中密度纤维板发展概况及环保性能分析

论述了中密度纤维板的发展概况、环保方面的现状及其必要性和紧迫性，介绍了降低中密度纤维板游离甲醛释放量的方法，并讨论了中密度纤维板的现存问题和发展趋势。     

中密度纤维板中氨释放量测定方法研究

企业在生产中使用氨处理来降低中密度纤维板中甲醛释放量的行为,引发了中密度纤维板的氨释放。氨对人体健康有很大的危害,而我国尚无中密度纤维板中的氨释放量检测方法。笔者采用气候箱法、干燥器法、气体分析法对中密度纤维板中氨释放量进行测定,分析不同氨释放量检测方法之间的相关性。结果表明,采用气候箱法、干燥器法、气体分析法能较好地检测出中密度纤维板中氨释放量,并且部分中密度纤维板中的氨释放量较高,同时不同方法测定的氨释放量之间存在一定的换算关系。     

浸渍纸饰面和封边对MDF甲醛释放的阻隔效应

采用干燥器法测定用不同浸渍纸饰面和不同材料封边的中密度纤维板甲醛释放量,分析饰面和封边对甲醛释放的阻隔效应,为企业优选浸渍纸和封边形式提供指导;探索饰面和封边对甲醛释放的阻隔机理,为控制中密度纤维板甲醛释放提供科学依据和方法。试验结果表明,饰面和封边可以大大降低中密度纤维板中甲醛向外扩散和蒸发的速率,实现降低中密度纤维板甲醛释放量;就对甲醛的阻隔作用而言,3种浸渍纸中耐磨纸的阻隔效果最差,装饰纸次之,平衡纸最好;而3种不同材料的封边方式对甲醛的阻隔效应是熔融石蜡聚氯乙烯热缩膜铝箔;不同的浸渍纸配置方式对中密度纤维板甲醛释放的影响也不同,饰面层越厚,饰面层越多,对甲醛的阻隔性能就越好。使用100g平衡纸、70g装饰纸和42g耐磨纸饰面中密度纤维板可以作为生产E_0级强化木地板的优选方案。     

低甲醛释放蔗渣中密度纤维板用脲醛树脂

以脲醛树脂结构形成特征为基础,研制了一种甲醛释放量低、内结合强度高的适用于蔗渣中密度纤维板生产的脲醛树脂胶粘剂。使用结果表明,所压制的蔗渣中密度纤维板物理力学性能达到国家标准要求,甲醛释放量可控制在２０ｍｇ／１００ｇ左右。     

几种人造板甲醛释放量探讨

用抽吸法测试了胶合板、细木工板、刨花板、中密度纤维板甲醛释放量并进行比较，结果表明：在所测板种中，胶合板的甲醛释放量最高，细木工板次之。     

环保阻燃胶的开发

为了改善人造板的阻燃性能及降低人造板游离甲醛释放量，在引进国外先进技术基础上，历经两年的消化、吸收、创新工作，开发出一种集环保、阻燃、抑烟、胶粘于一体的环保型阻燃胶。实验室及福州人造板厂生产性试验结果表明，这种胶粘剂符合中密度纤维板生产的要求，可生产出低游离甲醛释放的阻燃中密度纤维板。初步的成本分析表明，与常用阻燃剂相比，这种阻燃胶在价格上极具优势。     

硅藻土基中密度纤维板的研究

硅藻土作为主要功能填料,与施胶纤维复合,通过热压制备了硅藻土基中密度纤维板(D-MDF)。讨论了硅藻土种类和添加量对D-MDF的理化性能的影响。结果表明,硅藻土采用煅烧硅藻土,最大加入量为12%,与未添加硅藻土的中密度纤维板相比,D-MDF的甲醛释放量降低了58.1%,力学性能符合中密度纤维板GB/T 11718—2009中密度纤维板国家标准,吸水厚度膨胀率为13.16%、内结合强度0.671MPa、静曲强度31.03MPa和弹性模量为3 218MPa。     

中密板中的游离甲醛问题

本文阐述了我国对人造板甲醛释放的有关规定和生产现状,用中密度纤维板生产中的数据分析了胶粘剂、摩尔比、施胶量、板材厚度与板坯含水率等因素对游离甲醛释放量的影响,还提出在生产中如何处理好板材性能、生产效率与降低甲醛释放量的关系。     

三聚氰胺改性脲醛树脂胶粘剂在中密度纤维板上的应用研究

耐水性差、游离甲醛释放量高是我国中密度纤维板（ＭＤＦ）存在的两个主要问题。用三聚氰胺改性脲醛树脂（ＭＵＦ）胶粘剂生产ＭＤＦ可以有效地提高耐水性，降低游离甲醛释放量，并使得因管道施胶引起预固化问题得到有效控制。     

应用甲醛捕集剂压制环保型中密度纤维板

介绍了中密度纤维板环保的必要性,试验证明应用自制的甲醛捕集剂生产环保型中密度纤维板可行;采用正交试验,得到了合理的环保型中密度纤维板生产工艺参数：热压温度180±5℃、脲胶施加量10％、甲醛捕集剂施加量12％、热压时N25s／mm;压制的板材物理力学性能达到优等品要求,甲醛释放量满足E1级要求。     

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.     

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。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

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.     

Risk Perception Among Non-industrial Private Forest Owners

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.     

Interactions in decomposition and N mineralization between tropical legume residue components

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.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

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.