Poisson’s ratio of the MDF in respect to vertical density profile

The work deals with Poisson’s ratios (PR’s) of medium density fiberboard (MDF) measured using digital image correlation and correlated to vertical density profiles (VDP). MDFs of four different thicknesses were first scanned by X-ray to obtain VDPs and then subjected to compression while measuring by DIC. PR’s of MDF reveal low correlations with VDP (<0.08), but strong local behavior ranging from 0.025 to 0.06 for 12 mm thickness, from 0.018 to 0.105 for 18 mm, from 0.03 to 0.175 for 25 mm, and from 0 to 0.43 for 38 mm.     

Natural Fiber Improvement by Laccase; Optimization,Characterization and Application in Medium Density Fiberboard

Crystallinity of cellulosic fiber directly affects the physical and chemical behavior of the individual fiber and ultimately the product made from. In a controlled condition, if the natural fiber is exposed to enzymatic hydrolysis, its crystallinity improves without affecting the cellulose component of the fiber. In this work, four basic factors for enzymatic reaction, i.e., temperature, time, pH, and enzyme amount, were optimized using response surface methodology (RSM). The response was taken as the fiber crystallinity index, measured by X-ray diffraction method. The optimum treated fiber was further analyzed for the field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA) and results were compared with untreated fiber. Medium density fiberboards (MDF) were manufactured from optimum treated fiber and its tensile properties and water resistance properties were compared with MDF made from untreated fiber. The observation revealed a maximum of up to 14% increment in fiber crystallinity index (CrI) as compared to untreated fiber. The MDF prepared from optimum treated fiber exhibits improved tensile property and lower water absorption property as compared to MDF prepared from untreated fibers.     

Conductive Polyaniline/Cellulose/Graphite Composite Films with High Thermal Stability and Antibacterial Activity

Functional composite films were successfully prepared from cellulose, graphite (GP), and polyaniline (PANI) using a combination of physical and chemical processes. Cellulose was dissolved in N-methylmorpholine-N-oxide monohydrate (NMMO) and regenerated in water to form the matrix. GP was dispersed in the NMMO solvent prior to the dissolution of the cellulose, and PANI was deposited on the surfaces of the cellulose/GP films by in situ chemical polymerization. The structures of the PANI/cellusose/GP composite films were investigated using X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and SEM/energy-dispersive X-ray spectroscopy. The mechanical strengths, thermal stabilities, conductivities, and antibacterial activities of the films were studied in detail. The results showed that GP formed a multilayered structure in the cellulose matrix and that the PANI nanoparticles were tightly wrapped on the film surface. The film thickness increased from 40 m to 100 m after the addition of GP and PANI. The tensile strength of the composite films was 80~107 MPa, with the elongation at break being 3%~10%. The final residual weight of the composite films was as high as 65%, and the conductivity of the composite films reached 14.36 S/m. The cellulose matrix ensured that the films were flexible and exhibited desirable mechanical properties, while the GP filler significantly improved the thermal stability of the films. The PANI coating acted as a protective layer during burning and provided good electrical conductivity and antibacterial activity against Escherichia coli; both of these characteristics were slightly enhanced by the incorporation of GP. These PANI/cellulose/GP composite films should be suitable for use in electronics, antistatic packing, and numerous other applications.     

Improving physical and mechanical properties of new lignin- urea-glyoxal resin by nanoclay

To eliminate toxic formaldehyde from wood based panels, glyoxal, a low volatility and nontoxic aldehyde, was used to react with urea and lignin to prepare a glyoxalated lignin- urea-glyoxal (LUG) wood adhesive resin. Moreover, another objective of this research work was to improve the physical and mechanical properties of the new LUG resins by nanoclay addition. For the preparation of LUG resin, glyoxalated lignin (15 mass%) was added instead of second urea to the urea-glyoxal resin synthesis under acid conditions. The LUG resin so prepared was mixed with 1, 2 and 3 mass% nanoclay by mechanically stirring for 5 min at room temperature. Then, the physicochemical and structural properties of the prepared resins as well as the water absorption and the mechanical properties of the plywood panels bonded with it were measured according to standard methods. The physicochemical test results indicated that the gel time of the LUG resin was markedly slower than that of the UF resin. Plywood panels prepared with the LUG resin also presented lower water absorption as well as weaker shear strength than those prepared with the UF resin. Addition of nanoclay changed the physicochemical properties of the resins as the gelation time of the LUG resin was shorter when adding sodium montmorillonite (NaMMT). Higher shear strength values and lower water absorption were achieved by continuously increasing nanoclay proportion from 1 to 3 mass%. Furthermore, addition of nanoclay had more influence on panels bending strength than their flexural modulus. X-ray diffraction (XRD) analysis also indicated that NaMMT exfoliated completely when mixed with LUG resin.     

生物可降解聚（3-羟基丁酸-co-3-羟基戊酸共聚酯）/聚乳酸共混物的相容性和结晶性

针对聚（3-羟基丁酸-co-3-羟基戊酸共聚酯）（PHBV）热稳定性差、易分解的问题,通过与聚乳酸（PLA）采用熔融共混的方法制备了不同混合比例的的PHBV/PLA共混物,借助差示扫描量热仪、热重分析仪、动态热机械分析仪和X射线衍射仪研究了PHBV/PLA共混物的相容性、热学性能和结晶性等,并用热台偏光显微镜观察了PHBV/PLA共混物的动态热结晶过程。结果表明：PHBV/PLA共混物呈现分离的熔融温度和玻璃化转变温度,X射线衍射曲线上没有出现新的衍射峰,说明PHBV和PLA的相容性较差;PLA的加入提高了PHBV的热稳定性能,拓宽了PHBV的熔融加工窗口;随着共混物中PLA比例的增加,共混物的结晶相由“海-岛”相逐渐变成两聚合物分别连续成相。     

Preparation and characterization of graphene enriched poly(vinyl chloride) composites and fibers

In this paper, poly(vinyl chloride)/graphene (PVC/G) composite fibers are extruded through a set of wet spinning unit for the purpose of properties improvement, including mechanical strength, thermal stability, and electrical conductivity. PVC/G composite membranes are also prepared using a spin-coating method for the analysis on the distribution of graphene in PVC composite. The PVC/G composite fibers are systematically characterized by means of Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, and X-ray Diffraction. The mechanical, thermal, and electrical properties of the prepared PVC/G composite fibers are also analyzed. The experimental results show that the graphene sheets at a low concentration of 1–5 wt% can be distributed homogeneously in the PVC matrix; the mechanical properties, thermal stability, and electrical conductivity of PVC can be enhanced significantly by the blending of graphene sheets.     

玉米-小麦淀粉/玉米醇溶蛋白双层膜热学及微观特性

研究了玉米-小麦淀粉成膜液与玉米醇溶蛋白成膜液不同配比制作的5 种可食用复合膜理化特性的差异, 并分别通过扫描电子显微镜观察、热重分析、差示扫描量热分析、X射线衍射分析、傅里叶变换红外光谱分析对其 热学特性和微观结构进行研究。结果表明：添加一层玉米醇溶蛋白后,双层膜阻水性提高,机械性能得到改善,由 扫描电子显微镜观察结果可知双层膜间结合紧密,热重分析和差示扫描量热分析结果显示双层膜热稳定性得到提 高,X射线衍射结果表明生物大分子之间相容性较好,傅里叶变换红外光谱分析结果发现双层膜间产生了新的氢键 等作用力,为玉米-小麦淀粉/玉米醇溶蛋白双层膜在食品包装中的应用提供了重要的参考依据。     

Light medium-density fibreboards (MDFs): does acetylation improve the physico-mechanical properties?

Light medium-density fibreboards (MDFs) with a target density of 580 kg m³ were produced from fibres, which were obtained by defibrillation of chips of commercially available acetylated solid wood (“Accoya^®”). The fibres were produced by thermo-mechanical pulping under industry-oriented conditions in a laboratory refiner. Infrared spectra showed that after the refiner process and board production, the material exhibited the same acetyl content as the initially acetylated solid wood. The fibres were bonded with 4 and 8% (related to the dry fibre mass) polymeric methylene diphenyl isocyanate and the properties of the obtained MDFs were compared with comparable MDFs from untreated Scots pine fibres which were produced under the same conditions. The modulus of rupture tended to be slightly lower for the acetylated boards, while the modulus of elasticity and the internal bond strength (IB) were equal for the respective resin loads. Acetylation clearly reduced the thickness swelling and the water uptake during immersion in cold and boiled water compared to the unmodified boards. IB after the boil test increased with acetylation and with the resin content. The study indicates that acetylated MDFs can be produced with maintained mechanical properties but strongly enhanced moisture-related properties by defibrillation of acetylated solid wood chips in a refiner and subsequent conventional board production.     

壳聚糖/酸枣仁黄酮复合膜的制备与表征

采用流延法制备含有不同比例酸枣仁黄酮提取液的壳聚糖复合膜,并测试复合膜的物理性能(厚度、密度及透明度)和机械性能(抗拉强度、断裂伸长率),通过傅里叶变换衰减全反射红外光谱(fourier transform attenuated total reflection infrared spectrometry,ATR-FTIR)、X-射线衍射(X-ray diffraction,XRD)和扫描电镜(scanning electron microscope,SEM)对其结构进行表征。结果表明,酸枣仁黄酮提取液的添加量对复合膜的拉伸强度、断裂伸长率和透明度均呈现逐渐减小的趋势。壳聚糖复合膜红外光谱显示在溶解制膜过程中壳聚糖分子的基本骨架未发生改变,X-射线衍射分析表明壳聚糖复合膜的晶体结构被破坏,SEM分析证实复合膜表明有酸枣仁总黄酮的聚集。     

超声波处理对棉纤维结构与性能的影响

用XRD、TGA、SEM等方法测定并分析了超声波处理对棉纤维的形态结构、结晶形态、热性能和力学性能的影响,力求为超声波在棉织物染整加工中的应用奠定理论基础。实验结果表明:超声波处理改变了棉纤维的形态结构,使棉纤维的天然扭曲消失,纤维表面变得粗糙;使棉纤维的结晶度降低,结晶尺寸减小;棉纤维的热裂解温度降低,热稳定性变差;棉织物的断裂强度降低,断裂延伸度提高。     

Comparative Study of Starch Fibers Obtained by Electro-spinning of Indigenous,Commercial and Cationic Potato Starch

ABSTRACT

By using the electro-spinning process on natural polymers, it is possible to obtain biodegradable membranes with potential applications in filters and scaffolds for tissue engineering. In this study, a comparison was made between the respective chemical, physical and thermal properties of the fibers from two sources of starch: One derived from a local, indigenous variety of potato (Diacol Capiro), native to the Boyacá region of Colombia (from here on referred to as “local starch”); the other, commercially available starch. A cationization of fibers was also carried out on the two starches. Chemical, physical and thermal properties were analyzed by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (DRX), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed the fibers were cationized with a highly amorphous state, with a heat resistance of 300°C from physicochemical changes generated in the fibers.     

再生竹纤维的结构和热性能测试

应用扫描电镜(SEM)、红外光谱(FTIR)、X-射线衍射等测试手段对竹纤维的结构进行了研究，通过与棉纤维、黏胶纤维的结构的对比，分析了竹纤维结构的特点。利用热重分析简要分析了竹纤维的热性能。     

脉冲电场前处理玉米醋酸酯淀粉的物化性质

利用扫描电镜、激光粒度仪、X射线衍射仪、差示扫描量热仪对脉冲电场前处理玉米醋酸酯淀粉的物化性质进行研究,同时与未经脉冲电场前处理的玉米醋酸酯淀粉性质进行比较。结果表明:玉米淀粉经过脉冲电场处理后更容易引入乙酰基;激光粒度分析发现,脉冲电场前处理的醋酸酯淀粉颗粒较未经脉冲电场前处理的醋酸酯淀粉颗粒的体积平均粒径和表面积平均粒径都大;X射线衍射图谱表明,脉冲电场前处理玉米醋酸酯淀粉的相对结晶度较小;热特性分析发现,脉冲电场前处理醋酸酯淀粉较未经脉冲电场前处理的To,Tp和ΔH均下降。     

Use of aluminum oxide nanoparticles in wood composites to enhance the heat transfer during hot-pressing

In this study, the effect of Al₂O₃ nanoparticles on the heat-transfer properties of medium density fiberboard (MDF) was investigated. Al₂O₃ nanoparticles were added at two levels (0.5 and 1.0 %) by percentage weight fraction of dry wood fibers to urea formaldehyde (UF) resin. The core temperature profile and thermal conductivity tests showed higher rate of heat transfer after addition of nanoparticles, subsequently it has improved the bonding strength of MDF. Differential scanning calorimetry was used to estimate the heat evolved during the exothermic reaction of UF resin curing. Scanning electron microscopy shows good dispersion of nanoparticles. Thermal conductivity of UF resin improved after nanoparticles addition proved by KD2 pro results. Modulus of rupture, modulus of elasticity and thickness swelling also improved.     

Effect of surface modification of fibers on the medium density fiberboard properties

Surface modification of mixed hardwoods fibers by sodium hydroxide (NaOH) was conducted to investigate the effect of chemical treatment on the fiber properties along with physico-mechanical characteristics of the medium density fiberboard (MDF). The results indicated that the NaOH treatments can dissolve a portion of hemicelluloses and almost all amount of extractives from the fibers, but it was not strong enough to remove the lignin thoroughly. The FTIR results illustrated that chemical changes can occur during the various NaOH treatments of the fibers. X-ray diffraction analysis revealed that the crystallinity of the studied fibers increased after the alkaline treatment. Investigation of mechanical properties of the MDF showed that modulus of rupture and internal bond strength of the treated samples were decreased compared to the control ones. In addition, water absorption and thickness swelling of treated boards were higher than that of untreated samples. This study indicated that the physico-mechanical properties of the boards were negatively affected by the NaOH treatment.     

Fabrication of electrically conductive and improved UV-resistant aramid fabric via bio-inspired polydopamine and graphene oxide coating

Abstract

This study presents the fabrication of woven aramid fabric (AF) with integrated properties, especially with improved surface activity, UV resistance, electrical conductivity and thermal properties. A biomimicry surface functionalization with polydopamine (PDA) and a further modification by graphene oxide (GO) coating of the AF was demonstrated. The surface properties of AF were changed by repeated reduce graphene oxide (rGO) coating process. The scanning electron microscope (SEM) results showed that the rGO sheets were successfully formed on the surface of AF, and the deposition of GO/rGO was proven by X-ray photoelectron spectroscopy (XPS). The electrical conductivity was ascertained by the electrical surface resistance value of the AF. A low surface resistance value of 6.43 K?cm^?1 was obtained after five times of modification, resulting in an excellent conductivity. The ultraviolet protection factor (UPF) value of the modified AF increased to 73 in comparison to 37 for the original AF.     

Effects of pulsed electric fields (PEF) treatment on physicochemical properties of potato starch

Potato starch–water suspensions (8.0%, w/w) were subjected to pulsed electric fields (PEF) treatment at 30 kV·cm^− 1, 40 kV·cm^− 1 and 50 kV·cm^− 1, respectively. The physicochemical properties of PEF-treated potato starch samples were investigated using scanning electron microscopy (SEM), laser scattering technique, X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and the Brabender rheological method, with native potato starch as reference. It has been concluded from SEM analysis that dissociation and damage of PEF-treated potato starch granules appeared. Some granules aggregated with each other and showed gel-like structures. It was revealed from particle size analysis that there was an obvious increase of the granule size after PEF treatment. This has been attributed to the aggregation among granules. It was also demonstrated from other analysis that relative crystallinity, gelatinization temperatures, gelatinization enthalpy, peak viscosity as well as breakdown viscosity of modified samples all decreased with increasing electric field strength.

Industrial relevance

In this study, the effect of PEF treatment (up to 50 kV·cm^− 1) on physicochemical properties of potato starch has been investigated. The results from SEM images showed that dissociation, denaturation and damage of potato starch granules had been induced by the PEF treatments. Some of granule fragments showed gel-like structures, and congregated with each other or with other starch granules. Laser scattering measurements of particle size revealed that an obvious increase of granule size under electric field strength of 50 kV·cm^− 1, which was attributed to the aggregation of the starch granules. The X-ray diffraction pattern showed an obvious loss of crystalline structure after the PEF treatment at 50 kV·cm^− 1, which induced a trend of transformation from crystal to non-crystal in potato starch granules. DSC analysis showed a decrease in gelatinization temperatures (T_o and T_p) and gelatinization enthalpy (ΔH_gel) with increasing electric field strength. Brabender rheological method has been used to show that the peak viscosity and breakdown viscosity decrease with increasing electric field strength of PEF treatment. All the results reveal that the PEF treatment can lead to an intragranular molecular rearrangement of potato starch granules, which induces changes of various physicochemical properties of the treated starch thus may endow it some new characteristics and functions. This phenomena may warrant further more detailed study.     

Influence of hydrothermal modification of fibers on some physical and mechanical properties of medium density fiberboard (MDF)

Any treatment of fibers can influence properties of medium density fibreboard (MDF). In this research, the effects of hydrothermal treatment on physical and mechanical properties of MDF were studied. Industrial fibers were hydrothermally treated in a stainless steel reactor at 120, 150 and 180 °C for 0, 30 and 90 min as holding time. Test boards were made based on 0.7 g/cm³ target density, with 10 mm thickness under a pressure of 30 bar and at a temperature of 170 °C and a press time of 10 min. The boards were tested for internal bonding (IB), moduli of elasticity (MOE) and rupture (MOR), thickness swelling and water absorption. Results showed that the water absorption was not affected by the hydrothermal treatment; while the thickness swelling was improved and the boards became dimensionally stable. The MOE was slightly reduced due to the hydrothermal treatment. The MOR and the IB were significantly decreased by the hydrothermal treatment.     

A novel 4-(2-pyridylazo) resorcinol functionalised magnetic nanosorbent for selective extraction of Cu(II) and Pb(II) ions from food and water samples

This paper describes a novel sorbent based on 4-(2-pyridylazo) resorcinol functionalised magnetic nanoparticles and its application for the extraction and pre-concentration of trace amounts of Cu(II) and Pb(II) ions. The nanosorbent was characterised by Fourier transform infrared spectroscopy, X-ray powder diffraction, thermal analysis, elemental analysis and scanning electron microscopy. The effects of various parameters such as pH, sorption time, sorbent dosage, elution time, volume and concentration of eluent were investigated. Following the sorption and elution of analytes, Cu(II) and Pb(II) ions were quantified by flame atomic absorption spectrometry. The limits of detection were 0.07 and 0.7 μg l^?1 for Cu(II) and Pb(II), respectively. The relative standard deviations of the method were less than 7%. The sorption capacity of this new sorbent were 92 and 78 mg g^?1 for Cu(II) and Pb(II), respectively. Finally this nanosorbent was applied to the rapid extraction of trace quantities of Cu(II) and Pb(II) ions in different real samples and satisfactory results were obtained.     

Thermal properties of wood-gypsum boards

Transient simultaneous measurements of thermal conductivity, volume heat capacity and thermal diffusivity of laboratory wood-gypsum boards have been performed with ISOMET 2104 at room temperature. The influences of wood particle content, density and moisture content on thermal properties were investigated. The measurements were performed in a direction perpendicular to the board plane. The effect of density and wood particle content on the thermal properties may be related to the presence of voids both between and inside particles. It seems, that the dominant mechanism of heat transfer across the board is the heat conduction through the voids. Wood-gypsum boards with a density of 850–1300 kg/m³, a moisture content of 2–11% and a wood particle content of 0–35% have the following thermal conductivity of 0.189–0.753 W m^-1 K^-1, volume heat capacity of 0.683–1.43×10⁶ J m^-3 K^-1 and thermal diffusivity of 0.171–0.367×10^-6 m² s^-1; their magnitudes are higher than those ones of OSB, MDF, particleboard and plywood.