Plasma Treatment Induced Chemical Changes of Alkali Lignin to Enhance the Performances of Lignin-Phenol-Formaldehyde Resin Adhesive

Alkali lignin was processed by plasma and then used in modification of phenol formaldehyde resin in this study.Chemical structural changes of lignin which was processed by plasma as well as bonding strength,tensile property,curing performance and thermal property of the prepared phenol formaldehyde resin which was modified by the plasma processed lignin were analyzed.Results demonstrated that:(1)Alkali lignin was degraded after the plasma processing.The original groups were destroyed,and the aromatic rings collected abundant free radicals and oxygen-containing functional groups like hydroxyls,carbonyls,carboxyls and acyls were introduced into increase the reaction activity of lignin significantly.(2)The introduction of alkali lignin decreased the free formaldehyde content and increased bonding strength and toughness of the prepared phenol formaldehyde resin,especially after the introduction of lignin treated with plasma.(3)The introduction of alkali lignin led to high curing temperature for the prepared phenol formaldehyde resin,but that was reduced by the plasma processed alkali lignin.(4)The introduction of alkali lignin could also increase thermal stability of phenol formaldehyde resin,but that was modified by plasma processed alkali lignin was better than the unprocessed lignin.Based on the results,the plasma processed lignin was used to modify phenol formaldehyde resin,which could increase the strength and toughness of phenol formaldehyde resin significantly.

Analysis of Pyrolysates for Phenol Formaldehyde Resin by Py-GC/MS

Pyrolysis of phenol formaldehyde resin has been investigated by Pyrolysis Gas Chromatography-Mass Spectroscopy at the different temperatures from 500℃ to 750℃. Its composition of pyrclysates has been analyzed. Several compounds, especially benzene, toluene, p-xylene could only be formed above 500-550℃. Howerver, peak intensities for some pbend derivatives were decreased at the higher temperature. During pyrolysis, for thermo-setting phenol formaldehyde resins, polymeric chain scissions take place as a successive removal of the monomer units from the polymeric chain. The chain scissions are followed by secondary reactions, which leads to a variety of compounds. Addition reactions can also take place among the double-bond compounds during pyrolysis.

NaOH and Ba(OH)_2 Compound Catalyzed PhenolResorcinol-Formaldehyde Copolycondensation Resin Adhesive for Recombined Bamboo

In order to reduce the curing temperature, shorten the curing time of phenol-formaldehyde(PF) resin adhesive, and ensure the good water-solubility, NaOH and Ba(OH)_2 were used as compound catalysts. The influences of the adding time of Ba(OH)_2, the adding amount of NaOH, Ba(OH)_2 and resorcinol on the properties of adhesives were studied. The properties of NaOH catalyzed phenol-formaldehyde(PF) adhesive, NaOH and Ba(OH)_2 compound catalyzed PF adhesive, NaOH and Ba(OH)_2 compound catalyzed phenol-resorcinol-formaldehyde(PRF) adhesive, and the prepared recombinant bamboo with three kinds of adhesives were compared. The experimental results show that NaOH and Ba(OH)_2 compound catalyst not only shortens the curing time of PF adhesive, but also guarantees the suitable water solubility of adhesive. After copolycondensation with resorcinol, the curing time of adhesive is further shortened, the water solubility is improved obviously, and the highest bonding strength is obtained. Infrared spectrum analysis shows that the reaction activity point of NaOH and Ba(OH)_2 compound catalyzed PRF adhesive will increase, so that both the curing temperature and curing enthalpy decrease.

Tannin–Phenol Formaldehyde Resins As Binders for Cellulosic Fibers: Mechanical Properties

In this study Eucalyptus tannin (T) was isolated from outer bark of Eucalyptus trees;as sodium phenoxide salt and used as extender or copolymer into phenol formaldehyde (PF) resin at five percent (10, 20, 30, 40 and 50)% W/W. Tan-nin-phenol formaldehyde (TPF) and tannin formaldehyde-phenol formaldehyde (TFPF) resins that synthesized in this study were evaluated as adhesive material for cellulosic fibers by study the mechanical properties of the composite sheets .The results show that the substituting of (PF) with tannin at (10 –50)% W/W give resins with mechanical properties comparable or near to those of pure (PF) , where the tensile strength at break (Tb) ranging from 15.15 Mpa to 22.27 Mpa as compared with 17.6 Mpa for pure (PF);while the impact strength properties (Im) of composites sheets increased with increased the (T) percents which were about 5.16 KJ/m2 for (TPF – 10%) and 7.21 KJ/m2 for (TPF - 50%) .On the other hand modification of (T) to tannin formaldehyde resin (TF) appear less performance at the results of this study , this effect probably to low penetration of (TFPF) resins between the small voids of cellulose fibers when soaked it in resin solutions. In general the results of this study indicate that the Eucalyptus tannin can be used for par-tial substitution of (PF) to produce resins with feasible mechanical properties and can be used in some applications of (PF) resins.

Synergistic Reinforcement of Phenol-Formaldehyde Resin Composites by Poly(Hexanedithiol)/Graphene Oxide

In this paper, the preparation of graphene oxide was achieved by Hummers method and the surface modification was achieved by poly(hexaneditiol), which was a synthetic thermotropic liquid crystalline polymer. The c-PHDT/GO/PF composites were prepared by blending, rolling and compression molding techniques. Then, the as-prepared samples were characterized by FTIR, Raman, XRD, TGA and POM to obtain information on their structures and properties. After that, the effects of c-PHDT/GO content on the mechanical properties, friction performance and dynamic mechanical performance of c-PHDT/GO/PF composites were studied by Mechanical and Dynamic Mechanical Analysis (DMA) methods. Also, Scanning Electron Microscope (SEM) was used for the characterization of wear and fracture surface morphology. The results revealed that the reinforcing effect of c-PHDT/GO was significant as a considerable enhancement on the mechanical performance of c-PHDT/GO/PF composite as compared to pure phenol-formaldehyde composites was observed: the impact strength, bending modulus and bending strength increased from 1.63 kJ/m2, 8.61 GPa and 41.55 MPa to 2.31 kJ/m2, 10.16 GPa and 54.40 MPa respectively at the c-PHDT/GO content = 0.75%. Moreover, the initial storage modulus increased by 28.4%, while the wear mass loss decreased by 17.8%. More importantly, the reinforcement by c-PHDT/GO was further enhanced as compared to GO/PF and p-PHDT/GO/PF composites, the impact strength of c-PHDT/GO/PF composite increased by 27.6% and 11.1%, the bending strength increased by 11.8% and 7.6%, the initial storage modulus increased by 16.2% and 4.2% and the mass loss due to wear decreased by 12.7% and 8.8%, respectively. Based on these results, we can conclude that the surface modification of GO by poly(hexanedithiol), which includes synergistic effect by c-PHDT and GO, improves the interfacial adhesion between GO and the resin matrix, thus reinforcing the composites.

Synthesis of nanosized tungsten carbide from phenol formaldehyde resin coated precursors

Nanosized tungsten carbide was synthesized from phenol formaldehyde resin （PF） coated tungsten precursors. The process has three steps in which nanosized tungsten particles were first coated with PF, then the precursors were carburized at 950℃, and finally the carburized powders were treated in flowing wet hydrogen atmosphere at 940℃ to remove the uncombined carbon. The obtained powders were characterized using X-ray diffraction analysis （XRD）, field-emission scanning electron microscopy （FESEM）, small angle X-ray scattering （SAXS）, and combustion-gas-volume method. The results indicated that single-phase WC could be synthesized using excessive PF as carburizer at a much lower temperature compared with using mixed carbon black. After wet hydrogen treating, the mean size of the obtained WC particles was 94.5 nm and the total carbon content was 6.18 wt.%.

Reinforcement of Lignin-Based Phenol-Formaldehyde Adhesive with Nano-Crystalline Cellulose (NCC): Curing Behavior and Bonding Property of Plywood

The curing behavior of lignin-based phenol-formaldehyde (LPF) resin with different contents of nano-crystalline cellulose (NCC) was studied by differential scanning calorimetry (DSC) at different heating rates (5, 10 and 20&degC/min) and the bonding property was evaluated by the wet shear strength and wood failure of two-ply plywood panels after soaking in water (48 hours at room temperature and followed by 1-hour boiling). The test results indicated that the NCC content had little influence on the peak temperature, activation energy and the total heat of reaction of LPF resin at 5 and 10&degC/min. But at 20&degC/min, LPF0.00% (LPF resin without NCC) showed the highest total heat of reaction, while LPF0.25% (LPF resin containing 0.25% NCC content) and LPF0.50% (LPF resin containing 0.50% NCC content) gave the lowest value. The wet shear strength was affected by the NCC content to a certain extent. With regard to the results of one-way analysis of variance, the bonding quality could be improved by NCC and the optimum NCC content ranged from 0.25% to 0.50%. The wood failure was also affected by the NCC content, but the trend with respect to NCC content was not clear.

Research of Lignin Modified Phenol Formaldehyde Resin Bonded Magnesia Carbon Bricks

In order to reduce the cost and to improve the low temperature bonding strength of phenol formaldehyde resin（ PF）,the lignin modified phenol formaldehyde resin（ LPF） was synthesized using calcium lignosulfonate as a partial replacement of phenol,and sodium hydroxide as catalyzer. Then the magnesia carbon bricks were prepared using the LPF as binder. Different process conditions of LPFs such as calcium lignosulfonate additions（ 10%,20%,30%,40% and 50%,in mass,the same hereinafter）,catalyzer additions（ extra added,1%,2%,3%,4% and 5%） and reaction times（ 1,1. 5,2,2. 5 and 3 h） were investigated. Effects of prepared LPFs on properties of magnesia carbon bricks（ baked at 200 ℃ for 24 h） were researched in order to modify the synthesizing conditions of LPFs. Cold physical properties and hot modulus of rupture of magnesia carbon bricks bonded by LPF and by traditional PF after baked at 200 ℃ for 24 h and fired at 1 200 ℃ for 3 h were compared,respectively. The results show that the optimal synthesizing conditions of LPF for preparing magnesia carbon bricks are 30% calcium lignosulfonate,1% catalyzer,and 2 h reaction time. The magnesia carbon bricks bonded by the optimal LPF achieve：（ 1） the bulk densities 2. 84 g · cm- 3and 2. 82g·cm- 3,apparent porosities 9. 6% and 14. 6%,moduli of rupture 17. 8 MPa and 6. 4 MPa,crushing strengths72. 3 MPa and 48. 7 MPa,after baked at 200 ℃ and1 200 ℃,respectively;（ 2） the hot modulus of rupture7. 3 MPa after fired at 1 400 ℃. The above properties are better than those of the magnesia carbon brick bonded by PF.

Curing Process of Phenol Formaldehyde Resin for Plywood under Vacuum Conditions

The study characterized the curing behaviors of phenol formaldehyde(PF)resin under different vacuum degrees and explored the properties of 9-ply plywood panels hot-pressed under both vacuum and atmospheric conditions.The changes in core temperature and moisture content of the plywood mats during hot pressing were investigated as well.It was found that the gel times and gel temperatures of PF resin decreased with the increase of vacuum degree using a self-made device.FTIR spectra indicated the degree of polycondensation of hydroxymethyl gradu-ally increased with the increase in temperature.It was also observed that a higher degree of vacuum led to a slower polycondensation reaction rate of PF resin.During different hot-pressing processes,the bonding strengths in the innermost and uppermost gluelines of the vacuum hot-pressed plywood panels were up to 30%–50%higher than their counterparts of conventional hot-pressed products.A less difference in the bonding strengths between these two gluelines was also observed for vacuum hot-pressed products.In addition,the core of vacuum hot-pressed plywood was found to have a greater heating rate and higher temperature at thefinal stage of hot pressing,which was beneficial to cure the PF resin.The results from this study indicate a promising potential of introducing a vacuum during hot pressing to improve the quality and productivity of plywood products and provide a basis for adopting vacuum to hot press wood composites.

Effects of Resins with Different Molecular Structures on Properties of MgO-C Bricks

Resins PFG-4 , PFG-8 and a reference resin （resin A） were used as binders of MgO - C bricks, effects of the resins with different molecular structures on wettability of magnesia, on physical properties, mechanical properties, oxidation resistance and thermal expansion properties of MgO- C bricks were researched. The results show that the microstructures of solidified resins with different mo- lecular structures are different, which have obvious effect on the cold mechanical properties of MgO - C brick, but little effect on the oxidation resistance, thermal perform- ance and expansion properties.

苯酚-甲醛树脂MK-95在轿车子午线轮胎胎体胶中的应用

研究苯酚-甲醛树脂MK-95(简称MK-95)在轿车子午线轮胎胎体胶中的应用。结果表明:MK-95不含游离间苯二酚和其他添加剂,其软化点和挥发分含量低于间苯二酚-甲醛树脂;在胎体胶中以MK-95等量替代间苯二酚-甲醛树脂,胶料的硫化特性、物理性能、动态力学性能和粘合性能相当,成品轮胎的高速、耐久和路试性能均达到要求。

间苯二酚-苯酚-甲醛树脂制备及性能研究

主要研究催化剂、反应时间、摩尔比等反应条件对间苯二酚苯酚甲醛（ＲＰＦ） 树脂性能的影响。当甲醛／ 苯酚摩尔比为１ ～１－５∶１、间苯二酚／ 苯酚摩尔比为０－６∶１ 时可制得室外级冷固型胶粘剂。通过ＤＳＣ和ＩＲ 分析固化行为表明，低温下的放热量主要受多聚甲醛的影响，固化后的树脂中存在着大量的亚甲基醚键。

低游离甲醛羟甲基化木质素磺酸盐-酚醛复合胶黏剂研究

以工业木质素为原料,采用羟甲基化反应提高木质素反应活性,确定了羟甲基化反应木质素和催化剂的最佳配比:木质素与甲醛质量比为3∶1、催化剂用量为0.25%(以木质素原料计),并用FT-IR和13C NMR对羟甲基化反应结果进行了分析。通过羟甲基化木质素磺酸盐(HLF)与酚醛树脂(PF)共混制得木质素酚醛树脂(LPF)胶黏剂。实验结果表明,该胶具有制备工艺简单、游离甲醛低的特点,用HLF替代40%的PF时,其胶合强度达到国家Ⅰ类胶合板的要求。

E_0级碱木质素-酚醛复合胶粘剂的研究

以工业碱木质素为原料,采用羟甲基化反应提高木质素反应活性,确定了羟甲基化反应木质素与甲醛的最佳配比及最佳反应pH:木质素与甲醛比(KL/F)(质量比)为6∶1、反应pH为11.5,并用FT-IR和13C-NMR对羟甲基化反应结果进行了分析。通过羟甲基化木素(HKLF)与酚醛树脂(PF)共混制得木质素酚醛树脂胶粘剂,实验结果表明该胶具有制备工艺简单、再现性好的特点,用HKLF替代50%的酚醛树脂时,其胶合强度达到国家Ⅰ类胶合板的要求,压制的胶合板放置5~7天,甲醛释放量<0.2 mg/L。

尿素用量对苯酚-尿素-甲醛共缩聚树脂的影响

该文以13C-核磁共振分析和热机械性能分析为手段,研究了一定范围内尿素用量变化对苯酚-尿素-甲醛(PUF)共缩聚树脂结构和性能的影响,并通过压制胶合板,进一步评估了该影响。13C-核磁共振结构分析结果显示:改变尿素用量对PUF共缩聚树脂的结构构成无显著影响。热机械性能分析结果表明:在相同甲醛/苯酚摩尔比条件下,适量增加尿素用量对PUF树脂凝胶化或固化反应的影响并不显著;而相同甲醛/(苯酚+尿素)摩尔比条件下,随着尿素用量的增加,树脂凝胶化或固化反应呈逐渐提前的趋势,但速度呈下降趋势。胶合性能研究结果表明:尿素用量不超过苯酚质量25%左右时,PUF树脂性能优于酚醛(PF)树脂,增加尿素用量对PUF树脂胶合性能没有显著影响;超出该范围后,PUF树脂性能随尿素用量的增加而逐渐下降。

苯酚-尿素-甲醛共缩聚树脂结构形成比较

用13CNMR定量分析跟踪研究了两种不同合成路线中苯酚-尿素-甲醛共缩聚树脂(PUF)结构形成过程,比较了3种PUF树脂的结构构成。研究发现树脂制备过程中的酸性环境导致脲醛树脂初聚物含量增加以及尿素与苯酚之间的共缩聚增加;合成反应初期的介质环境对羟甲基酚的形成有着决定性的影响;合成过程中酸性环境所处阶段不同,最终树脂结构出现差异。

苯酚-尿素-甲醛共缩聚树脂结构与胶接性能关系研究

在树脂反应初期和后期分别添加尿素合成了苯酚-尿素-甲醛(PUF)共缩聚树脂。通过PUF树脂的胶合板制备实验,研究了反应后期尿素的添加量及热压温度对胶合板胶合强度的影响;使用13C液体核磁分析(13C-NMR)对不同尿素添加量的PUF树脂的微观结构进行表征,探讨了树脂结构与胶合板胶合强度之间的关系。结果表明:在PUF树脂的合成后期加入的尿素参与了树脂的共缩聚反应;当尿素添加量为89.4%、热压温度为150℃时,PUF树脂胶接胶合板符合Ⅰ类胶合板标准要求;PUF树脂中低分子的取代脲以及羟甲基脲共同影响着PUF树脂固化后的物理性能。

碱性环境下苯酚-尿素-甲醛共缩聚树脂结构形成研究

为了了解碱性环境中苯酚-尿素-甲醛(PUF)共缩聚树脂结构形成规律,为PUF树脂结构控制提供依据,使用13C NMR表征,采用分次加入苯酚、甲醛和尿素的技术路线,定量分析了PUF树脂合成过程中各种官能团的变化和聚合物分子链的构成。结果表明,碱性环境中各种加料方式合成的PUF树脂初聚物具有十分相近的化学结构,PUF树脂也具有十分相近的化学结构,但结构组分存在差异,在原料物质的量之比一定的条件下,最终反应进程基本接近。甲醛分次加入,减少了醚类的生成,有利于简化反应进程。初聚物的热机械性能分析表明不同加料方式对酚醛树脂固化性能无显著影响。

三聚氰胺-苯酚-甲醛共缩聚合成机理及性能研究

为得到环保阻燃等优良性能的防火板,该文在弱碱条件下对三聚氰胺与苯酚、甲醛进行共缩聚得到三聚氰胺-苯酚-甲醛(MPF)树脂,经红外光谱、核磁共振(H1NMR)分析表明,MPF树脂中显示三嗪环结构特征峰,苯酚环与三聚氰胺的三嗪环主要以亚甲基键(Ph—CH2—N<)结构相连存在;TG和DSC的分析显示,MPF树脂具有150、165℃2次固化温度。三聚氰胺加入量对树脂游离酚、贮存期以及纸质防火板的燃烧性产生重要影响,对防火板拉伸强度、耐沸水煮性能影响不明显,MPF树脂中甲醛摩尔数直接影响树脂贮存期和防火板的甲醛释放量。