Investigation of electromagnetic shielding effectiveness of needle punched nonwoven fabrics with staple polypropylene and carbon fibres

Conductive needle punched nonwoven fabrics are developed from staple polypropylene (PP) and varying weight fractions (10, 20 and 30 wt.%) of staple carbon fibres. A fibrous webs of staple PP and carbon fibres were formed at a wool-type carding machine, and these webs subsequently bonded on needle punching machine with 132 punches/cm² and 13.5 mm needle penetration depth. The electromagnetic shielding effectiveness (EMSE), absorption and reflection characteristics of as-produced needle punched nonwoven fabrics were determined using a network analyser as specified in ASTM D4935-10 in the frequency range 15–3000 MHz. The surface resistivity measurements were carried out in accordance with ASTM D 257-07 standard. These results indicate that the EMSE values increase incrementally with frequency in the 15–3000 MHz range. The nonwoven sample with 30 wt.% carbon fibre showed the lowest surface resistivity of 3.348 kΩ and corresponding highest EMSE of ~42.1 dB in the 3000 MHz frequency range. In comparison, the highest EMSE values from 10 to 20 wt.% staple carbon fibre were found to be 15.6 and 32.2 dB in the 3000 MHz frequency, respectively. It was observed that the absorbance and reflectance curves of each nonwoven fabric move at opposite directions to each other. It was found that as the amount of carbon fibre in the nonwoven fabric increases, absorbance values decrease, but reflectance values increase. The resultant nonwoven fabric samples are expected to be used as garment interlining after thermal bonding and wall interlayer in the future.     

Preparation and characterization of wood-plastic plywood bonded with high density polyethylene film

This paper presents a study on the potential use of high density polyethylene (HDPE) film as wood adhesive for formaldehyde-free plywood. The physical–mechanical properties of the plywood, including thickness swelling (TS), water absorption (WA), tensile shear strength, modulus of elasticity and modulus of rupture were evaluated. Results show that HDPE film dosage positively affects the properties when ranging from 61.6 to 246 g/m². The performance of these panels was comparable to those of plywood made with commercial urea–formaldehyde (UF) resins. Comparisons of the dimensional stability between the two plywood demonstrated that 7-day TS and WA values of the panels bonded with UF resins were 5.10 and 23.5 % higher than those bonded with HDPE film, confirming the suitability of HDPE for the use as adhesive in wood-based composites intended for indoor applications subjected to high moisture. DMA tests show that HDPE bonded plywood was significantly inferior in thermal stability at 120 °C and above while it presented almost the same dynamic mechanical properties as UF plywood when the temperature was lower than 100 °C, making it suitable to be used as geothermal floor.     

Study on needle punched jute nonwoven as an artificial medium for germination of seed: Effect of bulk density

A uniform, porous, and bulky mechanically entangled fibrous sheet, i.e., needle-punched nonwoven, from eco-friendly and natural, low-grade jute fiber, has been designed and engineered to use as an artificial medium for germination of seed in place of soil. Needle-punched nonwoven fabrics of different bulk densities have been prepared from low-grade jute. Bulk densities of needle punched nonwoven fabric can be changed due to change of punch density, area density and depth of needle penetration. In this case, bulk densities of fabric have been achieved by varying the punch densities only, keeping the area density and depth of needle penetration same/ unaltered. As per experimentation, 500 g/m² area density needle punched nonwoven with 0.116 g/cm³ bulk density shows the best quality of germination. This bulk density has been achieved using 160 punches/cm² and 13 mm depth of penetration as per the system applied and fiber used. It may be a good alternative as a medium of cultivation. The design of the bed is also proposed in the article. It is observed that in this artificial system, cultivation can be made in hostile condition and plant growth is better than that in soil. Its moisture-holding capacity and temperature control of medium help in better agriculture. This is highly applicable in the regions where soil is either not available or not suitable for cultivation.     

Characterization and analysis of ridge gourd (Luffa acutangula) fibres and its potential application in sound insulation

Ridge gourd, the fruit of Luffa acutangula, is extensively used throughout the world. Nevertheless, there is a dearth of scientific information related to the thermal, mechanical and chemical properties of these fibres to explore its potential application in textile industry. This research work is aimed to characterize the L. acutangula plant and investigate its potential application in sound insulation. The fibres are arranged in a cell like structure, when opened it gives a very lower fibre length of less than 10 mm. The chemical composition of fibres is as like other lignocellulosic fibres having around 64% cellulose, 21% hemicellulose and 10% lignin. The density is of fibre is around 1.46 g/cc and having the average linear density of 432 denier. The nonwovens were produced by blending the L. acutangula fibre with cotton as well polyester fibre webs using layering technique at three different blend proportions and their influence on bulk density, sound insulation, thermal resistivity and air permeability has been analysed. The ANOVA analysis showed that all the properties mentioned above was significantly influenced by the blend proportion of L. acutangula. The nonwoven sample produced from 50/50 blend proportion of cotton/luffa and polyester/luffa samples showed better sound reduction and thermal resistivity compared to other samples. The cell-like structure of luffa combined with low bulk density and higher thickness resulted in better results.     

The influence of calendering parameters on performance properties of needle-punched nonwoven cleaning materials including r-PET fiber

The aim of this study is to investigate the effect of calendaring process parameters on performance properties of needle-punched nonwoven materials including recycled polyester (r-PET) fiber. For this purpose; nonwoven materials produced by carding and needling processes with two different blend ratios have been calendered with different temperatures and roll clearances. The physical and performance properties of the samples such as thickness, bulk density, abrasion resistance, water absorption properties have been determined according to the standard test methods. The results derived from the tests were statistically evaluated by Design Expert^® software and the effects of chosen parameters on physical and performance properties of the samples were assessed. It was observed that additional thermal bonding process with calendering enhanced the performance properties compared to non-calendered samples and the excessive increase in calendering parameters yields to decrease in abrasion resistance and water absorption capacity.     

Investigation of physical and mechanical properties of oil palm wood core sandwich panels overlaid with a rubberwood veneer face

Low-density sandwich panels consisting of an oil palm wood core overlaid with a rubberwood veneer face were manufactured. Effects of two types of grain orientation of the oil palm wood core (parallel and perpendicular to board surface) and three different veneer thicknesses (0.7, 1.8 and 2.7 mm) and core densities (223 ± 14, 301 ± 35 and 418 ± 33 kg/m³) on some physical and mechanical properties of the boards were investigated. Results showed that higher core density increased the values of thermal conductivity, screw withdrawal resistance, modulus of rupture and modulus of elasticity but decreased the value of water absorption without effect on thickness swelling of the boards. Boards with the core grain direction oriented perpendicular to panel’s surface possessed lower value of thickness swelling but higher values of thermal conductivity and strain at fracture when the board failed in a mode of core shear under bending test than those of the others. Finally, the relationship between board density and the measured physical and mechanical properties of the oil palm wood core sandwich panels overlaid with a rubberwood veneer expressed as mathematical equations could be used to predict and design the expected properties of this type of sandwich board.     

Processing and flexural properties of surface reinforced flat pressed WPC panels

While extrusion and injection molding are the common technologies to produce wood-plastic composites (WPC), pressing may be an alternative, particularly when flat products are striven for. In this study, flat pressed WPC panels were surface-reinforced by two different types of thermoplastic face layers to improve flexural properties. The two face materials applied were a commingled fabric made of glass and polypropylene filaments (TWINTEX^®) and a glass fabric reinforced polypropylene laminate (S-TEX^®). Combination of face layers and WPC panels was achieved in a single and a two stage flat pressing process. Besides studying the effects of reinforcing material and number of process stages, the influence on flexural properties of the reinforced panels was identified. Unreinforced WPC panels were tested for comparison. The reinforced WPC panels exhibited greatly improved flexural properties, with MOE (MOR) values up to nearly 10,000 N/mm² (90 N/mm²).     

Kenaf fibre-reinforced polyester composites: flexural characterization and statistical analysis

This paper deals with the effect of the chemical treatment, fibre ratio and fibre reinforcement structure on the flexural properties of kenaf-polyester composites. Composites were made from an unsaturated polyester matrix reinforced with an alkali-treated and virgin kenaf fibres in a loose fibres and nonwovens. Results reveal that alkali treatment improves the flexural properties of composites expect elongation. The same result was obtained when using a nonwoven structure us reinforcement. The best flexural properties were observed for 11.1% fibre weight ratio with the nonwoven structure reinforce composite. The flexural strength and the flexural modulus were 69.5 MPa and 7.11 GPa, respectively, for this composite while it was 42.24 MPa and 3.61, respectively, for polyester samples (no fibre reinforcement). A statistical study was carried out in order to study the effect of the alkali treatment, reinforcement structure and the reinforcement weight ration on the composite properties. This study proved that the parameter with most impact on the measured properties is the fibre-to-matrix weight ratio. And also this study aims to determine the optimum parameters allowing maximising all measured properties and we found that when using a nonwoven structure made with chemically-treated fibre at 11.10% fibre weight ratio, is the optimum solution.     

Studies on Mechanical and Morphological Characterization of Developed Jute/Hemp/Flax Reinforced Hybrid Composites for Structural Applications

In the present study, an attempt has been made to develop and characterize natural fiber-based composites (jute/epoxy, hemp/epoxy, flax/epoxy) and their hybrid composites (jute/hemp/epoxy, hemp/flax/epoxy, and jute/hemp/flax/epoxy) using hand-lay-up technique. Mechanical characterization (tensile, flexural, impact, and hardness test) of the developed composites was performed. The interface between fiber and matrix was examined using scan electron microscopy (SEM). Among (jute/epoxy, hemp/epoxy, flax/epoxy), flax/epoxy composite has shown higher hardness (98 Shore-D) and tensile strength (46.2 MPa) whereas better flexural and impact strength have been shown by hemp/epoxy (85.59 MPa) and jute/epoxy (7.68 kJ/m²) composites respectively. Results showed that hybrid composites observed better mechanical properties. Jute/hemp/flax/epoxy hybrid composite showed the highest tensile strength, modulus and impact strength of 58.59 MPa, 1.88 GPa, and 10.19, kJ/m², respectively. Jute/hemp/epoxy hybrid composite achieved the maximum flexural strength of 86.6 MPa.     

Dynamic mechanical thermal analysis (DMTA) of aqueous phenol formaldehyde (PF) resin modified by nano copper oxide (CuO)

To improve the bio-resistance of engineered wood composites products via gluing process, aqueous phenol formaldehyde (PF) resin was modified using nano CuO containing alkane surfactant and polyvinyl alcohol (PVA) 17-99. The modified PF system was analyzed by dynamic mechanical thermal analysis, and the mechanical properties of the bonded plywood panels including tensile strength, modulus of rupture (MOR), modulus of elasticity (MOE) and shear strength under five test conditions were also evaluated. The results indicated that the addition of nano CuO incorporating PVA 17-99 separated the gel point and vitrification point in the curve of tan δ, which is related to the delaying of moisture loss in modified PF resin during the curing process. The modification showed adverse effect on tensile strength but only a minimal influence on MOR and MOE. Additionally, PVA 17-99 reduced the water resistance of cured PF resins. However, with the test conditions of dipping in 100 °C water for 6 h, then drying for 20 h at 63 °C in air, followed by dipping in 100 °C water for 4 h, PVA consolidated the re-curing effect on the PF resin and compensated the strength loss from hydrolysis. Thus, the modified PF system not only guaranteed bio-resistance of glued wood composites via CuO, but also has the potential for developing self-curing wood composites being applied as structural construction materials.     

Characterization of New Natural Cellulosic Fiber from Heteropogon Contortus Plant

Natural fibers are one of effective substitute for switching artificial fiber and concentrating to reinforce polymer matrixes due to their decomposable character. This study was implied to realize physico-chemical properties of bio fiber obtained from Heteropogon contortus (HC) plant. Heteropogon contortus fibers (HCFs) had cellulose (64.87 wt. %), hemicellulose (19.34 wt. %), lignin (13.56 wt. %), and low density (602 kg/m³). The chemical functional group of HCFs was established by Fourier transform infrared spectroscopy, thermal stability of the fiber up to 220°C discovered by thermogravimetric analysis. Further the assets of HCFs proved that it can act as an excellent reinforcement material as a bio composite. Finally, the tensile properties were carried out through single fiber tensile tests, such as tensile strength, tensile modulus and microfibrillar angle.     

Improving the physical and mechanical properties of particleboards made from urea–glyoxal resin by addition of pMDI

The effect of pMDI on physical and mechanical properties of the particleboards made from urea–glyoxal resin was investigated. The nontoxic and ecofriendly urea–glyoxal (UG) resin was synthesized under weak acid conditions, and its different properties were measured. Then, pMDI at various contents (4, 6 and 8% on resin solids) was added to the UG resin prepared. The thermal and physicochemical properties of the resins prepared as well as their water absorption, flexural properties (flexural modulus and strength) and internal bond (IB) strength of the particleboard panels bonded with them were measured according to standard methods. According to the physicochemical results obtained, the addition of pMDI significantly accelerated the gel time and increased the viscosity and solids content of UG resins. Differential scanning calorimetry indicated that the addition of pMDI decreases the onset and curing temperatures of the UG resin. Physical analysis results of the panels indicated that the particleboards made from UG resins with isocyanate yielded lower water absorption when compared to those bonded with the control UG resins. Based on the findings of this research work, the mechanical properties of particleboard panels bonded with UG resins could be significantly enhanced by the addition of increasing percentages of pMDI. The panels having 8 wt% pMDI exhibited the highest flexural modulus, flexural strength and IB strength value and the lowest water absorption among all the panels prepared.     

Potential of pulp and paper secondary sludge as co-adhesive and formaldehyde scavenger for particleboard manufacturing

This study investigated the potential of secondary sludge (SS) as urea–formaldehyde (UF) co-adhesive for particleboard manufacturing. Three proportions of SS from three conventional pulping processes were added in the formulation of particleboard manufacturing. A 3³ factorial design was used. All panels were tested for thickness swell (TS), linear expansion (LE), internal bond strength (IB), flexural modulus of elasticity (MOE), flexural modulus of rupture (MOR) and formaldehyde emission. Results indicated that particleboards made with SS from thermomechanical pulp (TMP) and kraft pulp (Kraft) met the ANSI standards for LE, IB, MOE, and MOR (with 7 and 9 % UF). However, the TS of panels made with SS was higher than that of control panels and adding SS to the formulation affected negatively this property. Most of the properties studied in the particleboards made with SS from chemical–thermomechanical pulping (CTMP) process failed to meet the ANSI standards. The main advantage of using SS as co-adhesive is the reduction of formaldehyde emission, in the best case here, about 50 %, with CTMP sludge added, of the particleboards.     

梯度结构双组分纺粘水刺非织造材料的制备及其性能

为探究梯度结构对超细纤维非织造材料性能的影响,通过双组分纺粘技术和不同水针压力作用下的水刺开纤技术,用一步法制备了不同面密度（80、120、160 g/m2 ）的梯度结构双组分纺粘水刺非织造材料,并分析了水针压力对结构和透气透湿、力学、过滤性能的影响。结果表明：当面密度一定时,随着水针压力从15 MPa 的增大到28 MPa,双组分纺粘水刺非织造材料的厚度减小,平均孔径减小,透气透湿性能下降;纵/横向断裂强力先增加后减小,断裂伸长率先减小后增加;过滤效率和过滤阻力均增加,其中当面密度为80 g/m2 ,水针压力为11MPa 时,过滤效率（0.85 μm 粒径）和过滤阻力分别达到66.8%和25.1 Pa。     

Effect of Chemical Treatment on Thermal,Mechanical and Degradation Behavior of Banana Fiber Reinforced Polymer Composites

ABSTRACT

The current research endeavor, explores the thermal, mechanical, and degradation behavior of alkaline treated banana fibers reinforced polypropylene composites. Composites incorporating BF (20% w: w) treated with NaOH (5% w: v) aqueous solution were developed using extrusion-injection molding processes. After chemical treatment, the tensile, flexural and impact strength of the composite increases by 3.8%, 5.17%, and 11.50%, respectively. Scanning electron microscope (SEM) observations of tested specimens confirm the fiber pull out and fiber fracture as the main reasons for failure of developed composites under tensile and impact loading. The specimens were exposed to two different environments, water immersion and soil burial for 5 weeks for the degradation studies. The degradation behavior of composites was measured in terms of variation in weight and mechanical properties (tensile, flexural, and impact). The maximum degradation in mechanical properties was observed for the composites buried under soil. The composite lost 7.69%, 12.06%, and 3.27% of tensile, flexural, and impact strength, respectively.     

Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood

In this study, the physical and mechanical properties of plywood panels made from pre-compressed birch (Betula verrucosa Ehrh.) veneer were evaluated. Veneer sheets underwent short-term thermo-mechanical (STTM) compression at temperatures of 150 or 180 °C and at pressures of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 or 3.5 MPa for a period of 1 min prior to adhesive being applied and pressed into panels using phenol formaldehyde adhesive at 100 g/m² spread rate; this was one-third less than the adhesive spread used for the control panels (150 g/m²). The pressing pressure was 1.0 MPa, which was almost half of the pressure used for the control panels (1.8 MPa); and pressing time was 3 min, also half of the pressing time used for the control panels (6 min). The results showed that surface roughness of compressed veneer, water absorption and thickness swelling of plywood panels made from compressed veneer were significantly improved. The shear strength values of plywood panels made from compressed birch veneer even with reduced adhesive spread were higher than those of plywood panels made from uncompressed veneer. The findings in this study indicated that compression of birch veneer could be considered as an alternative to produce more eco-friendly (owing to smaller adhesive spread) value-added material with enhanced properties.     

气流成网超柔软水刺卫生材料的生产

介绍水刺非织造布成布原理,分析德国Dilo公司涡轮式气流成网梳理机关键部位的工作机理及成网原理,通过对气流成网水刺非织造布物理性能的测试,以及对布面外观风格的分析,提出气流成网超柔软水刺卫生材料生产的控制要点。     

Physical,mechanical and biological properties of thermo-mechanically densified and thermally modified timber using the Vacu<Superscript>3</Superscript>-process

Densification and thermal modification change wood properties in different ways depending on the treatment conditions and the wood species. In the presented investigations, densification and thermal modification were applied consecutively. The primary objective of this treatment combination was the compensation of reduced mechanical properties due to the thermal modification by densification. The combined processes were applied to five European wood species: poplar (Populus nigra L.), beech (Fagus sylvatica L.), Norway spruce (Picea abies Karst.), English oak (Quercus robur L.) and European ash (Fraxinus excelsior L.). Depending on the mean density of the species, a thermo-mechanical densification of 43 or 50% was imposed to improve mechanical strength parallel to the grain. Subsequently, the densified material was thermally modified in the so-called Vacu³-process at 230 °C and 20 or 80% vacuum and at 240 °C and 20% vacuum. The thermal modification resulted in changing wood colour, mechanical strength, hardness, dimensional stability and durability. All the wood modification processes were carried out at industrial scale after pre-tests at laboratory scale. The modified material was characterized regarding flexural properties, static and dynamic hardness, structural integrity, abrasion resistance, moisture dynamics, dimensional stability, and durability against white, brown and soft rot fungi. In summary, the test results showed that the consecutive application of thermo-mechanical densification and thermal modification leads to significantly improved durability whilst mechanical properties at least for beech, ash and poplar remained and the material is dimensionally stable.     

Influence of different wood flour fractions on the mechanical properties of injection molded WPC with cellulose propionate

This research investigated the effect of different fractions of commercial wood flour (Type c100 from JRS, Germany) on mechanical and physical properties of wood-polymer composites (WPC). The fractions were named regarding the mean lengths of their particles in µm; 80, 130, 255, 405 and 485. The composite samples were manufactured with 30 wt% of wood flour fractions of all five groups as well as the not fractionated flour, and 70 wt% of cellulose propionate (CP). The melt mass-flow rate (MFR) of the different granules, tensile strength, and modulus of elasticity, flexural strength, flexural modulus and the impact strength of the injection molded specimens as well as the water uptake were determined in this study. WPCs with the specific size range used in this investigation exhibited improved strength and modulus of elasticity in tensile and flexural tests, compared to pure CP. Using fraction 255, the mechanical properties increased the most. Tensile strength rose by 28 and 13% compared to CP and to WPC with the not fractioned wood powder, respectively. Fraction 255 increased flexural strength by 33 and 5% compared to CP and WPC with the not fractioned flour. The MFR (tested at 190 °C with 7.16 kg) of WPC_255 is the lowest with 2.3 g/10 min. Composites with the smallest particles showed the least water uptake.     

用于气流成网非织造布的Trevira双组分纤维

纤维的线密度、纤维聚合物的种类和短纤维的长度对气流成网非织造布的性能有显著的影响。用线密度为１．７ｄｔｅｘ的纤维制得的非织造布的强度最高,Ｔｒｅｖｉｒａ公司提供适合各工厂和产品用户需要的纤维。