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1.
以天然腰果酚为原料制备了一种腰果酚基环氧磷酸酯(CGEP)稀释剂,并利用CGEP改性双酚A型环氧树脂(E-51)及异佛尔酮二胺(IPDA)固化体系。研究了CGEP用量对环氧树脂E-51的稀释效果及其固化物性能的影响,并采用扫描电镜(SEM)分析了固化物的断面微观形貌。结果表明:CGEP对环氧树脂E-51具有显著的稀释作用;CGEP参与固化交联反应后,环氧树脂固化物的机械性能明显提高,当CGEP添加量为E-51质量的15%时,固化物的冲击强度达到最大值22.06 kJ/m~2;当CGEP添加量为E-51质量的20%时,固化物的拉伸强度与弯曲强度分别达到最大值96.19和99.70 MPa。随着CGEP用量从0%增加到25%,固化物的玻璃化转变温度由144.82℃降至119.10℃,而氧指数(LOI)由19.0提高到23.0。SEM分析表明CGEP对环氧固化物具有显著的增韧效果。  相似文献   

2.
腰果酚(CD)和1,3-二溴丙烷经Williamson醚化反应得到一种腰果酚二醚化合物(CDE),然后以CDE、多聚甲醛和二乙烯三胺为原料,经Mannich反应制备得到一种浅色的腰果酚二醚曼尼希碱固化剂(MBCDE)。通过傅里叶红外光谱(FT-IR)和核磁共振氢谱(~1H NMR)表征了产物的化学结构,并与氨乙基哌嗪(AEP)进行对比研究其相关性能。通过热重分析(TGA)、扫描电镜(SEM)和力学性能测试研究了两种固化剂与双酚A环氧树脂(DGEBA)固化材料的相关性能。结果表明:MBCDE/DGEBA的最大分解温度为351.6℃,具有良好的热稳定性。AEP/DGEBA环氧固化物的冲击强度为3.641 J/m,而添加80%的MBCDE后固化物的冲击强度则为5.155 J/m,提高了41.6%。SEM分析结果表明MBCDE固化材料中存在相分离。  相似文献   

3.
乙酸木质素分级产物制备环氧树脂的研究   总被引：2，自引：2，他引：0  
采用沉淀法将乙酸木质素在乙酸水溶液中分成具有不同相对分子质量的3个级分。3个级分经苯酚酚化后,得到3种酚化木质素,其酚羟基含量明显提高。3种酚化产物与环氧氯丙烷反应得到3种木质素基环氧树脂。由最低相对分子质量的酚化木质素制备的环氧树脂环氧值最高为1.69 mmol/g,初始热分解温度最高达到256.3℃,残炭率最低41.6%。木质素基环氧树脂与E-44环氧树脂共混固化后,可以较大程度地提高E-44环氧树脂的黏接剪切强度。由相对分子质量最低的酚化木质素制备的环氧树脂,与E-44环氧树脂共混固化后黏接剪切强度最高达到7.9 MPa。  相似文献   

4.
采用月桂烯马来酸酐(AMMA),二聚酸(DA)与三乙烯四胺(TETA)共聚缩合合成反应型共聚酰胺固化剂(CPA),并通过红外光谱和核磁共振氢谱进行表征。对其与市售品双酚A缩水甘油醚型环氧树脂(E-51)按等当量配比在不同温度下的凝胶时间、力学性能和耐热性能进行了测定。结果表明:综合考虑该新型共聚酰胺的黏度和性能,m(DA)∶m(AMMA)=7∶3较为合适。与C36二聚酸型聚酰胺固化物的性能相比,采用Arrenhinus方程求出的E-51/共聚酰胺固化反应表观活化能(Ea)略低,固化反应活性略高;在二聚酸中加入月桂烯马来酸酐能提高环氧固化物的网络交联密度及刚性,拉伸强度、拉伸模量、弯曲强度和压缩强度均有所提高,断裂伸长率虽下降23.2%,但仍能达到3.47%;此外玻璃化转变温度(Tg)提高了38.8%,且在较高温度范围内(60~90℃)钢-钢剪切强度由13.92 MPa增加到21.68 MPa。该共聚酰胺固化物的综合性能更好,具有较好的市场应用前景。  相似文献   

5.
以腰果酚为原料,先合成一种分子主链结构上含有叔氨基的自催化型聚醚多元醇(CPO),然后与异多苯基多亚甲基多异氰酸酯(PAPI)在无催化剂下制备出一种腰果酚基自催化型聚氨酯泡沫(CPUF),再采用木质素对CPUF增强改性,制备腰果酚-木质素基复合自催化型聚氨酯泡沫(LCPUF),并研究了木质素添加量对此复合聚氨酯泡沫的结构与性能的影响。结果表明:采用木质素改性CPUF可有效提高泡沫的表观密度及压缩强度;当木质素添加量为CPO质量的20%时,所制备的LCPUF泡孔略有减小,表观密度和压缩强度最大,分别为81.48 kg/m~3、0.44 MPa;TG分析显示,木质素的加入对CPUF的热降解过程无显著影响。  相似文献   

6.
以马来海松酸(MPA)为原料合成了马来海松酸环氧树脂(MPAER),并将MPAER替代E-51环氧树脂制备了纸基覆铜板,对MPAER和其固化物分别进行了FT-IR表征和TGA测试,研究了MPAER固化物的热性能和MPAER对覆铜板浸胶料凝胶化时间的影响,讨论了MPAER的替代量对覆铜板耐焊性、剥离强度、弯曲强度和燃烧性的影响。研究结果表明:MPAER固化物具有较好的热性能;当MPAER替代量小于60%时,凝胶化时间缩短;MPAER替代量为20%时,所制备覆铜板的综合性能最好,其剥离强度达到1.7 N/mm、耐焊性达到55 s、经/纬向弯曲强度分别达到362.9 N/mm^2和317.7 N/mm^2,均优于E-51环氧树脂覆铜板,且当MPAER替代量小于40%时,覆铜板的阻燃效果达到UL94V-0的最高阻燃级别。  相似文献   

7.
采用偏光显微镜、差示扫描量热仪、热重分析仪、扫描电镜以及力学性能测试仪研究了液晶环氧树脂对生物基腰果酚-糠醛树脂热性能及力学性能的影响,结果表明:联苯二酚二缩水甘油醚(BP)与对氨基苯氨基砜(SAA)经高温固化后可形成液晶(LC)相结构,将BP、SAA与腰果酚-糠醛树脂共混固化,BP与SAA生成的LC相可分散在生物基腰果酚-糠醛树脂基体中,改性树脂的热稳定性及力学性能显著提高。BP-SAA添加量为50%时,玻璃化转变温度由60.4℃提高到70.2℃,热分解温度由300.3℃提高至377.4℃;BP-SAA添加量为30%时,冲击强度达到最大值15 kJ/m2,为未改性的生物基腰果酚-糠醛树脂(4.5 kJ/m2)的3倍。  相似文献   

8.
氨基腰果酚的合成、表征与特性的研究   总被引：3，自引：4，他引：3  
采用一步环氧化法对腰果酚侧链进行氧化，其环氧化物与多元胺反应生成氨基腰果酚。讨论了氨基腰果酚的合成条件，并通过元素分析、红外光谱等探讨氨基腰果酚的生成过程、结构特征和性能。结果表明，腰果酚侧链上烯烃基环氧化生成环氧基，然后环氧基与多元胺发生加成反应。该加成物结构中存在-OH、-NH-等功能基，具有能与环氧树脂进行固化交联以及吸附重金属离子的性能。  相似文献   

9.
水溶性腰果酚醛树脂胶的研制   总被引：2，自引：0，他引：2  
研究了用腰果油部分替代苯酚制备腰果酚醛树脂胶的最佳反应条件。结果表明:腰果油在总酚中的质量分数大于20%时,固形物从反应产物中析出,其量随腰果油质量分数的增大而增大;腰果酚醛树脂胶的拉伸强度和稳定性与反应温度密切相关。最佳反应条件为:总酚与甲醛的质量比为1∶1.2,腰果油在总酚中的质量分数为20%,混合催化剂用量为0.7%,反应温度为95℃,反应时间为60 min。  相似文献   

10.
以双酚A环氧树脂(E-12)为基体,4,4'-二氨基二苯砜(DDS)为固化剂,2-甲基咪唑(2-MI)为促进剂,经熔融共混制成的环氧粉状胶黏剂为研究对象,采用差示扫描量热分析(DSC)、热重分析(TGA)及力学性能测试分析了2-MI用量对E-12/DDS/2-MI体系的力学性能及固化性能的影响。结果表明:与E-12/DDS体系相比,加入2-MI在E-12/DDS体系中可以改善韧性。当2-MI含量为0.2%质量分数时,E-12/DDS/2-MI体系的力学性能最佳,其冲击强度和拉伸强度分别为11.2 k J/m~2和43.54 MPa,分别较E-12/DDS体系提高了28.7%和21.3%;与E-12/DDS体系相比,加入2-MI使起始分解温度降低,从而使E-12/DDS/2-MI体系的热稳定性有所降低; 2-MI的添加降低了E-12/DDS/2-MI体系的表观活化能,有助于降低固化温度和缩短固化时间。研究表明,E-12/DDS/2-MI体系的固化条件为:从93.43℃开始体系发生固化反应,在127.5℃时体系达到充分固化,至172.87℃下体系固化完全。E-12/DDS/2-MI体系的最佳固化工艺为130℃/12 min。  相似文献   

11.

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.  相似文献   

12.

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.  相似文献   

13.
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.  相似文献   

14.

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.  相似文献   

15.

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.  相似文献   

16.
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。  相似文献   

17.
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.  相似文献   

18.

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.  相似文献   

19.
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.  相似文献   

20.
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.  相似文献   

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