Preparation and characterization of urea-formaldehyde resin-sodium montmorillonite intercalation-modified poplar

To improve its overall performance, fast-growing poplar was modified using the vacuum-pressure-vacuum impregnation method with a urea-formaldehyde resin-sodium montmorillonite intercalation as the modification solution. The results showed that considerable amounts of urea-formaldehyde resin and montmorillonites entered the poplar tracheid, and some entered the microporous wood. These substances formed bonds with the active groups in timber, causing reduced crystallinity in the amorphous region of the poplar, a decreased level of free hydroxyl, and an enhanced association with hydroxyl and ether bonds. The density, dimensional stability, and mechanical properties of poplar were markedly improved. The best results were obtained with 14% sodium montmorillonite and 20% ureaformaldehyde resin: the bending resistance, compressive resistance, and elastic modulus increased by 19.37%, 30.24%, and 50.06%, respectively. With elevated levels of sodium montmorillonite, the impact toughness and wear rate decreased.     

有机/无机复合浸渍液对杨木的改性处理

利用脲醛树脂／丙烯酸酯乳液／硅溶胶三元复合浸渍液制备复合木材,并与杨木素材为对照。采用红外光谱研究复合木材的组成变化,热分析研究其热稳定性的变化,并研究了复合木材的力学性能。结果表明,杨木中的功能基团与复合浸渍液中的脲醛树脂可发生键合作用,使改性木材的热稳定性及力学性能均有所提高。     

山杨复合胶合板的制作

本文描述了利用山杨材制和复合胶合板的研究，研究结果表明，以其优质材料旋切的单板为表层材料，以劣质木材制作的刨花板为芯层材料制作和复合胶合板的主要物理力学性能指标与传统的胶合板板基本相同。     

Reducing set-recovery of compressively densified poplar wood by impregnation–modification with melamine–formaldehyde resin

ABSTRACT

Densification of resin impregnated wood under hot-pressing is a method that along with the potential for the reduction of set-recovery could additionally increase the density of wood and further improve other technical properties. In this study, the effect of the methylated melamine-formaldehyde modification on the shape memory effect of densified Populous nigra wood at various compression ratio levels was investigated. Furthermore, the effects on moisture content and compression ratio were also assessed. The most important conclusion drawn was that MF can act as a means for reducing set-recovery of compressed poplar wood since it is obvious that the use of MF significantly improved the stability of densified wood due to the formation of new bonds between cell wall components and MF. In the case of densification under stress of 10?kg/cm², the stabilization was improved by the use of MF to about 50% compared to water-treated specimens. The effect of MF on the stabilization of densified wood was not very clear for stresses higher than 10?kg/cm² since due to the outflow of MF solution during the first minutes of compression.     

栽培措施对短周期工业材材性影响规律的研究

对4种不同栽培措施的日本落叶松、湿地松、马尾松和杉木等多种短周期工业材309株样木的材性进行了全面测试分析研究，结果表明．立地指数大，木材生长率和纤维宽度大．但纤维长度、纤维长宽比、木材基本密度、顺纹抗压强度和抗弯弹性模量减小；立地指数相差两级，木材的年龄宽度、纤维宽度、长度和微纤线角度的差异达到显著或极显著水平栽植密度小，木材的年轮宽度和干缩比增大但纤维长宽比及体积全干缩率减小；栽植密度增大，杉木和昭林6号杨木材的力学强度提高，但尾叶桉和I－69杨降低；不同栽植密度的木材pH值及酸碱总缓冲容量，都是心材大于边材，但木材的脲醛树脂胶凝速度，则是边材快于心材.与未间伐林分的木材比较，随着间伐强度的增大、年轮宽度增大．但纤维长宽比和微纤丝角度减小；间伐强度增大，针叶树村的力学强度降低，阔叶树树则提高．但将强度间伐材（间代40％）与未间伐材比较，结果完全相反；北京杨木材心材的pH值、酸碱缓冲容量及总容量，均随间伐强度的增大而增大，但边材却减小．施肥措施能够增大纤维直径，但将导致纤维长宽比、木材密度和力学强度的降低施肥可以使树木速生，但会降低木材密度和质量，在培育建筑结构材的林分应慎用．     

人工林杉木和杨树木材物理力学性质的株内变异研究

按照中国国家标准研究杉木和I-214杨树木材的抗弯弹性模量、抗弯强度、顺纹抗压强度和密度,同时按照日本国家标准研究2个树种的顺纹抗剪强度.结果表明:杉木的抗弯强度、顺纹抗压强度和密度由胸高直径处向上呈波浪形增加,抗弯弹性模量则稳定降低,但不同高度间杉木的物理力学性质没有显著差异;近树皮处木材的物理力学性质高于近髓心处木材,并有极显著差异.对于I-214杨树,只有抗弯弹性模量从髓心到树皮逐渐增加,其他的物理力学性质,最小值在从髓心到树皮的过渡区,最大值在近树皮处,从髓心到树皮,杨树的物理力学性质有极显著的差异.杉木和杨树的径面顺纹抗剪强度从髓心到树皮有极显著差异,并且近树皮的高于近髓心的木材,而弦面顺纹抗剪强度从髓心到树皮没有显著差异.木材密度与力学性质有很好的线性相关关系,木材密度是一个很好的力学强度的预测手段.     

基于纳米压痕技术的木材胶合界面力学行为

【目的】研究木材胶合界面的静态和动态力学行为,探讨树脂渗透对木材管胞壁层力学性能的影响,为木质复合材料制造工艺优化和增强改性提供理论依据。【方法】采用纳米压痕静态和动态力学测试技术(Nano-DMA),对针叶材火炬松与酚醛树脂(PF)、脲醛树脂(UF)胶黏剂所形成胶合界面区域各相材料的静态弹性模量、硬度、蠕变性能以及储能模量和损耗模量等力学行为进行分析。【结果】静态力学行为方面,在界面区域,PF和UF渗透进入管胞壁层后,木材管胞壁的弹性模量( E r)和硬度( H )提高;经PF渗透后,木材管胞壁的 E r和 H 分别增加7%和26%;Burgers蠕变力学模型可有效描述胶合界面区域管胞壁的纳米压痕蠕变特性,经树脂渗透后,木材管胞壁的瞬时弹性模量增加,黏弹性模量和黏性系数减小;在保载初期,PF界面区域木材管胞壁的蠕变柔量约下降60%,UF界面区域木材管胞壁的蠕变柔量约下降58%。动态力学行为方面,随着加载频率增加,界面材料的储能模量( E ′ r)逐渐增大,而损耗模量( E ″ r)和损耗因子(tan δ)呈减小趋势;当加载频率为10 Hz时,PF和UF树脂渗透使得管胞壁层的储能模量分别增加16%和29%。【结论】胶合界面区域胶黏剂进入管胞壁层,对木材管胞的静态力学性能具有增强作用,同时胶黏剂可提高管胞壁的短期抗蠕变能力;木材管胞壁具有较高的储能模量和损耗模量,而树脂的储能模量和损耗模量较低,经树脂渗透后,木材管胞壁的储能模量增加,但损耗模量和损耗因子呈下降趋势,可能对界面传递和分散应力产生不利影响。     

The lamination influence on properties of agro-based particleboard

Abstract

Response surface methodology (RSM) based on a three-level, three-variable central composite rotatable design was applied to evaluate the effects of the parameters such as ratio of rice straw (Oryza sativa)/poplar (Populus deltoids) wood particle bonded with urea-formaldehyde resin in panels, species of wood veneer coating these panels and amount of adhesive in glue line on the modulus of rupture (MOR), internal bonding (IB), and thickness swelling (TS) of panels. Mathematical model equations were derived by computer simulation programming to optimize the properties of the particleboard. These equations that are second-order response functions representing MOR, IB, and TS were expressed as functions of three operating parameters of panel properties. Predicted values were found to be in a good agreement with experimental values (R ² values of 0.96, 0.98 and 0.98 for MOR, IB, and TS, respectively). This study has shown that the RSM could efficiently be applied for modeling panel properties. It was found that the variables affected the properties of panels. Straw usage up to 30% in the mixture did not cause a significant decrease in MOR, IB, and TS. Using beech veneer and 190 g/m² glue line had the highest MOR and lowest TS.     

提高杨木线性振动摩擦焊接胶合性能的研究

研究了杨木线性振动摩擦焊接的干剪切强度、湿剪切强度和木破率。为提高杨木摩擦焊接的湿剪切强度与木破率,采用表面氧化、表面磺化以及表面涂覆的方式处理杨木板材,再经线性振动摩擦焊接进行黏合,使用万能力学试验机测得其剪切强度,对比表面处理前后剪切强度的变化,并利用傅里叶红外光谱分析了其表面处理前后基材和摩擦焊接层的化学基团变化情况,对胶合性能的变化做出解释。研究结果表明:杨木经过表面氧化磺化涂覆醋酸锌处理后,摩擦焊接层的干剪切强度为5.41 MPa,木破率为63%,与未处理的杨木相比,分别提高了48.22%和96.88%;湿剪切强度从0提高到1.34 MPa;摩擦焊接时厚度损失减少了46.4%。杨木分别经过表面氧化和表面磺化处理后,摩擦焊接层的干剪切强度仅为3.45和4.10 MPa,木破率为28%和42%,湿剪切强度为0.76和0.96 MPa。摩擦焊接层的红外光谱分析表明,经表面氧化磺化涂覆醋酸锌处理后,杨木中的纤维素和半纤维素分解,使木质素的相对含量有所增加,且活化了杨木中的—OH,与醋酸锌生成多醚,消耗了亲水性的—OH。     

林下耕作对滩地杨树木材物理力学性质的影响研究

本文对长江滩地这一特定立地条件下经过人为耕作与非耕作模式下的杨树木材物理力学性质及应力木分布情况与力学性质间的关系进行了比较研究。结果表明：林下耕作可提高杨树木材密度,与对照木相比,基本密度和气千密度差异性分别达显著与极显著水平;能够减少应拉木的产生,与对照木相比差异百分率达24．82％,进而使木材的差异干缩减小,木材尺寸稳定性提高;各项力学指标均优于对照杨树,且与应力木的量呈线性负相关,其中抗弯强度与抗弯弹性模量与其相关性显著。     

人工林杨木的用途选择——实木或单板层积材

实木材性对单板层积材强度的贡献率可衡量单板层积材强度中源自实木材性的份额,是人工林杨木单项用途选择的基础。本文以３个无性系实体杨木和由３种不同厚度杨木单板分别组配的单板层积材为对象,以由贡献率引出的实木与单板层积材的份率差值为依据,研究得出人工林杨木的最终用途选择。结果表明：６９杨、７２杨和６３杨３个无性系杨木的平均份率差值分别为５７％、－１５％、－２９％,说明６９杨宜用作实木,７２杨和６３杨宜用作单板层积材;杨木用作不同组配结构的单板层积材时,实木与３５６５ｍｍ、２６１４ｍｍ、１５４５ｍｍ３种厚度单板组配的单板层积材的平均份率差值分别为４３％、－１３％和－４３％,说明实木与较厚的３５６５ｍｍ单板组配的单板层积材相比,杨木宜用作实木,与较薄的２６１４ｍｍ和１５４５ｍｍ单板组配的单板层积材相比,杨木宜用作单板层积材。不同荷载作用的结果下用途选择结果显示,在抗剪强度、弹性模量和冲击韧性３项性能上的份率差值为正,此时杨木宜用作实木;在抗弯强度、抗压强度和硬度３项性能上的份率差值为负,此时杨木则宜用作单板层积材。     

杨树浸渍改性材物理及力学性能研究

利用聚乙烯醇缩甲醛复合改性剂对杨树木材进行浸渍改性处理,对比研究了杨树素材与改性材的物理性能及主要力学性能的变化,并利用扫描电子显微镜(SEM)分析了改性剂在改性材中的分布情况。结果表明:改性材的气干密度和抗缩系数(PASE)随改性剂浓度的上升而增加,改性材的气干密度最高为0.41 g/cm3,比素材的提高了13.9%,抗缩系数(PASE)最大提高到47.8%。改性材吸水率随改性剂浓度的上升而下降,与素材相比最大下降了19.2%。当改性剂的浓度为25%时,改性材的弹性模量和静曲强度达最大,分别为27.4%和13%。SEM分析显示改性剂填充于部分木射线以及交错纤维间的空隙中。     

木粉增强P34HB生物复合材料的制备及其结构性能表征

【目的】通过木粉纤维增强生物塑料聚3-羟基丁酸酯-co-4-羟基丁酸酯(P34HB),为生物复合材料的理论研究和生物可降解塑料的广泛应用提供科学依据和理论支持。【方法】以毛白杨木粉和P34HB为原料,采用共混热压法制备P34HB/木粉生物复合材料,基于电子扫描显微镜(SEM)、差示扫描量热法(DSC)、热重分析(TGA)、傅里叶红外光谱(FTIR)、动态热机械分析(DMA)和力学性能分析等手段对其结构和性能进行表征。【结果】随着木粉含量增加,生物复合材料的拉伸强度、断裂伸长率和弯曲强度先增加后减小,冲击强度逐渐下降,拉伸强度、弹性模量和杨氏模量分别增加89%、59%和103%,储能模量E′逐渐增加,tanδ峰值先下降后上升。生物复合材料的高频率模量大于低频率模量,动刚度比静刚度好。相比P34HB,生物复合材料的热分解区间变宽,热解速率变慢,热解剩余质量增加。【结论】随着木粉含量增加,P34HB分子链运动受阻,生物复合材料的储能模量和脆性增大;同时,木粉纤维的成核作用诱导P34HB形成结晶度高、层状结构发达的横晶层,木粉与P34HB之间界面结合力增强,力学性能和热稳定性明显提高。综合考虑,P34HB/木粉生物复合材料的最佳木粉加入量为50%。     

木材树种对刨花/EPS泡沫复合轻质刨花板性能的影响

为实现刨花板轻量化,通过向芯层引入聚苯乙烯(EPS)泡沫颗粒,制备平均密度为500 kg/m^3的刨花板,探索表芯层刨花构成对板材的剖面密度分布和物理力学性能的影响。结果表明:以杨木细刨花为表层、桉木粗刨花和EPS泡沫颗粒混合物为芯层制备的复合轻质刨花板,其表芯层密度差异最为显著,力学性能达到GB/T 4897-2015《刨花板》中干燥状态下使用的家具型(P2型)刨花板的要求。     

金属网/木质材料复合性能的研究

用10日不锈钢金属网与木材(速生杉木板为芯层，杨木单板为表层)进行复合试验，并与相同工艺条件下制作不加金属网的细木工板的物理力学性能进行对比分析，结果表明：在一定的工艺条件下，可以生产出具有优良性能的金属网强化细木工板。     

木材高温干燥过程中的弹性应变

本文对美洲黑杨锯材高温干燥过程中的弹性应变进行了研究。结果表明：高温干燥使得木材表层产生较大的塑化变定,并对干燥后期木材内层的正常收缩造成障碍。心层的拉伸应力与木材内裂有关,当心层拉伸应力超过木材横纹拉伸极限强度时,木材产生内裂。因此,在用高温干燥工艺快速干燥杨木类软阔叶树材时,在干燥后期应注意由于干燥应力转向而引起的干燥缺陷。     

人工林杨木材性对单板层积材强度的贡献率

本文提出了衡量单板层积材强度中实木材性所占份额的贡献率概念,以揭示实木材性对单板层积材强度的贡献程度.以人工林杨木为对象,研究了实木材性对单板层积材强度的贡献率.结果表明,实木材性好或单板层积材中的单板较厚时,贡献率较高.材性较优的69杨和材性居中的72杨、材性较差的63杨3个无性系杨木的平均贡献率分别为74.34%、67.48%、64.72%,厚度为3.565mm、2.614mm、1.545mm单板组配的单板层积材中的平均贡献率分别为74.00%、67.48%和58.06%.研究的6项强度性能中,杨木实木材性对抗剪强度、弹性模量和冲击韧性的贡献率较高,约为80%.     

人工林杨木材性对单板层积材强度的贡献率

本文提出了衡量单板层积材强度中实木材性所占份额的贡献率概念,以揭示实木材性对单板层积材强度的贡献程度。以人工林杨木为对象,研究了实木材性对单板层积材强度的贡献率。结果表明,实木材性好或单板层积材中的单板较厚时,贡献率较高。材性较优的６９杨和材性居中的７２杨、材性较差的６３杨３个无性系杨木的平均贡献率分别为７４３４％、６７４８％、６４７２％,厚度为３５６５ｍｍ、２６１４ｍｍ、１５４５ｍｍ单板组配的单板层积材中的平均贡献率分别为７４００％、６７４８％和５８０６％。研究的６项强度性能中,杨木实木材性对抗剪强度、弹性模量和冲击韧性的贡献率较高,约为８０％。     

Particleboard made from hammer milled black spruce bark residues

Summary  The disposal of bark residues is an important problem for the forest industry. An important proportion of the bark produced by the paper and lumber industries is used for energy production, but a significant amount of bark is still unused. The objective of this study was to determine the technical feasibility of making particleboards from black spruce bark residues bonded with urea formaldehyde resin and meeting the indoor performance requirements for wood particleboards. In the positive case, this would define a new use for black spruce bark residues. Fresh black spruce bark residues were obtained from a sawmill located in the northeast part of the province of Quebec, Canada. The bark was kiln-dried at 60 °C, the particles were generated from a hammermill and sieved. Particles from 0.02 to 2.0 mm were used in the surface layers and particles from 2.0 to 6.0 mm were used in the core layer. Particleboards of 540 × 560 × 16 mm were made with a laboratory hot press following a factorial design with two manufacturing variables at three levels: (1) wood particles content of the surface layers (0, 25, 50 percent); and (2) UF resin content of the surface layers (12, 14 and 16 percent) with a UF resin content in the core of 8 percent. This resulted in a factorial design of 9 different combinations repeated 3 times for a total of 27 boards. It was observed that the heating kinetics varied according to the wood particles content in the surface layers. The compression ratio of the mat and the board internal bond, modulus of elasticity, modulus of rupture, linear expansion and thickness swell were determined. The results show that it is technically possible to make particleboard from bark residues meeting the American National Standard Institute indoor requirement for wood particleboard under certain conditions. The modulus of rupture of the boards was the most critical property in this study. The best mechanical properties were obtained with a 50 percent wood content and 14 percent resin content in the surface layers. The particleboards produced in this study did not meet the minimal requirements for linear expansion. The temperature measurements performed in the core of the mat during hot pressing show that heat transfer improves with an increase in wood particles content in the surface layers. Received 15 June 1998     

杨树浸渍改性处理材尺寸稳定性研究

利用聚乙烯醇缩甲醛改性剂对杨树木材进行浸渍改性,对其改性材的尺寸稳定性进行研究。结果表明:改性材的径向、弦向和体积干缩率与素材相比均有不同程度的下降;从全干到吸水饱和状态的过程中,当改性剂达到一定浓度时,改性材的径向、体积湿胀率与素材相比有明显下降,弦向线湿胀率下降不明显。从气干到吸水饱和状态的过程中,改性材的径向、弦向湿胀率与素材相比均有不同程度的下降;改性材体积湿胀率随着改性剂浓度的上升而呈下降趋势,当改性剂浓度为30%时,改性材体积湿胀率为6.85%,与素材相比下降了5.54%。改性材吸水率随改性剂浓度的上升而下降,最低可达159%;改性材的抗干缩系数(ASE)随改性剂浓度上升而增加,最大可达47.8%。改性材的尺寸稳定性能要明显优于杨树素材。