Language：English   Publishing type：Research paper (scientific journal)   Publisher：FOREST PRODUCTS SOC  

The demand for wood-based materials as an alternative to plywood is increasing, and a synthetic adhesive is typically used for the fabrication of such materials. The identification of replacements for standard adhesives poses a major challenge. In this study, we investigated the mechanical properties of particleboard bonded by cellulose nanofiber (CNF) and compared the mechanical properties of particleboard bonded by CNF with those of particleboard bonded by adhesive. CNF was added together with wood particles during the fabrication process. The target CNF addition amounts were 0, 3, 5, 10, and 20 weight percent. The bending and internal bond strengths of the particleboard with CNF increased, and its water absorption decreased as CNF content increased. The comparison between the boards prepared with adhesives and those with CNF showed that the properties of boards prepared with 20 weight percent CNF were comparable to those of boards prepared with 1 weight percent synthetic adhesive.

DOI： 10.13073/FPJ-D-18-00034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

Maleic anhydride-modified polypropylene (MAPP) is a compatibilizer used to improve the physical and mechanical properties of many wood/plastic composites (WPCs). The properties of WPCs containing MAPP differ according to the characteristics of the specific MAPP that it is used. In this study, the physical and mechanical properties, including shear viscosity, of polypropylene-based WPCs containing different types of MAPP were investigated before and after water absorption. The shear viscosity of MAPP increased with increasing molecular weight, but remained nearly constant for WPCs containing different types of MAPP. In dry conditions, the strongest WPC contained the MAPP with the highest acid value. The highest flexural modulus was observed with the WPC containing the MAPP with the highest molecular weight. In wet conditions, the WPC exhibiting the best mechanical properties contained a MAPP with a molecular weight of 58,000.

DOI： 10.1080/02773813.2018.1432655

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：FOREST PRODUCTS SOC  

Recently, the usage of wood-plastic composite (WPC) products has increased, mainly for exterior decking. The shape of fillers is one of the important factors deciding the mechanical and physical properties of WPCs. Surface-fibrillated wood flour (WF) improves the mechanical properties ofWPCs, although it requires a lot of energy and time to produce the fibrous structure during the pulverization process. Therefore, the adsorptive interaction between cellulose nanofiber (CNF) and WF by hydrogen bonding was investigated. We considered that CNF could form the fibrous structures on the WF surface by mixing CNF and WF. Also, it is thought that the addition of CNF could increase mechanical and physical properties of WPC because CNF has better physical and mechanical properties than most other fibers. The objective of this study was to produceWF-CNF fillers and to evaluate the mechanical and physical properties of WPCs containing WF-CNF fillers. WF-CNF fillers could be produced by freeze-drying after mixing WF, CNF, and water. The fibrous structures on the WF surface were observed through scanning electron microscope images of WF-CNF filler containing 3 weight percent CNF. A WPC with WF-CNF filler containing 22 percent (by weight) WF and 3 percent (by weight) CNF showed improved mechanical properties compared with WPCs without CNF. The water absorption of WPCs containing CNF was found to decrease with increasing CNF content.

DOI： 10.13073/FPJ-D-18-00006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Compatibilizers added into filler-reinforced polymer composites are supposed to bring about the enhancement of mechanical properties by binding with the filler and entanglement with the polymer matrix. We elucidated the binding of maleic anhydride-modified polypropylene (MAPP) compatibilizer and microcrystalline cellulose (MCC) filler. This is usually not readily detectable by spectroscopy. For this, we adopted a set of enzymatic digestion and refined but simple spectroscopy. A series of binary composites of MCC and MAPP was prepared by kneading. By the cellulolytic treatment and an adequate heat processing, we obtained clear IR signals due to the binding. Furthermore, by gel (swollen)-state NMR method which has attracted attention for analyzing plant cell wall, we acquired interface-specific liquidstate NMR spectra giving the information of the bonds between these components insoluble in commonly used solvents. Such analytical methods provide a useful perspective on the relationship between the microstructure and compatibility of composite materials. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2017.08.007

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN WOOD RES SOC  

A newly developed production method for wood flour was proposed for a wood-plastic composite (WPC) and its mechanical properties were investigated. This production process consists of step-wise wet milling using a disk mill, drying, and dry milling by a disk mill. The developed method makes it possible to easily produce fibrillated and uniformly-sized wood flour. The mechanical properties of polypropylene-based WPC were improved by the addition of the produced wood flour. These results suggest that wood WPC has the potential to be introduced into the field of automotive plastics.

DOI： 10.2488/jwrs.63.131

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Wood-based materials are fabricated with adhesives composed of various materials derived from fossil fuels. It is difficult to identify replacements for these chemical adhesives. This study explored nanofiber technologies as an alternative to these adhesives. In this study, we focused on reinforcement effects of lingo-cellulose nanofiber (LCNF) on fiberboards made from softwood and hardwood fiber. We discuss the density effects of reinforcement with LCNF because the density of medium-density fiberboard (MDF), which is widely used for construction, is standardized at about 0.60-0.80 g/cm(3). Fiberboards were manufactured with three densities (0.60, 0.75, and 1.00 g/cm(3)). For softwood fiberboards, the bending properties for LCNF-mixed boards were higher than those for the control fiberboards at all densities. In this paper, control fiberboard means fiberboard with fiber only. For hardwood fiberboards, the bending properties for LCNF-mixed fiberboard for 1.00 g/cm(3)-density board were higher than those for the control fiberboard. For internal bond strength (IB), the IB for LCNF-mixed fiberboard was higher than that for the control fiberboard. The thickness swelling (TS) and weight change (WC) with water absorption for fiberboards containing LCNF were lower than those for control fiberboards. As a conclusion, physical and mechanical properties of the resulting fiberboards were significantly improved with the addition of LCNF, especially for softwood fiberboards, due to close binding between LCNF and wood fibers.

DOI： 10.1007/s10086-016-1582-3

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.4028/www.scientific.net/KEM.715

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

Wood-plastic composites (WPCs) which consist of wood flour and plastics have been widely used as architectural materials for a long time. However, the impact resistance is not always high and basic mechanical properties at high strain rate are not fully understood. In order to clarify the tensile behavior at high strain rates, split Hokinson pressure bar method was used for WPCs consisting of polypropylene. The effects of mixing ratio on the maximum stress and elongation at break were examined at high strain rates.

DOI： 10.4028/www.scientific.net/KEM.715.23

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

In this study, we evaluated the influence of wood flour (particle size: < 90 mu m) on the physical properties of wood flour/polypropylene (PP) composites. Wood flour was obtained by dry ball-milling of forest-thinning material at a rotary speed of 250 rpm for 1, 2, 4, and 8 h. The milled wood flour was filtered using a 90 mu m sieve. The water content of the wood flour was adjusted to 5, 10, or 20 wt%. Composite properties, including mechanical properties, water absorption, and thermal expansion, were evaluated at wood flour loadings of 40 wt%. When wood flour with 5 wt% water content was milled for 2 and 4 h, the resulting wood flour was granular rather than fibrous; flocculation of the fine particles was observed for milling times exceeding 4 h. This morphological change in the wood flour reduced its influence on the physical properties of the composites, although some positive influences were observed on the molding properties of the composite, such as an increase in compound fluidity. Milled wood flour with 10 wt% or 20 wt% water content was fibrous. Scanning electron microscopy observation of milled wood flour with 10 wt% water content revealed partial surface fibrillation at widths of tens to hundreds of nanometers. The addition of wood flour with nanoscale surface fibrils to PP composites positively influenced the properties of the composite, resulting in a decrease in the linear coefficient of thermal expansion in the flow direction.

DOI： 10.1080/02773813.2015.1083583

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SOC FIBER SCIENCE TECHNOLOGY  

Fatigue fracture properties of wood plastic composites (WPC) were investigated. The material was based on a wood flour/polypropylene (PP) master batch, and prepared to be 30wt% and 50wt% wood flour contents by the addition of PP pellets. First, kneading temperature and screw speed of a uni-axial extruder were changed in some conditions, and 190 degrees C and 20rpm were decided from tensile test of the injection-molded WPC specimens as the optimum manufacturing conditions. Next, tensile and fatigue tests were carried out for WPC specimens with 30wt% and 50wt% wood flour contents. The resultant tensile strength and fatigue life were largely improved as compared to neat PP specimens. When a lump of the master batch remained in the WPC specimen, the strength and life were reduced. It should be noted that, while fatigue life of the neat PP specimens was only 10 to 102 cycles to failure range at 30MPa maximum cyclic stress, those of WPC specimens with 30wt% and 50wt% contents were drastically extended to 10(3) to 10(4), and 10(5) to 10(6) cycles to failure, respectively. It was estimated that the major cause of fatigue damage in WPC specimens was craze occurring in the matrix, which initiated near the specimen surface, extended into the inner, and fmally led to the unstable fracture.

DOI： 10.2115/fiber.71.339

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Wood-based materials are widely used in residential construction. These materials can be made from virgin or recycled wood, and most of the materials are fabricated with chemical adhesives. Finding replacements for such chemical adhesives poses major challenges. This study explored nanofiber technology as an alternative to these adhesives. Previous studies have shown that the three-dimensional binding effects of cellulose nanofiber (CNF) and ligno-cellulose nanofiber (LCNF), when mixed with wood flour, can significantly improve the physical and mechanical properties of wood flour board. We use the word "LCNF" as the surface nanofibrillated wood flour. Previous studies have also highlighted problems that occur during compounding and board manufacturing. In this study, a reliable method was established to mix wood flour and LCNF. The method involved a compounding machine, which facilitated board manufacturing safely. Physical and mechanical properties of the resulting wood flour boards were significantly improved with the addition of LCNF, due to close binding between LCNF and wood flour particles.

DOI： 10.1007/s10086-015-1493-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Lignocellulose nanofibers were prepared by the wet disk milling of wood flour. First, an ethylene-butene copolymer was pre-compounded with wood flour or lignocellulose nanofibers to prepare master batches. This process involved evaporating the water of the lignocellulose nanofiber suspension during compounding with ethylene-butene copolymer by heating at 105 degrees C. These master batches were compounded again with polypropylene to obtain the final composites. Since ethylene-butene copolymer is an elastomer, its addition increased the impact strength of polypropylene but decreased the stiffness. In contrast, the wood flour-and lignocellulose nanofiber-reinforced composites showed significantly higher flexural moduli and slightly higher flexural yield stresses than did the ethylene-butene/polypropylene blends. Further, the wood flour composites exhibited brittle fractures during tensile tests and had lower impact strengths than those of the ethylene-butene/polypropylene blends. On the other hand, the addition of the lignocellulose nanofibers did not decrease the impact strength of the ethylene-butene/polypropylene blends. Finally, the addition of wood flour and the lignocellulose nanofibers increased the crystallization temperature and crystallization rate of polypropylene. The increases were more remarkable in the case of the lignocellulose nanofibers than for wood flour.

DOI： 10.3390/ma7106919

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

Wood-based materials are used extensively in residual construction worldwide. Most of the adhesives used in wood-based materials are derived from fossil resources, and some are not environmentally friendly. This study explores nanofiber technology as an alternative to such adhesives. Previous studies have shown that the three-dimensional binding effects of cellulose nanofiber (CNF), when mixed with wood flour, can significantly improve the physical and mechanical properties of wood flour board. In this study, ligno-cellulose nanofibers (LCNF) were fabricated by wet disk milling of wood flour. Composite boards of wood flour and LCNF were produced to investigate the binding effect(s) of LCNF. The fabrication of LCNF by disk milling was simple and effective, and its incorporation into wood flour board significantly enhanced the physical and mechanical properties of the board.

DOI： 10.3390/ma7096853

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

The sizes and shapes of wet ball-milled wood flour were investigated based on their average particle size, size distribution, their solution viscosity, and scanning electronmicroscopy images. The ball-milling conditions were combinations of rotational speed (150, 200, and 250 rpm) and milling time (1 to 16 h). The average diameter of the wood flours decreased and the degree of fibrillation of the wood fibers increased with the ball-milling time at each rotational speed. Ball-milled wood flours having the same average particle size had similar surface fibrils that were tens to hundreds of nanometers wide. Ball-milling at 200 or 250 rpm could pulverize just as effectively as that at 150 rpm because the size reduction and fibrillation progressed more quickly. Tensile and bending properties of the composites prepared from the ball-milled wood flour (4 wt% in polypropylene) were evaluated. Morphological changes in the wood fillers had little effect on the properties of the composites. The tensile and bending properties of the composites containing the wood filler were 10% higher than those for the unfilled resin.

DOI： 10.1080/02773813.2013.817431

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Language：English   Publishing type：Part of collection (book)   Publisher：Wiley Blackwell  

Global measures for reducing the levels of CO2 gas, which has been identified as a cause of global warming, have begun to be implemented as discussed in the Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP). Since resin parts are manufactured from fossil fuels in most processes, the regulations that control the use of the fossil fuels are being enforced. For example, the resin waste produced in a factory has to be necessarily recycled. Furthermore, once poly(ethylene terephthalate) (PET) bottles and automobile bumpers are commercially marketed, they are collected again at the end of their useful life for recycling in factories. They are used as raw materials for other products by being combined with other materials or by modifying and improving their properties.

DOI： 10.1002/9783527674220.ch5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Wood-based materials are extensively used for residual construction worldwide, especially in Japan. Most wood-based materials are fabricated using adhesives, some of which are not environmentally friendly. As an alternative to chemical adhesives, we explored this issue using nanofiber technology, especially the use of cellulose nanofibers (CNF), as reinforcement in wood flour (WF) board to replace chemical adhesives. We found that CNF could be easily made by pulverization in a ball mill. The physical and mechanical properties of WF board were improved by the three-dimensional binding effects of the CNF.

DOI： 10.1007/s10086-013-1348-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

To improve the water resistance of bamboo flour/high-density polyethylene (HDPE) composites, the effects of plastic content, coupling agents, and the addition of micro-fibrillated cellulose (MFC) on formulations were studied, and their rheological and mechanical properties were evaluated. The composites were prepared by injecting molding with a basic composition of equivalent amounts of bamboo flour and HDPE, and the melting fluidity of the compounds, tensile strength, and tensile modulus of the composites were determined. An increase in water resistance was detected in all three tests. By increasing the plastic content, negative effects such as a decreased tensile modulus were observed. When evaluating the compatibility between bamboo flour and plastic using coupling agents and MFC addition, positive effects were noted for water resistance, melting fluidity, and tensile modulus. We also confirmed that the procedure used to increase the compatibility between bamboo flour and plastic could easily be used for industrial applications by changing the coupling agents. Overall, a novel positive property (increased tensile modulus) and an increased water resistance were observed after MFC addition.

DOI： 10.1080/02773813.2013.768672

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN WOOD RES SOC  

In the present study, we modified micro-fibrillated cellulose (MFC) mechano-chemically by a surface treatment with calcium silicate hydrate, in order to develop an effective filler material for producing wood-plastic composites (WPC). The surface modification could be performed efficiently by the combination of a wet ball-milling process in the presence of silica powder and Ca(OH)(2) and a subsequent hydrothermal treatment, giving rise to a formation of tobermorite crystals of calcium silicate hydrate. The surface-treated MFC products exhibited high heat resistance and no irreversible aggregation even after normal heat-drying at 60 degrees C. By an addition of the modified MFC filler to polypropylene-based WPC, the composite materials demonstrated high mechanical strength and high elastic modulus.

DOI： 10.2488/jwrs.59.375

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SOC FIBER SCIENCE TECHNOLOGY  

Even though fibrous wood filler is known to be effective for improving mechanical and water-resistant properties of wood plastic composite (WPC), it has not been commercially adopted because of its high cost and less handling ability. In the present study, with an expectation of similar positive effect of fibrous wood filler, we carried out a fibrillation of a surface of practical wood flour in pre-mixed compound, containing wood flour, polypropylene, and compatibilizer, for producing WPC with high filler content by means of wet disk-milling. Scanning electron micrography revealed a micro-fibrillation on the surface of wood flour in the ground pre-mixed compound. The size of the surface micro-fiber could be controlled by disk-milling conditions. The formation of the micro-fibrous structure affected the melt viscosity of the compounds and improved mechanical properties of molded samples. The positive effect of the surface micro-fiber formation can be attributed to an interaction among the micro-fibers such as hydrogen bonding and entanglement. The observed reinforcement effect by the surface fibrillation was essentially identical to that of wood fiber although fibrillation was attained just in the surface of wood flour.

DOI： 10.2115/fiber.67.1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

It is important to utilize reinforcement by fibers in wood plastic composites (WPC). However, when a thermoplastic polymer is mixed with fibrous wood material, the melt fluidity of the mixture usually decreases and its fabrication becomes difficult. This tendency is pronounced for the composite with a high cellulose content. In this study, the effects of added fly ash, which is a spherical silica, on the fluidity of melt mixture and injection molded composite are reported. Increase in fluidity of compound and fall of molding viscosity were observed by the addition of fly ash. The spherical shape of fly ash was maintained after molding. The increase in water-resistance of the injected mold was also confirmed. Addition of fly ash improved the molding of cellulose/plastic composites with high cellulose content and also improved their water-resistance.

DOI： 10.1080/02773810903349721

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

The effects of resin content (10-30%), cellulose fiber length (120 and 300 micrometer), and molding conditions (press, injection, and extrusion molding) on the thermal expansion of high filler content cellulose/polypropylene composites were evaluated. Other physical properties such as densities, bending strengths, and water absorption of composites were also determined. The results indicated that thermal expansion of composites is dependent on the above conditions. Small thermal expansion was observed for composites with low resin (high cellulose) content. Composites with long fibers (300 micrometer) showed smaller thermal expansion than those of 120 micrometer, except for injection-molded composites with 20% resin content. Composites prepared by injection and extrusion molding showed anisotropy of thermal expansion depending on the parallel and perpendicular directions of molding. The results of thermal expansion are discussed in the light of other physical properties and the interaction of fibers in the composites.

DOI： 10.1080/02773810903537119

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Language：Japanese   Publishing type：Research paper (scientific journal)  

For a study of wood (cellulose) polypropylene composite with high filler content, the effects of resin content and cellulose fiber length on the fluidity of compound and physical properties of mold products were evaluated and discussed. Results are summarized as follows: 1. In the compounding process, void induced by cellulose fiber had influence on the discharge rate, 2. Results of viscoelasiticity and wet strength indicated the effect of tangle of fiber is dependent on resin content and cellulose fiber length. 3. The compound of 300/an fiber length and 20% resin content showed thixotoropic flow and improved the molding characteristics. This paper would contribute for manufacture of high performance composites with high content of cellulose fiber. © 2009 The Society of Materials Science, Japan.

DOI： 10.2472/jsms.58.292

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

In wood/plastic composite of high wood filler content, filler dispersion in resin is important which determines mobility of compound and mechanical properties of products. This work reports on the dispersion of components in compound by evaluation of viscoelasticity using a cone rheometer. The effects of size of cellulose fiber and resin content on viscoelasticity were analyzed, and the dispersion of cellulose is discussed to reach the following conclusions: The viscoelasticity measured by a cone rheometer was dependent on the dispersion state of compound, and evaluation of viscoelasticity affords the evidence for dispersion state of filler in compound; On the basis of viscoelastic evaluation of compound with different resin content, a model for dispersion of cellulose and resin with tangle of fiber is proposed; Viscoelastic analysis showed that cellulose size has influence on tangle of fiber, and results of viscoelasticity and mechanical properties of mold products suggested that an important factor determining tangle of fiber is its average aspect ratio. The proposed analysis of viscoelasticity presents a new technique for estimating the dispersion state of compound of high filler content which is hardly accessible by conventional fluid evaluation methods. The present method is simple and useful for quality control in manufacture.

DOI： 10.1002/pen.20963

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS INC  

The dispersion of filler in resin is an important factor which determines the mobility of a compound in a molder and also the mechanical properties of molded products in wood/plastic composite, especially with high wood filler content. In this report, the dispersion of components in the melt-mixture of a compound in response to the size of cellulose filler and resin content was examined for compounds with a high content of cellulose in polypropylene by the evaluation of viscoelasticity using a cone rheometer, and the following conclusions were obtained: (1) The viscoelasticity measured by a cone rheometer was dependent on the dispersion state of the compound, and it was confirmed that the presented evaluation method of viscoelasticity affords information relevant to the dispersion state of filler in a compound; (2) On the basis of the viscoelastic evaluation of compounds with different resin contents, a model for the distribution of cellulose and resin is proposed in terms of the tangle of fibers; (3) Viscoelastic analysis showed that cellulose size has an influence on the tangle of fibers; (4) The results of viscoelasticity and mechanical properties of molded products suggested that an important factor determining the tangle of fibers is the average aspect ratio. The proposed analysis of viscoelasticity presents a simple technique for estimating the dispersion state of a compound with high filler content, which is hardly possible by conventional fluid evaluation methods.

DOI： 10.1002/pen.20946

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

Although wood/cellulose-plastic composites (WPC) of low wood/cellulose content have been more accepted worldwide and are promoted as low-maintenance, high-durability building products, composites containing high wood/cellulose content are not yet developed on an industrial scale. In this study, flow properties, mechanical properties, and water absorption properties of the compounds of cellulose microfiber/polypropylene (PP) and maleic anhydride-grafted polypropylene (MAPP) were investigated to understand effects of the high cellulose content and the dimensions of the cellulose microfiber. The molding processes studied included compression, injection, and extrusion. It was found that fluidity is not only dependent on resin content but also on the dimension of the filler; fluidity of the compound declined with increased fiber length with the same resin content. Dispersion of the composite was monitored by charge-coupled device (CCD) microscope. Increasing the plastic content in the cellulose plastic formulation improved the strength of mold in addition to the bond development between resin and filler, and the tangle of fibers. The processing mode affected the physicomechanical properties of the cellulosic plastic. Compression-molded samples exhibited the lowest modulus of rupture (MOR) and modulus of elasticity (MOE) and the highest water absorption, while samples that were injection-molded exhibited the highest MOR (70 MPa) and MOE (7 GPa) and low water absorption (2%).

DOI： 10.1007/s10086-007-0889-5

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