木材保护与改性2. Wood durability and Protection

The characteristics of Freshly felled logs and recently sawn lumber wood easy to be infected Do not deteriorate the cell walls of wood; Discolor wood surface and therefore, lower the aesthetic value Infection on wood Always cause severe human respiratory reactions if not ventilated. Often decrease wood toughness and increase permeability
Stain and mould fungi do not usually deteriorate the cell wall of wood but grow either on the surface or within the cell lumen Items Nutrition Mould fungi Sugars and starch within the lumen Stain fungi
(1) Physiological requirements for the growth of fungi
Condition Perfect
nutrition Cellulose,lignin, hemicellulose, starch ,sugar
water 30%
temperature oxygen pH value 20-32℃ ℃ little 4-6
Types of wood preservatives
Oil preservative Oil-soluble chemicals Waterborne preservatives Gaseous preservatives
油质类木材防腐剂 油溶类木材防腐剂 水溶性木材防腐剂 气体类木材防腐剂
Examples of the preservatives
Attack cellulose and hemicellulose, modify the lignin Wood have a brownish or reddish color Developed checks and when dried breaks into cubic pieces Cause dramatic strength loss
Mould fungi
Stain fungi
Brown rots Brown rots
White rots
Soft rots
White rots Degrade lignin and part of cellulosic components Bleached or whitish color The cellwall becomes thinner,but the wood does not shrink,check or collapse Retain its shape but eventually becomes a fibrous spongy mass
2. Innovative technology
Many types of preservatives: Creosote, CCA , ACQ, CA, etc.
3. Sound policies and regulations
China 1. ratio of preservative-treated timber
Application of preservatives: Utilizing the toxicity of
chemicals to prevent wood.
2.3.2 Wood preservatives
(1) Toxicity to a range of wood-inhabiting organisms; (2) A high degree of permanence (3) An ability to penetrate wood readily ; (4) Hydrophobicity (5) Noncorrosive to metals and noninjurious to wood; (6) Possesses safe handling and use characteristics; (7) Has low environmental impact; (8) Favorable economics
Oil-soluble chemicals
Waterborne preservatives
Gaseous preservatives
Characteristics of the preservatives Preservatives Oil preservatives Oil-soluble preservatives Merits 广谱性，且耐久性好、 广谱性，且耐久性好、不易 流失，对金属无腐蚀， 流失，对金属无腐蚀，处理 材变形小。 材变形小。 材面干净， 材面干净，可以进行其它 处理， 处理，其它同上 以水为溶剂，成本低， 以水为溶剂，成本低，材面 干净，无刺激气味， 干净，无刺激气味，不增加 可燃性。 可燃性。 渗入木材的速度较快， 渗入木材的速度较快，且能透 入难处理的木材中。 入难处理的木材中。可以和木 材干燥同步进行， 材干燥同步进行，处理后的木 材表面干净，不需重新干燥。 材表面干净面脏，不易进 行其它处理，且有溢油现象. 行其它处理，且有溢油现象 由于采用昂贵的有机溶剂， 由于采用昂贵的有机溶剂， 处理成本提高，防火要求高. 处理成本提高，防火要求高 处理材易膨胀收缩， 处理材易膨胀收缩，不宜对 尺寸要求高的部件进行处理， 尺寸要求高的部件进行处理， 且抗流失差。 且抗流失差。 不能长久保留在木材内，只 不能长久保留在木材内， 能暂时起到杀虫、杀菌作用 能暂时起到杀虫、 .
restrain
< 20% or > 100%
< 0 ℃ or >38 ℃
(2) Types of wood fungi
Decay fungi
Brown rot fungus White rot fungus Soft rot fungus Other rot fungus: dry-rot fungus
for the application of preservative-treated timber
The importance
science》 Wood has many advantages; 《 wood science》 Wood is ready to be deteriorated by fungi and insects; Conserve wood to protect the ecological environment.
Chapter 2 Wood durability and Protection
2.1 Introduction 2.2 Wood fungi, Insects and Marine borers 2.3 Preserving wood from decay fungi 2.4 Preserving wood from termite
2.2 Wood fungi, Insects and Marine borers
2.2.1 Wood fungi(详细内容 参看英文资料 详细内容 参看英文资料) Introduction 真菌(fungus)—— 真菌 菌丝(hyphae)在木材内蔓延，菌丝能分泌酶，分解木 在木材内蔓延， 以菌丝 在木材内蔓延 菌丝能分泌酶， 材细胞壁组织中的纤维素、半纤维素或木质素， 材细胞壁组织中的纤维素、半纤维素或木质素，同时还能 消化细胞腔中的内含物如淀粉、糖类等养料， 消化细胞腔中的内含物如淀粉、糖类等养料，使木材组织 破坏； 破坏； 此外，还能靠孢子 孢子(spore)传播，一个子实体能产生几千 传播， 此外，还能靠孢子 传播 亿个孢子。孢子既轻又小，可随气流四处漂播， 亿个孢子。孢子既轻又小，可随气流四处漂播，如果落在 木材上，条件适宜就发育成菌丝，危害木材， 木材上，条件适宜就发育成菌丝，危害木材，并能再形成 子实体使更多的的木材遭到破坏。 子实体使更多的的木材遭到破坏。
Situation on the development of wood preservation
Abroad 1. High ratio of preservative-treated timber
Canada 2,000,000m3 American 16,000,000m3 England 2,300,000m3 New Zealand 13% 15.6% 20% 43%
2.3 Preserving wood from decay fungi
2.3.1 Mechanism for wood preservation 2.3.2 Wood preservatives 2.3.3 Treating Methods 2.3.4 Tendency to wood preservation
Contents
Chapter 1 Preface Chapter 2 Wood durability and Protection Chapter 3 Preservation of bamboo Materials Chapter 4 Wood-polymer Materials Chapter 5 Wood color treatment Chapter 6 Chemistry of fire retardancy
2.3.1 Mechanism for wood preservation
Mechanically isolated: isolating wood from the environment,