Lignin as the main component of black liquor is generally employed to modify aliphatic superplasticizer（AFS）. However, the modification effect is hard to evaluate correctly due to the uncertain molecular structure o...Lignin as the main component of black liquor is generally employed to modify aliphatic superplasticizer（AFS）. However, the modification effect is hard to evaluate correctly due to the uncertain molecular structure of lignin and the disturbance from the complexity of black liquor compositions. In this paper, the purified lignin via acid precipitation from straw black liquor is used to modify AFS. The modified AFS named as LAFS for short presents lower molecular mass than AFS. It is assumed that it is due to the single active site of guaiacol segments in lignin by which lignin graft modifies AFS in virtue of methylolation reaction. In order to verify this assumption, guaiacol and dihydro eugenol as the typical segments of lignin macromolecule were selected, respectively, as the simplified model compounds of lignin to modify AFS, and corresponding products are abbreviated in GAFS and DAFS. Both GAFS and DAFS show the lower molecular mass than unmodified AFS. FTIR and TG-DTG analyses prove that lignin is successfully grafted onto AFS. The graft modification of lignin results in a decrease in electrostatic epulsion, but an enhanced steric hindrance. Therefore, although the replacement rate of lignin in LAFS was about 23.3%, the dispersion performance was only slightly affected.展开更多
Hardwood residue（HR）,a byproduct of paper industry,was liquefied by using polyethylene glycol 400（PEG400） and ethylene carbonate（EC） as the liquefaction solvents,and concentrated sulfuric acid as the catalyst to...Hardwood residue（HR）,a byproduct of paper industry,was liquefied by using polyethylene glycol 400（PEG400） and ethylene carbonate（EC） as the liquefaction solvents,and concentrated sulfuric acid as the catalyst to produce bio-polyols（HRLP）,which were used to synthesize polyurethane（PU） foams.The effects of conditions on the properties of HRLP and modified PU foams were investigated and the mechanism of biomass liquefaction was discussed.The optimum conditions of liquefaction were obtained as follows： reaction temperature of 160 °C,reaction time of 60 min,ratio of PEG400/EC of 8：2（w/w）,and ratio of liquid/solid of 5：1（w/w）.The characterization of HRLP modified PU foams suggested that HRLP could partially replace the petroleum polyols to synthesize PU foams.With the increase of the replacement percentage of HRLP,the apparent density and compressive strength of the foams increased firstly,and then decreased.Meanwhile,the thermal stability was improved slightly.展开更多
In this research,an effective method has been developed to bond wood panel adhesives of good performance using biosourced lignin and chitosan as the two main raw materials.Lignin was thus modified by a deep eutectic s...In this research,an effective method has been developed to bond wood panel adhesives of good performance using biosourced lignin and chitosan as the two main raw materials.Lignin was thus modified by a deep eutectic solvent(DES)and maleic anhydride(MA),respectively.Then DES/MA modified lignin was reacted with glyoxal to obtain a newenvironmentally friendly lignin-glyoxal(LG)resin.Next,chitosan was added as a bio-crosslinker to the synthesised LG resin.Finally,the performance of the resulting adhesives was evaluated by bonding plywood panels with them.Fourier Transform Infra Red(FTIR)analysis was used to confirm the chemical modification of lignin as well as the cross-links between lignin and chitosan.13C Nuclear Magnetic Resonance(13C NMR)and Matrix Assisted Laser Desorption Ionization Time of Flight(MALDI TOF)mass spectrometry analysis show that both DES lignin and chitosan readily react and link with glyoxal and indicate the type of structures that are formed.Differential Scanning Calorimetry(DSC)showed that the glass transition temperature(Tg)in pristine lignin decreased after DES treatment but it increases by functionalizing it with maleic anhydride.The DES/MA-modified lignin resin has higher solid content,viscosity and density compared to those prepared with either DES-modified lignin or pristine lignin.The results also indicated that the addition of chitosan to the LG resin prepared had consequent effects on improving the bond strength of the plywood panels as their dry shear strength can meet the required adhesion level of the EN-314 standard.Meanwhile,the dimensional stability of the plywood panels bonded with lignin-glyoxal resin was decreased by the addition of chitosan.Finally,the results suggest that the crosslinking of DES/MA-treated lignin with glyoxal in the presence of chitosan as a bio-crosslinker is a promising approach for developing lignin-based bioadhesives for wood bonding.展开更多
基金Funded by the National Natural Science Foundation of China(No.51778513)the China Ministry of Science and Technology(No.2015CB655101)
文摘Lignin as the main component of black liquor is generally employed to modify aliphatic superplasticizer（AFS）. However, the modification effect is hard to evaluate correctly due to the uncertain molecular structure of lignin and the disturbance from the complexity of black liquor compositions. In this paper, the purified lignin via acid precipitation from straw black liquor is used to modify AFS. The modified AFS named as LAFS for short presents lower molecular mass than AFS. It is assumed that it is due to the single active site of guaiacol segments in lignin by which lignin graft modifies AFS in virtue of methylolation reaction. In order to verify this assumption, guaiacol and dihydro eugenol as the typical segments of lignin macromolecule were selected, respectively, as the simplified model compounds of lignin to modify AFS, and corresponding products are abbreviated in GAFS and DAFS. Both GAFS and DAFS show the lower molecular mass than unmodified AFS. FTIR and TG-DTG analyses prove that lignin is successfully grafted onto AFS. The graft modification of lignin results in a decrease in electrostatic epulsion, but an enhanced steric hindrance. Therefore, although the replacement rate of lignin in LAFS was about 23.3%, the dispersion performance was only slightly affected.
基金Funded by the National Natural Science Foundation of China(Nos.51503041 and 51472050)
文摘Hardwood residue（HR）,a byproduct of paper industry,was liquefied by using polyethylene glycol 400（PEG400） and ethylene carbonate（EC） as the liquefaction solvents,and concentrated sulfuric acid as the catalyst to produce bio-polyols（HRLP）,which were used to synthesize polyurethane（PU） foams.The effects of conditions on the properties of HRLP and modified PU foams were investigated and the mechanism of biomass liquefaction was discussed.The optimum conditions of liquefaction were obtained as follows： reaction temperature of 160 °C,reaction time of 60 min,ratio of PEG400/EC of 8：2（w/w）,and ratio of liquid/solid of 5：1（w/w）.The characterization of HRLP modified PU foams suggested that HRLP could partially replace the petroleum polyols to synthesize PU foams.With the increase of the replacement percentage of HRLP,the apparent density and compressive strength of the foams increased firstly,and then decreased.Meanwhile,the thermal stability was improved slightly.
基金funded by the LERMAB,University of Lorraine,which is supported by a grant overseen by the French National Research Agency(ANR)as part of the“Investissements d’Avenir”program(ANR-11-LABX-0002-001)Lab of Excellence ARBRE.
文摘In this research,an effective method has been developed to bond wood panel adhesives of good performance using biosourced lignin and chitosan as the two main raw materials.Lignin was thus modified by a deep eutectic solvent(DES)and maleic anhydride(MA),respectively.Then DES/MA modified lignin was reacted with glyoxal to obtain a newenvironmentally friendly lignin-glyoxal(LG)resin.Next,chitosan was added as a bio-crosslinker to the synthesised LG resin.Finally,the performance of the resulting adhesives was evaluated by bonding plywood panels with them.Fourier Transform Infra Red(FTIR)analysis was used to confirm the chemical modification of lignin as well as the cross-links between lignin and chitosan.13C Nuclear Magnetic Resonance(13C NMR)and Matrix Assisted Laser Desorption Ionization Time of Flight(MALDI TOF)mass spectrometry analysis show that both DES lignin and chitosan readily react and link with glyoxal and indicate the type of structures that are formed.Differential Scanning Calorimetry(DSC)showed that the glass transition temperature(Tg)in pristine lignin decreased after DES treatment but it increases by functionalizing it with maleic anhydride.The DES/MA-modified lignin resin has higher solid content,viscosity and density compared to those prepared with either DES-modified lignin or pristine lignin.The results also indicated that the addition of chitosan to the LG resin prepared had consequent effects on improving the bond strength of the plywood panels as their dry shear strength can meet the required adhesion level of the EN-314 standard.Meanwhile,the dimensional stability of the plywood panels bonded with lignin-glyoxal resin was decreased by the addition of chitosan.Finally,the results suggest that the crosslinking of DES/MA-treated lignin with glyoxal in the presence of chitosan as a bio-crosslinker is a promising approach for developing lignin-based bioadhesives for wood bonding.
