Applicability of Oxidative Systems to Initiate Grafting on and Bonding of Wood

Graft polymerization techniques were applied to induce bonding in wood composites. Wood surfaces were activated with an oxidant such as hydrogen peroxide, nitric acid, peracetic acid, potassium ferricyanide or sodium dichromate. The activated wood surfaces were then chemically crosslinked with polymerizing materials such as furfuryl alcohol, ammonium lignosulfonate, mixtures of lignosulfonate with furfuryl alcohol, with formaldehyde or with maleic acid. The wood composites were pressed using conventional manufacturing conditions. The strength and water resistance properties of the wood composites were suitable for exterior structural applications. The various methods proposed to induce chemical bonding of wood are briefly reviewed.     

Effect of chemical treatments of wood fibers on the physical strength of polypropylene based composites

Wood plastic composites attract great attention in various applications. Chemical modification of the wood fiber with NaOH and various coupling agents was performed for wood fiber composites. Wood fibers treated with NaOH, APTES, TEVS, and BC coupling agents were compounded with PP matrix for measuring physical properties. All those chemical treatments increased physical properties much compared to the untreated case because of the elimination of impurities by NaOH treatment and because of the introduction of compatible molecular structure onto the wood fiber surfaces. Especially, the TEVS case showed the best tensile strength, and it could be attributed to the chain structure having double bond of the molecules for high compatibility with PP matrix. The SEM morphology also demonstrated increased adhesion between wood fibers and PP matrix with chemical treatments. The adhesion between wood fiber and PP matrix would be a key parameter in achieving high physical properties of the composite materials.     

On the Relationship between Classical Structure Determination and Retrosynthetic Analysis/Total Synthesis†

The relationship between classical structure determination and retrosynthetic analysis combined with total synthesis is examined in detail. The chemical degradation steps in the former are the counterparts of the retrosynthetic steps in the latter. And the gedankenexperiment, also known as “paper chemistry,” working forward and solving the structure from the degradation data, is the counterpart of the experimental forward steps in a total synthesis. The wide use of genealogic-like “trees” to organize and illustrate many reaction sets in organic chemistry is discussed. Excerpts from the writings of Sir Robert Robinson, R. B. Woodward, and Carl Djerassi reveal historically important insights about these activities in the 1940s–1960s.     

Foaming of PS/wood fiber composites using moisture as a blowing agent

This paper presents an experimental study on foam processing of polystyrene (PS) and high‐impact polystyrene HIPS/wood‐fiber composites in extrusion using moisture as a blowing agent. Wood‐fiber inherently contains moisture that can potentially be used as a blowing agent. Undried wood‐fiber was processed together with PS and HIPS materials in extrusion and wood‐fiber composite foams were produced. The cellular morphology and volume expansion ratios of the foamed composites were characterized. Because of the high stiffness of styrenic materials, moisture condensation during cooling after expansion at high temperature did not cause much contraction of the foamed composite and a high volume expansion ratio up to 20 was successfully obtained. The experimental results showed that the expansion ratio could be controlled by varying the processing temperature and the moisture content in the wood fiber. The effects of a small amount of a chemical blowing agent and mineral oil on the cell morphologies of plastic/wood‐fiber composite foams were also investigated.     

Supermolecular structure of wood/polypropylene composites: I. The influence of processing parameters and chemical treatment of the filler

Wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM) were used to investigate the effect of chemical modifications of wood as well as processing parameters on the supermolecular structure and morphology of wood/polypropylene (PP) composites. The surface of the filler was modified to enhance the adhesion between hydrophilic cellulose and hydrophobic polymer. Wood modification was performed by esterification with anhydrides (maleic, propionic, phthalic, crotonic and succinic) and by physical treatment with NaOH. The composites for structural characterization were prepared by the compression moulding method and injection technique. A new design of the compression mould, which ensured the wood pulling, was proposed. It was found that the polymorphs of PP matrix developed due to melt-shearing strongly depended on the pulling temperature as well as on the type chemical modification of wood. The modification of wood caused a significant decrease in the ability to generate the hexagonal phase of PP. Moreover, at a higher temperature of the mould, the amount of hexagonal phase of PP matrix slightly decreases. These investigations are very significant because characterize influence of real parameters processing as well as surface modification of filler on structure of composite materials.     

Microstructure and wear properties of SiC woodceramics reinforced high-chromium cast iron

Wood ceramization is a promising preparation technology. Ceramics made from natural wood can retain the original structural characteristics and unique microstructure of the wood, and also offer acceptable mechanical properties and wear resistance. In this study, the ceramization process of natural poplar wood is optimized. Three-dimensional silicon carbide prepared by ceramization of wood is used to strengthen high-chromium cast iron, and three-dimensional silicon carbide reinforced high-chromium cast iron (3D-SiC/HCCI) composite materials are obtained. The results demonstrate that the treated wood retained acceptable network structure and uniform pore size after ceramization. Based on the size, the pores can be classified into smaller pores (approximately 8 μm), medium-sized pores (20–40 μm), and larger pores (100–300 μm). The 3D-SiC/HCCI composites, obtained by casting and infiltrating these pore channels, show continuous network-like interpenetrating structures in space. The wear resistance of the 3D-SiC/HCCI composite materials was investigated and compared with high-chromium cast iron. The results indicate that under the same friction condition, the wear resistance of the composites is significantly improved, and the abrasion loss is reduced from 3.8% to 0.32%. The three-dimensional silicon carbide in the composites produces a shadow effect during friction, which can provide acceptable support and protection for the high-chromium cast iron matrix.     

Study of physicochemical properties of two current commercial dental self‐curing resin composites

The aim of the present work is the study of some physicochemical properties of two current commercial dental self‐curing two component composites, i.e., of Concise? (3M?, Dental Products, St. Paul, USA), and Alfacomp (VOCO GmbH, Germany). Based on their filler type Concise is characterized as “conventional” or “macrofilled” composite and Alfacomp as “hybrid.” The resin matrix of Concise is a copolymer of 2‐bis[4‐2‐hydroxy‐3‐(methacryloxy)‐propyl]phenyl propane (Bis‐GMA)/triethyleneglycol dimethacrylate, while that of Alfacomp a homopolymer of Bis‐GMA. The composites were prepared in accordance with the manufacturers' instructions by mixing equal amounts of the two components at room temperature. The degree of conversion of double bonds of resin matrix during curing was determined in thin film of composites using FTIR transmission spectroscopy. The degree of conversion of Concise and Aflacomp was found to be correspondingly (73.63 ± 4.33)% and (47.75 ± 1.80)% after a day‐polymerization. Sorption, solubility, and volumetric change were determined after storage of composites in water or ethanol/water solution 75 vol % at 37°C (a good food/oral simulating fluid) for 30 days. These properties for both composites were higher in ethanol/water solution than in water. Also these properties for Concise were lower than those for Alfacomp in both liquids. Thermal stability of composites was studied by thermogravimetric analysis which performed in air atmosphere from 50 to 800°C. This analysis of composites showed the degradation of their resin matrix in three steps. The organic resin content of Concise was found to be 18.0% w/w and that of Alfacomp 20.1% w/w. Concise showed generally better properties than Alfacomp. This behavior must due to the differences in the chemical structure of the organic resin matrix and the type of inorganic filler. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

木材溶剂液化技术及其在制备高分子材料中的应用

木质材料经过热化学液化,可进一步制备酚醛树脂、聚氨酯等高分子材料.本文介绍了木材液化技术制备高分子材料的发展状况,包括液化方法、木材主成分的液化机理以及液化生成物的应用,指出在木材液化反应机理、液化产物的利用和最佳液化工艺的开发等方面尚有待进一步研究,并提出充分利用木材的生物降解性,开发木材液化物与其他材料复合的新型高分子材料具有广泛的前景.     

木材溶剂液化技术及其在制备高分子材料中的应用

木质材料经过热化学液化,可进一步制备酚醛树脂、聚氨酯等高分子材料。本文介绍了木材液化技术制备高分子材料的发展状况,包括液化方法、木材主成分的液化机理以及液化生成物的应用,指出在木材液化反应机理、液化产物的利用和最佳液化工艺的开发等方面尚有待进一步研究,并提出充分利用木材的生物降解性,开发木材液化物与其他材料复合的新型高分子材料具有广泛的前景。     

Physical-Organic Chemistry: A Swiss Army Knife

“Physical-organic chemistry” is the name given to a subfield of chemistry that applies physical-chemical techniques to problems in organic chemistry (especially problems involving reaction mechanisms). “Physical-organic” is, however, also a short-hand term that describes a strategy for exploratory experimental research in a wide range of fields (organic, organometallic, and biological chemistry; surface and materials science; catalysis; and others) in which the key element is the correlation of systematic changes in molecular structure with changes in properties and functions of interest (reactivity, mechanism, physical or biological characteristics). This perspective gives a personal view of the historical development, and of possible future applications, of the physical-organic strategy.     

Preparation and characterization of LDPE and PP—Wood fiber composites

Natural fiber reinforced composites is an emerging area in polymer science. These natural fibers are low cost fibers with low density and high specific properties. These are biodegradable and nonabrasive. The natural fiber composites offer specific properties comparable to those of conventional fiber composites. However, in development of these composites, the incompatibility of the fibers and poor resistance to moisture often reduce the potential of natural fibers, and these draw backs become critical issue. Wood‐plastic composites (WPC) are a relatively new class of materials and one of the fastest growing sectors in the wood composites industry. Composites of wood in a thermoplastic matrix (wood–plastic composites) are considered a low maintenance solution to using wood in outdoor applications. WPCs are normally made from a mixture of wood fiber, thermoplastic, and small amounts of process and property modifiers through an extrusion process. In this study, Wood–plastic composites (WPC) are produce by adding a maleic anhydride modified low density polyethylene coupling agent to improve interfacial adhesion between the wood fiber and the plastic. Mixing is done with twin screw extruder. Subsequently, tensile strength, the modulus of elasticity, % elongation, hardness, Izod impact strength, melt flow index (MFI), and heat deflection temperature (HDT) are determined. Thermal transition temperatures and microstructure are determined with DSC and SEM, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Future prospects for wood cellulose as reinforcement in organic polymer composites

Wood cellulose, a versatile and renewable natural resource, has potential for use as a reinforcement for synthetic organic polymers. During the past 80 years a number of materials using the reinforcing properties of wood cellulose have found major markets. Forms of wood cellulose proposed as reinforcements include: wood fibers, cellulose fibers, microfibillar, and microcrystalline cellulose. Recent attention has been given to them as fillers/reinforcements in thermoplastics and elastomers. Most cellulosic composites derive their existence from their comparatively low materials cost and the filling rather than reinforcing properties of cellulose. However, cellulose chains have a potential stiffness much higher than glass and in the same range as superstiff aramid fibers. This paper examines the state of the art of combining wood cellulose with synthetic organic polymers to from composites and considers new ways for better using cellulose's reinforcing potential.     

Investigation on microstructure and properties of foamed (wood fiber)/(recycled polypropylene) composites

Microcellular foamed (wood fiber)‐reinforced recycled polypropylene composites (MFWPCs) were prepared by an injection molding process where azodicarbonamide was used as a chemical foaming agent. The influence of injection parameters (injection temperature, dwell pressure) on the microcellular structure (cell diameter and cell density) and the mechanical properties of the MFWPCs were investigated. The results indicated that when the melting temperature was 180°C and the dwell pressure was 12.5 MPa, a uniformly distributed microcellular structure of MFWPCs was obtained. Compared with solid wood plastic composites, the density of the MFWPCs decreased by 24.5%, and its impact strength of MFWPCs increased by 53%, because the propagation direction of the crack changed to the “skip” or “bifurcation” mechanism as a result of the microcellular structure, and the surrounding matrix of this structure made it easy to produce forced high‐elastic deformation. The toughening mechanism of the microcellular structure was analyzed. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Effects of raw fiber materials,fiber content,and coupling agent content on selected properties of polyethylene/wood fiber composites

This study investigated the effects of raw fiber materials, fiber content, and coupling agent (CA) content on mixing torque, rheological properties, and crystallization behavior of wood plastic composites (WPC). WPCs were prepared through melt molding processes. This study adopted a response surface strategy of 20 run optimal design for three factors including wood fiber type, fiber content, and CA content. Wood fiber type or wood fiber characteristics influence equilibrium torque and viscosity. The power index n for viscosity as a function of frequency was affected not only by wood fiber content, but also by CA content and wood fiber type. Addition of wood fibers to the system as nucleating agents favors polyethylene crystallization. The values of crystallization enthalpy and melt enthalpy were correlated with wood fiber content and CA content, but they were not affected by wood fiber type. The melt temperatures of polyethylene and composites were comparable. This indicates that the crystallite structure and lamellar thickness are similar. POLYM. ENG. SCI., 47:1678–1687, 2007. © 2007 Society of Plastics Engineers     

木塑复合材料的生产应用现状

木塑复合材料是以木材或各种木质纤维素材料为基体,通过与塑料以不同复合途径形成的一种新型材料。本文介绍了塑木复合材料的生产工艺,综述了挤出配混设备的现状和新的发展,由材料的特点对其应用现状进行了总结,展望了今后的发展趋势。     

Enhanced functionality of Scots pine sapwood by in situ hydrothermal synthesis of GdPO4·H2O:Eu3+ Composites in woods matrix

Luminescent lanthanide-doped phosphates have never been introduced as potential materials for wood functionalization. Wood–ceramic composites (WCC) may enable the extensive use of wood in construction due to different functionalization. Hence, this work proposes the inorganic GdPO₄·H₂O:Eu³⁺ compound as an alternative and innovative method to increase wood chemical resistance and confer new optical properties. Scots pine (Pinus sylvestris L.) sapwood – ceramic composite was obtained through in situ hydrothermal synthesis and compared with the untreated sapwood specimens. The enhanced characteristics of the WCC samples were demonstrated using scanning electron microscopy (SEM), x-ray computed micro-tomography (μCT), and thermogravimetric (TG) analysis. Optical properties were determined by luminescence analysis.     

PVC／木粉复合材料抗冲改性研究

用甲基丙烯酸、丙烯酸丁酯、甲基丙烯酸甲酯三元共聚物P（MAA—BA—MMA）对木粉进行预处理,再利用CPE、ACR和nano—CaCO3对PVC／木粉复合材料进行增韧改性。结果表明,木粉经P（MAA—BA—MMA）预处理后,使用ACR增韧时效果最好,其拉伸强度、弯曲强度、冲击强度和断裂伸长率分别提高了7．97％、5．26％、68．85％和571．26％。SEM结果表明,木粉预处理后再增韧,复合材料界面模糊,断面呈一定的韧性断裂特征。     

一种水性木器漆的研制

对水性聚氨酯木器面漆所用的乳液、助溶剂、助剂等原材料进行了大量的试验对比研究和筛选,制备出一种以脂肪族聚氨酯乳液为基料的水性木器漆,该产品具有漆膜丰满光亮、耐水性优良的特点,其性能高于化工行业标准HG／T、38282006《室内用水性木器涂料》指标要求。     

Performance of zircoaluminate coupling agents in wood flour/fibre-polyolefin composites

Wood flour and fibres do not bond well to polyolefins. Fillers or reinforcing agents for polyolefins based on these materials need to be treated before incorporation. This paper describes the property improvements obtained by treating papers, wood flour and wood fibres with zircoaluminate coupling agents before their forming into composites with polyolefins. The zircoaluminates were found to be effective coupling and hydrophobing agents in this system at low concentrations.     

蔗渣/聚氯乙稀复合材料的制备及表征

以制糖副产品蔗渣为原材料,经超声化学处理,表面化学改性后与聚氯乙稀(PVC)共混挤出,制备了木塑复合材料。通过常规分析和偏光显微镜,热失重分析仪等仪器分析、研究了蔗渣改性后成分及结构的变化,以及热稳定性能的变化。并对所制得的木塑复合材料的基本性能进行了表征,结果表明与市场上的同类产品具有相似的特性。