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。     

尿素对UF树脂固化动力学影响的研究

为了研究尿素对弱酸性起始合成的UF树脂固化性能影响,采用DSC研究了弱酸性起始合成UF树脂中碱性加成阶段尿素添加次数和间隔时间对树脂固化反应动力学影响.计算了碱性加成阶段尿素添加次数和间隔时间不同的UF树脂的固化表观活化能和反应级数,并建立相应的固化反应动力学方程.研究结果表明:弱酸性起始合成UF树脂,碱性阶段尿素添加次数和添加间隔时间影响树脂固化,尿素添加次数增加和尿素添加次数相同而添加尿素时间间隔延长能降低UF树脂固化体系的活化能.弱酸性起始合成UF树脂的固化反应是介于0.92～0.93级之间的非基元反应.     

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.     

尿素-双醛淀粉-甲醛共缩聚树脂胶黏剂的制备与性能表征

为扩大淀粉的应用领域和减小脲醛树脂胶黏剂游离甲醛的含量,采用双醛淀粉与尿素、甲醛进行共缩聚反应,制得尿素-双醛淀粉-甲醛(UDSF)共缩聚树脂胶黏剂。考察了双醛淀粉用量、第一次共缩聚时间和第一次尿素比例(F/U1)对胶黏剂固体含量、黏度、水溶性、固化时间和游离甲醛含量的影响。并通过与尿素-淀粉-甲醛(USF)进行对比,得出双醛淀粉用量为0. 075 mol,第一次共缩聚时间为60 min和F/U1为1. 5时,所制得的UDSF树脂胶黏剂的使用操作性能较好、固化速率较快、环保性能较优、胶合强度和耐水性满足Ⅱ类胶合板要求。利用傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)和热重测试仪(TGA)对UDSF树脂胶黏剂和对照样USF树脂胶黏剂进行了对比分析。结果表明,相比于原淀粉,双醛淀粉与尿素、甲醛反应活性更大,共缩聚反应更充分,显著提高了树脂的聚合度和交联度,使UDSF树脂成为连续的均相体系。解释了UDSF树脂胶黏剂固化时间缩短、游离甲醛含量降低、胶合强度和耐热性能提高的内在原因。同时UDSF树脂中游离-OH数量减少且缔合-OH数量增多,验证了UDSF树脂胶黏剂耐水性能的提高。     

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。     

脲醛树脂电子墨水微胶囊的制备与固化研究

以改进的两步原位聚合法制备脲醛(UF)树脂电子墨水微胶囊,比较了不同系统改性剂和不同固化方式对微胶囊表面形貌及固化性能的影响.结果表明,采用氯化钠、明胶和间苯二酚为系统改性剂可以控制脲醛树脂胶粒在油水界面富集凝结,改善微胶囊的表面光滑度和致密性;调节室温下的酸处理时间,可控制脲醛树脂微胶囊的囊壁厚度,采用氯化铵做微胶囊固化剂,调节体系温度可有效控制氯化铵与甲醛的反应速度,即可得到表面光滑、干燥后不坍塌、不破损的脲醛树脂电子墨水微胶囊.     

聚乙烯亚胺/聚磷酸铵复合聚电解质对脲醛树脂固化行为的影响及其阻燃木质刨花板

木质复合材料的阻燃处理和力学增强一直受到广泛的关注。阻燃剂的加入不仅会增大胶黏剂的黏度，而且阻燃剂中的活性基团可以通过化学交联键合到树脂分子上，阻碍胶黏剂的聚合过程，从而对树脂的固化过程产生不利影响。通过对阻燃剂的改性，使其能够提高胶黏剂的固化反应性，增强胶黏剂的粘接强度，同时可以最大限度地减少阻燃剂的迁移，有效提升材料的阻燃性能和力学强度。鉴于此，本文以聚磷酸铵(Ammonium polyphosphate,APP)和聚乙烯亚胺(Polyethyleneimine,PEI)为阴、阳离子聚电解质，通过自组装制备复合聚电解质(PEI/APP)，并进一步将其应用于木质刨花板中。PEI/APP提高了脲醛树脂(Ureaformaldehyde resins,UF)的固化反应性，同步赋予了刨花板优异的力学强度和阻燃性能。基于Kissinger和Ozawa动力学方程计算了不同添加量的PEI/APP与UF交联体系的活化能(E_a)，重点研究了PEI/APP对UF固化动力学的影响。结果表明：PEI/APP能够通过酰胺键和氢键作用与UF形成分子交联网络，促进UF的缩聚固化过程，使E<...     

酚醛树脂部分

无卤阻燃酚醛树脂组成物及其用作环氧树脂交联剂，新型含磷环氧树脂固化剂的合成和性能，加成固化酚醛树脂的热性能，高性能玻璃纤维增强酚醛塑料进展，具有降低甲醛生成率和良好的加工性的聚缩醛树脂组成物及其生产方法。     

利用强碱性降解大豆蛋白制备木材胶粘剂及其表征

采用凝胶渗透色谱(GPC)和差示扫描量热(DSC)分析等手段结合胶合板压制,对在90℃和9%(质量分数,下同)氢氧化钠存在下降解大豆蛋白及其与乙二醛、UF树脂和MF树脂共混制得的复合胶粘剂进行表征,结果表明,降解使大豆蛋白的大分子肽链断裂,高级结构破坏,得到在分子量在282～3404之间、适于制备木材胶粘剂的低黏度产物;随着降解时间延长,产物中大分子量组分含量和黏度逐渐降低,但甲醛反应性能力明显增加;DSC测试表明降解大豆蛋白能够与乙二醛、脲醛(UF)树脂、三聚氰胺-甲醛(MF)树脂等发生交联固化反应;由降解大豆蛋白制备的各种复合胶满足室内普通胶要求,而只有含MF树脂的复合胶可达到耐水胶要求。     

降低UF胶粘剂游离甲醛含量的研究

研究了甲醛与尿素的配比[n(F)/n(U)比值]、缩聚温度、时间与pH值,以及改性剂对以尿素、甲醛为主要原料制备脲醛(UF)树脂胶粘剂游离甲醛含量的影响,获得了确保其粘接强度不致下降,而游离甲醛含量只有0.25%的最佳制备工艺条件。     

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.     

对氨基酚改性脲醛树脂胶粘剂

研究了对氨基酚(p-aminophenol)对低物质量比脲醛树脂的胶合强度和甲醛释放量的影响.结果表明,添加1%对氨基酚就可以显著提高胶合板的胶合强度,达到255%,符合Ⅱ类胶合板国标要求,甲醛释放量达E2级.进一步添加对氨基酚到2%,甲醛释放量可达E1级.对氨基酚改性脲醛树脂的性价比基本与常用的三聚氰胺改性相当.     

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.     

Effects of hardener type,urea usage and conditioning period on the quality properties of particleboard

The effects of hardener type (ammonium chloride, ammonium sulphate and aluminium sulphate), urea usage (with urea and without urea), and conditioning period (one day and one month) of the particleboard on the physical (thickness swelling), mechanical (modulus of rupture, modulus of elasticity and internal bond strength), surface properties, and formaldehyde emission of particleboard and acidity of the wood particles were investigated. The hardener type was found to be effective all of the properties of particleboard. The pH of the wood particle with the urea was slightly higher than that of particles without urea.The lowest pH value for the resinated wood particles was obtained from ammonium chloride, followed by ammonium sulphate and aluminium sulphate, respectively. The best quality properties were obtained from the particleboards manufactured with ammonium chloride, followed by particleboard made with the ammonium sulphate and aluminium sulphate, respectively. The urea usage significantly decreased the formaldehyde emission of the particleboards while it slightly decreased the mechanical properties and increased thickness swelling. Increasing conditioning period of the particleboards from one day to one month improved the quality properties.     

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.     

Effect of Cross-linking Agent on Barbituric Acid-initiated Resin

To improve the tensile bond strength of denim bonding agents, the adhesion between denim and MMA resin was investigated by applying initiator systems containing 1-cyclohexyl-5-ethyl barbituric acid (CEB), copper acetyl acetonate (CAA), quaternary ammonium chloride (QAC). cupric ion, with the addition of TEGDMA, and pretreatment solution for denim, and an HEMA primer. The effects of a cross-linking agent on barbituric acid-initiated denim bonding resin were examined by measuring degree of conversion, molecular weight, hardness of bonding resin, and tensile bond strengths.     

防白蚁剂对三聚氰胺甲醛树脂胶粘剂性能的影响

目的研究加入防白蚁剂对胶粘剂的影响。方法测试了联苯菊酯、溴氰菊酯、高效氯氰菊酯等3种拟除虫菊酯类防白蚁剂对三聚氰胺甲醛树脂黏度、pH值、固化时间、润湿性及胶合性能的影响。采用模拟固化法,测试了三聚氰胺甲醛加入防白蚁剂前后的红外光谱特征。结果防白蚁剂的加入降低了三聚氰胺甲醛树脂的pH值,提高和延长了三聚氰胺甲醛树脂的黏度和固化时间,提高了三聚氰胺甲醛树脂在杨木单板上的润湿性,降低了胶层剪切强度;联苯菊酯、溴氰菊酯和高效氯氰菊酯等3种防白蚁剂的加入没有引起三聚氰胺甲醛树脂红外特征峰的改变。结论联苯菊酯、溴氰菊酯和高效氯氰菊酯一定程度上影响三聚氰胺甲醛树脂的常规特性;由于防白蚁剂中水份和原药微粒的影响,三聚氰胺甲醛树脂的胶层剪切强度有所下降;联苯菊酯、溴氰菊酯和高效氯氰菊酯对三聚氰胺甲醛树脂化学基团没有影响。     

季铵盐对热熔预浸料用环氧树脂胶膜室温贮存期的影响

采用通常用作阳离子型表面活性剂和相转移催化剂的苄基三乙基氯化铵,作为酸酐/环氧树脂体系的促进剂,制备了复合材料预浸料用环氧树脂胶膜,研究了其室温和高温固化特征。结果表明,与咪唑类促进剂相比,季铵盐作促进剂的环氧树脂室温固化反应速率小,而高温固化反应速率和凝胶时间几乎相等,在保证环氧树脂固化体系高温固化速率的前提下,季铵盐对环氧树脂胶膜的室温固化产生明显的阻缓作用,实测环氧树脂胶膜室温贮存期由使用咪唑类的5 d延长为8 d,理论室温极限贮存时间由8 d延长为11 d。     

改性羧甲基纤维素缓释肥包膜材料的制备与表征

以羧甲基纤维素为原料,甲醛为交联剂,氯化铵为反应体系酸性调节剂,1,2-丙二醇碳酸酯为增塑剂,制备了一系列交联羧甲基纤维素膜,研究了氯化铵、甲醛和1,2-丙二醇碳酸酯用量对交联膜性能的影响。通过傅里叶变换衰减全反射红外仪(ATR-FTIR),X射线衍射仪(XRD),热重分析仪(TGA),扫描电镜(SEM)对交联膜进行了结构和性能表征,通过吸水率,接触角对交联膜进行了亲疏水性测试,最后通过尿素渗透实验对交联膜进行了渗透性能测试。结果表明,制备的交联羧甲基纤维素膜疏水性增强,结晶度下降,随着甲醛含量的增加,对尿素7天的累积释放量从63.53%减小到53.77%,对尿素的释放具有一定的可调控能力。     

The influence of silane coupling agents on the polymer mortar

The aim of this work is to investigate the influence of silane coupling agents on the properties of vinylester resin and vinylester mortar. Research work is focused on two methods of modification: direct silane addition to the resin binder and the use of silane pre-treated silica flour as a filler. The results of such modification are described, taking into consideration mixture viscosity, curing conditions, mechanical strength and fracture process. The test results indicated that silane coupling agent can decrease the viscosity of the mortar mixture, extend its pot life, enhance its mechanical strength and resistance for fracture. However, changes in the curing process, which may be disadvantageous and the increase of composite brittleness were noticed and stressed.