三聚氰胺改性脲醛树脂胶粘剂研究进展

综述了三聚氰胺改性脲醛树脂(MUF)胶粘剂的性能改性[如耐水性、稳定性、游离F(甲醛)含量、耐热性、胶接强度和耐潮性等]、影响因素[如M(三聚氰胺)含量、pH、反应温度、反应时间、添加剂、缓冲剂和填料等]、化学结构及固化过程的表征方法。最后对MUF胶粘剂未来的研究方向进行了展望。     

三聚氰胺改性脲醛树脂胶粘剂研究进展

本文详细论述了三聚氰胺改性脲醛树脂胶粘剂（MUF）的和应用情况,总结了三聚氰胺改性脲模型树脂胶粘剂的机理。用三聚氰氨改性脲醛树脂胶粘剂提高了脲醛树脂粘剂的耐水性,并有效降低了游离甲醛含量。     

氧化淀粉改性脲醛树脂胶粘剂的合成工艺研究

以氧化淀粉作为改性剂,采用正交试验法探讨了最终n(甲醛或F)∶n(尿素或U)、淀粉氧化时间、氧化淀粉加入量和交联时间等对氧化淀粉改性UF(脲醛树脂)胶粘剂的游离甲醛含量和胶接强度的影响。研究结果表明:当最终n(F)∶n(U)=1.2∶1、淀粉氧化时间为3 h、氧化淀粉加入量为10%(相对于甲醛和尿素总质量而言)和交联时间为60 min时,氧化淀粉改性UF胶粘剂的游离甲醛含量低于0.09%、胶接强度为1.48 MPa且耐水性明显提高;此时,相应胶合板的甲醛释放量(0.04 mg/L)满足GB/T 9846.3—2004标准中E0级指标要求。     

E_0级胶合板用间苯二酚改性脲醛树脂胶粘剂的研制

以间苯二酚为改性剂,采用弱酸起始合成工艺制备了UF(脲醛树脂)胶粘剂,并着重探讨了合成工艺条件对UF胶粘剂游离F(甲醛)含量和胶接强度的影响。研究结果表明:当n(F)∶n[尿素(U)]=1.1∶1.0、初始p H=5.5、w(间苯二酚)=4%(相对于U质量而言)和反应温度为85℃时,UF胶粘剂中的游离F含量降至0.05%,胶合板的F释放量达到了E_0级水平(≤0.50 mg/L)、胶接强度(0.81 MPa)达到Ⅱ类胶合板的指标要求,并且耐水性明显提高。     

三聚氰胺共聚改性脲醛树脂固化性能研究

采用M(三聚氰胺)对低n[F(甲醛)]∶n[U(尿素)]比例的UF(脲醛树脂)进行改性,制备了MUF(M共聚改性UF);通过差示扫描量热(DSC)法表征了M的投料时间和比例对UF固化特性的影响,并对MUF的理化性能进行了评价。研究结果表明:随着M掺量的不断增加,MUF胶粘剂的固含量呈增长趋势,固化速率减慢,MUF中游离F含量显著降低。M投料时间对MUF的游离F含量、固含量和固化速率的影响不同,M在缩聚前期投料时,MUF的固含量较高,固化速率基本不变,游离F含量随M掺量增加而逐渐降低;当M在缩聚前期加入且w(M)=3%~4%(相对于U总质量而言)时,MUF中的羟甲基含量相对最低、MUF胶粘剂的综合性能相对最佳。     

三聚氰胺添加方式对胶合板用UF胶粘剂性能的影响

以聚乙烯醇(PVA)和三聚氰胺为改性剂,制备出一种环保型UF(脲醛树脂)胶粘剂。探讨了三聚氰胺的添加方式(包括其添加量、初期和中期投入比例等)对UF性能的影响。结果表明:在试验工艺条件下,当w(总三聚氰胺)=6%(相对于尿素质量而言)、w(前期三聚氰胺)=1%和w(中期三聚氰胺)=5%时,胶合板的甲醛释放量(0.27 mg/L)相对最低,胶接强度(0.71 MPa)达到II类板的标准要求;当w(前期三聚氰胺)=w(中期三聚氰胺)=3%时,胶合板的胶接强度(0.76 MPa)相对最高,但甲醛释放量(0.56 mg/L)只能达到E1级标准要求。     

三聚氰胺改性脲醛树脂胶粘剂的研究进展

三聚氰胺改性脲醛树脂胶粘剂具有比脲醛树脂胶粘剂更好的耐水性、耐热性及稳定性,井能减少游离甲醛的含量,已成为木材加工业的重要用胶。本文主要从发展概况、合成机理、合成工艺和应用等几个方面,介绍了三聚氰胺脲醛树脂胶粘剂的研究进展,并对其发展前景进行了展望。     

硫代硫酸钠/三聚氰胺改性脲醛树脂制备工艺研究

以硫代硫酸钠和M(三聚氰胺)作为复合改性剂,F(甲醛)和U(尿素)作为主要原料,采用弱酸-弱碱-弱酸-弱碱法合成了改性UF(脲醛树脂),并着重探讨了不同因素对UF中的游离F含量、胶合板的胶接强度及F释放量的影响。研究结果表明:合成改性UF的最佳工艺条件是反应温度为85℃,n(F)∶n(U)=1.10∶1,起始pH为5.0,M第2批加入,硫代硫酸钠第4批加入且加入量为U总质量的2%,U分批加入比例为55%、20%、15%和10%;此时UF中的游离F含量(降至0.11%)符合GB/T 14732—2006标准中的指标要求,胶合板的胶接强度(为1.05 MPa)满足国家标准中II类胶合板的指标要求、F释放量(为1.26 mg/L)达到普通胶合板通用技术条件中的E1级指标且耐水性也明显提高。     

改性脲醛树脂胶粘剂的研制

利用热塑性的聚乙烯醇缩甲醛树脂在酸性条件下有与大分子脲醛树脂进一步交联合成改性脲醛树脂胶粘剂,分步加入尿素降低了脲醛树脂中游离甲醛的含量,考察了影响合成反应的一些因素,适宜的工艺条件为聚乙烯醇用量和脲醛比（１：１．８）一定时,第一步Ｕ：Ｆ（１：４．０）,ｐＨ＝３．５,反应５０ｍｉｎ,第二步ｐＨ＝５．５,补加尿素,反应４０ｍｉｎ,两步反应温度均为４０℃。     

E_1级胶合板用改性脲醛树脂胶粘剂的制备方法研究

选用弱酸-弱碱-弱酸-弱碱工艺制备脲醛树脂(UF)胶粘剂,研究了n[甲醛(F)]∶n[尿素(U)]、初始p H、反应温度和三聚氰胺(M)掺量对游离F含量和胶接强度的影响。研究结果表明:当n(F)∶n(U)=1.2∶1.0、起始p H为6.5、反应温度为85℃和w(M)=6%(相对于U总质量而言)时,UF胶粘剂的游离F含量(0.17%)符合国家标准要求(≤0.3%),胶合板的F释放量(1.17 mg/L)达到GB/T 9846.3—2004标准中E1级指标要求(≤1.5 mg/L),胶接强度(从0.46 MPa提高到0.97 MPa)达到了国家标准中II类胶合板的指标要求,耐水性也明显提高。     

三聚氰胺添加方式对MUF胶粘剂性能的影响

以三聚氰胺作为脲醛树脂(UF)的共聚改性剂制备MUF(三聚氰胺甲醛树脂)胶粘剂。探讨了三聚氰胺的添加方式对MUF胶粘剂性能的影响,同时对其固化特性、分子结构和耐热性等进行了分析。结果表明:三聚氰胺2次投料法可有效降低MUF胶粘剂的甲醛释放量,但其胶接强度也随之下降;同时,该MUF固化体系的外推固化温度、表观活化能和反应级数均有所增加,耐热性降低;另外,2次投料体系使MUF的相对分子质量降低、相对分子质量分布变宽。     

Acetal‐induced strength increases and lower resin content of MUF and other polycondensation adhesives

Acetals such as methylal and ethylal are shown to be particularly effective additives in improving the strength of wood boards bonded with melamine‐ urea‐formaldehyde (MUF) resins, although they show some appreciable but lesser effect on other resins too, particularly phenol‐ formaldehyde resins. They equally allow a considerable decrease in resin loading, and thus, in melamine content, on the bonded wood panel and at parity of performance. Their development as additives is then primarily, but not only, targeted at the MUF adhesive resins. One‐third decreases in MUF adhesives loading at parity of performance or equally internal bond (IB) strength increases approximately up to 50% by addition of methylal are shown to be possible by laboratory particleboard as well as by thermomechanical analysis (TMA). The reasons for methylal and ethylal behavior were studied by a variety of techniques, including liquid‐ and solid‐ phase ¹³C‐NMR and could be mostly ascribed to the increased effectiveness and participation of the melamine to resin crosslinking due to its now preferentially homogeneous rather than heterogeneous reactions, consequences of the increased solubility in water afforded by the acetal cosolvents. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2561–2571, 2002     

Upgrading of MUF adhesives for particleboard production using oligomers of hyperbranched poly(amine-ester)

Oligomeric precursors of poly(amine-ester) were synthesized by a two-step condensation reaction of succinic anhydride with diethanolamine under mild conditions. The oligomers formed were characterized at each synthesis step using matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry. This showed that after step (1), the condensation adduct of both reactants (206?Da) was the main product mixed to high proportion of unreacted diethanolamine (106?Da). After step (2), the adduct at 206?Da decreased substantially, while other compounds at 275, 292, and 375?Da started to increase along with the appearance of a new compound at 392?Da. This indicates that the reaction proceeds slowly under these conditions to give higher branched oligomers (HP). In addition, some cyclic compounds were also identified by the 188, 275, and 375?Da peaks. MALDI-TOF of the melamine–urea–formaldehyde (MUF) resin before and after reaction with the hyperbranched oligomers mix showed clear indication of the coreaction of simple melamine–formaldehyde oligomers with several of the hyperbranched oligomers previously identified. Addition of small proportions of a mixture of the formed HP oligomers to a MUF adhesive improved the internal bond (IB) strength, both dry and wet, of wood particleboards bonded with it. The results obtained indicate that the addition of these HP oligomers can improve the dry IB strength by 17–24% according to conditions of preparation and the wet IB strength by as much as 47% when compared to the control sample.     

水溶性粘合剂的配制及其性能研究

先通过聚乙酸乙烯酯(PVAc)的醇解制备出聚乙烯醇(PVA),再用聚乙烯醇在酸性条件下与甲醛缩合,得到聚乙烯醇缩甲醛(PVF),再以聚乙烯醇和聚乙烯醇缩甲醛为基料,以邻苯二甲酸二丁酯(DBP)为增塑剂,聚乙二醇-400(PEG-400)为增韧剂,水为溶剂,以鱼油为分散剂,配制了不同工艺配方的水基粘合剂,考察了增塑剂、增韧剂的加入量对粘合剂的透明度、稳定性、溶解度、粘弹性等的影响。实验结果表明,当质量比PVA∶PVA∶水=9.6∶9.6∶80.8,鱼油、聚乙二醇-400、DBP的添加量分别为4%、1.6%、2.0%时,所配制的粘合剂有相对较好的综合性能。     

A study on durability of joints bonded with pressure-sensitive adhesives

The use of adhesive bonding as fastener presents very high usage potential, especially for different environments. However, the designers do not have enough data yet to address the changes in the mechanical properties of adhesives in the course of time. In this study, the ageing of film-type adhesives, Structural Bonding Tapes (SBT) 9244 and 9245, which are different in thickness and possess pressure-sensitive and visco-elastic properties, was investigated. First, the bulk adhesive specimens were prepared and exposed to two different environmental conditions until saturated. In the same time, single lap joints with two different adhesive layer thicknesses, consisting of AA2024-T3 as the adherend, were exposed to the same environmental conditions for exposure times of 90 days. The immersion environments were 100% relative humidity (RH) and 3.5% NaCl solution. At the end of exposure time, the failure surfaces were examined by Scanning Electron Microscopy (SEM) after the strength of joints was determined with the lap shear test. Both SBT adhesives absorb more water from 100% RH than from 3.5% NaCl solution and, therefore, they deteriorate rapidly in 100% RH. In addition, as the thickness of adhesive layer increases, the loss in the strength increased.     

A 13C-NMR analysis method for MF and MUF resins strength and formaldehyde emission from wood particleboard. I. MUF resins

A method based on the use of ¹³C-NMR relative peak intensity rations for different characteristic chemical groups, known or supposed to contribute to melamine-urea-formal-dehyde (MUF) resin strength and formaldehyde emission, is presented. The method relates results obtained by ¹³C-NMR analysis of liquid MUF resins with their strength and form aldehyde emission in the resin hardened state. Sets of correlation equations are presented which can be used to predict some of the physical properties of a hardened MUF resin by studying the ¹³C-NMR peak ratios of well-defined chemical groups in the liquid MUF resin. A true class of MUF resins, with characteristics all of their own, appear only to exist in the copolymers in which the mass ratio of M: U is in the approximate range 55 : 45 to 34 : 66, mass ratios outside this range resulting in resins which behave almost as pure melamine or as pure urea resins. Contrary to what was found for MUF glue mixes in which lower condensation pre-resins are used as scavengers and accelerators, in pure MUF resins, the ratios of NMR peaks of the downfield substituted and unsubstituted triazine and urea signals, while still important, do not exclusively dominate the correlation equations, other chemical groups such as methylene (Me), methylol (Mo), and methylene ether groups assuming considerable importance. © 1996 John Wiley & Sons, Inc.     

A comparative study on effects of thermal fatigue caused by thermal-oil cycling on tensile properties of single lap composite joints bonded with different kinds of adhesives

In this study, thermal-oil cycling process was applied to adhesively bonded glass fibre reinforced single lap composite joints (SLJs) in order to investigate the effects of thermal fatigue on their tensile properties. Joints were subjected to thermal cycling to achieve the thermal fatigue effect. Initially, separated specimens were heated on a magnetic stirrer from 25°C to 80°C, 25°C to 100°C and 25°C to 120°C and kept at these temperatures for 10 min. Right after that specimens were immersed into heat transfer oil cooled with dry ice at ?10°C for 10 min. and placed back into the magnetic stirrer to reach intended temperatures again. Thus, one cycle is completed. This thermal cycling process was repeated for 1, 10, 20, 30, 40 and 50 times for different groups of specimens. Single lap shear (SLS) tests have been performed for the determination of mechanical properties. As a result of this study, it is found that the load carrying capacities of specimens generally decrease as the thermal cycling count is increased. However, it is observed that specimens subjected to 30 times thermal cycling have the maximum load carrying capacity.     

三聚氰胺含量对MUF性能的影响

MUF(三聚氰胺-尿素-甲醛共缩聚树脂)兼具UF(脲醛树脂)和MF(三聚氰胺甲醛树脂)的优点,通过调节m(三聚氰胺)/m(尿素)配比,可得到性价比较高的MUF;然后采用MUF胶粘剂制备刨花板,并考察了三聚氰胺含量对刨花板的内结合强度、耐水性和耐沸水性等影响。结果表明:三聚氰胺的引入,虽能有效提高MUF的性能,但并非加量越多越好;当w(三聚氰胺)=11.0%~14.0%时,MUF的性价比相对最高,相应刨花板的内结合强度、耐水性和耐沸水性俱佳。     

A comparative study on combustion synthesis of Ta-B compounds

A comparative study on the preparation of various tantalum borides (including Ta₂B, Ta₃B₂, TaB, Ta₅B₆, Ta₃B₄, and TaB₂) in the Ta-B system was experimentally conducted by self-propagating high-temperature synthesis (SHS) from the elemental powder compacts of their corresponding stoichiometries. Both combustion temperature and reaction front velocity increased and then decreased with increasing boron content in the powder mixture. The fastest flame front with a reaction temperature of 1732 °C and a propagation rate of 11.2 mm/s was observed in the sample of Ta:B = 1:1. The combustion temperature (1205 °C) and flame-front velocity (3.82 mm/s) for the powder compact of Ta:B = 2:1 were the lowest. According to the XRD analysis, single-phase TaB and TaB₂ were produced from the samples of Ta:B = 1:1 and 1:2, respectively. However, multiphase products were synthesized from the samples of other stoichiometries. In the final products from Ta-rich samples of Ta:B = 2:1 and 3:2, two boride phases, Ta₂B and TaB, along with a large amount of residual Ta were detected. The products yielded from boron-rich reactants of Ta:B = 5:6 and 3:4 were composed of TaB, Ta₃B₄, and TaB₂. Based upon the temperature dependence of combustion wave velocity, the activation energies associated with the formation of TaB and TaB₂ by solid state combustion were determined to be 131.1 and 181.4 kJ/mol, respectively.     

A comparative study on corrosion-resistant performance of halogenated copolymers

Methacrylate-based copolymers are frequently used as anticorrosive organic coatings. Polymeric coating on metallic surfaces provides protection by a barrier action. Thermal properties have a significant influence on corrosion-resistance. This paper deals with the effect of thermal properties of 2,4,6-tribromophenyl methacrylate-co-glycidyl methacrylate and N-(p-bromophenyl)-2-methacrylamide-co-glycidyl methacrylate copolymers in corrosion-resistant behavior on low nickel stainless steel (LNSS). Hence attempts have been made to synthesize a set of copolymers by free radical polymerization and compare their corrosion-resistance properties. The copolymers were structurally characterized by Fourier transform-infrared, and ¹H-nuclear magnetic resonance spectroscopic techniques. The molecular weight of the copolymers was determined by gel permeation chromatography. Thermal studies were carried out using thermogravimetric analysis and differential scanning calorimetry. Corrosion performances of LNSS coated with two different copolymers was investigated in 1 M H₂SO₄ using potentiodynamic polarization and electrochemical impedance spectroscopic methods. The corrosion study reveals that poly(TBPMA-co-GMA) showed better corrosion-resistance than poly(PBPMA-co-GMA).