改性三聚氰胺-尿素-甲醛共缩聚树脂胶粘剂的合成

通过三聚氰胺-尿素-甲醛(MUF)共缩聚树脂胶粘剂的合成,探讨了三聚氰胺的用量对该MUF树脂耐水性能的影响及其规律。实验结果表明,当w(三聚氰胺)=43%～65%时,该MUF树脂的湿强度从0.93 MPa增加到2.74 MPa,耐沸水性明显提高;但是,当w(三聚氰胺)>65%时,该MUF树脂的湿强度增长极其缓慢,其耐沸水性提高并不明显;通过引入复合改性剂和适量的水,可使该MUF树脂的游离甲醛含量降低50%、成本降低10%～15%、固含量基本不变、胶合强度和耐沸水性均有所提高且适用期良好。     

Utilization of hydrophilic/hydrophobic hyperbranched poly(amidoamine)s as additives for melamine urea formaldehyde adhesives

Hyperbranched poly(amidoamine)s (PAMAMs), exhibiting various levels of hydrophilicity, were used as modifiers for melamine urea formaldehyde (MUF) adhesives. The modification was achieved either with or at expense of sodium hydroxide during the last pH adjustment. Their apparent co‐condensability was expected from the measured gel times and further proved using Fourier transform infrared (FTIR) spectroscopy as well as ¹³C nuclear magnetic resonance (¹³C NMR). Utilization of these structures as modifiers for MUF, which are frequently used in particleboards production, resulted in manifold advantages. Considering the economic point of view, their use is more practical and cheaper with respect to dendritic structures. Additionally, their application in finite quantities as final additives, either immediately before the final use or at the last stage of preparation, yielded considerable upgrading of the dry internal bond (IB) strength of the produced particleboards. The improvement was extended to the resistivity to hydrolytic degradation as revealed by the wet IB strength and thickness swelling. The results were explained on the light of an extensive investigation on the resins using thermomechanical analysis (TMA) while taking into account the relevant hydrophilicity and degree of branching of each hyperbranched structure. POLYM. COMPOS., 36:2255–2264, 2015. © 2014 Society of Plastics Engineers     

NMR structural elucidation of amino resins

Urea formaldehyde, melamine formaldehyde, and melamine urea formaldehyde (MUF) are important industrial amino resins that find application in numerous diverse areas, most notably in the bonding of wood products. To understand the physical properties of these amino resins and, hence, optimize their performance, a knowledge of their chemical structure is necessary. This article reports the use of NMR spectroscopy to acquire this information in the solid and liquid states. ¹³C‐NMR experiments, supported and augmented by ¹H‐NMR and ¹⁵N‐NMR results, showed that the two stages of resin synthesis, methylolation followed by condensation, occurred in each type of resin. However, in the various MUF samples analyzed, the second step appeared to be predominantly the self‐condensation of melamine and urea rather than the cocondensation of melamine and urea. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3504–3512, 2004     

Determination of formaldehyde and TVOC emission behavior from interior use plywood using various post heat treatment processes

To reduce the formaldehyde/TVOC emissions from plywood with melamine–urea–formaldehyde (MUF) resin, four heat treatment procedures were designed and applied. Five‐ply plywood was fabricated, and its formaldehyde/TVOC emissions and wet shear strength were tested. Results showed that a simple low/no pressure post heat treatment procedure was effective and practical to decrease the formaldehyde/TVOC emissions from plywood. This was attributed to completely cured of MUF resin, the breakage of unstable chemical bonds, the acceleration of free formaldehyde releasing, and the exposed surface of the plywood. Meanwhile, this process also balanced the interior force of the resultant plywood and improved its wet shear strength. Under a 12 h oven heat treatment procedure after hot press, the formaldehyde and TVOC emissions from plywood decreased to 0.020 and 0.036 ppm, respectively, while the surface and core layer wet shear strength of plywood was improved to 1.24 and 1.08 MPa. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44909.     

Low addition of melamine salts for improved melamine‐urea‐formaldehyde adhesive water resistance

The addition of melamine acetate salts to an adhesive glue mix can allow the use of melamine–urea–formaldehyde (MUF) resins of lower melamine contents (rather than just urea–formaldehyde resins) and lower total amounts of melamine. Performances can be obtained that are characteristic of the top‐of‐the‐line, generally higher melamine content MUF adhesive resins for the preparation of wood particleboard panels. Improvements in the panel internal‐bond strength of greater than 30% can be obtained by the addition of melamine acetate salts to top‐of‐the‐line MUF resins. The approach to the concept of increased melamine solubility with a melamine salt is compatible with the approach of increasing melamine solubility with solvents such as acetals (e.g., methylal). However, the synergy advantage of using the two approaches jointly is not very marked. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 287–292, 2003     

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     

Effects of diatomite inorganic fillers on the properties of a melamine–urea–formaldehyde resin

In this study, a low‐cost diatomite was used to partly substitute wheat flour as one type of melamine–urea–formaldehyde (MUF) resin filler. Five‐ply plywood was fabricated, and its performance was measured. The crystallinity, fracture surface, and functional groups were tested to determine the effects of diatomite on the performance of the MUF resin. The results show that diatomite was well distributed in the MUF resin system and formed an embedding structure; this improved the wet shear strength of the resulting plywood by 33% to 1.36 MPa. Diatomite captured the free formaldehyde in the resin and the microporous structure formed in the resin accelerate formaldehyde release of the plywood. Consequently, the formaldehyde emission of the plywood was reduced. The diatomite partly replaced wheat flour as an MUF resin filler and could be applied in the plywood industry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44095.     

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。     

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。     

Acetals‐induced strength increase of melamine–urea–formaldehyde (MUF) polycondensation adhesives. II. Solubility and colloidal state disruption

The strength improvement induced by addition of acetals such as methylal and ethylal in melamine–urea–formaldehyde (MUF) resins could be mostly ascribed to the increased effectiveness and participation of the melamine to resin cross‐linking. This phenomenon has been shown here, by matrix‐assisted laser desorption/ionization time of flight (MALDI‐TOF) mass spectroscopy, resin aging time stability, and mainly by laser light scattering, to be due to the following: (i) the increased solubility in water afforded by the acetals cosolvents of both the unreacted melamine and of the normally very much lower solubility, higher molecular weight, lower methylolated oligomers fraction, this leading to preferentially homogeneous and hence more effective reaction rather than heterogeneous reactions; and (ii) the effect that such acetals have on the size distribution of the resin colloidal particles, with the presence of acetals such as methylals markedly decreasing the average colloidal particles diameter of the resin. This latter effect appears to be due to the disruption of the molecular clustering of the MUF resin colloidal particles, but rearrangements in the size of the colloidal particles due to the decrease in surface tension of the system, which has also been noted, cannot be excluded. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1855–1862, 2002     

Melamine salts as hardeners for urea formaldehyde resins

Various salts derived from melamine and organic acids were prepared and used as melamine substitutes for melamine urea formaldehyde (MUF) resins. The synthesis of these melamine salts and a detailed characterization of their stoichiometry are described. All salts form 1 : 1 or 1 : 2 stoichiometries in a homogeneous reaction. They crystallize during cooling of the hot and diluted reaction mixture. Both ¹³C–NMR and ¹⁵N–NMR data are reported and point toward the formation of real ionic structures. Most salts have higher water solubility than that of pure melamine and are tested for their ability to substitute melamine in MUF resins. The mechanical and chemical properties of plywood panels made up of traditional MUF resins and mixtures of UF resins with melamine salts are investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1654–1661, 2001     

Production of melamine fortified urea‐formaldehyde resins with low formaldehyde emission

Melamine can be incorporated in the synthesis of urea‐formaldehyde (UF) resins to improve performance in particleboards (PB), mostly in terms of hydrolysis resistance and formaldehyde emission. In this work, melamine‐fortified UF resins were synthesized using a strong acid process. The best step for melamine addition and the effect of the reaction pH on the resin characteristics and performance were evaluated. Results showed that melamine incorporation is more effective when added on the initial acidic stage. The condensation reaction pH has a significant effect on the synthesis process. A pH below 3.0 results on a very fast reaction that is difficult to control. On the other hand, with pH values above 5.0, the condensation reaction becomes excessively slow. PBs panels produced with resins synthesized with a condensation pH between 4.5 and 4.7 showed good overall performance, both in terms of internal bond strength and formaldehyde emissions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

三聚氰胺-尿素-甲醛共缩聚树脂胶粘剂的研制

通过合成三聚氰胺-尿素-甲醛树脂(MUF)胶粘剂,探讨了三聚氰胺用量对该MUF胶粘剂耐水性和其它性能的影响。结果表明:随着三聚氰胺用量的增加,MUF胶粘剂的耐水性能提高、固含量增大、固化时间和储存期延长,并且胶合板剪切强度增大,但MUF胶粘剂中游离醛含量降低;当w(三聚氰胺)40%时,MUF胶粘剂性能提高并不明显,为了降低成本,选择w(三聚氰胺)=30%～40%时较适宜;三聚氰胺用量不同是影响MUF结构和基团含量的主要因素。     

地板基材用MUF树脂胶聚合过程研究

以甲醛（ F）、尿素（ U）、三聚氰胺（ M）为原料,采用弱碱-弱酸-弱碱工艺合成了三聚氰胺-尿素-甲醛（ MUF）共聚树脂胶,配方中F与U物质的量之比为（1.2-1.5）∶1,F与（U＋M）物质的量比为（1.1-1.2）∶1。在不同的反应阶段取样,采用IR和13C NMR对过程中所取样品进行了分析。结果表明,反应开始的碱性阶段主要生成二羟甲基三聚氰胺,在弱酸性阶段缩聚反应时分子间以醚键和亚甲基键联接为主。用反应最终产物压制的杨木胶合板,胶合强度1.07 MPa,甲醛释放量0.38 mg/L,浸渍剥离试验无剥离,达到E0级,胶合强度达到Ⅱ类板的要求（0.7 MPa）。     

Colloidal aggregation of aminoplastic polycondensation resins: Urea–formaldehyde versus melamine–formaldehyde and melamine–urea–formaldehyde resins

Colloidal particles formation followed by their clustering have been shown to be the normal way of ageing of aminoplastic resins, namely urea–formaldehyde (UF) resins, melamine–formaldehyde (MF) resins, and melamine–urea–formaldehyde (MUF) resins. Ageing or further advancement of the resin by other means such as longer condensation times causes whitening of the resin. This is a macroscopic indication of both the formation of colloidal particles and of their clustering. It eventually progresses to resins, which are mostly in colloidal, clustered state, followed much later on by a supercluster formation starting to involve the whole resin. The initial, filament‐like colloidal aggregates formed by UF resins have different appearance than the globular ones formed by MF resins. MUF resins present a short rod‐like appearance hybrid between the two. GPC has been shown to detect the existence of colloidal superaggregates in a UF resin, while smaller aggregates might not be detected at all. The star‐like structures visible in the colloidal globules of MF resins are likely to be light interference patterns of the early colloidal structures in the resins. These star‐like interference patterns become more complex with resin ageing or advancement due to the advancement of the resin to more complex aggregates, to eventually reach the stage in which filament‐like and rod‐like structures start to appear. The next step is formation of globular masses that are representative of the true start of physical gelation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1406–1412, 2006     

Variation of MUF and PMUF resins mass fractions during preparation

The variation of molecular mass distribution with the progress of the reaction was studied for the following: (i) sequential‐type melamine–urea–formaldehyde (MUF) resin formulations in which the sequence of addition of chemicals follows well‐defined species reactivity principles; (ii) a nonsequential MUF formulation in which simultaneous melamine and urea competition for formaldehyde yields a MF resin cocondensed with small amounts of urea. This resin became soaked with reacted and unreacted monomeric urea species. (iii) A PMUF resin, namely a MUF resin with a small proportion of phenol (7.8% by weight on melamine and urea) cocondensed with the main MUF fraction. All the formulations used were industrial resins formulations in current use. Development and variation of molecular mass fractions, from which performance and other useful resin parameters depend, have been found to depend on the type of resin formulation used for these type of aminoplastic resins. The two very different MUF resin formulations yielded different variations in molecular mass fractions during the progress of the reaction and during the so‐called ambient temperature “maturing” of the resin. The PMUF resin also showed both similar and different fractions present during manufacturing and during short term ageing at ambient temperature. While similarities in recurrent fractions and in trends are common to all the three different formulations, differences between them are also clearly observed. A major proportion of the reaction of some of the aminoplastic resins examined also occurs on ageing (i.e.“maturing” of the resin at ambient temperature), this appearing to be an essential phase of the resin preparation process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4842–4855, 2006     

Diffusion hindrance vs. wood-induced catalytic activation of MUF adhesive polycondensation

The reaction of hardening of melamine–urea–formaldehyde (MUF) adhesive resins in the presence of wood and cellulose was confirmed to have a lower energy of activation than the MUF adhesive alone, both in the presence or absence of ammonium chloride hardener, thus both in mildly acid and mildly alkaline environments. DSC exotherms showed that during hardening of melamine to melamine, melamine to urea, and urea to urea crosslinks through methylene bridges occur. Only the earliest reaction, mainly melamine to melamine crosslinking, presents a decrease in energy of activation which can be assigned to catalytic activation by the cellulosic substrate. The other types of crosslinking reactions (i) appear not to occur due to the more favorable and rapid melamine to melamine reaction which precedes them at lower temperature or (ii) do not present catalytic activation by the substrate but rather hindrance by it or (iii) variation of their energy of activation appears to be due to increased diffusion hindrance by the substrate caused by the increasing molecular weight of the resin while hardening. This because the Kissinger equation plots of the resin alone are in the main linear, for all the exotherms, indicating that in hardening of the resin alone diffusion problems appear to be limited. © 1995 John Wiley & Sons, Inc.     

Gemeinsame kondensation von bisphenol A,melamin und formaldehyd

The condensation reaction of bisphenol A, melamine, and formaldehyde was investigated by gel permeation chromatography, ¹³C-NMR-spectroscopy, IR-spectroscopy and elemental analysis. Because of the high reaction rates the condensation could be investigated only in the range of pH 6?10. At pH 6 and 7 the reaction of melamine with formaldehyde is dominating. With increasing pH-value the condensation of bisphenol A with formaldehyde is observed preferably. At pH 10 the condensation results in high molecular products. Cocondensation of melamine and bisphenol A through methylene bridges does not take place. But as a separation of the bisphenol A-formaldehyde condensates from the other condensation products was not possible, the three components may be connected through methylene-ether groups and/or intermolecular hydrogen bridges.     

Structural effect of prepared and commercial superplasticizers on performance of cement pastes

The sodium salt of melamine‐phenol formaldehyde sulfonate (MPhFS), melamine formaldehyde sulfonate (MFS), and phenol formaldehyde sulfonate (PhFS) were prepared according to a four‐step reaction procedure. The four steps of the reaction are hydroxymethylation, sulfonation, low pH condensation, and high pH rearrangement. Fourier transform IR and differential scanning calorimetry spectra were used to determine the structure of the synthesized resins. The effects of MFS, PhFS, MPhFS, and commercial superplasticizers on the rheological properties of cement pastes were investigated using a rotating coaxial viscometer. It was found that the prepared resins enhanced the rheological properties of cement pastes more than commercial ones. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 482–487, 2003     

MUF MF共缩合改性树脂胶黏剂的研究

同时采用共聚和共混的方法,合成了一种脲醛-三聚氰胺甲醛复合树脂胶黏剂。研究了合成工艺、三聚氰胺用量、MF与MUF共混比例对胶黏剂性能的影响。结果表明,反应后期加入5%三聚氰胺改性MUF树脂,MUF和MF树脂按M/U为40%共混时,共混树脂游离甲醛含量较低,耐水性能优良,综合性能较好。