热老化对刨花板力学性质的影响

为了探索改善刨花板力学性质的途径,采用全因素试验方法,对刨花板进行热老化处理。结果表明:在热老化过程中,时间对刨花板的内结合强度、静曲强度和弹性模量影响不显著;温度对刨花板的内结合强度影响显著,而对静曲强度和弹性模量影响不显著;厚度对刨花板的静曲强度和弹性模量影响极显著,而对内结合强度影响显著。在生产实践中,不同厚度的刨花板采用不同的热老化工艺,才有望获得理想的效果。     

烟秆制备刨花板的力学性能研究

烟秆为烟草采摘烟口t-后的废弃物,为了更好的利用这种原料,利用不同含水率（9％、6％、3％、0％）和烟秆不同部位（上部、中部和下部）的刨花制成刨花板,测定刨花板的内结合强度、弹性模量和静曲强度,分析含水率和烟秆部位对刨花板力学性能的影响。结果表明,随着含水率从0增加至9％,刨花板的内结合强度从0．35MPa增加至0．58MPa,其弹性模量和静曲强度呈先增后减趋势,当含水率在6％时,烟秆刨花板的弹性模量和静曲强度最大。不同部位的烟秆刨花对刨花板的内结合强度、弹性模量、静曲强度有显著影响,其中,利用中部烟秆刨花制备的刨花板的内结合强度、弹性模量、静曲强度最小。利用烟秆刨花制备的刨花板其力学性能能达到国家标准的要求,因此利用烟秆制备刨花板是可行的。     

关键参数对大豆胶桉木刨花板性能的影响

研究了刨花板密度、施胶量、施胶后含水率、增黏剂用量等参数对大豆胶刨花板各项性能的影响。结果表明:大豆胶刨花板的弹性模量和静曲强度随着密度的增大而增大;随着施胶量的增大,静曲强度、弹性模量和内结合强度呈上升趋势,而2h吸水厚度膨胀率基本没有变化;随着表层施胶后含水率的增大,静曲强度、弹性模量和内结合强度呈上升趋势,而2h吸水厚度膨胀率变小;增黏剂的加入显著改善了刨花板制备时的预成型性,提升了力学强度。     

主要工艺参数对生物油-酚醛树脂胶粘剂制备刨花板性能的影响

研究了5种主要工艺参数对生物油-酚醛树脂胶粘剂制备刨花板性能的影响。结果表明,密度对所制备刨花板的静曲强度、弹性模量、内结合强度和表面结合强度均具有显著影响。施胶量也是影响刨花板性能的主要因素之一,随着施胶量的不断增加,刨花板的各项性能显著提高;提高热压温度和延长热压时间,刨花板的性能也会随之提高,但影响因素并不显著;防水剂加入量对刨花板力学性能影响很小。     

枝桠材制备木质刨花板成板工艺及性能研究

采用柳树枝桠材制得的片状刨花制备木质刨花板;通过正交试验设计,研究施胶量、预设密度以及石蜡添加量对板材物理力学性能的影响。结果表明,预设密度对静曲强度和静曲弹性模量均有显著的正相关线性影响,对内结合强度有显著影响;施胶量对静曲弹性模量和内结合强度有一定的正相关影响;所有试验因素对2 h吸水厚度膨胀率均有一定影响。从板材性能和成本角度考虑,确定柳树枝桠材制备木质刨花板的最佳工艺为:施胶量7%,预设密度0.7 g/cm~3,石蜡添加量4%。     

有机硅防水剂对石膏刨花板性能的影响

主要讨论了添加有机硅防水剂对石膏刨花板物理力学性能的影响。研究表明,添加适量的有机硅防水剂能提高石膏刨花板的防水性能,并对板的内结合强度、静曲强度和弹性模量有一定的改进。     

聚磷酸铵分层阻燃处理对杨木大片刨花板性能的影响

针对传统均混阻燃剂工艺对刨花板性能的不利影响以及刨花板燃烧由表及里发展的特点,采用“表-芯-表”分层施加阻燃剂的方法制备阻燃大片刨花板。将总质量分数为12.5%的聚磷酸铵(APP)阻燃剂引入大片刨花板中,调控大片刨花板每层阻燃剂添加量,探究分层阻燃工艺对大片刨花板内结合强度、静曲强度、弹性模量及吸水厚度膨胀率等物理性能的影响。采用锥形量热仪表征产品的燃烧特性,并对大片刨花板燃烧后残炭的组成进行了分析。结果表明：分层施加阻燃剂有效调控了大片刨花板的力学性能和吸水厚度膨胀率,弹性模量均比未添加阻燃剂板材高226 MPa以上;分层工艺中APP424内结合强度和静曲强度提升最高,与均混工艺相比,分别提升0.15和8.59 MPa;无机阻燃剂APP在表层的施加量会影响大片刨花板的静曲强度,在芯层的施加量会影响大片刨花板的内结合强度;分层施加阻燃剂对大片刨花板的阻燃性能提升明显,第2放热峰延缓了255～435 s,且火灾危险性明显下降,其中APP343(上、下表层各施加质量分数为3.75%的APP,芯层施加5%的APP)防火安全性最佳;分层施加阻燃剂有效提高了阻燃大片刨花板的气相阻燃效果,且并未明...     

灰木比对水泥刨花板力学性能的影响

对不同灰木配比的水泥刨花板力学性能进行试验研究,结果表明:在研究范围内水泥刨花板的密度、内结合强度、弹性模量和静曲强度都随灰木比的升高而增强,吸水厚度膨胀率随着灰木比的升高而降低。当灰木比为1:1时,板材的静曲强度为8.4 MPa;当灰木比为1.5:1时,板材的静曲强度为14.6 MPa;当灰木比为2:1时,板材的静曲强度为15.6 MPa水泥刨花板的力学强度在灰木比为2:1时达到最高。     

秸秆刨花板性能分析

对普通木质刨花板、麦秸刨花板及稻草刨花板进行了密度、含水率、吸水厚度膨胀率、静曲强度和弹性模量、内结合强度、表面结合强度及握钉力的测试,结果表明,麦秸刨花板在强度方面不及木质刨花板,稻草刨花板在抗弯性能上也无法满足要求,两种秸秆板的握钉力都较差。产生上述差距的关键原因是板坯的密度,另外,与原料形态、加工工艺、机械设备等也有关系。     

烟秆/木材刨花板的初步研究烟秆

初步探讨了实验室条件下烟秆/木材刨花板的生产工艺,研究了热压时间、施胶量、密度、木刨花加入量等因素对板材的静曲强度、内结合强度、吸水厚度膨胀率的影响.实验结果表明,烟秆/木材刨花板的静曲强度和吸水厚度膨胀率较纯烟秆刨花板有所提高,内结合强度相差不大.     

Influence of Raw Material and Mat-forming on Physical-mechanical Properties of Panels

China is one of the major production countries forwood-based panel products, and its production wasranked in the second place in the world in 2003. Onthe other hand, however, China is also a country withshortage of forest resources. As the main raw material,wood supply is becoming a serious problem with thefast growing of panel production. Fortunately, thereare plenty of agricultural residues in China, and thisgives the possibility to use agri-based fibers instead ofwood. Many wood-based pane…     

Effects of preboiling on the acidity and strength properties of heat-treated wood

Heat treatment is an alternative to the chemical treatment in wood preservation, which has been used to some extent in improving timber quality. However, reduction in strength properties has been one of the major limitations in the use of this technique and therefore investigations on the use of various pre-treatment methods are highly essential. Wood samples from Scots pine were immersed in already boiling water (100°C) for 20 min followed by 2 h of heat treatment at 160 and 200°C. The acidity and strength properties were determined by measurement of pH and static bending test, respectively. There were no significant changes in pH due to preboiling in both heat-treated and untreated wood. Similarly, preboiling did not result in any appreciable differences in strength both before heat treatment and during heat treatment at 160°C. However, for 200°C heat treatment preboiling reduced significantly the degree of strength loss as indicated by 19.4% reduction in modulus of rupture in preboiled wood compared to 26.6% reduction in unpreboiled wood. From the results of this study it is evident that preboiling has a buffering effect on wood during heat treatment and the higher the intensity of heat treatment the higher the significance of the buffering effect of pre-boiling.     

Strength properties of thermally modified softwoods and its relation to polymeric structural wood constituents

Thermal modification at relatively high temperatures (ranging from 150 to 260 °C) is an effective method to improve the dimensional stability and resistance against fungal attack. This study was performed to investigate the impact of heat treatment on the mechanical properties of wood. An industrially-used two-stage heat treatment method under relative mild conditions (< 200 °C) was used to treat the boards. Heat treatment revealed a clear effect on the mechanical properties of softwood species. The tensile strength parallel to the grain showed a rather large decrease, whereas the compressive strength parallel to the fibre increased after heat treatment. The bending strength, which is a combination of the tensile stress, compressive stress and shear stress, was lower after heat treatment. This decrease was less than the decrease of only the tensile strength. The impact strength showed a rather large decrease after heat treatment. An increase of the modulus of elasticity during the bending test has been noticed after heat treatment. Changes and/or modifications of the main wood components appear to be involved in the effects of heat treatment on the mechanical properties. The possible effect of degradation and modification of hemicelluloses, degradation and/or crystallization of amorphous cellulose, and polycondensation reactions of lignin on the mechanical properties of heat treated wood have been discussed. The effect of natural defects, such as knots, resin pockets, abnormal slope of grain and reaction wood, on the strength properties of wood appeared to be affected by heat treatment. Nevertheless, heat treated timber shows potential for use in constructions, but it is important to carefully consider the stresses that occur in a construction and some practical consequences when heat treated timber is used.     

热处理对木材力学性能的影响综述

热处理可有效提高木材尺寸稳定性,同时对木材力学性能也有明显的影响。文中按照力学指标分别综述热处理工艺对静曲强度/弹性模量、抗压强度、脆性/冲击韧性及其他力学性能的影响,进而总结热处理对木材力学性能影响机理的研究进展;提出可以从以下方面深化热处理技术的研发:一是热处理技术研发时宜根据应用领域科学选择合适的力学指标,二是进一步拓展热处理介质以控制力学性能损失,三是进一步探索热处理对木材不同力学指标的影响机理。     

Effect of intermittent heat treatment on crystallinity in wood cellulose

The effect of intermittent heat treatment on cellulose crystallites in wood was studied to evaluate quantitatively the changes of crystallinity induced by intermittent and continuous heating. The changes in crystallinity were found to be strongly affected by the intermittent heat treatment. The increased crystallinity, the width of the crystals, and the piezoelectric properties were the same for the first intermittent heating as for continuous heating. Further intermittent heating for the same time duration and temperature had no effect on the above properties, probably due to the stopping of the thermal reaction during the interval. Our results suggested that intermittent heat treatment has certain critical cooling temperatures that stop the thermal reaction and are closely related to the duration of the interval. Samples once exposed to a certain duration of heat treatment and then cooled need more time, about twice that of the first duration of intermittent heating compared with continuous heating, to reach maximum crystallinity in wood cellulose.     

杜英大枝径切扦插培育生根苗技术的研究

应用大枝径切扦插开展对杜英扦插培育生根苗的试验研究，解决杜英扦插难生根的问题。试验研究结果表明：经用 ＫＯＨ溶液预处理的穗条生根率平均在 ９０％左右，最佳组合生根率可达 ９７％。经方差分析，与不经预处理的组合比较有显著差异，筛选出杜英用大枝径切穗条经预处理及激素处理是最理想的无性繁殖方法。     

Effects of borate impregnation on the response of wood strength to heat treatment

Based on the strong correlation between acidity and thermal degradation in wood reported in previous studies, the effect of borate impregnation as an alkali-buffering medium was investigated on the strength properties of thermally modified wood. Wood samples were impregnated with 0.1 M Sodium borate solution (pH=9) before they were subjected to heat treatment at temperatures of 180°C and 200°C for durations of 2 and 4 h. The borate impregnation results in some reductions in the severity of strength loss during heat treatment and this is invariably due to buffering effect of the alkali on the acidity of wood, which could have mitigated the degree of degradation. The positive effects of borate impregnation as a pretreatment on the strength properties of heat-treated wood depend on the degree of heat treatment. Hence, the use of borate impregnation as a pretreatment method for heat treatment is recommended only where a relatively mild heat treatment is involved.     

高温炭化热处理对杉木XRD特征的影响规律

采用X射线粉末衍射仪研究高温炭化热处理对杉木XRD特征的影响规律。结果表明：高温炭化热处理对杉木纤维素结晶区002晶面衍射峰位置的影响不显著;不同处理温度水平下处理时间对木材X射线衍射峰强度的影响表现出不同的变化趋势;当处理时间相同、处理温度不同时,随着温度的升高,衍射峰强度呈现出先升高、后降低、再升高的趋势。     

Analyzing the effectiveness of alternative fuel reductions of a forested landscape in Northeastern China

Successful management of forest fire risk in the Northeastern China boreal forest ecosystem often involves trade-offs between fire dynamics, fire hazard reduction, and fiscal input. We used the LANDIS model to study the effects of alternative fuel reduction strategies on fire dynamics and analyzed cost effectiveness for each fuel reduction strategy based on cost–benefit theory. Five levels of fuel treatment area (2, 4, 6, 8, and 10% for each decade) and two fuel treatment types (prescribed burning [PB] and mechanical treatments in combination with prescribed fire [PR]) under current fire suppression simulated by LANDIS were compared in a 5 × 2 factorial design over a 300-year period. The results showed that PR scenarios are more effective at reducing the occurrence and burn area of catastrophic fires than PB scenarios. In addition, area burned by high intensity fire can be tremendously reduced by increasing low intensity fires with a higher level of treatment area under the various PR scenarios. The cost effectiveness of alternative fuel reduction strategies is strongly dependent on treatment area. In general, PB scenarios will be more cost effective in larger treatment areas and PR scenarios in smaller. We recommend mechanical treatments in combination with prescribed fire, with 4% of landscape treated in each decade (PR04) to be the optimal fuel reduction strategy in the study area based on risk control and cost efficiency analysis. However, the most challenging work in China is to make local forest policy makers and land managers accept the ecological function of fire on forest ecosystems.