Study on the Soy Protein-Based Adhesive Cross-Linked by Glyoxal

Based on the ESI-MS and ^(13)C-NMR analysis of the forms of glyoxal in acidic and alkaline solutions,the soy-based adhesive cross-linked by glyoxal was prepared in this work.The results showed that glyoxal existed in water in different forms at different pH levels.Under alkaline conditions,glyoxal transformed to glycolate through the intramolecular disproportionation reaction.Under acidic conditions,although some of glyoxal transformed to glycolate as what happened under alkaline conditions,most of glyoxal molecules existed in the form of fiveor six-membered cyclic ether structure.No ethylene tetraol or free aldehyde group was actually detected under these conditions.Although glyoxal reacted with soy protein under both acidic and alkaline conditions,alkaline conditions were more favorable for the improvement of mechanical performance and water resistance of soybased adhesives than acid conditions.

Effects of Steam Heat-Treatment on Properties of Pinus massoniana Wood and Its Bonding Performance

Pinus massoniana wood was modified by steam heat-treatment at 160℃,180℃,200℃ and 220℃ respectively and effects of the changes of density,pH,surface wettability and apparent morphology of Pinus massoniana heat-treated wood on its bonding performance were studied in this paper.The results showed that Pinus massoniana wood underwent a series of physical and chemical changes during heat-treatment as the the following:(1)The degradation of hemicellulose and cellulose with low degree of polymerization,degradation and migration of the extract resulting in the decline of density and pH of heat-treated Pinus massoniana wood.(2)Brittle fracture occured on the cell wall surface,and the pit collapse,shrink and deformation,resulting in the formation of roughness and porosity on the wood surface.(3)The surface energy decreased with the improvement of temperature,the surface wettability of Pinus massoniana wood treated at 160℃–180℃ was good,while that at 200℃–220℃ showed hydrophobicity.(4)Changes of density,pH,surface roughness and porosity,and wettability resulted in a reduction in the bonding strength and reliability of heat-treated Pinus massoniana wood with MUF resin adhesive.(5)When the temperature was at 160℃–180℃,the better wettability of heat-treated Pinus massoniana wood could guarantee the better bonding performance.

Plasma Treatment Induced Chemical Changes of Alkali Lignin to Enhance the Performances of Lignin-Phenol-Formaldehyde Resin Adhesive

Alkali lignin was processed by plasma and then used in modification of phenol formaldehyde resin in this study.Chemical structural changes of lignin which was processed by plasma as well as bonding strength,tensile property,curing performance and thermal property of the prepared phenol formaldehyde resin which was modified by the plasma processed lignin were analyzed.Results demonstrated that:(1)Alkali lignin was degraded after the plasma processing.The original groups were destroyed,and the aromatic rings collected abundant free radicals and oxygen-containing functional groups like hydroxyls,carbonyls,carboxyls and acyls were introduced into increase the reaction activity of lignin significantly.(2)The introduction of alkali lignin decreased the free formaldehyde content and increased bonding strength and toughness of the prepared phenol formaldehyde resin,especially after the introduction of lignin treated with plasma.(3)The introduction of alkali lignin led to high curing temperature for the prepared phenol formaldehyde resin,but that was reduced by the plasma processed alkali lignin.(4)The introduction of alkali lignin could also increase thermal stability of phenol formaldehyde resin,but that was modified by plasma processed alkali lignin was better than the unprocessed lignin.Based on the results,the plasma processed lignin was used to modify phenol formaldehyde resin,which could increase the strength and toughness of phenol formaldehyde resin significantly.

Self-Cross-Linked Tannin-Aminated Tannin Surface Coatings for Particleboard

Aminated tannins were prepared by reacting mimosa condensed tannin extract with ammonia yielding the substitution of many,if not all of the tannin hydroxyl groups with–NH_(2)groups.A tannin-aminated tannin(ATT)particleboard coating was then prepared by reacting raw tannin extract with aminated tannin extract and thus cross-linking the two by substituting tannin’s hydroxyl groups with the–NH_(2)groups on the aminated tannin to form–NH-bridges between the two.The resulting particleboard coating gave encouraging results when pressed at 180℃for 3 min.Conversely,the system in which tannin was reacted/cross-liked with urea(ATU)by a similar amination reaction did not perform as well as the ATT system,and this even when a higher curing temperature and longer hot press time were used.In particular its water repellence was worse probably due to the presence of urea and such a system with lower reactivity.Nonetheless,substituting the tannin–OHs with the urea–NH_(2)groups appeared to also take place.ATT gave better results than ATU as regards water repellence and mechanical resistance as shown by the cross cut test.The ATT system was shown to be between 95%and 98%biosourced.The difference appeared to be due,by TMA analysis,to the much faster formation of the ATT hardened network leading to a better cross-linked polymer coating.The chemical species formed for both the ATT and ATU system were studied by MALDI ToF and CP MAS^(13)C NMR.

Static Bending Creep Properties of Glass Fiber Surface Composite Wood

To study the static bending creep properties of glass fiber reinforced wood,glass fiber reinforced poplar(GFRP)specimens were obtained by pasting glass fiber on the upper and lower surfaces of Poplar(Populus euramevicana,P),the performance of Normal Creep(NC)and Mechanical Sorptive Creep(MSC)of GFRP and their influencing factors were tested and analyzed.The test results and analysis show that:(1)The MOE and MOR of Poplar were increased by 17.06%and 10.00%respectively by the glass fiber surface reinforced composite.(2)The surface reinforced P with glass fiber cloth only exhibits the NC pattern of wood and loses the MSC characteristics of wood,regardless of the constant or alternating changes in relative humidity.(3)The instantaneous elastic deformation,viscoelastic deformation,viscous deformation and total creep deflection of GFRP are positively correlated with the stress level of the external load applied to the specimen.Still,the specimen’s creep recovery rate is negatively correlated with the stress level of the external load applied to the specimen.The static creep deflection and viscous deformation of GFRP increase with the increase of the relative humidity of the environment.(4)The MSC maximum creep deflection of GFRP increased by only 7.41%over the NC maximum creep deflection,but the MSC maximum creep deflection of P increased by 199.25%over the NC maximum creep deflection.(5)The Burgers 4-factor model and the Weibull distribution equation can fit the NC and NC recovery processes of GFRP well.

Study of Burning Behaviors and Fire Risk of Flame Retardant Plywood by Cone Calorimeter and TG Test

A flame retardant composition was prepared by using phosphoguanidine,guanidine sulfamate,disodium octaborate tetrahydrate and dodecyl dimethyl benzyl ammonium chloride.Veneers were immersed in such flame retardant mixture to prepare plywood.The combustion characteristics and thermal stability of plywood were assessed using a cone calorimeter and TG.Results showed that:(1)High concentration and loading of flame retardant were beneficial for the fire resistance of the plywood.(2)The limiting oxygen index(LOI)and residual mass of plywood processed using the flame retardant was increased by 87.52%and 58.66%compared to those of the untreated plywood,while the average heat release rate(av-HRR),total heat release(THR),effective heat of combustion(EHC),total smoke release(TSR),CO yield(COY),CO_(2) yield(CO_(2)Y)and oxygen consumption were decreased by 44.3%,82.9%,47.0%,86.0%,89.9%,50.1%and 83.1%,respectively.(3)Treated plywood which had a low fire growth index(FGI)displayed a later combustion heat release rate peak and slower flame spread than observed for the untreated material.Combustion of treated plywood displayed a higher fire performance index(FPI),indicating a longer time to ignition.This suggests that burning structures from this material would be subject to a longer time for escape from the structure and would present lower fire risk than similar structures containing treated plywood.(4)TG results demonstrated that the presence of the flame retardant can decrease the pyrolysis temperature for hemicellulose and cellulose,change the decomposition and reaction progress for plywood degradation and promote dehydration carbonization and accelerated charformation.Moreover,the formed char was more stable than that combustion of untreated plywood.(5)The flame retardant contains nitrogen(N),phosphorus(P),boron(B),chlorine(Cl)and guanidine(Gu)compounds.The adhesive also contains N and P compounds.These substances display flame resistance and supplement each other to generate flame retardance than any one used alone.By changing the thermolysis and thermal decomposition processes,the heat release and smoke release from plywood,undergoing combustion was reduced.This controlled generation of combustible substances and promoted dehydration and carbonization to form char.As a result,the flame resistance of plywood was improved significantly.The probability of smoke asphyxia or poisoning death of those trapped in structures containing treated plywood during fire accidents can be decreased dramatically.

An Eco-Friendly Wood Adhesive from Alfalfa Leaf Protein

According to the preparation method commonly used for soy proteinαbased adhesives,alfalfa leaf protein was used as the raw material to prepare alfalfa leaf protein-based wood adhesive.Differential scanning calorimetry analyzer(DSC),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTαIR)were used to characterize properties of the alfalfa leaf protein-based adhesive in this paper.The results revealed the following:(1)Chemical compositions and chemical structures of the alfalfa leaf protein were basically identical with those of the soy protein,both belonging to spherical proteins with the basis and potential for protein adhesives preparation,and spatial cross-linked network structures would be easily formed.(2)Alfalfa leaf protein and soy protein adhesives had the similar curing behaviors,curing temperature of alfalfa leaf protein-based adhesive was relaαtively lower,and the heating rate had minor influence on curing temperature of alfalfa leaf protein-based adhesive.At different heating rates,change tendencies of curing reaction degrees of both the two adhesives were not totally the same.(3)Activation energy and reaction frequency factor of the alfalfa leaf protein-based adhesive were higher than those of soy protein-based adhesive,indicating that the curing reaction of the alfalfa leaf protein adhesive was more difficult than soy protein-based adhesive,thus the dry shear strength and water resistance of alfalfa protein-based adhesive were lower than those of soy protein-based adhesive.Dynamics models of curing reactions of alfalfa leaf protein-based adhesive and soy protein-based adhesive are dα=dt/1.06×10^(13)e^(-97370/RT)(1-α)^(0.938) and dα/dt=1.09×10^(11)e^(-84260/RT) 1-α)^(0.928) respectively.The results of this study will expand the selection of raw materials for protein-based wood adhesives.

A Melamine–Dialdehyde Starch Wood Particleboard Surface Finish without Formaldehyde

Melamine-dialdehyde starch resins used for wood surface finishes have been developed.The reaction of melamine with dialdehyde starch has been shown to occur by FTIR and MALDI ToF spectrometry,with several oligomer species due to the reaction of the two materials being identified,and the resin thermal stability was studied by thermogravimetric analysis.The resins were prepared by two different procedures when it was realized that dialdehyde starch is sensitive to too high a temperature for prolonged times.The melamine-dialdehyde starch resins were applied on particleboard supports as a direct liquid surface finish and a resin-impregnated paper.The surface finishes were tested for adhesion by the cross-cut test,their initial sessile drop contact angle,and the contact angle evolution as a function of time.The best results were obtained by the resins catalyzed by 2% ammonium sulfate and applied to the support surface as a resin-impregnated paper hot pressed for 3 min at 200℃,although the results at 180℃ also looked promising.

Nail Holding Performance of Self-Tapping Screws on Masson Pine and Chinese Fir Dimension Lumbers

Screw connection is a type most commonly applied to timber structures.As important commercial tree species in China,Masson pine and Chinese fir have the potential to prepare wood structures.In this study,the effects of the diameter of the self-tapping screw and the guiding bores on the nail holding performance on different sections of Masson pine and Chinese fir dimension lumbers were mainly explored.The results showed that:(1)The nail holding strength of the tangential section was the maximum,followed by that of the radial section,and that of the cross section was the minimum.(2)The nail holding strength of Masson pine was higher than that of Chinese fir.(3)The nail holding strength grew with the increase in the diameter of self-tapping screws,but a large diameter would lead to plastic cracking of the timber,thus further affecting the nail holding strength.Masson pine and Chinese fir reached the maximum nail holding strength when the diameter of self-tapping screws was 3.5 mm.(4)Under a large diameter of screws,prefabricated guiding bores could mitigate timber cracking and improve its nail holding strength.(5)Prefabricated guiding bores were more necessary for the screw connection of Masson pine.The results obtained could provide a scientific basis for the screw connection design of Masson pine and Chinese fir timber structures.

Schisanhenol ameliorates non-alcoholic fatty liver disease via inhibiting miR-802 activation of AMPK-mediated modulation of hepatic lipid metabolism

Non-alcoholic fatty liver disease(NAFLD),characterized by hepatic steatosis,is a common metabolic liver disease worldwide.Currently,satisfactory drugs for NAFLD treatment remain lacking.Obesity and diabetes are the leading causes of NAFLD,and compounds with anti-obesity and antidiabetic activities are considered suitable candidates for treating NAFLD.In this study,biochemical and histological assays revealed that a natural lignan schisanhenol(SAL)effectively decreased lipid accumulation and improved hepatic steatosis in free fatty acid(FFA)-treated HepG2 cells and high-fat diet(HFD)-induced NAFLD mice.Further,molecular analyses,microRNA(miRNA)-seq,and bioinformatics analyses revealed that SAL may improve NAFLD by targeting the miR-802/adenosine monophosphateactivated protein kinase(AMPK)pathway.Liver-specific overexpression of miR-802 in NAFLD mice significantly impaired SAL-mediated liver protection and decreased the protein levels of phosphorylated(p)-AMPK and PRKAB1.Dual-luciferase assay analysis further confirmed that miR-802 inhibits hepatic AMPK expression by binding to the 3’untranslated region of mouse Prkab1 or human PRKAA1.

Transcriptome-wide analysis of PIP reductase gene family identified a phenylpropene synthase crucial for the biosynthesis of dibenzocyclooctadiene lignans in Schisandra chinensis

Phenylpropenes,such as isoeugenol and eugenol,are produced as defend compounds,floral attractants,and flavor constituents by phenylpropene synthases belonging to the PIP reductase family.Moreover,isoeugenol is proposed to be involved in the biosynthesis of dibenzocyclooctadiene lignans,the main active compounds of Schisandra chinensis(Turcz.)Baill.fruits(SCF).S.chinensis,a woody vine plant,is widely used for its medicinal,horticultural,edible,and economic values.In this study,nine ScPIP genes were identified and characterized from the transcriptome datasets of SCF.The expression profiles revealed that ScPIP genes were differentially expressed during different developmental stages of SCF.Three ScPIPs were selected and cloned as candidate genes encoding phenylpropene synthases according to phylogenetic analysis.ScPIP1 was proved to function as isoeugenol synthase(IGS)and designated as ScIGS1 through in vivo functional characterization in Escherichia coli.Subcellular localization analysis demonstrated that ScIGS1 was localized in both the cytoplasm and nucleus.The three-dimensional(3D)model of ScIGS1 was obtained using homology modeling.Site-directed mutagenesis experiments revealed that the substitution of residues at positions 110 and 113 impacted the product specificity of ScIGS1 and the mutation of Lys157 to Ala abolishing catalytic function.Moreover,the kcat values of mutants were lower than that of ScIGS1 using a deep learning approach.In conclusion,this study provides a basis for further research on PIP reductases and the biosynthetic pathway of dibenzocyclooctadiene lignans.

Complete chloroplast genome sequences of Schisandra chinensis:genome structure,comparative analysis,and phylogenetic relationship of basal angiosperms

Dear Editor, Schisandra chinensis （Turcz.） Baill. belongs to family Schisandraceae. Its fruit called ＂Wu Wei Zi＂ in Chinese is a well-known medicinal material, which is used to treat chronic cough and dyspnea, nocturnal emission, enuresis, etc. （National Pharmacopoeia Committee, 2015）. Except for S. chinensis, many species of Schisandraceae, such as S. sphenanthera, S. lancifolia and S. rubriflora, are used as the original olants of folk medicines.