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 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.展开更多
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 pr...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.展开更多
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 ...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.展开更多
In this study on the curing dynamics of phenol-formaldehyde novolac resins(PFNR) and hexamethylene tetramine(HMTA), two typical commercial PFNR were selected as examples and the curing reactions of the resins with HMT...In this study on the curing dynamics of phenol-formaldehyde novolac resins(PFNR) and hexamethylene tetramine(HMTA), two typical commercial PFNR were selected as examples and the curing reactions of the resins with HMTA were studied by differential scanning calorimetry(DSC). Based on the data calculated by the Kissinger equation and the Crane equation, a thermocuring dynamic model was established, from which the process conditions, activation energy, reaction kinetics equation and a f irst-order reaction of the curing reactions were derived.展开更多
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 pyrolysates has been analyzed. Sever...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 pyrolysates has been analyzed. Several compounds, especially benzene, toluene, p-xylene could only be formed above 500550℃. However, peak intensities for some phenol 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.展开更多
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-PHD...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.展开更多
A new aqueous alkaline resol phenol-formaldehyde resin has been prepared from phenol and formaldehyde using NaOH as catalyst; the optimum synthetic process has been determined. With addition of some cross-linking agen...A new aqueous alkaline resol phenol-formaldehyde resin has been prepared from phenol and formaldehyde using NaOH as catalyst; the optimum synthetic process has been determined. With addition of some cross-linking agents, after passing carbon dioxide gas through the resin bonded sand, high as-gassed strength and 24 h strength are achieved. The bonding bridge of the resin bonded sand fracture has been analyzed by using SEM.展开更多
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 precur...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.%.展开更多
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 5...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.展开更多
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 ...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°C/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°C/min. But at 20°C/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.展开更多
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...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.展开更多
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 p...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.展开更多
文摘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.
基金supported by National Natural Science Foundation of China(No.31800481)Yunnan Fundamental Research Key Projects(No.2019FA012)+2 种基金Science-Technology Support Foundation of Guizhou Province of China(Nos.[2019]2308,[2020]1Y125)Forestry Department Foundation of Guizhou Province of China(No.[2018]13)Cultivation Project of Guizhou University of China(No.[2019]37).
文摘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.
基金Funded by the China Postdoctoral Science Foundation Funded Project(2015M572276)the Natural Science Foundation of Hunan Province,China(2016JJ3184)the Hunan Major Science and Technology Projects(2011FJ1006)
文摘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.
基金financially supported by the Fundamental Research Funds for the Central Universities of China(SWU.113003 and XDJK 2015C097)
文摘In this study on the curing dynamics of phenol-formaldehyde novolac resins(PFNR) and hexamethylene tetramine(HMTA), two typical commercial PFNR were selected as examples and the curing reactions of the resins with HMTA were studied by differential scanning calorimetry(DSC). Based on the data calculated by the Kissinger equation and the Crane equation, a thermocuring dynamic model was established, from which the process conditions, activation energy, reaction kinetics equation and a f irst-order reaction of the curing reactions were derived.
文摘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 pyrolysates has been analyzed. Several compounds, especially benzene, toluene, p-xylene could only be formed above 500550℃. However, peak intensities for some phenol 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.
文摘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.
文摘A new aqueous alkaline resol phenol-formaldehyde resin has been prepared from phenol and formaldehyde using NaOH as catalyst; the optimum synthetic process has been determined. With addition of some cross-linking agents, after passing carbon dioxide gas through the resin bonded sand, high as-gassed strength and 24 h strength are achieved. The bonding bridge of the resin bonded sand fracture has been analyzed by using SEM.
基金This Work was financially supported by Beijing Municipal Science & Technology Commission(No.2052015).
文摘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.%.
文摘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.
文摘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°C/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°C/min. But at 20°C/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.
基金New Century Excellent Talents Program of Ministry of Education ( NCET - 09 - 0137 )The open foundation of the State Key Laboratory of Refractories and Metallurgy ( 2014QN17 )
文摘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.
文摘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.