High Pressure Laminates(HPL)panels consist of stacks of self-gluing paper sheets soaked with phenol-formaldehyde(PF)resins.An important requirement for such PFs is that they must rapidly penetrate and saturate the pa...High Pressure Laminates(HPL)panels consist of stacks of self-gluing paper sheets soaked with phenol-formaldehyde(PF)resins.An important requirement for such PFs is that they must rapidly penetrate and saturate the paper pores.Partially substituting phenol with bio-based phenolic chemicals like lignin changes the physico-chemical properties of the resin and affects its ability to penetrate the paper.In this study,PF formulations containing different proportions of lignosulfonate and kraft lignin were used to prepare paper-based laminates.The penetration of a Kraft paper sheet was characterized by a recently introduced,new device measuring the conductivity between both sides of the paper sheet after a drop of resin was placed on the surface and allowed to penetrate the sheet.The main target value measured was the time required for a specific resin to completely penetrate the defined paper sample(“penetration time”).This penetration time generally depends on the molecular weight distribution,the flow behavior and the polarity of the resin which in turn are dependent on the manufacturing conditions of the resin.In the present study,the influences of the three process factors:(1)type of lignin material used for substitution,(2)lignin modification by phenolation and(3)degree of phenol substitution on the penetration times of various lignin-phenolic hybrid impregnation resins were studied using a complete twolevel three-factorial experimental design.Thin laminates made with the resins diluted in methanol were mechanically tested in terms of tensile and flexural strains,and their cross-sections were studied by light microscopy.展开更多
Lignin is a natural biopolymer with a complex three-dimensional network, commercially obtained from wasteliquid of paper pulp and bioethanol production, and could be a candidate for preparation of environment-friendly...Lignin is a natural biopolymer with a complex three-dimensional network, commercially obtained from wasteliquid of paper pulp and bioethanol production, and could be a candidate for preparation of environment-friendlybio-based polyphenol material. In the present work, the demethylated wheat straw alkali lignin (D-Lig), preparedby demethylation of wheat straw alkali lignin (Lig) using an in-situ generated Lewis acid, was used to synthesizebio-based phenol formaldehyde resin adhesive (D-LPF) applied in plywood. Effects of synthetic process’s factors,including lignin substitution for phenol, NaOH concentration and molar ratio of formaldehyde to phenol, on thebonding strength and free formaldehyde content of D-LPF were investigated in detail, and the optimum syntheticprocess of D-LPF was obtained as following: Lignin substitution for phenol 60%, NaOH concentration 5.0% andmolar ratio of formaldehyde to phenol 2.0, and under the optimum reaction condition, the D-LPF presented lower free formaldehyde content (0.18%) and higher bonding strength (2.19 MPa), which was better than those ofcontaining-lignin phenol formaldehyde resin adhesive (LPF). Additionally, the curing behavior of the adhesivewas studied by differential scanning calorimetry (DSC) combined with gel time. It can be obtained that D-LPFresin adhesive had the shortest gel time, and fastest curing rate, compared with those of PF and L-PF resin adhesives. The curing kinetics data was fitted well by Kissinger model using non-isothermal DSC method, and theaverage activation energy value was 85.3 kJ/mol, slightly higher than that of commercial PF resin, while lowerthan that of LPF (90.2 kJ/mol). Finally, based on the analytical results of high temperature fourier transform infrared spectroscopy (FTIR), a possible curing mechanism of D-LPF was proposed.展开更多
基金This work was carried out within the COMET program funded by the Austrian FFG,project number 844608.
文摘High Pressure Laminates(HPL)panels consist of stacks of self-gluing paper sheets soaked with phenol-formaldehyde(PF)resins.An important requirement for such PFs is that they must rapidly penetrate and saturate the paper pores.Partially substituting phenol with bio-based phenolic chemicals like lignin changes the physico-chemical properties of the resin and affects its ability to penetrate the paper.In this study,PF formulations containing different proportions of lignosulfonate and kraft lignin were used to prepare paper-based laminates.The penetration of a Kraft paper sheet was characterized by a recently introduced,new device measuring the conductivity between both sides of the paper sheet after a drop of resin was placed on the surface and allowed to penetrate the sheet.The main target value measured was the time required for a specific resin to completely penetrate the defined paper sample(“penetration time”).This penetration time generally depends on the molecular weight distribution,the flow behavior and the polarity of the resin which in turn are dependent on the manufacturing conditions of the resin.In the present study,the influences of the three process factors:(1)type of lignin material used for substitution,(2)lignin modification by phenolation and(3)degree of phenol substitution on the penetration times of various lignin-phenolic hybrid impregnation resins were studied using a complete twolevel three-factorial experimental design.Thin laminates made with the resins diluted in methanol were mechanically tested in terms of tensile and flexural strains,and their cross-sections were studied by light microscopy.
基金This work was supported by the National Natural Science Foundation of China(51473024)by University Science Research General Project of Jiangsu Province(16KJD430001)。
文摘Lignin is a natural biopolymer with a complex three-dimensional network, commercially obtained from wasteliquid of paper pulp and bioethanol production, and could be a candidate for preparation of environment-friendlybio-based polyphenol material. In the present work, the demethylated wheat straw alkali lignin (D-Lig), preparedby demethylation of wheat straw alkali lignin (Lig) using an in-situ generated Lewis acid, was used to synthesizebio-based phenol formaldehyde resin adhesive (D-LPF) applied in plywood. Effects of synthetic process’s factors,including lignin substitution for phenol, NaOH concentration and molar ratio of formaldehyde to phenol, on thebonding strength and free formaldehyde content of D-LPF were investigated in detail, and the optimum syntheticprocess of D-LPF was obtained as following: Lignin substitution for phenol 60%, NaOH concentration 5.0% andmolar ratio of formaldehyde to phenol 2.0, and under the optimum reaction condition, the D-LPF presented lower free formaldehyde content (0.18%) and higher bonding strength (2.19 MPa), which was better than those ofcontaining-lignin phenol formaldehyde resin adhesive (LPF). Additionally, the curing behavior of the adhesivewas studied by differential scanning calorimetry (DSC) combined with gel time. It can be obtained that D-LPFresin adhesive had the shortest gel time, and fastest curing rate, compared with those of PF and L-PF resin adhesives. The curing kinetics data was fitted well by Kissinger model using non-isothermal DSC method, and theaverage activation energy value was 85.3 kJ/mol, slightly higher than that of commercial PF resin, while lowerthan that of LPF (90.2 kJ/mol). Finally, based on the analytical results of high temperature fourier transform infrared spectroscopy (FTIR), a possible curing mechanism of D-LPF was proposed.
文摘通过羟甲基化改性增加木质素反应活性,制备性能更好、成本更低且健康环保的环氧树脂基体,采用预浸料成型技术制备碳纤维增强改性木质素基环氧树脂复合材料.通过红外光谱分析羟甲基化木质素的反应活性基团,检测复合材料静曲强度、拉伸强度、弹性模量等力学性能.结果显示:所制备的碳纤维增强改性木质素基环氧树脂复合材料具有优良的力学性能,最佳工艺参数为固化温度150℃,固化压力0.65 MPa,固化时间30 min.
