【作者】 兴丰；

【导师】 张双保； 鹿振友；

【作者基本信息】 北京林业大学 ， 木材科学与技术， 2014， 博士

【摘要】 人的一生80-90%时间在室内度过,室内空气品质影响着人们的生产和生活。但我国装修广泛使用的人造板的甲醛污染制约着产业发展以及人们生活品质和生存健康的提高。弄清污染特征,调控其甲醛释放量是材料界研究的热点。本文关注中密度纤维板的甲醛污染,基于甲醛传输特性探索简便且经济的方法对中密度纤维板中的甲醛释放进行调控。通过研究散发过程、扩散机制归纳中密度纤维板甲醛释放关键特性参数,考察几种不同调控手段与释放量间的相关性,再据此设计出一种低释放量中密度纤维板的方法并生产出低甲醛产品,主要学术贡献包括如下六个方面：(1)采用密闭环境舱模拟使用条件调查甲醛宏观传输特性。结果表明板边是中密度纤维板甲醛散发的主要通道,通过封边,甲醛浓度峰值可以降低52%。此外,甲醛浓度随环境温湿度和环境湿度上升而增大,随板厚或换气率上升而减小,对指导有效控制中密度纤维板甲醛释放有重要意义；(2)采用扫描电子显微镜调查中密度纤维板甲醛微观传输特性并结合中密度纤维板内甲醛宏微观孔径d界线450nm,即10倍分子自由程λ,分别发生菲克和过渡/努森扩散,描绘出中密度纤维板特征单元体,确定宏微观孔串联是甲醛的主要传输路径,同时建立了一种宏观-微观结构模型,为有效控制中密度纤维板甲醛释放提供了理论依据；(3)通过检测中密度纤维板及其原料和过程产品(脲醛胶、木片、施胶纤维等)的甲醛释放量研究中密度纤维板的初始散发浓度Co,结果表明中密度纤维板所用脲醛树脂胶是中密度纤维板中甲醛释放的主要来源,建立了二者间的甲醛浓度线性关系式,通过调控干燥和热压工艺可以有效控制中密度纤维板的甲醛释放量,例如干燥和热压工序可使释放量下降47%和66%,为生产实践预测和控制中密度纤维板甲醛释放提供了指导；(4)通过比较不同吸附剂(活性炭纤维、硅烷化AL2o3、SiO2和沸石粉)在中密度纤维板中的甲醛吸附效果研究对中密度纤维板甲醛分离系数Ks的影响效果,结果表明2%硅烷化Al2O3与胶混添后压制中密度纤维板效果较好,甲醛释放量降低63%,物理力学性能全部达标,为生产低释放量中密度纤维板提供了方法和思路；(5)通过比较不同饰面材料(耐磨纸、平衡纸、装饰纸)和其组合方式以及不同封边材料(石蜡、聚氯乙烯和铝箔)研究其对中密度纤维板中甲醛有效扩散系数De的影响效果,结果表明采用100g平衡纸+70g装饰纸+42g耐磨纸饰面和采用石蜡封边效果较好,甲醛释放量分别降低了45%和60%,为优选阻隔材料和生产低释放量复合木质材料提供了优选方案；(6)理论与实际相结合,通过添加吸附剂设计出一种生产低甲醛释放量的新方法并生产出了低释放量产品,甲醛释放量由0.47mg/L降低到0.25mg/L,降低了47%。通过饰面封边甲醛释放量更是降低幅度达95%,产品满足日本F甲醛释放限量要求,内结合强度降低0.04Mpa,成本增加1.5-2.5%,产品具有较强的市场竞争力。更多还原

【Abstract】 People usually spend80-90%of their time in building environment; hence, indoor air quality significantly influences efficiency of production and comfort of life. However, medium density fiberboard (MDF) is widely used for refurbishment in China, the formaldehyde pollution from which has been hindering industrial development and social harmony. Therefore, it has been a hot issue in the field of material science to control formaldehyde emission based on understanding its transport characteristics.This dissertation focuses on pollution of MDF and explores effect of emission control with the help of technologically simple and economically cheap approaches in the light of transport features. Here, emission process and diffusion mechanism were investigated to analyze key parameters characterizing MDF emission; then, the relationships between several modified methods and formaldehyde emission were studied. According to above researches, a new kind of low formaldehyde emission MDF was designed and applied in production. The main academic contributions are the following six areas:(1) Environmental chamber was applied to simulate actual situation for investigating macroscopic transport characteristics. It is revealed that edge of MDF is the primary channel for formaldehyde emission and a52%reduction in peak chamber concentration was observed after edge sealing. In addition, emission can be promoted by higher environmental temperature and relative humidity but constrained by larger panel thickness and air exchange rate. It is important to guide the effective control of the formaldehyde emission from MDF.(2) Scanning electron microscopy was applied to observe surface and edge of MDF for investigating microscopic transport characteristics. It is illustrated that critical diameter between macroscopic and microscopic pores in MDF is450nm, i.e.,10times of mean free path for formaldehyde molecule; in the two pores, Fick and transition/Knudsen diffusion respectively occur. In terms of characteristic element for MDF, series connection between macroscopic and microscopic pores is considered as the significant transport channel and a macroscopic-microscopic structure model was established for providing a theoretical basis on control of formaldehyde emission.(3) Investigating material in different production stages (including urea formaldehyde adhesive, wood chip, fiber mixed with adhesive and MDF) for initial emittable concentration C0, it is indicated that adhesive is the major source of formaldehyde release from MDF while a liner correlation for formaldehyde emission was fitted. Besides, drying and hot pressing process can respectively reduce emission for47%and66%. It provides guidance to control and predict the formaldehyde emission in MDF production.(4) Investigating effect of adsorbent (including activated carbon fiber, silanated Al2O3, SiO2and zeolite) for partition coefficient Ks, it is demonstrated that2%silanated Al2O3mixed with adhesive for manufacturing MDF is better, leading to63%reduction of formaldehyde emission. Meanwhile, physical and mechanical properties after this treatment can also be acceptable. It is a better method to reducing the formaldehyde emission from MDF.(5) Investigating effect of finishing (with abrasion resistant paper, balance paper and decorative paper) and edge sealing (with paraffin wax, PVC and aluminum foil) for effective diffusion coefficient De, it is shown that finishing with100g balance paper+70g decorative paper+42g abrasion resistant paper and edge sealing with paraffin wax are better, respectively attaining45%and60%reduction of formaldehyde emission and also provide a preferred solution fro the low emission products with optimized barrier material.(6) Linking theory with practice, a new environmentally friendly design of MDF was proposed combined with doping adsorbent, obtaining47%reduction of formaldehyde emission and even95%after further finishing and edge sealing and meeting the need of Japanese Fstandard. On the other hand, this method causes0.04MPa decrease in internal bond strength and1.5-2.5%increase in cost with strong market competitiveness.更多还原