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.

Preparation of phenol formaldehyde resin from phenolated wood

The technique for preparing phenol formaldehyde resin from phenolated wood (PWF) and its characters were studied and analyzed. Poplar (Populus spp.) wood meal was liquefied by phenol in the presence of sulfuric acid as a catalyst. After the liquefied products were cooled, alkaline catalyst and formaldehyde were added. The mixture was kept at (60?) C for 1h and then was heated to (85?) C for 1h. The influence of molar ratio of formaldehyde to phenol (F/P) was investigated. The results showed when the molar ratio of formaldehyde to phenol was over 1.8, the PWF adhesives had high bond quality, bond durability and extremely low aldehydes emissions.

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.%.

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.

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.

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.

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.

酚醛树脂/蒙脱土浸渍改性杉木工艺及密实化研究

以酚醛树脂和蒙脱土混合后溶液为改性剂,正负压仿呼吸环境下浸渍改性杉木板材,探讨了负压压力、负压时间、正压压力、正压时间对杉木板材增重率的影响;通过正交试验确定最佳处理工艺,在最优工艺浸渍杉木板材基础上进行压缩密实化处理,分析改性后杉木的密度、增重率、表面硬度、力学性能、尺寸稳定性和阻燃性,并通过扫描电镜和红外光谱对木材微观形貌、官能团进行表征。结果表明:当负压压力–0.095 MPa、负压时间20 min、正压压力1.5 MPa和正压时间1.5 h,改性杉木的增重率最大。在此浸渍工艺处理下,压缩密实化处理后的杉木密度由0.328 g/cm3提升至0.784 g/cm^(3),静曲强度、弹性模量和表面硬度分别提升了34.7%、38.4%和85.6%;尺寸稳定性结果表明改性杉木的吸水率和体积膨胀率明显降低。扫描电镜表明改性剂主要通过管胞、射线细胞和纹孔渗透,且木材内部孔隙被很好地填充。红外分析表明木材内部游离羟基减少,缔合羟基和醚键数目增多,木材内部引入Si-O-C键,耐火试验结果表明改性材具有良好的阻燃效果。

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。

萘硼酸结构修饰酚醛树脂的合成及其热性能研究

以萘硼酸、苯酚和甲醛水溶液为原料,盐酸和二水合草酸为催化剂,制备了萘硼酸酚醛树脂(BPF)。通过傅里叶变换红外光谱仪、核磁共振分析仪对其进行结构表征,利用差示扫描量热仪考察了升温速率对BPF特征温度的影响,通过热重分析仪、热变形维卡软化点测定仪、电子万能试验机测试了BPF的热性能、软化点和力学性能。结果表明:硼元素以化学键的形式接入到酚醛树脂结构当中;BPF凝胶化温度T_(gel)为113.3℃、固化温度T_(cure)为142.2℃、后处理温度T_(treat)为157.6℃;当萘硼酸含量为10%(wt,质量分数,下同)时,BPF的热分解峰值温度、800℃残炭率比未改性酚醛树脂分别提高了17.39%和28.79%,软化温度提高了16.79%;萘硼酸含量为10%时,BPF拉伸剪切强度、弯曲强度比未改性酚醛树脂分别提高了262.5%和128.3%;萘硼酸含量为6%时,BPF冲击强度提升最大,为2.5kJ/m 2。

麦草碱木素酚化改性及其制备LPF胶粘剂工艺研究

利用碱性条件下酚化改性的麦草碱木素代替部分苯酚制备了高木质素/苯酚比例和胶粘强度高的木质素酚醛树脂(LPF)胶粘剂。利用傅立叶红外光谱(FT-IR)和凝胶色谱(GPC)研究了麦草碱木素在碱性条件下酚化改性前后的结构变化。FT-IR分析表明,麦草碱木素发生了酚化反应,伴随着酯基的断裂和甲氧基的脱落;GPC结果显示,木质素平均分子量降低,分子量分布范围变宽。接着,研究了木质素/苯酚比例、氢氧化钠浓度、甲醛/木质素比例、酚化温度、酚化时间、缩聚温度、缩聚时间等反应工艺参数对LPF胶粘剂性能的影响,优化了麦草碱木素酚化改性制备LPF胶粘剂的反应工艺参数。最后,比较了反应工艺参数优化的LPF胶粘剂与传统PF胶粘剂的各项性能,结果显示,麦草碱木素酚化改性后代替70%的苯酚制备得到的LPF胶粘剂的胶粘强度与传统PF胶粘剂相近。

PF/MCMB/石墨/CF复合材料燃料电池双极板的研制

针对目前机加工燃料电池石墨双极板、金属双极板的不足,研究了采用酚醛树脂(PF)、中间相碳微球(MCMB)、石墨和碳纤维(CF)为原料通过模压成型、渗碳烧结工艺制备复合材料双极板。结果表明,所研制的复合材料双极板具有更佳的综合性能,其制造成本低、效率高,碳元素含量达95%,压缩强度大于100MPa,弯曲强度大于30MPa,体积电阻率小于50×10-6Ω·m,所组装的单电池能满足燃料电池苛刻工作条件和性能上的要求。

PF与PVB共混炭化制备双电层电容器用多孔炭材料的研究

以酚醛树脂(PF)为原料,聚乙烯醇缩丁醛(PVB)为成孔剂,采用聚合物共混炭化法制备双电层电容器 用多孔炭材料。通过热重(TG)和差热(DTA)分析,初步探讨了单一PF、PVB和PF与PVB的共混物在炭化 过程中的热解行为。考察了炭化温度和PF／PVB质量比对所得多孔炭的收率、BET比表面积、孔径分布和比 电容的影响,并进一步探讨了以这种多孔炭材料作电极的模拟双电层电容器的充放电特性。结果表明,共混 聚合物中PF与PVB是不相容的,热解过程各自独立进行,但存在一定的协同作用。随着炭化温度的升高, 所得多孔炭的收率下降,比表面积、总孔容积和比电容先增大后减小,在800℃时达到最大值。随着PF／PVB 质量比的增加,所得多孔炭的收率增加,比表面积和总孔容减小,比电容也减小。聚合物的混合方式及状态也 是影响多孔炭性能的因素之一。以比电容为26.3F/g的多孔炭作电极的模拟双电层电容器具有良好的充放 电性能。

不同分子量麦草碱木素性能及其对LPF胶性能的影响

应用超滤分级方法,将麦草碱木素分成3种不同分子量范围的级分。分析表明:随着分子量的降低,麦草碱木素的甲氧基含量降低,酚羟基含量升高,其反应活性随之升高;同时,羧基含量降低,其溶液表面活性升高。进一步实验结果表明,随着麦草碱木素分子量的降低,LPF胶的胶黏强度升高,游离甲醛含量和黏度降低,综合性能提高。

PF和PUF树脂分子结构对比研究

为了判断苯酚-尿素-甲醛(PUF)树脂中原料共缩聚反应是否发生,并确认共缩聚分子形成特点,借助13C核磁共振(13C NMR)和基质辅助激光解析电离飞行时间质谱(MALDI-TOF-MS)两种主要分析仪器,对比研究了苯酚-甲醛(PF)树脂和PUF树脂的结构特点,结果证实了PUF树脂中苯酚、尿素和甲醛3种原料之间共缩聚反应的存在,认为PUF树脂结构以PF树脂为主体,且共缩聚结构主要形成于合成反应初期。

改性水溶性酚醛(PF)浸渍胶的研制

用不同材料对水溶性酚醛(PF)浸渍胶进行改性,并对改性后的酚醛浸渍胶的黏度和水数变化进行跟踪,并用不同固化剂对各种胶进行固化实验。在纸张、相同上胶量和相同固化度的条件下,对涂覆不同PF胶的纸张进行耐沸水性的测定。笔者还考察了不同碱量对胶液本身及涂胶后纸张性能的影响。其数据可为不同要求的水泥模板生产提供依据。