共查询到20条相似文献，搜索用时 46 毫秒
1.
本研究选用水曲柳、核桃楸、长白鱼鳞云杉3个树种木材和水性高分子聚合物-异氰酸酯、单组分湿固性聚氨酯两种胶黏剂制造集成木方,然后进行薄木刨切,并对木方刨切的集成薄木的厚度偏差、表面粗糙度进行检测。结果表明,经水热软化处理后,湿粘法制作的集成木方经水热软化处理后胶层均未发生出现剥离现象;干粘法制作的集成木方经水热软化处理后,除水曲柳集成木方胶层发生部分胶层剥离外,而核桃楸和长白鱼鳞云杉集成木方胶层均未发现剥离现象;厚0．60mm集成薄木的表面粗糙度检测值均达到了GB／T13010—1991国标中相应树种的指标要求。 相似文献
2.
3.
欲达到良好的界面胶合或高强度的胶接接头,胶黏剂在木材表面上的润湿性是非常重要的,而含水率对木材润湿性具有极为重要的影响。以胶黏剂在桦木表面的润湿眭能为着眼点考虑胶接问题,采用单组分湿固化异氰酸酯胶黏剂粘接高含水率桦木,引入润湿模型,用平衡接触角θ和扩散-渗透系数K分别从胶滴的最终铺展状态和胶滴的扩散、渗透能力两个不同方面对润湿性能进行了描述,探讨了在高含水率条件下,桦木的润湿性能与胶接性能的内在联系。结果表明:桦木含水率从50%增大到90%时,含水率越高,桦木初始接触角越小,平衡接触角越大,扩散-渗透系数K值越小,胶液在桦木表面的润湿性能越不好,其胶接强度越低。 相似文献
4.
单组分聚氨酯胶生产多层复合地板工艺分析 总被引：1，自引：1，他引：0
单组分湿固化液态聚氨酯胶(PUR)不同于传统水基胶黏剂,用于生产多层复合地板时,可避免生产过程中因水分和热量的介入对木材尺寸稳定性的影响.配合专用设备,可以优化传统复合地板的生产工艺,节省资金投入和场地,是一种发展前景广阔的新型木材胶黏剂. 相似文献
5.
以尿素为改性剂,亚硫酸氢钠、过硫酸铵(APS)为引发剂,将甲基丙烯酸缩水甘油酯(GMA)接枝到大豆分离蛋白(SPI)上制备改性大豆蛋白胶黏剂基料.研究了尿素浓度及处理时间、引发剂用量、反应温度、单体用量等因素对改性大豆蛋白胶黏剂基料的黏度和耐水性的影响,确定了最佳的工艺条件.最佳工艺条件为:尿素浓度3 mol/L,预处理时间30 min,反应温度50℃,NaHS03、APS和GMA分别占大豆蛋白的质量分数为5％、10％和84％.合成的基料黏度为59.68(mPa.s),胶膜水溶物含量为44.12％,对桦木的拉伸剪切强度为5.85 MPa,基本满足木材胶黏剂要求.红外光谱证明GMA和SPI发生了接枝反应. 相似文献
6.
采用己二酸(AA)、二乙烯三胺、环氧氯丙烷(ECH)合成聚酰胺多胺环氧氯丙烷树脂(PAE),将其与大豆蛋白按比例混合制备PAE大豆胶黏剂。在合成预聚体(PA)后,通过单因素试验,探究AA与ECH摩尔比、大豆蛋白添加量对胶合板胶合强度的影响,研究了PAE对大豆蛋白的改性作用及胶接机理。结果表明:在胶黏剂合成过程中AA与ECH摩尔比为1:1.0,大豆蛋白添加量为30%,热压温度为120℃、压力1.0 MPa、热压时间6 min条件下,PAE大豆蛋白胶黏剂胶合强度可达1.02 MPa,满足GB/T 9846-2015Ι类板指标要求。 相似文献
7.
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。 相似文献
8.
9.
将生物乙醇木质素与自合成的聚酰胺多胺环氧氯丙烷(PAE)树脂进行接枝共聚改性大豆蛋白,制备环保型胶合板用胶黏剂,并通过单因素试验确定了木质素种类、木质素与PAE质量比、木质素与PAE树脂反应时间、大豆蛋白添加量等工艺条件对大豆蛋白胶黏剂胶合强度的影响。结果表明:当选用生物乙醇木质素与PAE进行接枝共聚、木质素与PAE质量配比为1∶4、反应时间为30 min、大豆蛋白添加量为50%(以木质素-PAE总质量而言)时,制得的三层胶合板湿胶合强度(1.03 MPa)可达到GB/T 9846—2015Ι类杨木胶合板的指标要求。 相似文献
10.
为解决醛系合成树脂胶黏剂甲醛释放、热稳定性差和阻燃效果较差的难题,探讨了一种功能叠加型无机镁质胶黏剂的制备技术,以期替代醛类合成树脂胶黏剂在木材工业上的使用。本研究中镁质胶黏剂的优化配方为n(MgO)/n(MgCl_2)=6,n(H_2O)/n(MgCl_2)=16,胶合板制备工艺为施胶量700 g/m~2(双面),冷压时间28 h,养护时间15 d。试验结果显示,养护天数对镁质胶黏剂制备胶合板胶合强度的影响最显著。当养护天数为3～19 d时,胶合板的干、湿胶合强度均呈现先增大后下降的趋势,13 d时干、湿胶合强度均达到峰值,干、湿胶合强度分别为1.40和1.08 MPa。通过对胶合板剪切破坏界面进行扫描电镜观察发现,镁质胶黏剂渗透到木材孔隙中形成了胶钉,产生了机械咬合结构。利用热重分析仪和锥形量热仪等对镁质胶黏剂的热稳定性和燃烧性能进行了测试,结果表明,镁质胶黏剂在本研究温度范围(30～800℃)内的总质量损失率为48%。在50 k W/m~2的热辐射功率下,镁质胶黏剂制备胶合板的平均热释放速率(HRR)为35.84 k W/m~2,总热释放量(THR)为20.97MJ/m~2。与普通酚醛树脂胶黏剂相比,镁质胶黏剂具有较好的热稳定性和阻燃性能。 相似文献
11.
《Scandinavian Journal of Forest Research》2012,27(5):427-435
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.
《Scandinavian Journal of Forest Research》2012,27(3):206-217
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.
《Scandinavian Journal of Forest Research》2012,27(1):53-61
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
14.
《Scandinavian Journal of Forest Research》2012,27(1):15-27
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
15.
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
16.
《Scandinavian Journal of Forest Research》2012,27(2):131-138
The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided. 相似文献
17.
18.
《Scandinavian Journal of Forest Research》2012,27(5):472-479
Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken. 相似文献
19.
Srisuda Thippayarugs Banyong Toomsan Patma Vityakon Viriya Limpinuntana Aran Patanothai Georg Cadisch 《Agroforestry Systems》2008,72(2):137-148
In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic
or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts
(stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea
(Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content
as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest
N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized
to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea,
largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for
N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant
components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N
released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures
were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality
components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in
the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols.
Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest
age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its
components are mixed. 相似文献
20.
A. Rigueiro-Rodríguez M. R. Mosquera-Losada E. Gatica-Trabanini 《Agroforestry Systems》2000,48(3):245-256
The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste
disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization,
(2) milk sewage sludge at 40 kg N ha−1 target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two
pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha−1. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1); (2) Lolium perenne L. var. Tove (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea
(Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m2, with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect
on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage
sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but
affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral
systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献