Effects of nanoclay on physical and mechanical properties of wood-plastic composites

Effects of nanoclay (NC) on physical and mechanical properties of wood-plastic composite (WPC) were studied here. Virgin, recycled, and mixed (50/50% of virgin/recycled) polyvinyl chloride (PVC) were used as the matrix in the WPC. Specimens with three NC contents of 1.5%, 3%, and 5% were manufactured; they were then compared with control specimens. Totally, 12 treatments were manufactured. The physical and mechanical properties were measured in accordance with the ASTM standards. The highest properties were found in specimens made from virgin PVC. Addition of recycled PVC resulted in significant decrease in all properties. NC improved all physical and mechanical properties studied in the present research project; the highest properties were observed in specimens with 5% of NC content. The improvement in properties was as a result of formation of bonds between the hydroxyl groups of NC with the wood flour components. It was concluded that NC would significantly improve the properties in all the three PVC types of virgin, recycled, and mixed. From an industrial point of view, it was concluded that mixing virgin and recycled PVC can be recommended not only to decrease production costs, but also to partially solve the problem of PVC residue which are not bio-degradable.     

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.     

The effect of compression and incision on wood veneer and plywood physical and mechanical properties

ABSTRACT

Drying takes the largest share of energy in plywood production, and varying moisture content of veneers necessitates re-drying that often leads to over-dry veneers with deactivated surfaces, which may promote imperfect bonding. In order to decrease the drying time, reduce the need for re-drying of veneers, and improve the quality of plywood, birch and spruce veneers were subjected to pre-treatment by cold compression, incision, or a combination of the two. The effects of pre-treatment on the veneer and plywood quality were assessed by standard tests. Compression had a beneficial effect on water removal of the wettest veneers (spruce sapwood (SW) and birch), but some thickness reduction was observed in the veneers as well as the finished birch plywood. Compression led to thickness reduction of spruce veneers, but had no effect on SW plywood thickness likely due to higher viscoelasticity. Both compression and the combination of incising and compression levelled the moisture variation within the compressed stacks. Incision improved the modulus of elasticity of birch plywood, shear strength of SW plywood, and both bending and shear strengths of heartwood plywood. Higher surface pressure decreased the drying time of spruce SW in both plain compression and combined incision and compression pre-treatment.     

Relation of chemical and mechanical properties of Eucalyptus nitens wood thermally modified in open and closed systems

ABSTRACT

In the present work, Eucalyptus nitens was thermally modified in an open (atmospheric pressure) and a closed (under pressure) reactor system. The effect of the changes of the chemical composition on the mechanical properties was investigated. Hemicelluloses, cellulose, lignin, extractives, acetic acid, formic acid, total phenols and the cellulose degree of polymerization (DP) as well as modulus of elasticity (MOE) and modulus of rupture (MOR) were measured for each modification. The results indicated that the closed system modification, particularly at high pressure, presented stronger variations on the chemical structure of the modified wood than the modifications in the open system. In both modifications, MOR showed a better correlation with the chemical changes than the MOE, especially xylose, cellulose DP, lignin and total phenols. These correlations suggest a tendency of a more brittle wood in the closed system modification at high pressure than in the modifications in the open system. Results can be used as a reference for future applications of thermally modified E. nitens wood.     

木质材料力学性能无损检测方法的研究现状与趋势

木质材料用途广泛,在建筑、家具和包装等领域发挥着重要作用。目前,木材无损检测技术发展很快,应用到木材性质检测的无损检测方法已达几十种,然而对木质材料力学性能的检测还处于相对初级阶段,具有较大的挑战性。本文对木质材料力学性能的无损检测方法和原理进行归纳与总结,阐述几种主要检测技术（如应力渡检测、超声渡检测、振动法检测）的国内外研究现状、检测特点及存在问题。在此基础上,提出木质材料力学性能无损检测技术的发展趋势。     

闽南格木木材物理力学性质的研究

通过对格木木材物理力学性质进行测定和分析,结果表明:格木木材密度大、变形大,其气干密度为0.857 g·cm-3,基本密度为0.746 g·cm-3,体积干缩系数为0.615,顺纹抗压强度为67.59 MPa,抗弯强度为141.82 MPa,综合强度为209.41 MPa,属于高。该研究结果解决了格木营林和木材利用上的一个基础性问题。     

Compressive failure of spruce wood rings reinforced with glass epoxy composite

We experimentally tested under radial compressive loads and statistically analyzed rings constructed from spruce wood and reinforced with glass fiber.We used the Weibull distribution in statistical analysis,and tested five types of rings including unreinforced and composite reinforced(CR) as wound around the ring,oriented as two layers at angles of 45°,60°,75° and 90° to the column axis.We calculated 95 % reliability of load carrying capacity of the rings by Weibull distribution.The highest load carrying capacity was obtained with CR rings at 60° to the axial axis of the ring.Load carrying capacities of rings at CR90,CR75,CR60 and CR45 were 137,192,215 and 126 %greater,respectively,than unreinforced rings.For unreinforced rings,failures resulted from catastrophic breaking of wood materials.None of the reinforced rings failed catastrophically because the outer surface of the rings was reinforced with glass–epoxy composite fiber.Cracks began at the core of the materials under the composite layer for all specimens and resulted in failure of the rings.     

Effects of impregnation and heat treatment on the physical and mechanical properties of Scots pine (Pinus sylvestris) wood

Wood modification, of which thermal modification is one of the best-known methods, offers possible improvement in wood properties without imposing undue strain on the environment. This study investigates improvement of the properties of heat-treated solid wood. Scots pine (Pinus sylvestris) was modified in two stages: impregnation with modifiers followed by heat treatment at different temperatures. The impregnation was done with water glass, melamine, silicone, and tall oil. The heat treatment was performed at the temperatures of 180°C and 212°C for three hours. The modified samples were analyzed using performance indicators and scanning electron microscope micrographs. The mechanical and physical properties were determined with water absorption, swelling, bending strength, and impact strength tests. All the modifiers penetrated better into sapwood than hardwood; however, there were significant differences in the impregnation behavior of the modifiers. As regards the effect of heat treatment, generally the moisture properties were improved and mechanical strengths impaired with increasing treatment temperature. In contrast to previous studies, the bending strength increased after melamine impregnation and mild heat treatment. It is concluded that the properties of impregnated wood can be enhanced by moderate heat treatment.     

聚丙烯比例对木塑复合材料性能的影响

通过正交试验,以木材纤维和废旧聚丙烯塑料为原料,异氰酸酯或马来酸酐作偶联剂,压制木材纤维/聚丙烯复合材料,研究聚丙烯(简称PP)用量对木塑复合材料性能的影响。结果表明,聚丙烯比例对复合材料的内结合强度、吸水厚度膨胀率、静曲强度和弹性模量有不同的影响。在热压时间、热压温度、复合材料密度相同的条件下,用异氰酸酯(简称MDI)作偶联剂,聚丙烯用量40%时复合材料的性能最佳;而用马来酸酐(简称MA)作偶联剂,聚丙烯用量50%时复合材料的性能最佳。     

三种速生杨木材物理力学性质的比较研究

测试、分析比较了不同树龄3种速生杨木材的物理力学性质,结果表明:①树种对物理力学性能有较大的影响,三倍体圆叶毛白杨的物理力学性能最好,三倍体裂叶毛白杨次之,中林-46最差;方差分析表明,3种杨树的主要物理力学性质均达到显著和极显著差异。②树龄对物理力学性质的影响不大,随着树龄的增长,不同杨树木材的密度已趋于稳定,但力学性能有上升的趋势;方差分析表明,抗截切强度和抗弯强度受树龄影响较大,差异达到显著水平,其他性质无显著差异。     

Selected physical and mechanical properties of the Chilean wood species roble,lingue, manio and alerce

Abstract

Data sets with mechanical and physical properties of wood species can aid the recognition of biomechanical correlations, and they can also be valuable tools to assist decision making regarding the practical industrial employment of the species. However, such data sets are still lacking for many species, particularly non-European and non-North-American species. Therefore, the goal of this study was to determine the mechanical properties of four Chilean species (the softwoods alerce and manio, and the hardwoods lingue and roble), including the three Young's moduli and the three shear moduli. Dynamic methods were applied as well as static ones. The results suggest that Brinell hardness, compression strength and Young's moduli are clearly correlated with the density and can partly be related to anatomical details. Since the investigated species cover only a fraction of the Chilean species that are suitable for construction purposes, for example, further future examination of relevant species would be beneficial for basic research and industry.     

Finger-jointing green softwood: Evaluation of the interaction between polyurethane adhesive and wood

Abstract

Existing European standards for finger-jointing of load-bearing lumber require the wood to be dried before gluing. This article presents a study on the properties of green-glued finger joints, wet wood being bonded prior to drying. Issues to consider, in comparison to finger-jointing of dry wood, are mechanical performance of the joint, absorption of the polymer by the wood in its natural/wet state, and the chemical reactions of the adhesive on contact with water. Finger-jointed samples were tested in bending, and the glue joints analysed by optical microscopy, scanning electron microscopy and microdensitometry. A patented one-component polyurethane adhesive developed for gluing-green wood which has a moisture content usually higher than 70% was used in the study. The resulting green-glued joints showed improved strength properties in comparison to dry-jointed joints. The results confirm that green-glued joints provide a wide, continuous wood/adhesive interface from one substrate to the other. The adhesive penetrates several cells deep and the density of the wood adjacent to the joint surfaces is increased. The results also indicate that the patented adhesive forms covalent bonds to the wood substrate.     

Finger-jointing green softwood: Evaluation of the interaction between polyurethane adhesive and wood

Existing European standards for finger-jointing of load-bearing lumber require the wood to be dried before gluing. This article presents a study on the properties of green-glued finger joints, wet wood being bonded prior to drying. Issues to consider, in comparison to finger-jointing of dry wood, are mechanical performance of the joint, absorption of the polymer by the wood in its natural/wet state, and the chemical reactions of the adhesive on contact with water. Finger-jointed samples were tested in bending, and the glue joints analysed by optical microscopy, scanning electron microscopy and microdensitometry. A patented one-component polyurethane adhesive developed for gluing-green wood which has a moisture content usually higher than 70% was used in the study. The resulting green-glued joints showed improved strength properties in comparison to dry-jointed joints. The results confirm that green-glued joints provide a wide, continuous wood/adhesive interface from one substrate to the other. The adhesive penetrates several cells deep and the density of the wood adjacent to the joint surfaces is increased. The results also indicate that the patented adhesive forms covalent bonds to the wood substrate.     

STUDIES ON PHYSICAL AND MECHANICAL PROPERTIES OF DAHURIAN LARCH-WOOD OF TWO WOOD COLOURS

Dahurian1arch[Larixgmelini(Rupr.)Rupr.jisamaintimbertreespe-ciesinDaxing'anLingForestRegion,and'itisalsoafast-growingandregenerationtreeinNorthChina-Becauseitsecologicalamplitudeisverywild,therearemanyva-riabletypesinvarioushabitats.Themostsignificativetypes,whichhavebeenfoundrecentlyininvestigation,aretheredwoodandwhitewood.Theformerisfromyellow-browntored-brown,andthelat-tCrisfrompaleyellowtowhite.Theyaresimilarto'Redscotchpine#and'Whitescotchpine#.Theparametersofwoodcol-ourandphysico-…     

木材物理力学试验试样数的研究

木材是变异性很强的各向异性材料。适当地确定试样的数量才能既保证试验的精确度,又避免枉费人力、物力。为了修订国家标准《木材物理力学试验方法》中的取样方法,本文分析、比较了国际标准与中国现行标准之不同,得到了比较符合我国实际情况并向国际标准靠拢的取样     

Mechanical and physical screw withdrawal properties behavior of agglomerated panels reinforced with coir and pejibaye fibers

The screw withdrawal resistance and the mechanical behavior of agglomerated panels reinforced with coir and pejibaye fibers were evaluated using through and non-through screw withdrawal tests. Widespread commercially materials, such as Pinus solid wood, Medium Density Fiberboard (MDF) and plywood, were also tested in order to compare the behavior and results obtained with the lignocellulosic-reinforced agglomerated panels. Among the conventional materials tested, the highest maximum withdrawal load/thickness ratio was measured in solid wood. Panels reinforced with natural fibers showed lower withdrawal resistance than conventional materials. However, panels reinforced with coir fibers reached about 74% of the maximum strength achieved by MDF samples. Panels reinforced with pejibaye showed the worst mechanical performance. Hybridization between pejibaye and coir fibers resulted, however, in a performance improvement of approximately 50% in the maximum withdrawal load comparing with panels reinforced only with pejibaye fibers. The behavior along screw withdrawal was analyzed and could be split into four different steps. Each of these steps was correlated to the screw withdrawal rate, and also with the interactions between the material and the screw. The mechanisms involved in each step are presented and discussed.     

木纤维PP/PE共混物复合材料的流变和力学性能(英文)

For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.     

丛生竹物理力学性能及其对制造竹建筑材料的影响

研究了两种最重要的丛生竹种云南黄竹和龙竹的物理和化学性能。实验结果表明,黄竹的物理性能,如纵横干缩性等优于龙竹,而且黄竹的力学性能如静曲强度、静曲弹性模量及顺纹压缩与剪切强度也比龙竹高。与建筑用木材相比,两种丛生竹的物理力学性能均达到了建筑材料的性能要求。     

杨村新无性系木材物理力学性质的研究

研究了7个杨树新无性系和I－69杨的木材物理力学性质。结果表明，杨木新无性系的物理力学性质等主要指标均属于小至甚小级，无性系间物理力学性质差异显著，据此可用木材物理力学性质因子选育优良无性系。尽管新无性系的生长速度超过I－69杨，但由于其某些强度指标低于I－69杨，8年生的速生材尚不能完全替代11年生的I－69杨使用，因此不能作为建筑结构材使用。     

树龄对日本落叶松木材物理力学性质的影响

选取日本落叶松为试验材料,开展不同树龄日本落叶松物理力学性质的比较研究.结果表明:43年生、30年生和17年生日本落叶松木材气干密度分别为0.607,0.567和0.507 g/cm3,气干体积干缩率分别为7.7％,7.7％和7.1％;全干到气干体积湿胀率分别为5.1％,4.9％和4.5％;抗弯弹性模量分别为17.527,16.775和12.510 GPa,抗弯强度分别为121.1,110.3和90.9 MPa,顺纹抗压强度分别为56.8,51.8和44.0 MPa.随着树龄增大,日本落叶松木材密度、顺纹抗压强度、抗弯强度和抗弯弹性模量等各项物理力学性能指标提高,差异干缩逐渐变小.日本落叶松木材的气干密度与抗弯弹性模量、抗弯强度、顺纹抗压强度呈线性正相关,相关系数分别为0.760,0.816和0.900.