleys of the southern Tasek Bera swamp system. Before onset of peat accumulation, a thick (>40 cm) white, fluvial silty clay with wood fragments was deposited. The clay-rich sediments are overlain by limnic black mud, sandy clay and dark-brown mud-rich peat up to 70 cm thick. The ash content of the mud-rich peat is as high as 31 wt.%. The high-ash peat is overlain by low-ash, sapric to hemic peat up to 5 m thick. The basal 3 m of the peat deposits contain abundant logs and large woody fragments, whereas the top 2 m have less hard wood, but more arborescent fragments of palmae, such as roots from Pandanus atrocarpus. The acrotelm (top 50 cm) has a low-to-medium ash content (<10 wt.%). With burial, the deposits of southern Tasek Bera Basin would yield a dendritic sediment pattern of sandstone, shale, carbonaceous shale and a dulling-upward, vitrain-rich coal, overlain by carbonaceous shale. Because of the dendritic nature of the Tasek Bera Basin, coal seams would most likely have a similar pattern as the Carboniferous humic coal deposits of the Black Warrior Basin in Alabama (USA). However, the good quality coals with dulling-upward characteristics would be concentrated in the southern tributaries of the basin.