桐油酰亚胺酚醛树脂耐热性研究

采用创新工艺,以廉价二胺和马来酸酐为原料,合成成本低廉的新型双马来酰亚胺(ABMI).以此双马来酰亚胺与桐油及酚醛树脂反应,制备了具有较好耐热性的桐油酰亚胺酚醛树脂.重点讨论了不同原料,如桐油、双马来酰亚胺及酚醛树脂的用量、固化反应温度及固化反应时间等因素对树脂耐热性的影响.当桐油、双马来酰亚胺、酚醛树脂的质量比为10.30.2,温度180℃烘烤3 h固化时,所得树脂具有较好的耐热性,温度指数可达168℃.     

桐油酰亚胺酚醛树脂耐热性研究

采用创新工艺，以廉价二胺和马来酸酐为原料，合成成本低廉的新型双马来酰亚胺（ABMI）。以此双马来酰亚胺与桐油及酚醛树脂反应，制备了具有较好耐热性的桐油酰亚胺酚醛树脂。重点讨论了不同原料，如桐油、双马来酰亚胺及酚醛树脂的用量、固化反应温度及固化反应时间等因素对树脂耐热性的影响。当桐油、双马来酰亚胺、酚醛树脂的质量比为1：0．3：0．2，温度180℃烘烤3h固化时，所得树脂具有较好的耐热性，温度指数可达168℃。     

桐油酸酐酰亚胺环氧树脂耐热性研究

以桐油、双马来酰亚胺、马来酸酐及环氧树脂为基本原料,合成了具有较好耐热性的桐油酸酐酰亚胺环氧树脂.重点讨论了不同原料,如桐油、马来酐、双马来酰亚胺及环氧树脂的用量、固化反应温度及固化反应时间等因素对树脂耐热性的影响.当桐油、双马来酰亚胺、马来酐和环氧树脂的质量比为1∶0.25∶0.2∶0.4,150 ℃烘烤5 h固化时,所得树脂具有较好的耐热性,温度指数(T20000)可达160.8 ℃.     

不同恒温条件下有机酯改性酚醛树脂动态力学性能的研究

以甲醛和苯酚为原料,经丙烯酸甲酯和邻苯二甲酸二烯丙酯(DAP)共同改性制得碱性酚醛树脂,采用动态热机械分析仪(DMA)研究温度对有机酯改性酚醛树脂动态力学性能的影响,并采用相关仪器对碱性酚醛树脂的性能进行了表征。结果表明:随着丙烯酸甲酯和邻苯二甲酸二烯丙酯(DAP)加入量的增加,储存模量与损耗模量都相应提高,PF树脂固化温度下降了5.43℃。有机脂对碱性酚醛树脂固化的作用,是通过快速促进树脂分子生成活性中间体亚甲基醌来实现的;有机脂的加入对树脂的耐热性能影响不大。     

松香和桐油改性氨基聚酯树脂烘漆性能研究

将不同量的乙二醇马来来海松酸酯多元醇（EMA）和乙二醇桐马酸酐酯多元醇（ETM）用六甲氧基甲基三聚氰胺树脂（HMMM）交联，制备了松香和桐油改性氨基聚酯树脂烘漆，重点讨论了不同EMA／ETM配比和固化条件等因素对洪漆性能（特别是耐热性）的影响，研究结果表明，该烘漆具有优异的性能，可作为氨基聚酯烘漆使用。     

氢化萜烯马来酸酐与环氧树脂固化物的性能研究

研究了氢化萜烯马来酸酐(HTMA)与环氧树脂固化物的机械强度、热稳定性及电气绝缘等性能及其主要影响因素.实验结果表明,采用氢化萜烯马来酸酐固化后的环氧树脂具有较好的机械强度、热稳定性及电气绝缘性能.氢化萜烯马来酸酐的化学结构与固化物的机械强度及热稳定性密切相关.不同化学结构脂环酸酐固化后的环氧树脂电气绝缘性能相近.     

生物油的氨基甲酸酯化改性及其酚醛树脂的制备

以生物油为原料,生物油与尿素按质量比100∶20、100∶30、100∶50进行氨基甲酸酯化改性,制备氨基甲酸酯生物油UO-20、UO-30和UO-50,进一步合成了生物基酚醛树脂UOR-20、UOR-30和UOR-50;对改性生物油及其酚醛树脂进行了结构表征,并研究了酚醛树脂的固化和耐热性能。结果表明:氨基甲酸酯化改性在生物油中引入了酰氨基,有利于生物基酚醛树脂的合成反应;随着生物油氨基化程度的增加,生物基酚醛树脂的软化点和凝胶化温度均有所降低;生物基酚醛树脂固化过程中在178和205℃有两个吸热峰,同时具有良好的流变性和加工成型性;在氮气气氛下800℃时,生物基酚醛树脂的残炭率可达42%~46%,热分解温度为245~325℃,具有很好的耐热性,并且残炭率和热分解温度均随生物油氨基化程度的增加而提高。     

马来海松酸聚酯氨基树脂耐热性研究(英文)

以马来海松酸和线性小分子二醇为原料，合成马来海松酸聚酯多元醇，再用氨基树脂交联，制备马来海松酸聚酯氨基树脂。利用热重分析，讨论了不同原料种类及配比对树脂耐热性的影响。研究结果表明，马来海松酸聚酯多元醇和氨基树脂以及它们的配比直接影响最终树脂的耐热性。只有选用耐热性好，官能度高的聚酯多元醇组分和自缩聚少的氨基树脂组分，并且在它们的最佳配比下，才能获得具有较好耐热性的聚酯氨基树脂。     

氢化萜烯马来酸酐与环氧树脂固化反应特性研究

采用FT-IR光谱研究了氢化萜烯马来酸酐(HTMA)与双酚A型环氧树脂的固化反应过程,并分析了固化度、凝胶时间及其主要影响因素.实验结果表明:HTMA与环氧树脂的固化反应过程与促进剂作用下的酸酐固化环氧树脂的交联反应机理一致;固化度随温度升高、时间延长而提高,而凝胶时间随温度升高、促进剂用量的增加明显缩短.HTMA与双酚A型环氧树脂在110℃、8h以上可完全固化.空间位阻效应及电子效应的协同作用使HTMA与环氧树脂的固化反应速度降低,固化过程中放热量小,放热平缓.     

萜烯马来酸酐催化加氢反应的研究

研究了反应温度、压力、催化剂用量等因素对萜烯马来酸酐催化加氢制备氢化萜烯马来酸酐合成工艺的影响.实验结果表明,采用钯碳催化萜烯马来酸酐加氢生成氢化萜烯马来酸酐的最佳反应条件为:反应温度150～160 ℃、氢气压力8～10 MPa、催化剂用量4 %～6 %.该催化氢化工艺具有催化效率高、选择性好、反应时间短等优点.     

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.     

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.     

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.     

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.     

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.     

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。