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.     

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.     

Strength reduction of spruce wood through slow freezing

Some selected mechanical properties of spruce wood (Picea abies L.) were determined after freezing green timber boards under different conditions. The influence of the freezing rate and the time of exposure to negative temperatures were evaluated by applying three different freezing conditions which may occur in winter when green timber is stored in an open yard. It was found that a high freezing rate (?10 °C/h) does not affect wood strengths at all, while slow freezing (by ?1 °C/h) significantly reduces all mechanical wood properties, especially MOR, MOE and the compressive strength (by 20…30 %), the Janka hardness (by 18 %), and also the tensile strength (by 10 %). A longer time of exposure, involving repeated freezing and thawing due to natural temperature variations led to further reduction of MOR, MOE and the compressive strength (up to 37 %), but without further affecting the tensile strength, shear strength and hardness. The obtained results may be useful to industrials with respect to a more careful planning of green timber purchase and storage in wintertime.     

Mechanical and physical properties of thermally modified Scots pine wood in high pressure reactor under saturated steam at 120, 150 and 180 °C

Scots pine sapwood and heartwood were thermally modified under saturated steam at 120, 150 and 180 °C in a high pressure reactor. Mechanical properties such as dynamic and static modulus of elasticity (MOE), static modulus of rupture (MOR), Brinell hardness and impact toughness were evaluated. The static MOE for sapwood did not decrease substantially (approximately 1 %), not even with a high mass loss of more than 12 %, when the wood was modified at 180 °C. Static MOE of the wood increased approximately 14 %, when modified at 150 °C. Surprisingly, MOR increased by 15 %, when modified at 150 °C with mass loss of 2.3 %. Whereas impact strength and hardness decreased somewhat, when modified at 180 °C. Moreover, high anti-swelling efficiency values were obtained (60 % for sapwood and 52 % for heartwood) when modified at 180 °C.     

Mechanical,Thermal, and Interfacial Characterization of Randomly Oriented Short Sisal Fibers Reinforced Epoxy Composite Modified with Epoxidized Soybean Oil

Short sisal fibers were reinforced in epoxidized soybean oil (ESO) modified toughened epoxy blends to improve the mechanical and thermo mechanical properties. Tensile modulus and tensile strength of the composite with 15 wt% sisal fiber were found to be increased as compared with bio-based epoxy blend. From DTG analysis, rate of degradation peak is found to be shifted to higher temperature revealing enhanced thermal stability of composite over base matrix. Dynamic mechanical analysis predicted higher storage modulus and higher glass transition temperature of bio-based epoxy composite. Scanning electron micrographs showed strong fiber-matrix adhesion. Contact angle measurement reveals the hydrophilic character of bio-based epoxy composite     

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.     

Improvement of termite resistance,dimensional stability and mechanical properties of pine wood by paraffin impregnation

Paraffin has been used as surface protection of wood throughout the ages but its use for impregnation to improve wood resistance to biodegradation is recent. This study determined the main improvements on wood properties with paraffin impregnation. Healthy Pinus pinaster Ait. wood was impregnated with paraffin at different levels using a hot–cold process. Weight gain, equilibrium moisture content and dimensional stability (ASE) at 35 and 65 % relative humidity, termite durability against Reticulitermes grassei (Clément), bending strength, bending stiffness (MOE) and Janka hardness were determined. Density increased from 0.57 to 0.99, ASE ranged between 38–96 % and 16–71 % for 35 and 65 % relative humidity, respectively. Equilibrium moisture content decreased from 9.9 and 12.0 % to 0.8 and 3.6 % for 35 and 65 % relative humidity. Termite durability improved from level 4 to level 3 of attack, and higher termite mortality was found in treated wood (52 % against 17 %). Bending strength (MOR) increased with paraffin weight gain, reaching a 39 % increase. MOE also increased by about 13 % for wood with a weight gain around 80 %. Janka hardness increased significantly reaching about 40 % for wood with 80 % weight gain. Paraffin impregnated wood has improved properties with regard to equilibrium moisture content, dimensional stability and density, bending strength and Janka hardness, and resistance against termites.     

鱼皮胶原纤维-淀粉复合膜的制备及性能研究

为明确鱼皮胶原纤维尺寸及其添加量对鱼皮胶原纤维-淀粉复合膜性能的影响,本研究利用醋酸预处理鱼皮(3、6、9、12 h)获得了不同尺寸的胶原纤维(CF3、CF6、CF9、CF12),考察了不同类型胶原纤维及其添加量对共混膜性能的影响。采用傅里叶红外光谱技术、差示扫描量热法及扫描电子显微镜对复合膜进行结构表征。结果表明:添加鱼皮胶原纤维后,复合膜的断裂伸长率和水蒸气透过系数均增加,溶解性降低;当CF3和CF6添加量分别为7.5%和10%时能增强复合膜的抗拉强度,而且以10% CF6制备的复合膜抗拉强度性能最好,添加CF9和CF12时,复合膜的抗拉强度呈降低现象。对添加10% CF6制备的复合膜和纯淀粉膜进行表征,发现胶原纤维与淀粉相容性良好,在成膜过程中,胶原纤维交错在淀粉膜中,两者之间形成了氢键,但复合膜的热稳定性下降。     

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.     

Airlaid nonwoven panels for use as structural thermal insulation

Thermal-bonded airlaid nonwoven webs consisting of fiber glass and polyester bicomponent fibers were manufactured, and then multilayer webs were formed into composite panels using compression molding technique. The consolidation process was optimized and the effect of bulk density on air permeabilites, mechanical properties, and thermal resistance was studied. Increasing binder amount and bulk density improved the flexural and tensile strength. Thermal resistance of the panels were found to be very dependent on the bulk density such that the resistance increased exponentially with an initial increase in density, then leveled off and decreased linearly with further increment in density. Depending on the composition and bulk density, the panels provided thermal resistance between 0.52 and 0.88 Km²/W, tensile strength between 2 and 7 MPa, and flexural strength between 600 and 3500 kPa. The findings revealed that airlaid nonwoven panels can be designed to use as structural thermal insulation materials in constructions.     

乙二醇二缩水甘油醚/蒙脱土协同增强大豆蛋白膜的性能研究

为了提高大豆分离蛋白(SPI)材料的耐水性能与力学性能,扩大其在食品工业领域的应用。本研究以SPI和蒙脱土(MMT)为原料,乙二醇二缩水甘油醚(EGDE)为交联剂,制备SPI/MMT复合膜,并对其物理力学性能及水阻隔性能进行探究。结果表明:MMT和EGDE的加入均能够有效提高复合膜的物理力学性能,当SPI复合膜中同时添加MMT和EGDE(20%)时,各项性能最佳,复合膜拉伸强度为14.95 MPa,比纯SPI膜增加了239.77%、弹性模量增加88.98%、含水率降低16.12%、吸湿性降低31.07%、总溶解物降低39.68%、水蒸气透过率降低35.85%。EGDE与MMT的协同增强作用,提高了SPI复合膜的物理力学性能与水阻隔性。     

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.     

花状氧化石墨烯原位展开共聚聚酰胺6及其功能纤维

为实现复合纤维中石墨烯的分子级分散,从而改善现有石墨烯复合纤维制成率低、强度低、耐用性差等问题,提出了一种原位展开共聚的机制,使得聚酰胺6(PA6)分子接枝的石墨烯片能够均匀分散在体系内,从而批量制备多功能PA6/石墨烯纤维,建立起全新的纤维制备-加工-性能一体化系统,实现了多功能性和高力学性能的兼顾。结果表明：在聚合过程中,花状氧化石墨烯呈现出逐步展开、分散的形貌变化,同时参与聚合反应中;反应结束后,PA6分子均匀接枝在石墨烯片表面,并诱导PA6发生了晶型转变;加入0.1%石墨烯后复合纤维单丝的拉伸强度相比纯PA6纤维提高25.4%,拉伸模量提高49.5%;此外,石墨烯复合PA6面料兼具优异的抗菌、抗病毒、远红外发射、负离子发生、防紫外线等功能,具有广阔的市场前景。     

桦木锯屑／聚丙烯挤出复合技术研究

桦木锯屑/聚丙烯熔融复合,通过单双螺杆挤出机组进行挤出木塑复合材料的制备。改变锯屑与聚丙烯的比例、添加MAPP、马来酸酐与过氧化二异丙苯等偶联剂,研究复合材料的弯曲强度、抗拉强度、冲击强度和弹性模量等与锯屑比例和偶联剂之间的关系,探讨最优的桦木锯屑/聚丙烯挤出复合工艺技术参数。结果表明:桦木锯屑比例为30%时强度和模量值较高;加入MAPP可以提高复合材料的强度,MAPP的加入量5%时复合材料的综合性能较好,MAPP的加入量与强度的提高没有呈现显著的正相关;随着MAPP的加入,复合材料的强度得到提高,桦木锯屑和聚丙烯之间的比例关系对于强度的提高影响不显著;无论桦木锯屑和聚丙烯之间的比例如何,加入马来酸酐和过氧化二异丙苯(DCP)都可以提高复合材料的强度,但是马来酸酐和过氧化二异丙苯(DCP)二者之间要有合适的比例;在一定的温度和压力等工艺条件下,桦木锯屑/聚丙烯能够制作出性能优良的木塑复合材料;添加哪种偶联剂都可以改善复合材料的力学性能,偶联剂用量有一定的范围。     

Influence of fiber surface modifications on the mechanical behavior of Vetiveria zizanioides reinforced polymer composites

The natural fiber is pretreated with chemicals namely, alkali, peroxide, and benzoyl chloride. Composites are prepared using chemically treated fibers as reinforcements and mechanical characteristics are tested. The results confirmed that, benzoylation improved the tensile, compressive, and impact strengths of the composite by 113%, 56.78%, and 95%, respectively. Peroxide treatment has improved the flexural strength by 56.13% and improved the elongation of the composite during tension, flexure, and compression tests. The surface morphology showed minimal defects in the benzoylated composite and hence, benzoylation is suggested for the best overall behavior and peroxidation for enhanced bending and elongation.     

Influence of temperature of thermal treatment on surface densification of spruce

Spruce (Picea abies L. Karst) wood lamellae, thermally treated at 170, 190, 210 and 230 °C were surface densified by compression at a temperature of 150 °C to three degrees of compression. Immediate springback, set recovery, mechanical properties in 3-point flexure, Brinell hardness and density profiles measurements were used to determine the effect of thermal treatment on the properties of surface densified wood. The highest immediate springback occurred in wood specimens thermally treated at the highest temperature (230 °C) and decreased with decreasing thermal treatment temperature. The untreated samples had the highest set recovery, which decreased with the temperature of thermal treatment. The surface densification increased hardness and bending strength. The highest increase was in the case of untreated wood and decreased with the temperature of thermal treatment. The modulus of elasticity (MOE) and modulus of rupture (MOR) of surface densified wood decreased with increasing thermal treatment temperature. The trend was similar for specimens which were thermally treated but not surface densified. Surface densification increased the density of the specimens in the first few millimetres below the surface. The highest density was achieved in untreated specimens and the lowest in specimens thermally treated at the highest temperature.     

竹炭涤纶纤维的性能检测与分析

为了进一步了解竹炭涤纶纤维的力学性能,解决在纺织生产中存在的问题,测试了竹炭涤纶纤维的力学性能,包括直接拉伸性能、非直接(结节、钩接)拉伸性能和松弛性能等;比较了竹炭涤纶纤维与普通涤纶纤维之间的不同;选择了适当的力学模型,应用Origin8.0数据分析软件对竹炭涤纶纤维的非直接(结节、钩接)拉伸性能和松弛性能分别进行拟合,综合分析了实验结果和拟合参数。结果表明:在常温干态条件下,竹炭涤纶纤维的断裂强度、初始模量均低于普通涤纶纤维,断裂伸长和断裂功有所增加;经湿处理后,各项性能较干态时普遍下降。非直接拉伸状态下,竹炭涤纶纤维的断裂强度、断裂伸长、初始模量和断裂功等全部减小;对于竹炭涤纶纤维,多项式模型可以很好地拟合其直接拉伸、结节拉伸和钩接拉伸性能。标准线性固体模型可以很好地拟合竹炭涤纶纤维的松弛性能。     

Effect of grafting generations of poly(amidoamine) dendrimer from the sisal fiber surface on the mechanical properties of composites

In order to improve the mechanical properties of sisal fiber-reinforced polypropylene composites, the sisal fibers were grafted with poly(amidoamine) dendrimer and the effects of grafting generations on the mechanical properties of composites were studied. The results reveal that the tensile, flexural, and impact strength of the composites are improved considerably with the poly(amidoamine) dendrimer grafting treatment. For the 2.0 generation treatment with the poly(amidoamine) dendrimer, the tensile, flexural, and impact strength of the composites at 30 wt% fiber loading increase by 29%, 13%, and 54%, respectively. However, the thermal and mechanical properties of the sisal fibers decrease after prolonged grafting treatment.     

Influence of drying temperature upon some mechanical properties of beech wood

The paper presents the results obtained in an experimental study concerning the influence of drying temperature upon the mechanical properties of beech wood (Fagus sylvatica L.). Sound wood samples without red heart were cut from white (unsteamed) beech timber parts, dried at different temperatures: 20 °C, 80 °C, 90 °C, 100 °C, 115 °C and same relative air humidity: 50%. After performing classical tests for evaluation of some selected mechanical properties, the following conclusions could be drawn: all bending properties (static bending strength, modulus of elasticity and impact bending strength) increased with increasing temperature, confirming thus the benefiting effect of heat upon wood plasticity. The tensile strengths, both parallel and perpendicular to grain, increased with increasing temperature, but only in the range below 100 °C; as soon as the temperature exceeded this value, the tensile strengths began decreasing. As far as compression strength parallel to grain, shearing strength and splitting resistance is concerned, no significant influence of temperature could be established. However, it seems that these properties are negatively affected by kiln-drying, as even with low kiln-drying temperatures these strengths are much lower than in case of air-drying.