国内外木材耐光老化技术研究现状

木材在户外利用时,进行耐光老化处理可以有效提高木材制品的使用寿命。文中主要从木材涂饰处理和化学改性2个方面对木材耐光老化处理技术进行较为系统、全面的介绍,分析了无机紫外吸收剂、有机紫外吸收剂、木蜡油、化学改性及抗氧化剂等方法的优缺点。未来的耐光老化技术应主要满足以下几点:价格便宜,处理容易,低毒环保,紫外线屏蔽性能好,不损害木材表面性能及涂料涂饰性能;应主要开发多组分复配涂料以满足上述要求,克服单组份耐光老化技术的不足。     

氮羟甲基树脂/蔗糖改性木材的耐候性能

木材在户外应用过程中易发生开裂、变色、霉变、腐朽等材性劣化现象。利用10%氮羟甲基树脂(1,3-二羟甲基-4,5-二羟基乙烯脲)/20%蔗糖作为改性剂对杨木和辐射松进行改性处理,系统评价了改性处理对木材在哈尔滨户外39个月老化后的性能动态影响。结果显示:老化过程中木材表面的颜色变化主要发生在第1年,未处理木材表面由浅黄色向灰色转变,而氮羟甲基树脂/蔗糖改性木材则由改性后的棕色逐渐褪色至灰色,表明改性处理不能长期保护木材表面颜色。改性处理在最初的12个月内能够明显抑制木材表面微裂,之后抑制效果减弱。老化期间,改性木材含水率及含水率波动均低于未处理材,因此,改性处理有效抑制了木材在户外的变形。傅里叶变换红外光谱和X射线衍射分析显示,改性处理可有效减缓木材三大组分在老化初期(12个月)的降解速度,但经39个月老化后,改性与未改性木材表面木质素浓度和纤维素相对结晶度均下降到相似水平,表明改性处理对木材表面组分的长期保护能力有限。木材老化表面微观形貌观察显示,改性处理抑制了木材表层细胞(尤其是早材细胞)的脱落及变色菌在木材内部生长的深度。氮羟甲基树脂/蔗糖改性能够有效抑制木材在户外老化过程中的含水率波动、变形及变色菌的生长,有助于增强木材的户外耐久性。     

纳米涂层对竹材色度稳定性的影响

为了提高竹材的耐光老化性能和延长竹制品户外使用寿命,利用氙弧灯老化箱模拟室外环境,以寻找一种性能优越的耐光老化改性剂。采用正交试验法测试了4种纳米颗粒(TiO_2、ZnO、SiO_2和AW)和4种成膜物质(蒸馏水、丙烯酸树脂、三聚氰胺树脂和酚醛树脂),测量光老化时竹材表面色度变化;利用扫描电镜对涂层中纳米颗粒分散情况进行表征。结果表明:纳米颗粒分散效果较好,纳米涂层改性处理明显改善了竹材表面色度的光稳定性,其中涂刷三聚氰胺与质量分数为10%的TiO_2配制的改性剂的竹材光老化时色度稳定性能最佳。     

糠醇改性处理对户外用木材耐老化性的影响研究

木材在户外使用过程中易发生材性劣化现象,糠醇改性是一种增强木材耐老化性能的环境友好型改性技术。总结了糠醇改性机理、工艺及糠醇改性处理对木材性能的影响;简述了户外用木材耐老化性研究,为糠醇改性材在户外的应用提供理论指导。     

户外用木材耐光老化技术研究进展

概述了木材光降解机理,主要从涂饰处理和改性处理两方面介绍了国内外木材耐光老化技术,分析了不透明涂层、透明涂层、表面添加剂复配涂层、木蜡油和化学改性、预处理固色等耐光老化处理技术的优缺点,为户外木质产品的耐老化技术研究提供参考。     

木材光老化的研究进展

介绍了日光的分布、木材组分对日光的吸收情况以及木材光老化的机理,并从木材的化学成分、颜色以及微观结构变化等方面,分析了光波对木材性质的影响,为木材及木质材料在室外应用的耐老化性能研究提供参考。     

热处理木材材色变化机理研究现状北大核心

热处理是一种应用广泛的木材改性方法,不仅能改善木材材色,还能提高木材的尺寸稳定性和生物耐久性。总结了热处理工艺对木材性能的影响,详述了热处理过程中木材化学组分变化。从处理过程和老化过程讨论了环境对处理材性能的影响,并概括了热处理木材材色变化机理。未来应深入解析热处理化学反应路径及其内在机理,建立木材材色与其他材性的关系,并通过联合改性处理提升热处理木材的耐久性。     

太阳光对生物炭性能的影响:增强表面活性

生物炭是缓解环境和农业问题的重要生物质材料。室外环境（包括太阳辐射）对生物炭化学结构具有较大影响,从而影响到生物炭户外应用功能。本文通过对生物炭加速光老化,研究光辐射对其物理化学性能的动态影响。研究发现,光辐射400 h后,生物炭物理化学性能发生了明显的变化,生物炭C、N含量呈现下降趋势,而O含量呈现上升趋势;生物炭O/C比值（元素分析）、C₄和O₂含量平均增长了17.04%、13.88%和86.63%。上述结果表明在光老化过程中生物炭经历了一系列的光氧化过程,含氧官能团增加有利于改良生物炭表面活性,从而提高生物炭在土壤改良、污染物降解处理和污水吸附处理等方面的能力。     

木塑复合材料耐候性能研究进展

木塑复合材料(WPC)的耐候性能决定了材料的户外使用寿命。文中介绍了国内外在WPC耐热氧老化、耐光氧老化、耐真菌腐朽及耐潮湿与冻融性能方面的研究进展。现有研究表明, 热氧老化与光氧老化均使得WPC发生褪色现象, 力学性能下降, 添加抗氧化剂与光稳定剂可分别改善二者对WPC的破坏作用。WPC中木粉含量较高时更易发生真菌腐朽现象, 添加化学防腐剂或其他助剂、木粉改性及涂饰可有效抑制真菌腐朽。WPC的吸水性是其热氧老化、光氧老化、真菌腐朽及冻融循环过程的催化剂。文中还总结了目前WPC耐候性能研究存在的主要问题, 并对其未来趋势进行了展望。     

抽提物对高温热处理材光降解进程的影响

将经3种不同抽提处理的高温热处理欧洲赤松(Pinus sylvestris L.)和山毛榉(Fagus longipetiolata Seem.)木材及其对照材置于氙灯老化箱中加速老化1 008 h,测定老化过程中表面颜色的变化,并使用扫描电镜(SEM)、傅里叶红外光谱(FT-IR)和X射线光电子能谱(XPS)分析老化前后木材表面宏观和微观结构的变化,旨在探究不同抽提物对高温热处理材的光降解进程的影响。结果表明:1)高温热处理材中抽提物的存在有利于缓解其光老化进程,提高热处理材的颜色稳定性;2)碱抽提物对热处理山毛榉表面材色的影响最为显著,其存在有利于延缓老化过程中热处理材表面颜色的变化,苯醇及冷水抽提出的极性抽提物对热处理材的颜色稳定性具有积极作用,冷水抽提后的热处理山毛榉在老化过程中出现射线细胞剥离现象;3)在老化过程中,热处理欧洲赤松的表面颜色变化相对山毛榉大,这是因为热处理欧洲赤松的材色较山毛榉浅,碱抽提物对热处理欧洲赤松颜色稳定性的影响相对较小,而苯醇抽提物及冷水抽出物可提高其耐老化性。     

Evaluation of the photo stabilising efficiency of clear coatings comprising organic UV absorbers and mineral UV screeners on wood surfaces

A study of the surface discolouration of clear coated wood during artificial and outdoor weathering and its prevention using clear coatings comprising organic UV absorbers (UVA) and mineral UV screeners was carried out. It was shown that the use of UVA and UV screeners in clear coatings was very effective in reducing photodegradation of the wood surface. Preliminary irradiation trials with Xenon arc light showed that the UV screener TiO₂ led to the least discolouration of the coated wood surface, closely followed by UVA of the hydroxyphenyl-s-triazine class (HPT). The artificial and outdoor weathering trials indicated that UVA of the HPT class stabilised the colour of the wood surface better than UVA of the 2-(2-hydroxyphenyl)-benzotriazole class (BTZ). Comparison of different artificial weathering methods indicated that Xenon arc light weathering showed the best match to the proceeding discolouration of the clear coated wood panels during outdoor weathering.     

Analysis of Markov model on predicting wood composite weathering

Summary This paper evaluated the wood composite weathering over time step by Markov theory. By the null hypothesis (H₀), the panel weathering under the long-term outdoor exposure was determined to be a Markov process. The transition matrix which derived from the practical data can be calculated by program Markov and thus the future outcome of wood composite weathering can be forecasted. Also, the utility of the Markov model was successfully testified from the example of 3-year natural aging waferboard in Ottawa, Saskatoon, Fredericton areas.     

Methodology to assess both the efficacy and ecotoxicology of preservative-treated and modified wood

? Wood used in outdoor conditions out of ground contact is susceptible to weathering, inducing both fungal decay and leaching of components to the environment.

? This paper presents a methodology to determine these two parameters for untreated, preservative-treated and modified wood. Therefore, the wood was first leached and subsequently exposed to fungal decay of the most prominent wood-rotting fungi. The crustacean Daphnia magna was exposed to the leachates to provide information on their impact on the environment.

? Combining both parameters reveals that preservative-treated wood and modified wood are capable of protecting the wood adequately for application under use class 3 conditions without posing a threat to the environment.

? This proves the suitability of the concept of combining efficacy and ecotoxicology for the evaluation of new types of wood treatments.

     

Resistance of wood from black pine (<Emphasis Type="Italic">Pinus nigra</Emphasis> var. <Emphasis Type="Italic">austriaca</Emphasis>) against weathering

At present tapped wood of black pines (Pinus nigra var. austriaca) is mainly combusted. The priority of material use over thermal recycling has led to some considerations regarding the utilization of tapped wood. The high content of extractives suggests a higher natural durability, and therefore, the suitability for outdoor applications. Tapped and not tapped wood boards from black pine (sapwood and heartwood) were subjected to weathering tests to find out its resistance against abiotic stress. Additionally tapped wood particles with a high content of resin were exposed to weathering and to composting. Weathering caused roughness to increase. Infrared spectral characteristics revealed the differences before and after tapping and weathering. Principal component analyses supported the grouping according to the chemical changes. In heartwood the lignin band at 1510 cm^??1 disappears and the typical resin band at 1688 cm^??1 decreases considerably. The lignin band of resinous parts is affected neither by weathering nor by composting. However, the resin band shows an intensity decrease and broadening due to weathering and disappears during composting.     

Effects of chemical modification with glutaraldehyde on the weathering performance of Scots pine sapwood

Scots pine sapwood was treated with glutaraldehyde (GA) in aqueous solution using magnesium chloride as a catalyst in order to evaluate the durability towards weathering. Infrared spectroscopy suggested that GA treatment increased the photo-stability of lignin during artificial weathering of micro-veneers in a QUV over 168?h; photo-protection increased with increasing GA concentration. In comparison with the unmodified controls, GA-modified pine micro-veneer strips exhibited a lower tensile strength loss measured in a zero-span mode in the course of weathering. During 18?months of outdoor exposure, GA-modified pine wood boards exhibited a lower moisture content and water uptake than the unmodified ones. GA treatment also clearly restricted the penetration of blue stain fungi into deeper layers of wood. On the macroscopic scale, the surface of the GA-modified boards was significantly smoother due to less erosion, cracking and minor peeling of tracheids. Scanning electron microscopy further revealed that individual tracheids were detached from the cell compound and then washed away from the unmodified wood surface, whereas tracheids on surfaces of GA-modified wood remained in the tissue compound but displayed many axial and transversal cracks.     

Effects of Natural Weathering on A Wood Fiber/HDPE Composite and Application of Additives

In this study,the durability of rubber wood(Hevea brasiliensis) which was thermally treated at 170,185,200,and 215℃for 3 h respectively was investigated.The results showed that the durability of heat-treated rubber wood was improved,and the improvement became more obvious with the increase of the treating temperature. When treated at 185℃or lower temperature,the decay resistance of treated wood had no significant improvement.The lowest weight losses were 21.6%and 6.8%after attack by brown rot fungi(Gloeophyllum trabeum) and white rot fungi (Coriolus versicolor) respectively,which were reached by the specimens treated at 215℃.Their resistance to mold fungi was not improved,but the heat-treated wood performed better than untreated wood when both were painted.In field test,the heat-treated specimens exhibited no advantage in termite resistance compared to untreated.     

Review on Thermal Characteristics of Compound Outdoor Wall of Wood Framed Construction

INTRODUCTION China has a long history of wood framed construction. But, due to the increasing of population and lack of timber, wood framed construction is limited in the market, its research and development is relatively scarce. The modern wood framed construction has been developed and widely applied in the North American area and other countries for several decades. Recently, with the rapid development of economy and the requirement of society, especially energy saving, the wood frame…     

自然老化对木粉/HDPE复合材性能的影响及添加剂的应用

研究木粉/高密度聚乙烯(WF/HDPE)复合材在不同朝向的自然老化条件下使用时颜色与表面化学成分的变化,并分析采用光稳定剂、抗氧剂和颜料作为防老化剂的效果.户外使用的木粉/HDPE复合材在夏天暴晒1个月颜色就会发生明显变化,南面和东面更加显著,红外分析表明:复合材料表面C=O增加、木材指数下降,有氧化现象发生.人工加速稳定老化检测结果表明:与抗氧剂和光稳定剂相比,颜料的使用对减小变色有明显作用,但颜料、抗氧剂和光老化剂3种助剂对延缓WF/HDPE复合材的抗弯性能下降没有起到明显作用.     

木材腐朽机理研究现状及展望

木材在生产应用过程中易受真菌侵害导致木材性能劣化，极大地限制了木制品在户外推广应用。近年来，为了增强木材防腐技术开发的理论基础，木材腐朽机理得到普遍关注与研究。文中从以下3个方面梳理、归纳、总结木材腐朽机理研究现状:1）木材腐朽过程中结构成分与性能的变化规律；2）木材酶降解理论；3）木材非酶降解理论。在此基础上，阐明现有木材腐朽机理研究中存在的问题及今后重点研究方向，以期为绿色环保型木材防腐技术的研发提供理论指导，为2030年我国实现“碳达峰”提供战略技术支撑。