木质素磺酸钠预聚体改性脲醛树脂研究

脲醛树脂(UF)胶粘剂的胶合强度高、价格低廉,在木材加工业应用广泛,但是UF化学结构不稳定,在使用过程中会不断释放出甲醛,危害环境。以造纸行业的废弃物——木质素磺酸钠为原料,通过纯化-活化-预聚的工艺,合成了一种新型木质素磺酸钠预聚体。该预聚体结构中的多个胺基可与脲醛树脂中的羟甲基和游离甲醛反应,改善了UF不稳定结构,减少了甲醛来源,同时可以提升树脂的胶合强度。使用上述预聚体改性的UF胶粘剂制备的胶合板粘结强度高,甲醛释放量达到E0级标准,小于0.5mg/L。     

核桃壳三聚氰胺改性脲醛树脂的制备及其热降解性能表征

将超微粉碎后的核桃壳(W S)与甲醛溶液共混,在测定共混溶液反应活性的基础上将共混液作为添加剂与三聚氰胺改性脲醛树脂(MUF)进行共缩聚反应合成核桃壳粉胶(WSMUF),并对WSM U F树脂进行了基本性能检测和热行为分析.研究结果表明:在反应温度为90℃,反应时间为1 h条件下WS与甲醛具有较好的反应活性.WS用于树脂合成的最佳添加量为mWS(核桃壳质量)/m(WS+U)(核桃壳与尿素的质量和)=0.15,所制备的板材甲醛释放量为0.35 mg·L-1,相比未添加WS合成的M U F0树脂,甲醛释放量降低了69.43％,板材湿胶合强度降低21％,热降解峰值温度向高温方向偏移,同时炭残留量偏低.WS超微粉的添加在不改变胶层脆性基础上,能有效降低树脂体系游离甲醛和板材甲醛释放量.     

脲醛树脂胶黏剂改性研究进展:分子结构优化与改造

脲醛树脂(UF)胶接制品因长期释放甲醛,是家居环境污染的主要来源。目前,生产企业普遍通过降低甲醛与尿素摩尔比生产UF树脂以减轻胶接制品产生的甲醛污染,但摩尔比下降会造成UF树脂支化结构大量减少、固化交联度下降,最终导致树脂胶合强度和耐水性能变差。UF树脂性能好坏的关键在于其微观结构的形成,从分子水平优化与改造UF树脂结构是实现其固化速率、甲醛释放量和胶合性能之间平衡的有效方法。文中总结了利用三聚氰胺、乙二醛、树枝状大分子等改性剂优化与改造UF树脂结构的作用机理,阐述了不同改性方法与改性工艺对UF树脂胶固化性能、胶合强度及胶接制品甲醛释放量的影响,最后提出了改性UF树脂胶黏剂未来研究与发展面临的主要挑战。     

弱酸性固化剂对UF树脂固化性能的影响分析

为研究不同种类固化剂对弱酸性起始合成脲醛树脂(UF)固化性能的影响,选用6种固化剂研究固化剂对弱酸性起始合成UF树脂的固化速度、适用期、胶接材料的胶接强度和材料甲醛释放量的影响.研究结果表明:单组份固化剂中,双氧水作为固化剂时UF树脂适用期最长,氯化铵固化速度最快;双氧水加入量是UF树脂质量的5%时,树脂胶接材料的甲醛释放量最低,胶合强度最高;聚醋酸乙烯酯、磷酸二氢铵、氯化铝、柠檬酸和尿素组成的多组分固化剂适用期最长.氯化铵、硫酸铝和尿素组成复合固化剂的UF树脂固化物的甲醛释放量和固化温度最低.     

低甲醛释放脲醛树脂基复合高分子材料研究进展

本文阐述了低游离甲醛脲醛树脂基复合高分子材料的研究进展,分析了复合高分子材料产生游离甲醛的途径和解决方法,探讨了脲醛树脂对低游离甲醛复合材料的影响,最后阐述了采用脲醛树脂基复合高分子材料的改性来解决游离甲醛的释放量。     

E0级人造板用微游离醛脲醛树脂的制备工艺研究

以尿素、甲醛为主要原料,聚乙烯醇、三聚氰胺为改性剂,采用分级、分步聚合反应工艺制备了微游离醛脲醛树脂。采用单因素试验法研究和优化了制备工艺,结果表明,在甲醛/尿素摩尔比为1.12∶1,加成反应pH为7.5~8.5,反应温度为60~65℃,缩聚反应pH为4.8~5.1,缩聚反应温度85~90℃条件下,添加0.4%(wt)的聚乙烯醇和4%(wt)的三聚氰胺为改性剂,制成了微游离醛脲醛树脂胶黏剂。经在杨木板材人造板中应用,该脲醛树脂胶黏剂的胶合性能和环保等级满足E0级人造板用胶黏剂的质量标准。     

利用苯酚液化树皮制备环保耐水性木材胶粘剂及其表征

采用高效液相色谱(HPLC)和凝胶渗透色谱(GPC)方法结合胶合板评价,对6种酸性催化剂存在下的落叶松树皮苯酚液化产物,以及所制备的6种树皮胶粘剂进行表征,结果表明,液化催化剂的酸性对苯酚液化树皮产物的结合酚含量、活性功能基数目和分子量有着重要影响,进而影响所制备树皮胶粘剂的活性、凝胶时间、游离甲醛含量、耐水性和甲醛释放量;采用复合酸催化剂液化树皮所制备树皮胶的胶合强度、耐水性和甲醛释放量都优于硫酸单独做催化剂液化树皮制备的树皮胶,可用于环保耐水性结构胶合板的制备,并以硫酸/磷酸=1/1的复合酸催化剂为最佳。     

热解油脲醛树脂有机覆盖垫制备工艺研究

以园林废弃物为原料,热解油脲醛树脂作为胶粘剂,制备了一种新型的裸土覆盖用有机覆盖垫产品。以热压温度、热压压力、热压时间及施胶量为考察因素,以抗压强度、保水性和甲醛释放量为评价指标,优选出有机覆盖垫的最佳制备工艺。结果表明,有机覆盖垫的最佳制备工艺为热压温度140℃,热压压力0.7MPa,热压时间7min和施胶量10%(相对于有机覆盖垫原料质量百分数)。在此工艺条件下制备的有机覆盖垫强度大于体重100kg实验者行走时对地面的最大压强(约0.52MPa),甲醛释放量达到国标E1级标准(≤1.5mg/L),保水性良好(≥40%)。     

GB18580—2001《室内装饰装修材料人造板及其制品中甲醛释放限量》的制定和实施

人造板是由不同尺度和不同形态的木材（如薄木片、小木块、刨花和木纤维等）经胶合而成的板材、方材或其他异形材料。胶合要用胶粘剂，人造板生产常用胶粘剂有酚醛树脂、脲醛树脂和三聚氰胺甲醛树脂等。其中脲醛树脂因价格低廉、使用方便和胶合性能优良而成为人造板生产上最为常用的胶粘剂。特别是室内使用的各种类人造板，几乎都使用脲醛树脂作胶粘剂。缺点是使用脲醛树脂的人造板会向周围环境长时期释放甲醛气体。甲醛是无色气体，有特殊气味，空气中只要有微量甲醛存在就会对人的眼鼻产生刺激，人们长期生活在这种环境中，会对人体的呼吸…     

有机覆盖垫用常温固化热解油脲醛树脂合成工艺及性能研究

以热解油、尿素、甲醛为主要原料,制得常温固化热解油脲醛树脂(CSBUF)有机覆盖垫。研究结果表明:在甲醛∶尿素摩尔配合比为1∶1.6,热解油加入量为30%,初始pH=8.5的条件下,制得的CSBUF有机覆盖垫的甲醛释放量为1.37mg/L,达到国标E_1级环保标准(≤1.5mg/L);抗压强度为0.72MPa,满足体重100kg实验者行走时承受的强度(最大压力为1300N,受力面积约25cm~2,最大压强约0.52MPa),具有较好的应用前景。     

Evaluation of mechanical and physical properties of industrial particleboard bonded with a corn flour–urea formaldehyde adhesive

The aim of this study was to determine the effect of corn flour content of urea formaldehyde (UF) resin on the panel properties of particleboard. Corn flour was added to UF resin to decrease the free formaldehyde content of particleboard panels. Some physical (thickness swelling and rheological characterization), mechanical (modulus of elasticity, modulus of rupture, internal bond strength and withdrawal of screws) properties and formaldehyde emission of particleboards were evaluated. The results showed that the introduction of small proportions of corn flour (7%, by weight) in UF resins contributes to the improvement of mechanical and physical properties of the boards and reduced their formaldehyde emissions. Hazardous petrochemical UF could be partially substituted in industrial applications by addition of corn flour. To our knowledge, this is the first study on this kind of wood adhesives.     

Effect of γ-irradiation on the hydrolytic stability and thermo-oxidative behavior of bio/inorganic modified urea–formaldehyde resins

In order to minimize emission of formaldehyde from urea–formaldehyde resins (UF) and to improve their thermo-oxidative behavior, the effect of low γ-irradiation on hydrolytic and thermo-oxidative stability of nano-silica modified UF resin, modified UF resin with wood flour (Pinus silvestris L.) as natural filler and modified UF resin with mixture of SiO₂/WF fillers were investigated. The hydrolytic stability of modified UF resins was determined by measuring the mass loss and liberated formaldehyde concentration of modified UF resins after acid hydrolysis. The studied modified UF resins have been irradiated (50 kGy) and effect of γ-irradiation was evaluated on the basis of percentage of liberated formaldehyde before and after irradiation. The minimum percentage (1.23%) of liberated formaldehyde and mass loss of a 25.35% were obtained in wood flour modified UF resin after γ-irradiation which indicate significant improvement in the hydrolytic stability compared to other modified UF resins. The effect of γ-irradiation was evaluated also on the basis of thermo-oxidative behavior of the same modified UF resins before and after irradiation. The thermo-oxidative behavior was studied by non-isothermal thermo-gravimetric analysis (TG), differential thermo-gravimetry (DTG) and differential thermal analysis (DTA) supported by data from IR spectroscopy. After γ-irradiation, the shift of DTA peaks a higher temperature indicates that thermo-oxidative stability of modified UF/SiO₂/WF is increase.     

Development a new method for pilot scale production of high grade oil palm plywood: Effect of resin content on the mechanical properties,bonding quality and formaldehyde emission of palm plywood

The main objectives of this research were to investigate the formaldehyde emission, some mechanical properties and bonding quality of oil palm trunk (OPT) plywood treated with low molecular weight phenol–formaldehyde (LmwPF), as affected by resin concentration. The mechanical properties are affected by different of amount resin solid contents used. The OPT veneer were treated at either 40%, 32%, 23% or 15% of resin concentration and 12 mm thickness of 3-ply plywood panel were manufactured for each group. In this study the formaldehyde emission, modulus of rupture (MOR), modulus of elasticity (MOE) and bonding quality (shear strength) of OPT plywood were determined. The results revealed that the resin-treatment method was tend to significantly improved the mechanical properties of the OPT plywood panel in which increased solid absorption gives better mechanical properties. Apparently, high mechanical properties were obtained for panel manufacturer from veneer treated with 32% and 40% resin content. The resin-treated OPT plywood provided superior mechanical strength with improvements at least 202% MOE and 159% MOR compared to commercial OPT plywood. Whereas, mechanical properties of the resin-treated OPT plywood were drastically decrease with increasing the water substitution. Formaldehyde emission content of OPT panels decreased upon reduction of resin content into treatment process and were significant at resin concentration. The resin-treated OPT panels at 32% solid content provided a reasonable amount of free formaldehyde (0.359 mg/L) which attained F⁷⁷ according to Japanese Agriculture Standard (JAS). The shear strength of resin-treated OPT plywood panel with 32% and 40% resin content achieved minimum requirements according to the standard European Norms EN 314-1 and EN 314-2 for the interior and exterior application.     

Characterisation of tannin resin blends for particle board applications

Tannins and cashew nut shell liquid (CNSL) are groups of natural resins that are receiving wide attention as substitutes to synthetic binders in the production of biocomposites. In this work, blends of hydrolyzed tannin, CNSL, and urea formaldehyde (UF) have been tested to determine their mechanical and physical properties for particle board applications. The blending of hydrolyzed tannin with UF resin has been found to reduce the formaldehyde emission levels significantly. A blend of hydrolyzed tannin and CNSL has been found to possess better dimensional stability. Tannin-blended resins cure faster, i.e. have shorter pot life, and result in composites with better water and moisture resistance when compared to UF. Thermal analysis by differential scanning calorimetry has shown that tannin blends exhibit better thermal stability and have a higher glass transition temperature than UF resin. Generally, it was found that particle boards made from coffee husks, and bonded using the tannin resin blend that include UF and CNSL, possessed superior properties to those made using UF alone. The mechanical and physical properties of coffee husk-particle boards produced using this new resin blend are presented and discussed.     

The efficiency of tannin as a formaldehyde scavenger chemical in medium density fiberboard

The aim of this study was to determine the effect of tannin content of urea formaldehyde (UF) resin on the panel properties of medium density fiberboard (MDF). Tannin extracted from the bark of white oak (Quercus alba) was added to UF resin at different ratios (based on the resin) to decrease the free formaldehyde content of MDF panels in this study. It was determined that free formaldehyde values of MDF panels decreased when the ratio of tannin content in UF resin increased. However, the modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength (IB) of these panels were a little lower, and the thickness swelling (TS) (24 h) and water absorption (WA) (24 h) values were a little higher compared to the control MDF panels.     

防白蚁胶合板的制备及性能研究

目的实现包装人造板的防白蚁功能。方法采用联苯菊酯、溴氰菊酯和高效氯氰菊酯为防白蚁剂,制备具有防白蚁功能的三聚氰胺甲醛树脂胶(MF)速生杨胶合板。研究防白蚁剂对MF胶黏剂的初粘度和胶合强度,白蚁作用方式,胶合板的防白蚁性能和力学性能等的影响。结果所用的防白蚁剂在MF中分散性良好,无分层现象。防白蚁剂对胶合强度有不良影响,溴氰菊酯和高效氯氰菊酯对弹性模量、静曲强度产生不良影响,但其浓度对弹性模量、静曲强度无显著影响。结论当联苯菊酯占MF的质量分数为1.25%,或溴氰菊酯占MF的质量分数为5%,或高效溴氰菊酯占MF的质量分数为2.2%时,胶合板的防白蚁性能最佳,白蚁死亡率达到100%,而且其主要力学性能指标均达到国家标准要求。     

Improving core bond strength and dimensional stability of particleboard using polymer powder in core layer

Low density polyethylene powder (LDPE) was used as polymer binder in the core layer of three layer particleboard. In the first phase, six levels of the LDPE powder (5–30 wt.%) based on the composition by weight, were mixed with the core particles with 8 wt.% urea–formaldehyde (UF) resin. In the second phase, the LDPE powder content was kept constant at 10 wt.% in all treatments and the UF resin content applied to the core layer was decreased gradually from 8 to 4 wt.%. Thickness swelling and water absorption of the particleboards significantly decreased with increasing the LDPE content in the core layer. Similarly, incorporation of the LDPE powder into the core layer of the particleboard greatly improved internal bond strength. The flexural properties of the particleboards, the modulus of rupture (MOR) and modulus of elasticity (MOE), were positively affected by increasing LDPE content up to 10 wt.% but the further increment of the LDPE decreased the MOR and MOE. The UF resin content can be reduced in the core layer of the particleboard as a function of increasing the LDPE powder.     

废弃ACQ防腐木苯酚液化物合成酚醛树脂的研究

利用废弃ACQ防腐杉木苯酚液化物与甲醛在碱性环境中反应,进行热固型酚醛树脂合成实验;通过正交试验方法研究了单因素变量对树脂化反应的影响。得出最优化的树脂化合成工艺为:合成温度80℃,合成时间120min,氢氧化钠/液化物摩尔比(mrNaOH/P)=0.6,甲醛/液化物摩尔比(mrF/P)=2.0。在此工艺条件下制备的酚醛树脂压制的胶合板胶合强度达到1.33MPa,符合GB/T17657-1999中Ⅰ类胶合板的强度要求。