木材科学与技术研究新进展

木材作为世界四大基础材料中(钢铁、水泥、塑料、木材)唯一的可再生资源,广泛应用于家具、建筑、能源、新材料等领域,与人们的生活息息相关,已成为国民经济重要支柱产业.从木材微观分子生物学到宏观木结构,再到新型木质纳米材料进行全面阐释,对于木材科学与技术领域的基础理论研究和重大核心技术突破具有重要指导意义.木材科学与技术已发...     

Design of wood/montmorillonite (MMT) intercalation nanocomposite

Studying new wood composites through nano science and technology (NSC) will develop new compounding theory of wood, and accelerate the combination of new technology, wood science, material science and other disciplines. The compounding of wood and inorganic MMT on nanoscale molecular level has high potential to greatly improve the mechanical properties, fire retardance, abrasion resistance, decay resistance, dimensional stability and other properties of wood. Based on the great achievements of polymer/montmorillonite (MMT) nanocomposites, this paper reviewed nano intercalation compounding methods (i.e. in-situ intercalative polymerization and direct polymer intercalation), and discussed the structure, properties and modification of montmorillonite (MMT). According to the main chemical components and particular structure of wood, the authors discussed the liquefaction and plasticization of wood, compared the dissolvability and meltability between wood and polymer, and then systematically put forward the basic idea, technological processes and schematic diagram to prepare wood/MMT nanocomposites (WMNC). The key technology to prepare WMNC is either to introduce delaminated MMT nanolayers into wood with the help of some intermediate polymers, or to obtain liquefied wood or plasticized wood from the complicated natural composite. It is applicable and effective to realize wood/MMT nanoscale compounding with the help of proper intercalation agent and medium polymer through the proposed “one-step” or “two-step” impregnating processes.     

纳米二氧化硅/纳米纤维素复合材料制备及性能分析

使用造纸方法快速成功的制备了纳米纤维素,纳米二氧化硅复合材料,对并材料的力学性能,热性能和吸湿性能进行了分析。研究结果表明:随着纳米二氧化硅的添加量逐步提高,纳米复合材料的理论密度逐渐下降,材料的拉伸性能和模量值都有大幅度的下降。材料热解的初始降解温度和热解活化能随着纳米二氧化硅质量分数的增多提升,当纳米二氧化硅质量分数为20%时,材料初始热解温度为280℃。纳米复合材料的含水率随着吸湿时间的延长而增加,且随着纳米二氧化硅添加量的增多,材料的最终含水率不断提高,当纳米二氧化硅质量分数为20%时,纳米复合材料的最终含水率约26%,纳米复合材料的表面接触角值仅为40.4°。该研究结果可为制备了纳米纤维素/纳米二氧化硅复合材料提供参考。     

Nanoscale in Wood,Nanowood and Wood—Inorganic Nanocomposites

In order to introduce nano science and technology(NST) into the research field of wood science and technology,and promote the research of wood science and wood-inorganic composites to nanoscale ,some new concepts,such as the nano space in wood,nano structure units of wood and nanowood are put forward in this paper based on the layer structure of wood cell wall and the pile-up model of its main components.Furthermore,the process of preparing nanowood is discussed,and wood-inorganic nanocomposites may be operated in three ways with wood (matrix) and inorganic filler phase in 0-2,0-3 or 2-3 dimensions respectively.The following results are obtained:(1) The nanoscale voids in wood indicate that wood has inherent space to accommodate nanosized materials,such as nanoparticles,nanotubes and nanosticks;(2) According to the size from top down,the nano structure units in wood can be classified as :nanolayers,nano CMF (cellulose microfibril) and matrixd,nano crystallite units and cellulose chain clusters,and these can theroretically from nanowood;(3) The preparation of wood-inorganic nanocomposites can be operated on 0-2,0-3 or 2-3 dimensions.     

Polyaniline–polypyrrole nanocomposites using a green and porous wood as support for supercapacitors

Wood is an ideal type of support material whose porous structure and surface functional groups are beneficial for deposition of various guest substances for different applications. In this paper, wood is employed as a porous support, combined with two kinds of conductive polymers (i.e., polyaniline (PANI) and polypyrrole (PPy)) using an easy and fast liquid polymerization method. Scanning electron microscope observations indicate that the PANI–PPy complex consists of nanoparticles with a size of ~20 nm. The interactions between oxygen-containing groups of the wood and the nitrogen composition of PANI–PPy were verified by Fourier transform infrared spectroscopy. The self-supported PANI–PPy/wood composite is capable of acting as a free-standing supercapacitor electrode, which delivers a high gravimetric specific capacitance of 360 F·g⁻¹ at 0.2 A·g⁻¹.     

短链葡聚糖-姜黄素纳米乳液的制备及结构表征

利用短链葡聚糖(short glucan chains,SGC)的螺旋空间结构来包埋姜黄素(curcumin,CUR)。通过使用高剪切分散乳化机高速剪切溶液5 min,用纳米均质机在50 MPa压力下高压均质经剪切后的乳液2次制备成纳米乳液以提高其包埋率和载药量。XRD (x-ray diffraction)和TGA (thermogravimetric analysis)很好的验证了包合物的形成,通过TGA、SEM (scanning electron microscopy)、激光粒径分析仪等各种表征分析得出短链葡聚糖-姜黄素纳米乳液制备成功,所制得的乳液对姜黄素的包埋率和载药量都高于短链葡聚糖-姜黄素包合物,分别达到了71.11%和12.07%,说明制备成纳米乳液对姜黄素的包埋率和载药量都有了明显的提高。所制备的纳米乳液的粒径小于300 nm,粒径分布均一,Zeta电位观测表明所制得的乳液的稳定性有所提高。为提高食品及医药领域姜黄素的生物利用率提供了一定的参考意义。     

Preparation of Chitosan Nanocompositeswith a Macroporous Structure by Unidirectional Freezing and Subsequent Freeze-Drying

Chitosan is the N-deacetylated derivative of chitin, a naturally abundant mucopolysaccharide that consists of 2-acetamido-2-deoxy-β-d-glucose through a β (1→4) linkage and is found in nature as the supporting material of crustaceans, insects, etc. Chitosan has been strongly recommended as a suitable functional material because of its excellent biocompatibility, biodegradability, non-toxicity, and adsorption properties. Boosting all these excellent properties to obtain unprecedented performances requires the core competences of materials chemists to design and develop novel processing strategies that ultimately allow tailoring the structure and/or the composition of the resulting chitosan-based materials. For instance, the preparation of macroporous materials is challenging in catalysis, biocatalysis and biomedicine, because the resulting materials will offer a desirable combination of high internal reactive surface area and straightforward molecular transport through broad “highways” leading to such a surface. Moreover, chitosan-based composites made of two or more distinct components will produce structural or functional properties not present in materials composed of one single component. Our group has been working lately on cryogenic processes based on the unidirectional freezing of water slurries and/or hydrogels, the subsequent freeze-drying of which produce macroporous materials with a well-patterned structure. We have applied this process to different gels and colloidal suspensions of inorganic, organic, and hybrid materials. In this review, we will describe the application of the process to chitosan solutions and gels typically containing a second component (e.g., metal and ceramic nanoparticles, or carbon nanotubes) for the formation of chitosan nanocomposites with a macroporous structure. We will also discuss the role played by this tailored composition and structure in the ultimate performance of these materials.     

Preparation,physical properties and ultraviolet resistance of wood nanocomposites based on modified soybean oil and bentonite

ABSTRACT

Safer environmental requirements have resulted in significant interest in natural polymer-based materials to increase sustainability. In this perspective, wood polymer nanocomposites are of particular interest. Wood polymer nanocomposites were prepared from modified soybean oil, wood flour and cetyl trimethylammonium bromide modified bentonite using the compression-molding technique. Fourier transform infrared spectroscopy and X-ray diffractometric studies were used to confirm the successful modification of bentonite. Incorporation of 3?wt% of bentonite in the composites produced significant improvement in properties compared to those of 1 and 5?wt%. Furthermore, in comparison to the unfilled nanocomposites, nanoclay-filled ones showed an enhanced UV resistance property as judged by lower weight loss and carbonyl index. The decrease in mechanical properties of UV-exposed unfilled composites was more significant compared to those of nanoclay-filled composites. Scanning electron microscope and transmission electron microscope were used to study the surface morphology and distribution of the bentonite into the composites. In addition, with the incorporation of bentonite, significant increase in thermal, mechanical and flame-retarding properties was observed.     

EA/MMT纳米复合材料的制备及其光固化动力学研究

通过4 - 溴甲基二苯甲酮与二甲基正十八胺反应合成的季铵盐光引发剂苯甲酰苄基二甲氨基十八烷基溴化铵(BDOB),进行插层修饰蒙脱土(MMT),通过层间引发聚合法光固化制备环氧丙烯酸酯/蒙脱土(EA/MMT)纳米复合材料;利用红外光谱法对EA/MMT的光固化行为进行了研究.XRD和TEM分析结果表明,MMT在光固化复合材料中已得到插层和部分剥离;增加光引发剂浓度及提高环境温度均可提高其固化速率和双键最终转化率,氧气的存在使体系的诱导期延长,双键转化率降低;光固化反应总级数约为6～7,表观活化能为9.8 kJ/mol.     

聚合物基纳米复合材料的制备方法及其性能评述

简单介绍聚合物基纳米复合材料的的分类,着重介绍聚合物纳米复合材料的制备方法、结构、性能和研究现状,并对纳米材料的发展进行展望。