【作者】 周箭；

【导师】 杨辉；

【作者基本信息】 浙江大学 ， 材料学， 2009， 博士

【摘要】 木塑复合材料（WPC）具有热伸缩性和吸水性小,尺寸稳定性好,耐菌噬,使用、维修简便等优点,充分体现了可再生资源有效利用,开始代替木材广泛应用于户外建筑等多个领域。目前,以聚乙烯、聚丙烯、聚氯乙烯等为基体的木塑复合材料存在抗紫外线、耐水性及阻燃性三项功能难以兼顾的技术难题。本论文提出采用聚偏氟乙烯（PVDF）作为木塑复合材料的基体树脂,通过硅烷提高PVDF和木粉的界面相容性,系统研究了复合材料界面结构、外界环境作用下界面响应行为及对力学、耐水、阻燃等物性的影响规律,揭示了力学性能增强机制、抗紫外老化及破坏机理、耐水界面结构形态和凝聚相协同阻燃机制,成功开发了集抗紫外线、耐水及阻燃于一体的高性能PVDF基木塑复合材料。主要研究工作包括:（1）针对PVDF基木塑复合材料界面结构及特性要求,优选出三氟丙基三甲氧基硅烷（TF3）、十七氟癸基三甲氧基硅烷（TF17）等四种木粉表面改性剂,木粉表面通过形成醚共价键Si-O-Cellulose均获得了不同程度疏水改性;含氟长链的空间位阻效应使得形成于木粉表面的Si-O-Cellulose数量减少。（2）系统研究了硅烷改性复合材料的界面性质及力学性能增强机制。硅烷改性优化使复合材料力学性能得到明显增强,2.0wt%TF3改性的复合材料抗弯和IZOD冲击强度分别达到53.7MPa和3.576KJ/m²。力学性能增强机理是硅烷改性木粉表面的有机功能基团-R与PVDF之间较强的范德华力和机械咬合力,反映在复合材料的冲击断面中有木粉纤维纵向截断,且断面层次分明。（3）首次考察了硅烷改性复合材料在紫外线辐照条件下的界面和聚集态结构特性及抗老化机理。经紫外线辐照后,复合材料的界面相及基体连续相发生交联和断链,影响了不同硅烷改性界面相的分子间作用力,聚合物链段运动能力及复合材料的力学性能得到相应改变;KH-550、TF3、TF17改性复合材料界面相的固态无定形区域形成新结晶。（4）研究了硅烷改性木塑复合材料界面结构对水汽传输特性的影响。研究表明,硅烷改性木粉与基体的界面结合较好,界面层间隙小,材料吸水率低。紫外线辐照后复合材料吸水总量因木粉纤维上光降解产生的羟基数量增加而升高;界面层与木粉内产生的多通道孔隙增加了其浸渍初始阶段的吸水速率。（5）研究了硅烷协同增强复合材料的阻燃特性及机制。硅烷可以协同增强PVDF基木塑复合材料的阻燃性能,材料的燃烧热分解产物H₂O、CO₂等形成气相阻隔屏障,阻碍氧气和热量的渗透;A-151、TF3和TF17协效催化木粉纤维在燃烧表面形成大量堆叠炭粒,有效阻隔火焰及热量的传播。2.0wt%TF3改性的PVDF复合材料LOI为38.7%,0.8mm试样可以达到UL94-VO燃烧等级。更多还原

【Abstract】 Wood plastic composites（WPC） are extensively applied to several realm instead of timber, which embodied the valid application of rebirth resources. Comparing with timber, wood plastic composites have less hot flexibility and water absorbability, excellent size stability, anti-bacteria corrosion, convenient usage and maintainability. At present, WPC are mainly composed of wood flour and thermoplastic including polypropylene, polyethylene and poly（vinyl chloride）. There are some technique difficulties for these WPC that stil could not generally present the high-durability of ultraviolet ray, the high efficiency of flame retardance and water resistance. Therefore, in this research, polyvinylidene fluoride （PVDF） was chosen to manufactured the WPC, and a technique was put forward. To improve the compatibility of wood flour and PVDF, the surface modification of wood flour was carried out using four different silane. The interface structure of composites, interface response behavior under surroundings action outside which affected the mechnical properties, water resistance and flame retardance were studied systematically. The mechanism of reinforced mechnical properties, high-durability of ultraviolet ray, water resistance and condensed phase synergistic flame retardance were concluded. Finally, PVDF/wood flour composites presenting high properties composed of anti-ultraviolet, water resistance and flame retardance was invented successfully. The main researches are summarized below:（1） To aim at the interface structure and characteristic of PVDF/wood flour composites, the surface modification of wood flour was carried out using vinyltriethoxysilane （A-151）, gamma-aminopropyltriethoxysilane （KH-550）, Trifluoropropyl-trimethoxysilane （TF3） and （Heptadecafluoro-1,1,2,2- tetradecyl） trimethoxysilane （TF17）. The results showed that the wood flour surface acquired hydrophobic modification with different degree by forming Si-O-Cellulose on wood flour surface. Because of the steric hindrance of fluorinated long-chain, the sum of Si-O-Cellulose covalent bonding on the wood flour surface decreased.（2） The effects of interface characteristic on the reinforced mechanical properties of composites were investigated systematically. The results showed that the mechanical of composites were reinforced while the wood flour being modified by appropriate silane. When the concentration of TF3 was 2.0 wt% with respect to the wood flour content, flextual and IZOD impact strength increased to 53.7 MPa and 3.576 KJ/m² respectively. The mechanism of reinforced properties is high van der waals force between organic functional group on wood flour surface and PVDF, and mechanical combinative force. The analysis of interface between wood and PVDF indicated that the fracture surface of reinforced composites presented lengthways-truncation of wood flour. The clear fracture surface were observed.（3） The interface, aggregate structure and anti-aging mechnism of PVDF/wood flour composites exposure to ultraviolet radiation were investigated for the first time. The analysis indicated that there were crosslinking and chain scission at the interface and continuous phase of composites while exposure to ultraviolet radiation. Van der waals force at the interface was affected. The movement ability of polymer chains and mechnical properties of composites were changed accordingly, KH-550、TF3 and TF17 facilitated crystallization in solid amorphous phase of composites interface.（4） The effects of silane on water transmission of composites were investigated. The results showed that interface between silane-modified wood flour and polymer were improved, interface gap shorten and water absorption of composites decreased. Total water absorption of composites exposure to ultraviolet increased, indicating that ultraviolet radiation degradation initiated the increasing amounts of hydroxy group on wood flour surface; multiple hole gererated at the interface and the inside of wood floor cellulose increased the initial water absorption of composites.（5） Synergistic flame-retarded effects between silane and PVDF/wood flour composites were studied. The study showed that synergistic flame-retarded effects were enhanced by silane. H₂O, CO₂ etc generated from materials pyrolytic decomposition form the gas obstruction, which prohibite penetration of oxygen and heat; Wood flour modified by A-151, TF3 and TF17 facilitate the formation of combustion char particles, which effectively obstruct the dispersion of flame and heat. The LOI of PVDF/wood flour composites treated by 2.0 wt%TF3 was 38.7%, 0.8mm sample could be passed by UL94-V0 flame-retarded rating.更多还原