A non-isocyanate-based polyurethane(NIPU)wood adhesive was produced from organosolv lignin,which is a bio-sourced raw material,available in large quantities and produced as a by-product of the paper industry.The formu...A non-isocyanate-based polyurethane(NIPU)wood adhesive was produced from organosolv lignin,which is a bio-sourced raw material,available in large quantities and produced as a by-product of the paper industry.The formulation of this new lignin-based NIPU adhesive,which is presented,was chemically characterised by Matrix-Assisted Laser Desorption Ionization Time of Flight(MALDI ToF)mass spectrometry and by Fourier Transform Infra-Red(FTIR)spectrometry analyses.The oligomers formed were determined and showed that the three species involved in the NIPU adhesive preparation were formed by the co-reaction of the three reagents used:lignin,dimethyl carbonate,and hexamethylene diamine.Linear and branched structures were both identi-fied.Mechanical properties of the adhesive were determined using the Automated Bonding Evaluation System(ABES)and internal bond(IB)strength test of the laboratory particleboard bonded with it.The adhesive has shown satisfactory mechanical properties after hot pressing at 230℃.Such a temperature is used industrially in the most modern particleboard factories,but since it is hardly feasible for more conventional wood bonding equipment,the reactivity of the NIPU adhesive was successfully increased with the addition of a small percentage of a silane coupling agent.With the addition of the silane,the proposed NIPU adhesive could also be used at a hot-pressing temperature lower than 200℃.展开更多
The curing process of two biobased adhesives:pine tanninhexamine(TH)and organosolv lignin non-isocyanate polyurethane(NIPU),suitable for interior nonstructural use,were compared with commercial urea-formaldehyde(UF)ad...The curing process of two biobased adhesives:pine tanninhexamine(TH)and organosolv lignin non-isocyanate polyurethane(NIPU),suitable for interior nonstructural use,were compared with commercial urea-formaldehyde(UF)adhesive.Changes in chemical structure before and after the curing process were observed with Fouriertransform infrared spectroscopy(FTIR).The process of adhesive curing was monitored with differential scanning calorimetry(DSC)and the automated bonding evaluation system(ABES).Both DSC and ABES measurements confirmed UF as the fastest and NIPU as the slowest curing adhesive observed.Taking into account the ABES results,the optimal pressing parameters for the TH adhesive would be 4 min at 175℃,for the NIPU adhesive 7 min at 200℃and for the UF 1.5 min at 100℃.Strong linear correlation was observed between mechanical and chemical curing for the UF and NIPU adhesives,whereas lower correlation was observed for the TH adhesive.At all observed adhesives,the DSC measurements were underestimating the curing process determined by ABES in the first part and overestimating it at the end.The underestimation was the most evident with the TH adhesive and the less with the UF adhesive.When comparing the uncured and cured FTIR spectra of all three types of adhesives,a drastic decrease in the characteristic band of-OH groups at 3330–3400 cm^(−1)and an increase in the signal intensity at 2920 cm^(−1)of aliphatic-CH2-groups were observed.For the UF adhesive,the C=O stretching frequency has shifted from 1632 cm^(−1)for uncured to three different bands at 1766,1701,and 1655 cm^(−1)for cured UF.The sharp band for phenolic alcohols at 1236 cm^(−1)of C–O stretch and hydroxyl O–H functional group at 1009 cm^(−1)and at 684 cm^(−1)of uncured TH adhesive diminished during curing,which indicates that a crosslinking reaction occurs via-OH groups.The peak of the C=O group of urethane bridges at 1697 cm^(−1)for uncured NIPU shifted to lower wavenumber at 1633 cm^(−1)for cured NIPU.展开更多
Various crosslinking agents can be added to the formulations of natural-based adhesives for wood bonding in order to achieve better durability and higher strength of the formed joints.In the present study,the effect o...Various crosslinking agents can be added to the formulations of natural-based adhesives for wood bonding in order to achieve better durability and higher strength of the formed joints.In the present study,the effect of hexamethylenediamine(HMDA)addition on the performance of liquefied wood(LW)adhesive for wood bonding is investigated.Differential scanning calorimetry showed the improved thermal stability and crosslinking of the LW adhesive with HMDA.The intensified presence of amide linkages(C–N bonds)was found in LW+HMDA with attenuated total reflection Fourier transform infrared spectroscopy.Analysis of the bonded joints using an automated bonding evaluation system showed that a higher press temperature resulted in stronger bonds for both types of adhesives.Moreover,the addition of HMDA to LW adhesive improved the bond strength of the joints and accelerated the crosslinking of the adhesive.However,with a tensile shear strength of(6.76±2.16)N×mm^(−2)(for LW)and(6.89±2.10)N×mm^(−2)(for LW+HMDA),both adhesives were found to be unsuitable for interior non-structural use.In addition,the acidity of LW resulted in relatively high wood failure(70%)in the adhesive joints tested.Improved crosslinking of LW with HMDA was reflected in improved resistance of LW+HMDA adhesive joints to water degradation.In conclusion,HMDA is a promising additive for improving the adhesive performance of LW adhesives.展开更多
As additive manufacturing technologies advance,new opportunities are opening up for their application in the furniture industry.Wood remains one of the leading raw materials in the furniture industry;therefore,possibl...As additive manufacturing technologies advance,new opportunities are opening up for their application in the furniture industry.Wood remains one of the leading raw materials in the furniture industry;therefore,possible options for combining it with 3D printing have been researched.The bonding of 3D-printed polymer parts with wood or 3D printing with wood-plastic composites is already known,but in our research we attempted to directly 3D print polylactic acid(PLA)on wood surfaces.The effect of printing parameters,as well as the surface preparation of wood on the shear strength of the bond between wood and on-printed material was tested.Microscopic images of cross-sections of samples were analyzed.The results show that with a lower initial layer thickness(0.1 mm),a higher printing temperature(220℃),and with the use of polyvinyl acetate(PVAc)primer on the wood surface before 3D printing,a higher bond strength(5.4 MPa)was achieved,but the values for the bond strength remain low compared to the conventional bonding of wood to wood with PVAc adhesive(around 10 MPa).Microscopy studies revealed barely visible penetration of PLA into the lumens of the wood cells.However,the PVAc adhesive used as primer penetrated more into the cell lumens and served as interface layer between deposited melted PLA and the wood,thus creating stronger joints.展开更多
基金This research was financed by the ERA-CoBioTech project WooBAdh(Environmentally-friendly bioadhesives from renewable resources).The University of Ljubljana,Biotechnical Faculty was financed by the Slovenian Ministry of Education,Science and Sport and the Slovenian Research Agency within the framework of program P4-0015.The LERMAB was financed by the French Agence Nationale de la Recherche(ANR)as part of the laboratory of excellence(LABEX)ARBRE.
文摘A non-isocyanate-based polyurethane(NIPU)wood adhesive was produced from organosolv lignin,which is a bio-sourced raw material,available in large quantities and produced as a by-product of the paper industry.The formulation of this new lignin-based NIPU adhesive,which is presented,was chemically characterised by Matrix-Assisted Laser Desorption Ionization Time of Flight(MALDI ToF)mass spectrometry and by Fourier Transform Infra-Red(FTIR)spectrometry analyses.The oligomers formed were determined and showed that the three species involved in the NIPU adhesive preparation were formed by the co-reaction of the three reagents used:lignin,dimethyl carbonate,and hexamethylene diamine.Linear and branched structures were both identi-fied.Mechanical properties of the adhesive were determined using the Automated Bonding Evaluation System(ABES)and internal bond(IB)strength test of the laboratory particleboard bonded with it.The adhesive has shown satisfactory mechanical properties after hot pressing at 230℃.Such a temperature is used industrially in the most modern particleboard factories,but since it is hardly feasible for more conventional wood bonding equipment,the reactivity of the NIPU adhesive was successfully increased with the addition of a small percentage of a silane coupling agent.With the addition of the silane,the proposed NIPU adhesive could also be used at a hot-pressing temperature lower than 200℃.
基金the ERA-CoBioTech project WooBAdh(Environmentally-friendly bioadhesives from renewable resources)and by the Slovenian Ministry of Education.Science and Sport and the Slovenian Research Agency within the framework of the program P4-0015.
文摘The curing process of two biobased adhesives:pine tanninhexamine(TH)and organosolv lignin non-isocyanate polyurethane(NIPU),suitable for interior nonstructural use,were compared with commercial urea-formaldehyde(UF)adhesive.Changes in chemical structure before and after the curing process were observed with Fouriertransform infrared spectroscopy(FTIR).The process of adhesive curing was monitored with differential scanning calorimetry(DSC)and the automated bonding evaluation system(ABES).Both DSC and ABES measurements confirmed UF as the fastest and NIPU as the slowest curing adhesive observed.Taking into account the ABES results,the optimal pressing parameters for the TH adhesive would be 4 min at 175℃,for the NIPU adhesive 7 min at 200℃and for the UF 1.5 min at 100℃.Strong linear correlation was observed between mechanical and chemical curing for the UF and NIPU adhesives,whereas lower correlation was observed for the TH adhesive.At all observed adhesives,the DSC measurements were underestimating the curing process determined by ABES in the first part and overestimating it at the end.The underestimation was the most evident with the TH adhesive and the less with the UF adhesive.When comparing the uncured and cured FTIR spectra of all three types of adhesives,a drastic decrease in the characteristic band of-OH groups at 3330–3400 cm^(−1)and an increase in the signal intensity at 2920 cm^(−1)of aliphatic-CH2-groups were observed.For the UF adhesive,the C=O stretching frequency has shifted from 1632 cm^(−1)for uncured to three different bands at 1766,1701,and 1655 cm^(−1)for cured UF.The sharp band for phenolic alcohols at 1236 cm^(−1)of C–O stretch and hydroxyl O–H functional group at 1009 cm^(−1)and at 684 cm^(−1)of uncured TH adhesive diminished during curing,which indicates that a crosslinking reaction occurs via-OH groups.The peak of the C=O group of urethane bridges at 1697 cm^(−1)for uncured NIPU shifted to lower wavenumber at 1633 cm^(−1)for cured NIPU.
文摘Various crosslinking agents can be added to the formulations of natural-based adhesives for wood bonding in order to achieve better durability and higher strength of the formed joints.In the present study,the effect of hexamethylenediamine(HMDA)addition on the performance of liquefied wood(LW)adhesive for wood bonding is investigated.Differential scanning calorimetry showed the improved thermal stability and crosslinking of the LW adhesive with HMDA.The intensified presence of amide linkages(C–N bonds)was found in LW+HMDA with attenuated total reflection Fourier transform infrared spectroscopy.Analysis of the bonded joints using an automated bonding evaluation system showed that a higher press temperature resulted in stronger bonds for both types of adhesives.Moreover,the addition of HMDA to LW adhesive improved the bond strength of the joints and accelerated the crosslinking of the adhesive.However,with a tensile shear strength of(6.76±2.16)N×mm^(−2)(for LW)and(6.89±2.10)N×mm^(−2)(for LW+HMDA),both adhesives were found to be unsuitable for interior non-structural use.In addition,the acidity of LW resulted in relatively high wood failure(70%)in the adhesive joints tested.Improved crosslinking of LW with HMDA was reflected in improved resistance of LW+HMDA adhesive joints to water degradation.In conclusion,HMDA is a promising additive for improving the adhesive performance of LW adhesives.
文摘As additive manufacturing technologies advance,new opportunities are opening up for their application in the furniture industry.Wood remains one of the leading raw materials in the furniture industry;therefore,possible options for combining it with 3D printing have been researched.The bonding of 3D-printed polymer parts with wood or 3D printing with wood-plastic composites is already known,but in our research we attempted to directly 3D print polylactic acid(PLA)on wood surfaces.The effect of printing parameters,as well as the surface preparation of wood on the shear strength of the bond between wood and on-printed material was tested.Microscopic images of cross-sections of samples were analyzed.The results show that with a lower initial layer thickness(0.1 mm),a higher printing temperature(220℃),and with the use of polyvinyl acetate(PVAc)primer on the wood surface before 3D printing,a higher bond strength(5.4 MPa)was achieved,but the values for the bond strength remain low compared to the conventional bonding of wood to wood with PVAc adhesive(around 10 MPa).Microscopy studies revealed barely visible penetration of PLA into the lumens of the wood cells.However,the PVAc adhesive used as primer penetrated more into the cell lumens and served as interface layer between deposited melted PLA and the wood,thus creating stronger joints.
