氰酸酯树脂/纳米氧化铜复合材料制备及性能

将无机纳米氧化铜(CuO)粒子加入氰酸酯树脂(CE),以有机锡(DBTDL)实现自由基引发,定量加入环氧树脂(E–54)制得CE/CuO系列复合材料.测试了复合材料的力学性能、导热性能和耐酸碱腐蚀性能,讨论了复合材料性能得以改变的原因.结果表明,无机纳米CuO粒子的引入,有利于CE基体树脂的聚合,无机纳米CuO粒子含量...     

13C CP/MAS NMR studies on the curing characteristics of phenol formaldehyde resin in the presence of nano cupric oxide and surfactants

The effect of nano cupric oxide (CuO) in combination with surfactants on the curing characteristics of phenol formaldehyde (PF) resin analyzed using solid ¹³C CP/MAS NMR, including the bonding strength of plywood prepared by modified resin, was investigated in this study. The results showed that nano CuO alone improved the cure of PF resin. The intensity of the functional groups of the PF mixture was maintained during the curing process as sodium lignosulfonate was simultaneously introduced. Furthermore, nano CuO and alkane surfactant together modified the PF resin conformation. The shear strength of the plywood showed that the addition of nano CuO (1%) alone or in combination with alkane surfactant (0.55%) or sodium lignosulfonate (0.55%) to the PF resin mixture was effective. And this approach met the important criteria for its application in the manufacture of plywood. POLYM. COMPOS., 35:113–117, 2014. © 2013 Society of Plastics Engineers     

Curing kinetics of nano cupric oxide (CuO)-modified PF resin as wood adhesive: effect of surfactant

The effect of nano cupric oxide (CuO) in combination with surfactants on the curing kinetics of phenol-formaldehyde (PF) resin, as well as the bonding strength of plywood prepared using the modified resin was investigated in this study using dynamic and isothermal differential scanning calorimetry. The result showed that the incorporation of nano CuO along with alkane surfactant made in the laboratory clearly reduced the apparent activation energy of the PF resin and improved the addition and condensation reactions of the PF resin. Inclusion of the surfactant had the further effect of compensating the influence of diffusion control caused by nano CuO alone. The shear strength of plywood suggested that the addition of nano CuO (1%) alone or in combination with alkane surfactant (0.55%) or sodium lignosulfonate (0.55%) in the PF resin mixture was sufficient to meet the requirement of wood-based composites manufacturing.     

In situ fabrication of CuO/UHMWPE nanocomposites and their tribological performance

Polymer nanocomposites present remarkably enhanced mechanical and tribological properties with respect to their matrices even at a low loading of nanofillers. Here, cupric oxide (CuO) nanoparticles (nano-CuO) were in situ filled into ultra-high-molecular-weight polyethylene (UHMWPE) to inhibit a possible agglomeration encountered in the preparation by mechanical mixing. The filled CuO nanoparticles were highly dispersed in UHMWPE with a reliable interface combination. The CuO nanoparticles in the matrix play a role for heterogeneous nucleation, resulting in an enhancement in degree of crystallinity of UHMWPE. The elastic modulus and the elongation at break of the nanocomposites also presented an improvement, indicating a good compatibility between the nano-CuO and the matrix. The average sliding friction coefficient of UHMWPE against 45^# steel was reduced by up to 34% after the in situ filling of CuO nanoparticles, and the wear mechanism was found to transform from adhesive to fatigue wear after the introduction of nano-CuO. It is concluded that the in situ filling can improve the dispersion of CuO nanoparticles in UHMWPE, and markedly promote the mechanical properties and tribological performance of UHMWPE. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47925.     

13C CP/MAS NMR studies on the curing characteristics of phenol formaldehyde resin in the presence of nano cupric oxide and surfactants. II. Effect of CuO loading levels

The effect of various loadings of nano cupric oxide (CuO) and surfactants in the formulation of phenol formaldehyde (PF) adhesive was investigated using solid ¹³C CP/MAS NMR. Bonding strength and water resistance of plywood made with the modified adhesive were conducted. Solid NMR analysis showed that the addition of nano CuO alone or in combination with surfactant together was effective in improving the curing property of PF resin, which was confirmed by the NMR reveal that the amount of aliphatic carbons from methylene linkages increase with the addition of nano CuO in the PF resin. The addition of the mixture of alkane surfactant and nano CuO in the resin improved the water resistance property of the resulted plywood as well. POLYM. COMPOS., 37:949–954, 2016. © 2014 Society of Plastics Engineers     

PF/PDMS-OH流变性能对其泡沫材料泡孔结构的影响

分别将质量分数为10%,15%和20%的端羟基聚硅氧烷(PDMS–OH)通过机械共混的方法改性酚醛树脂(PF),进而采用化学发泡的方法制备PF/PDMS–OH泡沫复合材料。采用旋转式流变仪表征共混体系的稳态及动态流变性能,研究黏弹性对树脂发泡过程的影响。傅立叶变换红外光谱表征PDMS–OH与树脂在固化过程中的化学反应。扫描电镜表征不同共混体系下泡孔的结构与形态。结果表明,加入15%PDMS–OH的共混体系具有最利于发泡成型的黏弹性,且可与PF形成化学交联作用,对PF泡沫的泡孔形态影响显著。同时红外表征显示,PDMS–OH与PF在固化过程中发生化学交联,这种互穿交联网状结构为PF及泡沫提供了更多稳定的柔性链段。     

Fast advancement and hardening acceleration of low condensation alkaline phenol‐formaldehyde resins by esters and copolymerized urea. II. Esters during resin reaction and effect of guanidine salts

Guanidine carbonate is shown to be an accelerator of phenol‐formaldehyde (PF) resins that while yielding slightly slower gel times than triacetin when added to a PF resin glue mix, is also capable of giving glue‐mix pot lives on the order of several days. Hence, this is long enough to be premixed with the resin long before use. Both triacetin and guanidine carbonate used as simple glue‐mix additives are shown to increase the ultimate strength of the resin bond, whatever the length of the curing time used for the purpose. This is shown by thermomechanical analysis and the application to wood particleboard. Triacetin is shown to be usable during PF resin preparation rather than just being added to the glue mix, yielding better resins capable of giving higher bond values without a great acceleration of the geling of the resin itself. The mechanisms involved in the acceleration of PF resins introduced by both compounds appears to be based on facilitating reactions of crosslinking involving carbonic acid ions present in the resin solution. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 249–259, 2000     

Effects of recycled fiber addition on high‐density fiberboard for laminated flooring bonded with phenol‐formaldehyde resin adhesive

The effects of old corrugated cardboard (OCC) fiber addition on high‐density fiberboard (HDF) were investigated in this study. A phenol‐formaldehyde (PF) resin was synthesized in the laboratory with resin solids at 50% content as an HDF binder. The physical characteristics and molecular weight of the PF resin are described herein. The laboratory HDFs were made using the OCC fiber based on 0, 20, 40, and 60% oven‐dry weight addition with the laboratory‐synthesized PF resin. The HDFs were tested for physical strength and dimensional stability properties according to the procedure of ASTM D 1037‐99. Evaluation of the HDFs manufactured using the PF resin showed that the internal bond and bending strength properties were decreased gradually with increasing OCC fiber content. Overall, the OCC fiber can be used at a content of 40% in the substitution of raw materials for HDF manufacture. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Bark extractives-based phenol–formaldehyde resins from beetle-infested lodgepole pine

In this study, phenol–formaldehyde (PF) resins derived from the bark extractives were synthesized and characterized. Bark of lodgepole pine (Pinus contorta Dougl.) infested by mountain pine beetle (Dendroctonus ponderosae Hopkins) was first extracted with 1% NaOH. The bark extractives with and without acid-neutralization were then dried to the solid state. The neutralized and non-neutralized extractives were used to partially replace petroleum-based phenol for synthesizing the bark extractives-PF resins. In comparison with a commercial PF resin and a laboratory made PF resin (Lab PF), the bark extractive-PF resins were found to have higher molecular weights, higher viscosities, and shorter gel times. Acid neutralization of the bark extractives increased the molecular weight of the extractives and modified the performance and curing behavior of the resulting bark extractive-PF resins. Bark extractive-PF resins (BEPF) showed a similar level of post-cured thermal stability to that of the lab PF at higher temperatures, but they differed significantly from that of the commercial PF resin. The bark extractive-PF resins made from both neutralized and non-neutralized extractives at 30% replacement of phenol (by weight) exhibited similar dry and wet bond strengths to the commercial PF resin. At 50% substitution level, BEPF had dry and wet bond strengths similar to the lab PF resin. Our findings suggest that alkaline extractives from mountain pine beetle-infested lodgepole pine bark are suitable for partially substituting phenol in the synthesis of phenolic resin for use in wood adhesives.     

13C CP/MAS NMR analysis of cure characteristics of phenol formaldehyde resin in the presence of wood composite preservatives and wood: effect of ammonium pentaborate and copper compounds

The effect of typical wood composite preservatives, ammonium pentaborate (APB), nanosize copper oxide and basic copper carbonate, on the cure characteristics of phenol formaldehyde (PF) resin in the presence of wood was evaluated by solid-state ¹³C nuclear magnetic resonance with cross-polarization and magic angle spinning (CP/MAS). With the introduction of APB the absorption intensity and peak area of PF resin at 129.5?ppm was reduced, and the carbons in methylene bridges shifted from 65.8 to 73.5?ppm, which were the result of hydrogen bond formation between ammonium in APB and oxygen of phenolic hydroxyl, as well as coordination bond between the boron in APB and oxygen in phenolic hydroxyl and/or unreacted hydroxymethyl. In addition, the peak area at 152.7?ppm increased with the addition of poplar powder for the overlap of cellulose, hemicellulose, and lignin chemical shifts with the active groups in PF resin. However, the connection status of critically active chemical groups of condensed polymer structure in cured PF resin such as the existence of phenolic ring, phenolic hydroxyl, methylene bridges, and hydroxymethyl linkage are unchanged. Combined with relative increase in the amount of carbon in methylene bridges from 2.42 to 2.56, drop in number of carbons of unreacted hydroxyls from 1.19 to 1.07, and the reported increase in physical and mechanical properties, the nanosize copper oxide improved the curing degree of PF. Furthermore, the similar analysis indicated that basic copper carbonate delayed the curing degree of PF.     

Effect of resin type and content on properties of composite particleboard made of a mixture of wood and rice husk

This study investigated the effect of resin type and content on the dimensional stability and mechanical properties of single-layer composite particleboards made of a mixture of wood particles (70 wt%) and rice husk particles (30 wt%). Two types of resin, urea–formaldehyde (UF) resin and phenol–formaldehyde (PF) resin, were used in the experiments at three different contents which were 8, 10, or 12 wt%. The dimensional stability of the samples was significantly improved by increasing the resin content. When the contents of the UF and PF resins increased from 8 to 12 wt%, the WA values of the samples decreased to18% and 33%, respectively. Similar results were also observed for the TS values. The UF resin bonded samples swelled two times more than the PF resin bonded particleboard. The mechanical properties of the PF resin bonded samples were better than the UF resin bonded samples. When the contents of the UF and PF resins increased from 8% to 12 wt%, the internal bond strength values of the samples increased to 21% and 41%, respectively. The bending strength and modulus of elasticity of the samples were not significantly increased by increasing contents of the UF and PF resins, except for the 12 wt% content.     

Ionic liquid modified lignin-phenol-glyoxal resin: a green alternative resin for production of particleboards

The aim of this research was to evaluate the properties of particleboard panels bonded with ionic liquid treated lignin- phenol- glyoxal (LPG) resin. For this purpose, soda bagasse lignin was modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid and then various contents of virgin and modified lignin (20, 30 and 40 wt% based on weight of phenol), phenol and glyoxal were used for synthesis of LPG resins. After resin synthesis, thermal and physicochemical properties of the synthesized resins such as curing behavior, gelation time, viscosity, solid content and density were measured. Finally, the resins so prepared were used for laboratory particleboard manufacturing. The panels physical (water absorption, thickness swelling) as well as mechanical (MOE, MOR and internal bond strength) properties were measured according to standard methods. The resins tests indicated that modification of lignin with ionic liquid not only can accelerate the gelation time and increase viscosity, density and solid content of LPG resins but also decrease the temperature required for curing the LPG resins. Based on the results of this work, the mechanical strength and dimensional stability of the particleboards bonded with a LPG resin can be improved by using modified lignin. The particleboards prepared with the LPG resin, using either modified or virgin lignin, presented higher water absorption as well as weaker mechanical strength than those prepared with the control PF resin. However, there does not appear to be any statistically significant difference between the some properties of the panels bonded with the control PF resin and those bonded with the LPG resin containing modified lignin.     

Properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde resin

The aim of this research was to investigate the physical and mechanical properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde (LPF) resin. For this purpose, soda bagasse lignin was modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid, and then, various contents of modified lignins (10, 15, and 20 wt%) were added as a substitute of phenol in phenol–formaldehyde (PF) resin synthesis. The properties of the synthesized resin were compared with those of a control PF resin. The changes in curing behavior of the resins prepared were analyzed by differential scanning calorimetry (DSC). The physical properties of the resins prepared, as well as the water absorption, thickness swelling, shear strength, and formaldehyde emission of the plywood panels bonded with these adhesives, were measured according to standard methods. DSC analysis indicated that in comparison with PF resins, curing of the LPF resin occurred at lower temperatures. The physical properties of the synthesized resins indicated that viscosity and solid content increased, while gel time and density decreased by addition of treated lignin to the PF resin. Although the panels containing resins with modified lignin yielded low formaldehyde emission, their dimensional stability was worse than those bonded with a commercial PF adhesive. The plywood prepared using IL-treated lignin PF resins has shear strength, which satisfy the requirements of the relevant standards specifications and significantly better than that of panels prepared with the control PF resin. The mechanical properties of the panels could be significantly enhanced with increased percentage of treated lignin content from 0 to 20 wt%.     

木质素改性高耐磨酚醛树脂的制备及性能研究

利用酶解木质素(EHL)和腰果壳油(CNSL)改性热塑性酚醛树脂,讨论了不同酚醛摩尔比、CNSL用量和1,4-丁二醇对改性树脂性能的影响。研究表明,木质素及腰果壳油双改性的酚醛树脂耐热性能优于腰果壳油改性的酚醛树脂。改性后酚醛树脂基摩擦材料具有良好的摩擦磨损性能,更适合作为摩擦材料的树脂基体。     

Mechanical properties and microstructure of acrylonitrile–butadiene rubber vulcanizates reinforced by in situ polymerized phenolic resin

The phenolic resin (PF) was incorporated into acrylonitrile–butadiene rubber (NBR) vulcanizates by in situ polymerization during the vulcanization process. It was found that the tensile strength, tearing strength, and tensile strength (300% elongation) could be considerably enhanced 59.4, 80.2, and 126.4%, respectively, at an optimum PF content of only 15 phr, but the elongation at break and shore A hardness were only slightly affected on the basis of silica‐reinforced NBR vulcanizates. A systematic study of the PF structure formed within the NBR matrix using various experimental schemes and procedures has revealed that the PF resin would form the localized discontinuous three‐dimensional interconnected network structures in the NBR matrix. The substantial reinforcement of PF on the mechanical properties of vulcanized NBR were attributed to the morphology, high flexibility, and moderate stiffness of the PF phases and their excellent bonding with rubbers through “rubber to rubber” and interface layer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

N-(4-羟基苯基)马来酰亚胺改性酚醛树脂的制备与表征

采用N-(4-羟基苯基)马来酰亚胺(4-HPM)改性酚醛树脂(PF),改性后PF的耐热性能明显优于传统的热塑性PF。质量分数2%的4-HPM改性PF的热分解温度比纯PF提高104.6℃,冲击强度提高130%。改性PF的固化过程分为两个固化阶段:第一阶段是少量羟甲基的缩合;第二阶段为马来酰亚胺的双键打开进行自交联。     

PU/PA纳米粒子改性酚醛树脂胶粘剂的研究

采用自乳化法制备PU/PA纳米粒子,并对酚醛树脂进行增韧改性.考查了丙烯酸酯单体种类、用量以及环氧树脂用量对改性酚醛树脂粘接性能的影响.借助TG、DSC、SEM和TEM对改性酚醛树脂体系的耐热性能、固化反应和微观形态进行了表征.结果表明,PU/PA纳米粒子的加入使酚醛树脂的常温和高温粘接强度显著增加,提高了酚醛树脂的固...     

Study on the microstructural evolution of high temperature adhesives for graphite bonding

Development of high-temperature adhesives (HTAs) can provide a way to produce carbon materials with a large size or a complex shape. Some HTAs were developed for joining graphite materials. These HTAs were prepared using phenol formaldehyde (PF) resin as matrix and B₄C powders as fillers. The results showed that these HTAs had satisfactory adhesive properties for graphite bonding even though the bonded graphite components were heat-treated at temperatures up to 1500 °C. In order to clarify the effects of the microstructure of HTAs on adhesive strength, the bonded graphite parts were heat-treated at high temperatures ranging from 400 to 1500 °C. The microstructural evolution of HTAs was investigated using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Analyses of the HTAs at the interface revealed that during microstructural evolution, carbonization of PF resin and complex interactions between PE and B₄C powders occurred. A high chemical bonding force was introduced at the interface through interactions between the glassy carbon from the PF resin and B₄C fillers, and the B₄C fillers restrained the volume shrinkage of PF resin during carbonization, which can be responsible for the good adhesive properties of HTAs for graphite bonding.     

环氧及酚醛树脂增韧改性氰酸酯树脂研究

用环氧树脂(EP)及酚醛树脂(PF)对氰酸酯树脂(CE)进行增韧改性,对改性CE的凝胶时间和DSC曲线进行研究并确定了改性CE的固化工艺。红外光谱分析表明改性CE固化时形成了柔韧性结构。研究了改性CE的力学性能、热性能、电性能及微观形态,发现EP的加入可增加CE的柔韧性,PF的加入可使CE的热稳定性损失减小。当CE/EP/PF的质量比为70/15/15时改性CE的弯曲强度和冲击强度分别从改性前的123.6 MPa、5.2 kJ/m2提高到134.5 MPa、16.7 kJ/m2,耐热性及电性能改变不大。     

Phenol–formaldehyde‐type resins made from phenol‐liquefied wood for the bonding of particleboard

Liquefaction of southern pine wood in phenol in 30–40 : 70–60 weight ratios resulted in homogeneous liquefied materials, which were directly used to synthesize phenol–formaldehyde (PF)‐type resins. The synthesized resins showed good physical and handling properties: low viscosity, stability for storage and transportation, and resin applicable by a common sprayer. Particleboard panels bonded with the synthesized resins showed promising physical properties and significantly lower formaldehyde emission values than those bonded with the urea–formaldehyde resin control. One deficiency observed for the synthesized resins was lower internal bond values, which might be overcome the use of a hot‐stacking procedure. Overall, the process of wood liquefaction with limited amounts of phenol as a solvent was shown to have the potential of providing practical, low‐cost PF‐type resins with very low formaldehyde emission potentials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009