In this study,cellulose nanofibrils(CNF)of high charge(H-P-CNF)and screened size(H-P-CNF-S)were fabricated by increasing the charge of phosphorylated cellulose nanofibrils(P-CNFs)during the pre-treatment step of CNF p...In this study,cellulose nanofibrils(CNF)of high charge(H-P-CNF)and screened size(H-P-CNF-S)were fabricated by increasing the charge of phosphorylated cellulose nanofibrils(P-CNFs)during the pre-treatment step of CNF production.Results show that the H-P-CNF have a significantly higher charge(3.41 mmol g^(-1))compared with P-CNF(1.86 mmol g^(-1)).Centrifugation of H-P-CNF gave a supernatant with higher charge(5.4 mmol g^(-1))and a reduced size(H-P-CNF-S).These tailored nanocelluloses were added to polyvinyl alcohol(PVA)solutions and the suspensions were successfully coated on porous polysulfone(PSf)supports to produce thin-film nanocomposite membranes.The humid mixed gas permeation tests show that CO_(2)permeability increases for membranes with the addition of H-P-CNF-S by 52%and 160%,compared with the P-CNF/PVA membrane and neat PVA membrane,respectively.展开更多
Derived from renewable resources,cellulose based materials are gaining new importance due to their recyclability and biodegradability.Still,one fundamental challenge is their high sensitivity to water.The addition of ...Derived from renewable resources,cellulose based materials are gaining new importance due to their recyclability and biodegradability.Still,one fundamental challenge is their high sensitivity to water.The addition of wet strength agents(WSA)is hence necessary to maintain strength and integrity in humid or wet conditions.In this article,technical lignin was used as WSA in bleached kraft pulp,which was thermopressed to materials with the potential to replace plastics.Cationic starch or a cationic flocculant(PCB 20)was used as a retention aid during the filtration process.The effect of moisture during thermopressing and lignin particle size were also studied.The results showed that elevated moisture during pressing had the biggest impact both on dry and wet strength.Wet strength(tensile test),up to 9 MPa,and wet strength retention,up to 12%,were obtained when moisture was present during pressing.However,the type of flocculant and the size of the lignin particles also had a limited effect on the strength.Wet strength improvement was most probably due to the plasticization of lignin at high temperatures,which was further aided by water.The cellulose-lignin network was strengthened by the melting of lignin,consolidating the network after cooling.The wet stiffness of the cellulose substrates was also increased from 200 to 938 MPa in the presence of lignin,while the elongation was maintained and no embrittlement was observed.The results in this article might hence pave the way for new developments in molded pulp and cellulose based plastics replacement.展开更多
Three-dimensional(3D)printing is a useful technique that allows the creation of objects with complex structures by deposition of successive layers of material.These materials are often from fossil origin.However,effor...Three-dimensional(3D)printing is a useful technique that allows the creation of objects with complex structures by deposition of successive layers of material.These materials are often from fossil origin.However,efforts are being made to produce environmentally friendly materials for 3D printing.The addition of lignocellulosic fibres to a polymer matrix is one of the alternatives to replace,for instance,glass fibres in composites as reinforcing materials.The fields of biocom-posites and 3D printing open innovative application areas for pulp fibres from the pulp and paper industry.In this work,biocomposites of poly(lactic acid)(PLA),poly(hydroxyalkanoate)(PHA)and kraft pulp fibres were prepared in order to find a suitable formulation for filaments for 3D printing.The effect of two different types of kraft fibres(bleached(B)and unbleached(U))and of PHA on the mechanical and thermal properties of the biocomposites was assessed.The addition of 30%kraft fibres to PLA resulted in an increase of the tensile modulus from 3074 to∼4800 MPa.In the case of biocomposites containing PHA(50%PLA/20%PHA/30%kraft)the increase in modulus was more moderate(PLA+PHA+U:3838 MPa,and PLA+PHA+B:3312 MPa).The tensile strength of PLA(66 MPa)increased to 77 MPa in PLA+kraft biocomposites,while a reduc-tion in strength was observed for PLA+PHA+U(43 MPa)and PLA+PHA+B(32 MPa).Filaments prepared with PLA,PHA and bleached and unbleached pulp fibres showed similar printability of complex geometries,demonstrating that unbleached pulp fibres could also be utilized in the preparation of biocomposites with good mechanical performance and 3D printing properties.展开更多
Linseed oil is a common wood treatment agent,which is often blended with naphthenic oil during its application.In this study,we developed new types of linseed oil blends,where the naphthenic oil was substituted with a...Linseed oil is a common wood treatment agent,which is often blended with naphthenic oil during its application.In this study,we developed new types of linseed oil blends,where the naphthenic oil was substituted with alcohols and pyrolysis oil.As miscibility tests revealed,linseed oil can be blended indefinitely with primary alcohols containing three carbon atoms or more.In addition,kinetic stability of three-component-mixtures was found,which comprised linseed oil,alcohol and pyrolysis oil.The developed blends were further tested for their viscosity and rate of solvent evaporation.At last,trial impregnations of wood were done to test this new treatment agent.The uptake of treatment oil and the effect on water repellency varied,and substituting white spirit with propanol and pyrolysis oil showed potential.The latter were miscible with 50%(wt)linseed oil at concentrations of 37.5%1-or 2-propanol and 12.5%pyrolysis oil.Compared with the reference case,treatment with this agent markedly decreased the water-uptake of the wood.Our study hence attributes great potential to the newly developed linseed oil blends,which may introduce additional product characteristics and generate value to byproducts via pyrolysis.展开更多
In this study,the influence of thermoforming conditions on the resulting material properties was investigated,which aimed at developing advanced wood-fiber-based materials for the replacement of fossil plastics.Two bl...In this study,the influence of thermoforming conditions on the resulting material properties was investigated,which aimed at developing advanced wood-fiber-based materials for the replacement of fossil plastics.Two bleached softwood pulps were studied,i.e.,northern bleached softwood Kraft pulp(NBSK)and chemi-thermomechanical softwood pulp(CTMP).The thermoforming conditions were varied between 2–100 MPa and 150–200℃,while pressing sheets of 500 g/m^(2)for 10 min to represent thin-walled packaging more closely.As our results showed,the temperature had a more pronounced effect on the CTMP substrates than on the Kraft pulp.This was explained by the greater abundance of lignin and hemicelluloses,while fibrillar dimensions and the fines content may play a role in addition.Moreover,the CTMP exhibited an optimum in terms of tensile strength at intermediate thermoforming pressure.This effect was attributed to two counteracting effects:1)Improved fiber adhesion due to enhanced densification,and 2)embrittlement caused by the loss of extensibility.High temperatures likely softened the lignin,enabling fiber collapse and a tighter packing.For the Kraft substrates,the tensile strength increased linearly with density.Both pulps showed reduced wetting at elevated thermoforming temperature and pressure,which was attributed to hornification and densification effects.Here,the effect of temperature was again more pronounced for CTMP than for the Kraft fibers.It was concluded that the thermoforming temperature and pressure strongly affected the properties of the final material.The chemical composition of the pulps will distinctly affect their response to thermoforming,which could be useful for tailoring cellulose-based replacements for packaging products.展开更多
基金financial support to the work through the Nano 2021 program(NanoMBE project,number 239172)。
文摘In this study,cellulose nanofibrils(CNF)of high charge(H-P-CNF)and screened size(H-P-CNF-S)were fabricated by increasing the charge of phosphorylated cellulose nanofibrils(P-CNFs)during the pre-treatment step of CNF production.Results show that the H-P-CNF have a significantly higher charge(3.41 mmol g^(-1))compared with P-CNF(1.86 mmol g^(-1)).Centrifugation of H-P-CNF gave a supernatant with higher charge(5.4 mmol g^(-1))and a reduced size(H-P-CNF-S).These tailored nanocelluloses were added to polyvinyl alcohol(PVA)solutions and the suspensions were successfully coated on porous polysulfone(PSf)supports to produce thin-film nanocomposite membranes.The humid mixed gas permeation tests show that CO_(2)permeability increases for membranes with the addition of H-P-CNF-S by 52%and 160%,compared with the P-CNF/PVA membrane and neat PVA membrane,respectively.
基金supported by funding from the Research Council of Norway.
文摘Derived from renewable resources,cellulose based materials are gaining new importance due to their recyclability and biodegradability.Still,one fundamental challenge is their high sensitivity to water.The addition of wet strength agents(WSA)is hence necessary to maintain strength and integrity in humid or wet conditions.In this article,technical lignin was used as WSA in bleached kraft pulp,which was thermopressed to materials with the potential to replace plastics.Cationic starch or a cationic flocculant(PCB 20)was used as a retention aid during the filtration process.The effect of moisture during thermopressing and lignin particle size were also studied.The results showed that elevated moisture during pressing had the biggest impact both on dry and wet strength.Wet strength(tensile test),up to 9 MPa,and wet strength retention,up to 12%,were obtained when moisture was present during pressing.However,the type of flocculant and the size of the lignin particles also had a limited effect on the strength.Wet strength improvement was most probably due to the plasticization of lignin at high temperatures,which was further aided by water.The cellulose-lignin network was strengthened by the melting of lignin,consolidating the network after cooling.The wet stiffness of the cellulose substrates was also increased from 200 to 938 MPa in the presence of lignin,while the elongation was maintained and no embrittlement was observed.The results in this article might hence pave the way for new developments in molded pulp and cellulose based plastics replacement.
基金The authors thank Elopak AS and the Research Council of Norway for funding(NEPP project Grant:309441)。
文摘Three-dimensional(3D)printing is a useful technique that allows the creation of objects with complex structures by deposition of successive layers of material.These materials are often from fossil origin.However,efforts are being made to produce environmentally friendly materials for 3D printing.The addition of lignocellulosic fibres to a polymer matrix is one of the alternatives to replace,for instance,glass fibres in composites as reinforcing materials.The fields of biocom-posites and 3D printing open innovative application areas for pulp fibres from the pulp and paper industry.In this work,biocomposites of poly(lactic acid)(PLA),poly(hydroxyalkanoate)(PHA)and kraft pulp fibres were prepared in order to find a suitable formulation for filaments for 3D printing.The effect of two different types of kraft fibres(bleached(B)and unbleached(U))and of PHA on the mechanical and thermal properties of the biocomposites was assessed.The addition of 30%kraft fibres to PLA resulted in an increase of the tensile modulus from 3074 to∼4800 MPa.In the case of biocomposites containing PHA(50%PLA/20%PHA/30%kraft)the increase in modulus was more moderate(PLA+PHA+U:3838 MPa,and PLA+PHA+B:3312 MPa).The tensile strength of PLA(66 MPa)increased to 77 MPa in PLA+kraft biocomposites,while a reduc-tion in strength was observed for PLA+PHA+U(43 MPa)and PLA+PHA+B(32 MPa).Filaments prepared with PLA,PHA and bleached and unbleached pulp fibres showed similar printability of complex geometries,demonstrating that unbleached pulp fibres could also be utilized in the preparation of biocomposites with good mechanical performance and 3D printing properties.
文摘Linseed oil is a common wood treatment agent,which is often blended with naphthenic oil during its application.In this study,we developed new types of linseed oil blends,where the naphthenic oil was substituted with alcohols and pyrolysis oil.As miscibility tests revealed,linseed oil can be blended indefinitely with primary alcohols containing three carbon atoms or more.In addition,kinetic stability of three-component-mixtures was found,which comprised linseed oil,alcohol and pyrolysis oil.The developed blends were further tested for their viscosity and rate of solvent evaporation.At last,trial impregnations of wood were done to test this new treatment agent.The uptake of treatment oil and the effect on water repellency varied,and substituting white spirit with propanol and pyrolysis oil showed potential.The latter were miscible with 50%(wt)linseed oil at concentrations of 37.5%1-or 2-propanol and 12.5%pyrolysis oil.Compared with the reference case,treatment with this agent markedly decreased the water-uptake of the wood.Our study hence attributes great potential to the newly developed linseed oil blends,which may introduce additional product characteristics and generate value to byproducts via pyrolysis.
文摘In this study,the influence of thermoforming conditions on the resulting material properties was investigated,which aimed at developing advanced wood-fiber-based materials for the replacement of fossil plastics.Two bleached softwood pulps were studied,i.e.,northern bleached softwood Kraft pulp(NBSK)and chemi-thermomechanical softwood pulp(CTMP).The thermoforming conditions were varied between 2–100 MPa and 150–200℃,while pressing sheets of 500 g/m^(2)for 10 min to represent thin-walled packaging more closely.As our results showed,the temperature had a more pronounced effect on the CTMP substrates than on the Kraft pulp.This was explained by the greater abundance of lignin and hemicelluloses,while fibrillar dimensions and the fines content may play a role in addition.Moreover,the CTMP exhibited an optimum in terms of tensile strength at intermediate thermoforming pressure.This effect was attributed to two counteracting effects:1)Improved fiber adhesion due to enhanced densification,and 2)embrittlement caused by the loss of extensibility.High temperatures likely softened the lignin,enabling fiber collapse and a tighter packing.For the Kraft substrates,the tensile strength increased linearly with density.Both pulps showed reduced wetting at elevated thermoforming temperature and pressure,which was attributed to hornification and densification effects.Here,the effect of temperature was again more pronounced for CTMP than for the Kraft fibers.It was concluded that the thermoforming temperature and pressure strongly affected the properties of the final material.The chemical composition of the pulps will distinctly affect their response to thermoforming,which could be useful for tailoring cellulose-based replacements for packaging products.
