| Native lignins were separated from bamboo using phase separation system in this study. Alkaline lignins?ALs? were isolated from cooking black liquor. The structure features of bamboo lignophenols?LPs? and ALs were analyzed and compared; LPs and ALs were soaked into papers and studied the effect of different lignins to papers. LPs and alkaline ALs were respectively modified by hydroxymethylation to study and compare the potential of two lignins then added them into papers and observed the effect of them to papers. The results are listed as follows. The results showed that the weight-average molecular weight of bamboo LPs?circa 4000? were larger than that of alkaline lignophenols?circa 2000?, dispersing proportion of the molecular weight of LPs?Mw/Mn=1.43? was smaller than that of the latter?Mw/Mn=2.31?. The FT-IR spectra of bamboo LPs had the absorption of combined cresols at 815 cm-1. The content of phenolic hydroxyl group and amount of combined cresols in bamboo LPs were calculated to be 1.2 mol/C9 and 0.8 mol/C9, respectively, by using 1H-NMR spectra. The atomic force microscopy?AFM? images showed that ALs formed agglomerates and layered supramolecular assemblies, and LPs maintained the original spatial structure of lignin and produced relative linear type lignin based polymer. Dynamics light scattering?DLS? analyzed the average dimension of the LPs aggregates was smaller than 1000 nm,and that of ALs was larger than 1000 nm when the solution was at p H=8, 0.1g/L. In the HSQC spectra, the prominent correlating signals observed were ?-O-4 aryl ether linkages, ?-5 linkages, ?-? linkages, ?-O-4 linkages and ?-1 aryl ether linkages in the side-chain regions of LPs,but only ?-O-4 aryl ether linkages and ?-? linkages were observed in the side-chain regions of ALs. In the aromatic region of LPs, besides of the prominent correlating signals of syringyl?S?, guaiacyl?G? and p-hydroxyphenyl?H? lignin units, signals of oxidized ?-ketone structures S?, oxidized ?-ketone structures G?, cinnamyl aldehyde end-groups?J?, tricin?T?, p-coumarate?p-CA? and ferulate?FA? were also observed. In the aromatic region of ALs, signal of oxidized ?-ketone structures G? was not observed and there was signal of p-hydroxycinnamyl alcohol end groups?F?. Minor signal of phenyl glycoside was discovered in the 2D?HSQC? Nuclear Magnetic Resonance?2DHSQC NMR? spectra of LPs and ALs. In the 2DHSQC-NMR spectra of LPs, the obvious signal of methyl of p-cresol was found at ?C/?H 21.0/2.30 ppm. The S/G?syringyl/guaiacyl? ratios were estimated to be 3.9 and 6.4 for LPs and ALs in the 2DHSQC-NMR spectra.The same concentrations of LPs acetone solution and ALs dioxane solution?10g/L? were used to soak hardwood pulp fiber sheets?80 g/m2?. The properties on tightness of sheets soaked with LPs acetone solution declined from 0.51 g/cm3 to 0.49 g/cm3, tensile index of sheets increased from 15.00N*m/g to16.80N*m/g, tear index increased from 2.45 m N*m2/g to 3.10 m N*m2/g, folding number was the same and burst index increased from 0.87 k Pa*m2/g to 1.10 k Pa*m2/g. But the properties on tightness of sheets soaked with ALs dioxane solution declined from 0.51 g/cm3 to 0.46 g/cm3, tensile index of sheets declined from 15.00N*m/g to13.75N*m/g, tear index increased from 2.45 m N*m2/g to 2.55 m N*m2/g, folding number was the same and burst index increased from 0.87 k Pa*m2/g to 0.90 k Pa*m2/g. With the concentrations of LPs acetone solution increasing, the degree of improvement of hardwood pulp fiber sheets strength was increased. When the concentrations of LPs acetone solution reached to 80g/L, the strength of hardwood pulp fiber sheets was the best, tightness of sheets was 0.56g/cm3,tensile index was 31.75N*m/g,tear index was 4.70 m N*m2/g,folding number was six times, burst index was 2.09 k Pa*m2/g.The function and dispersion between LPs and hardwood pulp fiber in the sheets soaked by 80g/L LPs acetone solution were characterized by Attenuated Total Reflectance Fourier Transform Infrared spectroscopy?ATR-FTIR?, X-ray Photoelectron Spectroscopy?XPS? and Scanning Electron Microscopy?SEM?, the results indicated that LPs uniformly adhered on the pulp fibers, but no chemical bond has been found between them. The O/C ratio on the surface of the sheet fibers was obviously decreased from 0.52 to 0.29. Peak area of C1 which was from lignin and extractive increased from 15.65% to 57.57%. Peak area of C2 which was from carbohydrate decreased 42.66%. But dispersion between ALs and hardwood pulp fiber in the sheets soaked by 80g/L ALs dioxane solution was characterized by SEM and it indicated that ALs non-uniformly adhered on the pulp fibers. Compare the porosity of three kinds of sheets, that of hardwood pulp fiber sheet?0.68%? was larger than that of softwood pulp fiber sheets?0.66%? and that of softwood pulp fiber sheets was minimize?0.64%?. Meanwhile, recycled softwood pulp fiber sheets and softwood pulp fiber sheets?80 g/m2?were soaked with the 80g/L LPs acetone solution, more obvious improvement in the physical strength was found in sheets made up of hardwood pulp fibers but both of physical strength had been improved when compared with original sheets.LPs and ALs were respectively modified by hydroxymethylation. With m?lignins?: m?methanal? was from 1.35:1 to 5:1, yield of modified LPs was from 75.37% to 75.40% and that of modified ALs was from 57.54% to 84.88%. FT-IR spectras of LPs and ALs showed that the absorption of hydroxy at 3387 cm-1, the absorption of methylene at 2936 cm-1 and 2836 cm-1 and the absorption of C-O in hydroxymethyl at 1 043 cm-1 were obviously increased. It indicated that LPs and ALs were successfully introduced amounts of hydroxymethyl functional groups. Modified LPs and ALs, which were produced with m?lignins?: m?methanal? =3:1, were tested by GPC. The weight-average molecular weight of modified LPs?Mw=8267g/mol? was larger than that of modified ALs?Mw=1580g/mol?, and dispersing proportion of the molecular weight of the former?Mw/Mn=5.47? was much larger than that of the latter?Mw/Mn=1.62?. In the HSQC spectra of modified lignins, the signal of hydroxymethyl was at ?C/?H 60/4.55 ppm. Compared two kinds of modified lignins by using 13C-NMR quantitative calculation. The integral of the peak at ? 142 and 127.7 ppm to that of the C9 unite at ?100-160 ppm were 0.032 and 0.191 in the 13C-NMR spectra of LPs. The integral of the peak at ? 142 and 127.7 ppm to that of the C9 unite at ?100-160 ppm were 0.060 and 0.061 in the 13C-NMR spectra of ALs. The content of the hydroxymethyl group in LPs was larger than that in ALs after hydroxymethylation. The same concentrations of modified LPs acetone solution and modified ALs dioxane solution?10g/L? were used to soak hardwood pulp fiber sheets?80 g/m2?. The properties on tightness of sheets soaked with modified LPs acetone solution declined to 0.45 g/cm3, tensile index of sheets increased to 19.50N*m/g, tear index increased to 4.10 m N*m2/g, folding number increased to 3 times and burst index increased to 1.20 k Pa*m2/g. However the tightness of sheets soaked with modified ALs dioxane solution declined to 0.47 g/cm3, tensile index of sheets declined to 14.10N*m/g, tear index increased to 2.98 m N*m2/g, folding number was same and burst index increased to0.90 k Pa*m2/g. The ability of modified LPs to enhance the strength of sheets was improved but the effect of modified ALs to the strength of sheets was still negative.Layer-by-layer?LBL? self-assembly of LPs and Cu2+ were applied to the hydrophobic modification of pulp fiber sheet surface. The results showed that with the increase o f self-assembly layers, the contact angle of fiber surface increased, when the fiber surface has been modified with four self-assembly layers, the contact angle of fiber surface reached the maximum, hard pulp fiber sheet surface contact-angle reached 110.00° and soft pulp fiber sheet surface contact-angle reached 105.50°, which meant that the excessively hydrophilic fiber surface was modified to a hydrophobic one in a certain degree. |
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