工艺参数对无纺布基装饰薄木剥离强度的影响

用聚醋酸乙烯酯乳液作为胶黏剂,将黑胡桃、红栎、白桦薄木与无纺布复合制备成无纺布基装饰薄木,探讨涂胶量、热压温度、热压时间和热压压力等因素对柔性装饰薄木剥离强度的影响规律,研究表明,柔性装饰薄木树种对剥离强度影响显著,工艺参数中涂胶量和热压温度对柔性装饰薄木剥离强度的影响显著。     

塑膜增强柔性装饰薄木的制备工艺及性能研究

采用改性低密度聚乙烯(LDPE)薄膜作为增强和胶粘材料制备柔性装饰薄木,探讨热压压力、温度、时间和LDPE膜厚等因素对薄木柔韧性、剥离强度等性能的影响。结果表明:塑膜增强柔性装饰薄木的较优工艺参数为:热压压力1.0 MPa、温度150℃、时间120 s,LDPE膜厚0.03 mm;在此工艺条件制备的装饰红栎薄木的柔韧性优良,柔韧性卷曲试验的钢棒直径可小至4 mm,浸渍剥离强度达到Ⅰ类胶试验要求,总体性能优于无纺布增强薄木。     

重组装饰材制备用改性玉米淀粉乳液-脲醛树脂胶

为了解决常规脲醛树脂胶生产重组装饰材料韧性较差等问题,将改性玉米淀粉乳液(CSG)与脲醛树脂(UF)胶混合,并加入聚醋酸乙烯酯乳液(PVAc)、聚乙烯醇水溶液(PVA)、阴离子聚丙烯酰胺(APAM)等改性剂及多亚甲基多苯基异氛酸酯(PAPI)增强剂,制备一种改性胶,用于重组装饰材生产。通过试验优选改性胶的配比,制备的装饰薄木比用常规UF胶时柔韧性增强,甲醛释放量达到E_1级,且成本降低。     

聚乙酸乙烯酯乳液胶的改性

本文介绍了用该改性乳液胶合的贴面胶合板的性能改性聚乙酸乙烯酯共聚乳液胶粘剂的聚合工艺，经过改性的乳液胶具有良好的耐水性，达到并超过日本二类特种合板标准，且生产工艺简单，原料易得，成本与普通乙酸乙烯酯均聚液接近,具有较强的实用性。     

杉木/珍贵阔叶树材复合地板的研制

利用人工林杉木或杉林间伐材与珍贵树种（如檀木）落木组合，采用改性聚乙酸乙烯酯共聚乳液胶胶合、表面淋涂耐磨耐烫的UV漆饰保护层，具有不易变形、不开裂的特点。     

柔性人造装饰薄木制造工艺的研究

柔性人造装饰薄木是为克服人造薄木的脆性大、强度低、破损多等缺陷而研究开发的新型装饰材料.对人造薄木与无纺布胶合制造柔性人造装饰薄木的工艺及其参数和生产设备进行了研究,结果表明:用平压法生产柔性人造装饰薄木的工艺参数为上胶量20～30 g/m2,热压温度100°C,时间90 s,压力1.0 MPa. 该柔性人造装饰薄木具有良好的柔韧性能、外观质量和粘合性能,可广泛应用于室内装饰、直线和曲线封边及异型包覆等.     

塑膜增强柔性装饰薄木热压复合卷曲变形特性分析

【目的】采用不同种类装饰薄木与塑膜热压复合,以卷曲曲率半径为表征,探寻塑膜与装饰薄木热压复合卷曲变形的影响因素,为控制塑膜增强柔性装饰薄木卷曲变形提供理论依据和实践支持。【方法】以红栎为试验对象,分析含水率、热压温度、塑膜和装饰薄木厚度等工艺条件对卷曲变形的影响,并以不同材质种类的柚木、水曲柳、红栎和花梨装饰薄木为试验材料,研究不同种类装饰薄木与塑膜热压复合的卷曲变形情况。【结果】热压温度对塑膜增强柔性装饰薄木卷曲变形具有显著影响,随热压温度增高,卷曲曲率半径逐渐减小,卷曲变形程度不断增大;装饰薄木与塑膜厚度比越大,塑膜增强柔性装饰薄木的卷曲变形相对越小,考虑成本和后续饰面加工,装饰薄木以0.3 mm厚为宜;含水率对塑膜增强柔性装饰薄木卷曲变形影响较小,实际生产中以8%～12%为宜;密度大、木材组织比率相对较大、结构致密的装饰薄木,热压复合卷曲变形相对较小。【结论】热压温度对塑膜增强柔性装饰薄木卷曲变形影响极显著,实际生产中,应尽可能降低热压温度,以增大曲率半径、减小卷曲变形。装饰薄木与塑膜厚度比对卷曲变形具有显著影响,一般而言,装饰薄木厚度越厚、塑膜厚度越薄,其热压复合卷曲变形程度越小,需结合生产实际进行厚度选择。本研究可为控制双层薄型材料热压复合特别是塑膜增强柔性装饰薄木卷曲变形提供思路。     

等离子体改性制备塑膜增强柔性装饰薄木工艺

为提高塑膜与薄木之间的界面胶合特性,采用低温等离子体分别对塑膜和装饰薄木的胶合面进行改性处理,制备塑膜增强红栎柔性装饰薄木。优化工艺参数为:等离子体处理速度4 m/min,热压压力0.6 MPa、温度120℃、时间150 s;柔性装饰薄木的剥离强度达0.52 k N/m,横向抗拉强度达4.13 MPa,柔韧性卷曲钢棒直径可小至4 mm,浸渍剥离强度达到I类试验要求,同时热压温度明显降低,减少了能耗。     

酚醛树脂改性对铝木复合材料性能的影响

对采用聚乙酸乙烯酯乳液与偶联剂改性酚醛树脂制备铝木复合材料性能的影响进行研究.结果表明:改性酚醛树脂肢粘剂制备复合材料表面胶合强度大于酚醛树脂胶粘剂,胶合强度都超过1.0 MPa,以杨木单板为基材不同混合比例之间表面胶合强度差异性极显著,但以中密度纤维板为基材不同混合比例之间表面胶合强度差异性不显著,随着聚乙酸乙烯酯乳液比例的增加,浸渍剥离性能降低,聚乙酸乙烯酯乳液与酚醛树脂最佳混合比为1:2;偶联剂的添加提高了复合材料的表面胶合强度,两者差异极显著,但偶联剂的加入对静曲强度和弹性模量影响较小,影响不显著.     

高耐水性乳白胶的研制

通过引入疏水性单体、反应性有机硅单体、交联单体参与乙酸乙烯酯共聚反应,以提高聚乙酸乙烯酯乳液(PVAc乳液)的耐水性能.采用正交试验,确定了乳液合成中各种单体的最佳配比.试验结果表明,通过单体共聚改性,可提高PVAc乳液的耐水性能.     

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.     

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.     

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.     

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.