不同胶黏剂不同树种结构用集成材胶合性能的研究

分别采用LX1-1、KR-134、S309和RF-C05 4种胶黏剂依次胶合欧洲云杉、欧洲赤松、兴安落叶松木材层板,制备成对应的结构用集成材。再依照GB/T26899—2011《结构用集成材》和GB/T 50005—2003《木结构设计规范》国家标准对制得的试样进行检测。实验结果表明,4种胶黏剂的胶合性能存在较大的差异:1)剥离率:4种胶黏剂在胶合欧洲云杉、赤松2种集成材时,浸渍剥离率均满足国标要求,但KR-134和RF-C05在第二次煮沸剥离率均未能满足国标。在胶合落叶松集成材时,LX1-1、KR-134在浸渍时剥离能满足国标要求,煮沸剥离未能满足国标要求,S309和RF-C05 2种剥离率均不满足国标。2)剪切强度和木破率:除S309落叶松集成材的湿剪强度和木破率均未能达到标准要求外,LX1-1、KR-134和RFC05胶合欧洲云杉、欧洲赤松和落叶松结构用集成材试样的湿剪强度均在3.9MPa以上,干剪强度均在5.9MPa以上,且木破率均大于75%,满足国标相关要求。3)LX1-1型异氰酸酯胶黏剂在胶合性能上优于其他3种胶黏剂,且兴安落叶松相比较其他2种木材,更加难以被胶粘。     

环氧化合物改性大豆蛋白胶黏剂制备工艺与性能研究

通过三羟甲基丙烷三缩水甘油醚(THPTG)交联聚合大豆蛋白降解液制备低黏度大豆蛋白胶黏剂,研究THPTG用量、反应时间、反应温度等工艺参数对大豆蛋白胶黏剂黏度、耐水胶合强度和固化性能的影响,优化大豆蛋白胶黏剂制备工艺条件。结果表明:THPTG用量与反应时间对大豆蛋白胶黏剂黏度、耐水胶合强度均有显著影响,而反应温度仅对黏度影响较大;THPTG用量为9%时,大豆蛋白胶黏剂固化温度为130.20℃,固化反应热达到最大值199.7 J/g。大豆蛋白胶黏剂优化的制备工艺条件为THPTG 9%、反应时间50 min、反应温度70℃,制备的胶黏剂黏度为106 mPa·s,耐水胶合强度达到0.76 MPa,满足GB/T 9846—2015对于Ⅱ类胶合板标准要求。     

基于高频热压成型的竹集成材制备及力学性能评价

【目的】探索竹材含水率、热压压力、施胶量和热压温度对高频热压成型竹集成材力学性能的影响,并优化高频热压加工工艺获得力学性能较优的竹集成材,为竹集成材高频热压成型提供技术参考。【方法】设计正交试验,采用高频热压加工工艺,以酚醛树脂(PF)为胶黏剂,研究竹材含水率、热压压力、施胶量和热压温度4个参数变量对高频热压成型竹集成材抗弯强度和剪切强度的影响,建立抗弯强度和剪切强度数学模型,分析力学性能最优解。【结果】极差分析表明,热压参数对抗弯强度的影响顺序为热压压力、竹材含水率、热压温度和施胶量,对剪切强度的影响顺序为施胶量、竹材含水率、热压压力和热压温度;主效应分析表明,4级竹材含水率、1级热压压力、1级施胶量和3级热压温度为最佳抗弯强度的热压参数,1级竹材含水率、1级热压压力、2级施胶量和3级热压温度为最佳剪切强度的热压参数;交互分析表明,各热压参数间存在交互作用;方差分析表明,热压压力是影响竹集成材抗弯强度的最重要因素,施胶量是影响竹集成材剪切强度的最重要因素;数学模型分析得出,竹材含水率15%、热压压力2.0 MPa、施胶量260 g·m-~(-2)、热压温度130℃为抗弯强度最优解(168.51 MPa);竹材含水率10.2%、热压压力2.0 MPa、施胶量240 g·m~(-2)、热压温度130℃为剪切强度最优解(263.26 MPa)。【结论】竹材含水率、热压压力、施胶量和热压温度4个参数变量对高频热压成型竹集成材力学性能均有影响,提出的热压参数对竹集成材抗弯强度和剪切强度影响的数学模型,可有效反映热压参数与竹集成材力学性能间的关系,优化高频热压加工工艺生产的竹集成材,其力学性能满足相关标准和使用要求。     

浸渍杨木用间苯二酚树脂剪切强度的研究

主要研究了间苯二酚树脂胶黏剂的制备,用其冷压氨基类树脂改性浸渍杨木,用于木结构房屋建筑。通过正交试验研究了甲醛与间苯二酚物质的量比、胶黏剂与固化剂质量比、冷压时间等条件对间苯二酚树脂胶黏剂性能湿剪切强度结果的影响。采用红外光谱、电镜分析与热重分析仪等分析,表征了间苯二酚树脂的结构与性能,且对树脂与试件断面处进行断面微观形貌分析。研究结果表明:当甲醛n(F)∶间苯二酚n(R)=0.8∶1,胶黏剂∶固化剂=10∶3,冷压60 min时,其检测结果为湿剪切强度6.12 MPa,煮沸剥离满足2个周期,满足GB/T 26899—2011《结构用集成材》标准要求。     

玉米酒精粕基木材胶黏剂的制备及其性能

以玉米酒精粕(DDGS)为原料、聚酰胺环氧氯丙烷树脂(PAE)为交联剂、水溶性豆粕(SM)为增强剂制备玉米酒精粕基木材胶黏剂,对比了DDGS与SM蛋白质含量及其氨基酸种类与含量,测试了胶黏剂黏度与制备胶合板的胶合强度,表征了固化胶黏剂功能性基团、热稳定性、断面形态,解析了DDGS基胶黏剂组分对性能的影响规律与增强作用机制。结果表明:与SM相比较,DDGS中蛋白含量低46.3%,蛋白质亲水侧链氨基酸含量低22.0%,疏水侧链氨基酸高43.4%,DDGS蛋白溶解性和反应活性低于SM蛋白;当原料m(DDGS)∶m(SM)=3∶1时,胶黏剂制备胶合板耐水胶合强度为0.91 MPa,较DDGS胶黏剂提高727.3%,达到国家Ⅱ类胶合板标准要求,同时原料成本降低29.2%;相比SM胶黏剂,m(DDGS)∶m(SM)=1∶3时,胶黏剂制备胶合板耐水胶合强度提高7.5%,达1.43 MPa,其原因是SM的加入提高了胶黏剂交联密度;胶黏剂黏度降低了32.4%,更容易渗透到木材孔隙中形成机械结合力;DDGS中含有7%纤维,可以对胶黏剂产生物理增强作用,阻碍裂隙延伸,提高内聚力。因此,利用DDGS为原料可有效制备耐水木材胶黏剂并用于胶接人造板,有利于推动蛋白基木材胶黏剂的工业化应用。     

利用脱脂豆粉制备木材胶黏剂合成工艺初探

由于世界范围内石油资源的紧缺和传统木材用胶黏剂引发的环境问题,使得木材胶黏剂工业重新重视研发豆基胶黏剂。笔者以脱脂豆粉为原料,以尿素、戊二醛为改性试剂制备复合改性木材胶黏剂。分别探讨了尿素浓度、反应温度、反应时间以及戊二醛添加量对改性胶黏剂胶合性能及耐水性的影响,并采用FT-IR分析复合改性胶黏剂样品中活性基团的变化,探索耐水胶合强度增强机理。通过试验结果分析,在试验研究范围内较优合成工艺参数为:尿素浓度为2.0M、反应时间1.0h、反应温度40℃、戊二醛添加量为2.0%(以脱脂豆粉质量为基准)。经30℃热水浸泡处理后,胶合强度达到0.85MPa。     

热熔胶胶层温度对单板/MDF胶合强度的影响

以EVA和APAO热熔胶为胶黏剂粘接木材单板和中密度纤维板(MDF),探讨胶层温度对单板/MDF胶合强度的影响。结果表明:单板/MDF的胶合强度随胶层温度的升高显著降低;APAO胶合试样的耐温性能优于EVA胶;当EVA和APAO胶胶层温度分别低于41和47℃时,粘接的材料均有足够的胶合强度,可进行后续工序加工。为框架集成材在线异形拼接加工及封边自动化生产,提供重要依据。     

防腐前处理对竹集成材力学性能的影响

以季铵铜(ACQ)和铜唑(CuAz)加压浸渍处理的毛竹精刨竹条为单元,以酚醛树脂为胶黏剂,制作防腐竹集成材,并测试其力学强度,分析了药剂种类和载药量对竹集成材抗弯弹性模量(MOE)、抗弯强度(MOR)和胶层剪切强度的影响.结果表明,防腐处理前后,竹集成材的MOR、胶层剪切强度差异不显著,MOE差异性显著(0.05水平);防腐剂种类对竹集成材MOE影响显著,载药量水平对MOE影响不显著;总体上看,防腐竹集成材的MOE和MOR略有下降或保持不变,胶层剪切强度略有提高.     

不同胶黏剂对俄罗斯落叶松木材胶合性能的影响研究

为验证进口俄罗斯落叶松木材胶合性能,选用4种具代表性的结构用室温固化胶黏剂,根据GB/T 26899—2011《结构用集成材》进行胶合性能试验,对俄罗斯落叶松及胶黏剂的胶合性能进行分析研究。结果表明:对于俄罗斯落叶松,单组份聚氨酯、双组份聚氨酯和水性高分子异氰酸酯3种胶黏剂的胶层剪切强度和胶层剥离率均满足标准要求,其中双组份聚氨酯和水性高分子异氰酸酯胶黏剂胶合性能优异,单组份聚氨酯胶黏剂胶合性能良好;间苯二酚-甲醛树脂胶黏剂的胶合性能虽能达到标准要求,但不推荐作为结构用胶黏剂。     

水性异氰酸酯交联剂的应用研究

采用不同链长的聚醚多元醇与多亚甲基多苯基多异氰酸酯（PAPI）反应,制备了两种不同结构的水性异氰酸酯（P-C、P-D）,联剂分别加入到氧化玉米淀粉胶黏剂和脲醛树脂胶黏剂中,以改善胶黏剂的胶接性能。通过粘接强度测试研究不同结构、不同用量的水性异氰酸酯对改性胶黏剂的胶接强度和耐水性的影响。实验结果表明：氧化玉米淀粉和脲醛树脂中加入水性异氰酸酯交联剂制备胶合板,胶接强度及耐水性均有显著提高。氧化玉米淀粉胶黏剂中加入10%的水性异氰酸酯P-D后,所制备胶合板的干态剪切强度可达2.64MPa。脲醛树脂胶黏剂中加入7.5%的P-D后,干态、湿态剪切强度分别为1.24MPa和1.23MPa,甲醛释放量为0.31mg/L,达到E0级标准。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.