Sustainable and invisible anti-counterfeiting inks based on waterborne polyurethane and upconversion nanoparticles for leather products

Counterfeit leather products infringe the intellectual property rights of the business,cause enormous economic loss,and negatively influence the business enthusiasm for innovation.However,traditional anti-counterfeiting materials for leather products suffer from complicated fabrication procedures,photobleaching,and high volatile organic com-pound(VOC)emissions.Here,a sustainable and invisible anti-counterfeiting ink composed of waterborne polyure-thane and water-dispersible lanthanide-doped upconversion nanoparticles(UCNPs)featuring ease of preparation,high photostability,non-toxicity,low VOC emissions,and strong adhesion strength for leather products is designed and synthesized.After decorating on the surface of leather products,the obtained patterns are invisible under normal light conditions.Upon irradiation at 808 nm,the invisible patterns can be observed by naked eyes due to the visible light emitted by 808 nm excited UCNPs.Our approach described here opens a new pathway to realize the long-term,stable anti-counterfeiting function of leather products.

Investigations on the general properties of biomass-based aldehyde tanned sheep fur for its selective post-tanning processing

Dialdehyde sodium alginate(DSA)is an alternative chrome-free tanning material for fur production.To obtain satisfactory resultant fur and provide suggestions for the usage of DSA in fur making,the general properties of DSA tanned sheep fur were systematically investigated.The tanning mechanism of DSA was analyzed and it was verified that DSA was mainly combined with collagen fiber by forming Schiff base covalent bonds while supplemented by a small number of hydrogen bonds and ionic bonds.Due to the acid sensitivity of Schiff base structure,DSA tanned fur had poor resistance to acid rinsing but had excellent resistance to washing and good fatliquoring performance.Also,it had good resistances to yellowing and reductant.After being retanned by chrome tanning agent,the fur was capable of enduring a high-temperature dyeing process(68°C for 8 h).Overall,DSA tanned sheep fur had favorable properties under appropriate post-tanning processing conditions to manufacture light-colored or dark-colored fur products with desirable physical properties.

Collagen fiber membrane-derived chemically and mechanically durable superhydrophobic membrane for high- performance emulsion separation

Developing high-performance separation membrane with good durability is a highly desired while challenging issue.Herein,we reported the successful fabrication of chemically and mechanically durable superhydrophobic membrane that was prepared by embedding UiO-66 as size-sieving sites within the supramolecular fiber structure of collagen fiber membrane(CFM),followed by the polydimethylsiloxane(PDMS)coating.The as-prepared CFM/UiO-66(12)/PDMS membrane featured capillary effect-enhanced separation flux and homogeneous porous channels guaranteed high separation efficiency.When utilized as double-layer separation membranes,this new type of composite membranes separated various surfactant stabilized water-in-oil microemulsions and nanoemulsions,with the separation efficiency high up to 99.993%and the flux as high as 973.3 L m−2 h−1.Compared with commercial polytetrafluoro ethylene(PTFE)membrane,the advantage of the double-layer CFM/UiO-66(12)/PDMS membranes in separation flux was evident,which exhibited one order of magnitude higher than that of commercial PTFE membrane.The CFM/UiO-66(12)/PDMS membrane was acid-alkali tolerant,UV-aging resistant and reusable for emulsion separation.Notably,the CFM/UiO-66(12)/PDMS membrane was mechanically durable against strong mechanical abrasion,which was still capable of separating diverse water-in-oil emulsions after the abrasion with sandpaper and assembled as double-layer separation membranes.We anticipate that the combination of CFM and metal organic frameworks(MOFs)is an effective strategy for fabricating high-performance separation membrane with high mechanical and chemical durability.

A deeper exploration of the relation between sulfonation degree and retanning performance of aromatic syntans

It is well‑known that the sulfonation degree(DS)of aromatic syntan is an important factor affecting its retanning performances.But the quantitative relation between DS and syntan property and the influencing mechanism of DS on syntan property are not clarified.In this work,five phenolic formaldehyde syntans(PFSs)with the same polym‑erization degree but varying DS were prepared to investigate the effect of DS on the properties of syntan and crust leather.It was found that the absolute value of zeta potential and the particle size of PFS decreased with increasing DS in aqueous solution.Molecular dynamic simulation results proved that the DS of PFS was a major contributor to electrostatic interaction and hydrogen bonding in the PFS–water system and greatly affected the aggregation and dispersion of PFS in aqueous solution.The PFS with a low DS was prone to aggregate to large particles in aqueous solution because of low intermolecular electrostatic repulsion and less hydrogen bonds and therefore can be used to increase the thickness and tightness of leather.The PFS with a high DS presented a small particle size with more anionic groups in aqueous solution,thereby sharply decreasing the positive charge of leather surface and facilitat‑ing the penetration of the post‑tanning agents into the leather.These results might be scientifically valid for rational molecular design of syntans and more productive use of syntans in leather making.

The improvement of dispersity, thermal stability and mechanical properties of collagen fibers by silane modification: an exploration for developing new leather making technology

The effect of hydrophobic modification on the performances of collagen fibers(CFs)was investigated by using silane coupling agents with different alkyl chains as hydrophobic modifiers.It was found silane could be easily grafted onto CF surface through covalent bonds under 5%water content.This modification led to the transformation of surface wettability of CF from hydrophilic to hydrophobic.Interestingly,the change of surface wettability resulted in substantial improvement of the modified CF properties,presenting well dispersity of collagen fibers,higher thermal stability and enhanced mechanical properties in comparison with natural CF.The degree of improvement mainly depended on the length of alkyl chain in silane.Longer alkyl chain produced strong hydrophobicity and subsequently more superior performances of the modified CF.When the length of alkyl chain increased to 18 carbon atoms,the modified CF possessed durable superhydrophobicity even exposed to aqueous solutions of different pH,UV,and organic solvents,and had excellent thermal and mechanical properties like leather fibers.In general,this work clearly revealed that the properties of CF are closely and positively related to the hydrophobicity,which is suggestive in developing new leather making technology.

Synthesis and application of non- bioaccumulable fluorinated surfactants: a review

Due to negative effects of conventional fluorinated surfactants with long perfluorocarbon chain(C_(x)F_(2x+1),x≥7)like perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS),these conventional long perfluorocarbon chain surfactants have been restricted in many industrial applications.Nowadays,their potential non-bioaccumulable alternatives have been developed to meet the requirements of environmental sustainable development.In this paper,the recent advances of potential non-bioaccumulable fluorinated surfactants with different fluorocarbon chain structures,including the short perfluorocarbon chain,the branched fluorocarbon chain,and the fluorocarbon chain with weak points,are reviewed from the aspects of synthesis processes,properties,and structure-activity relationships.And their applications in emulsion polymerization of fluorinated olefins,handling membrane proteins,and leather manufacture also are summarized.Furthermore,the challenges embedded in the current non-bioaccumulable fluorinated surfactants are also highlighted and discussed with the hope to provide a valuable reference for the prosperous development of fluorinated surfactants.

Toxicity evaluation of collagen hydrolysates from chrome shavings and their potential use in the preparation of amino acid fertilizer for crop growth

Resource utilization of chrome shavings(CS)has attracted a lot of attention from scientists and technologists in leather industry.Especially,the collagen hydrolysates extracted from CS are expected to find potential application values in agricultural field.However,there is no biotoxicity analysis of collagen hydrolysates from CS.Herein,the collagen hydrolysates with different molecular weights were produced from CS by three hydrolysis dechroming methods including alkaline hydrolysis,enzymatic hydrolysis and alkaline-enzymatic synergistic hydrolysis,and the optimal hydrolysis process of CS was designed and conducted.To evaluate their toxicity,the three collagen hydrolysates were formulated into a nutrient solution for zebrafish development.The obtained results indicated that the hydrolysates with low concentrations(less than 0.6 mg/mL)were safe and could promote the development for zebrafish embryos.Furthermore,the three collagen hydrolysates were utilized as organic nitrogen sources and formulated into amino acid water-soluble fertilizers(AAWSF)including alkaline type fertilizer(OH),enzymatic type fertilizer(M)and alkaline-enzymatic type fertilizer(OH-M)for the early soilless seeding cultivation of wheat,soybean and rapeseed.It is worth mentioning that the chromium contents in the prepared AAWSF were less than 10 mg/kg,which is far less than the limit value in the standard(China,50 mg/kg).The growth and development of seedlings(germination rate,plant height,fresh weight of leaves,soluble sugar content and chlorophyll content)were investigated.The corresponding results showed that the growth of seedlings watered with AAWSF was better compared with the other treatments,and the OH-M fertilizer had the best promoting effect on the seedlings growth and development,followed by the M and OH fertilizers.The safe toxicity assessment of the collagen hydrolysates will expand their application scope,and the use of collagen hydrolysates extracted from CS for seedlings growth also provides an effective and reason-able way to deal with the chromium-containing leather solid waste,which is an effective way to realize its resource utilization.

A light-activatable antibiotic with high activation efficiency and uncompromised bactericidal potency in the activated state

Achieving activatable antibiotics represents one promising solution to tackle the occurrence of side effects,one major issue now plaguing antibiotic usage in collagen-based biomaterials.Despite considerable effort,however,rationale design of activatable antibiotics that display high activation efficiency and uncompromised bactericidal potency in the activated state remains difficult.Here,we demonstrate a design principle that helps to address this challenge.This strategy differs from previous attempts by underscoring photolytic removal of a functionality directly conjugated to the pharmacophore of an antibiotic,enabling not only an activation efficiency significantly improved beyond previous light-activatable antibiotics,but also bactericidal activity in the activated state as potent as the parent drug.

Diagnosing the environmental impacts of typical fatliquors in leather manufacture from life cycle assessment perspective

The environmental impacts of typical fatliquors were diagnosed by the life cycle assessment of industrial production and use(post-tanning)processes.Life cycle impact assessment and sensitivity analysis showed that fatliquor and fatliquoring operation were the major contributors to the environmental impacts of post-tanning because a large amount of fatliquors was consumed during fatliquoring operation.The environmental impacts of fatliquors decreased in the following order:chlorinated paraffin(CP)>sulfonated rape oil(SNR)>sulfated rape oil(SR)>phosphated rape oil(PR)>oxidized-sulfited rape oil(OSR).Sulfuric acid,fuming sulfuric acid,and chlorine used for fatliquor modification gave the main contribution to most impact categories for SR,SNR,and CP production,whereas rape oil contributed the most for PR and OSR production.OSR use process reduced the primary energy demand,abiotic depletion potential,and global warming potential by 38.5%,56.0%,and 48.5%,respectively,compared with CP use process.These results suggested that biomass-derived fatliquors,especially oxidized-sulfited and phosphate modified fatiliquors,helped reduce the environmental burdens in leather manufacturing.

Synthesis of sulfonated Sesamum indicum L.seed oil and its application as a fatliquor in leather processing

Fatliquor is an oil-in-water emulsion that improves the physical properties of leather such as tensile strength,flexibility,and softness by lubricating the leather fibres.Sulfonated Sesamum indicum oil was synthesized,characterized,and examined for consideration as a substitute for imported fatliquor in Nigeria.The sulfonation of the oil was confirmed by the significant observations made in the FTIR,1 H NMR,13 C NMR,and 13 C NMR DEPT analysis results.A remarkable difference was observed in the physicochemical properties results of both unsulfonated and sulfonated oils.The sulfonated sesame fatliquor was applied onto goatskin and compared with a commercial sulfated fatliquor in the processing of shoe upper leather using standard methods.The average results for tensile strength,double edge tear,elongation,and softness results for the commercial and synthesized fatliquors are as follows:14.27 N/mm^(2);13.77 N/mm^(2),50.61N;60.11 N,38.06%;54.28%,25.2;25.0.A comparable level of lubrication of the leather treated with the sulfonated Sesamum indicum oil and that treated with the commercial leather fatliquor was revealed by the Sudan IV stain test as well as scanning electron microscopy analysis results.Experimental analyses,therefore,show that the as-synthesized sulfonated Sesamum indicum oil could be considered as a substitute for imported fatliquor in the leather industry.

Effect of cationic monomer structure on the aggregation behavior of amphoteric acrylic polymer around isoelectric point

Amphoteric polymer can be used as retanning agent in leather manufacture. It is particularly useful in chrome-free tanning systems since it can regulate the charge properties of chrome-free leather and enhance the fixation of anionic post-tanning chemicals in leather. However, the aggregation and precipitation of amphoteric polymer retanning agents around the isoelectric point (pI) hinder their wide application. Herein, we synthesized five amphoteric acrylic polymers (AAPs) by free radical copolymerization with acrylic acid and five different cationic acrylic monomers. The effect of cationic monomer structure on the aggregation behavior of AAPs was investigated. The aggregation of AAPs in aqueous solution showed pH and concentration dependence. Light scattering analysis showed that Poly (AA-co-MAPTAC) and Poly (AA-co-DMAPMA) were in the shape of coiled linear flexible chains with small particle size (Rg 7.6 nm and 14.8 nm, respectively) near the pI. However, Poly (AA-co-DAC), Poly (AA-co-DMC) and Poly (AA-co- DMAEMA) were in the shape of hollow spheres and exhibited serious aggregation. Quantum chemical calculations suggested that the amide groups in the cationic monomers MAPTAC and DMAPMA enhanced the nucleophilicity of AAPs. Thus the corresponding AAPs could carry a large number of cationic charges to slow their aggregation when the pH just climbed over the pI. The results are expected to provide theoretical reference for the synthesis and widespread application of AAPs.

Preparation and assistant-dyeing of formaldehyde-free amphoteric acrylic retanning agent

With the enhancement of environmental protection consciousness,concerns have been raised about non-toxic and biodegradable leather retanning agents.According to the European standard 2002/231/EC,the free formaldehyde content of leather products should be less than 150 mg/kg.As one of the retanning agents in the market,the content of free formaldehyde in the Multifunctional retanning agent(MTA)is 372.22 mg/kg and higher than the limit value.In this work,glutaraldehyde as an alternative of formaldehyde was used to modify acrylic polymer and an amphoteric acrylic retanning agent was prepared.Then it was used in retanning process,and its retanning and assistant-dyeing properties were investigated.The results showed that the free formaldehyde content of amphoteric acrylic retanning agent modified with glutaraldehyde was only 4.17mg/kg.Meanwhile,the presence of amino groups in the amphoteric acrylic retanning agent improved the dyeing properties of leather by electrostatic attraction.Compared with the leather treated with anionic acrylic retanning agent,the residual dye concentration of the dyeing effluent of the retanned leather with amphoteric acrylic retanning agent decreased from 17.4mg/L to 10.0mg/L,and the dyed leather had better resistances to friction and water-washing.In addition,the BOD 5/COD value of the wastewater after Mannich base polymer retanning was only 0.32,indicating that the retanning agent was biodegradable.Moreover,the leather retanned with amphoteric acrylic retanning agent had good thermal stability,fullness and physical and mechanical properties.

Polycaprolactone strengthening keratin/ bioactive glass composite scaffolds with double cross-linking networks for potential application in bone repair

In this study, we aimed at constructing polycaprolactone (PCL) reinforced keratin/bioactive glass composite scaffolds with a double cross-linking network structure for potential bone repair application. Thus, the PCL-keratin-BG com-posite scaffold was prepared by using keratin extracted from wool as main organic component and bioactive glass (BG) as main inorganic component, through both cross-linking systems, such as the thiol-ene click reaction between abundant sulfhydryl groups of keratin and the unsaturated double bond of 3-methacryloxy propyltrimethoxy silane (MPTS), and the amino-epoxy reaction between amino groups of keratin and the epoxy group in (3-glycidoxymethyl) methyldiethoxysilane (GPTMS) molecule, along with introduction of PCL as a reinforcing agent. The success of the thiol-ene reaction was verified by the FTIR and 1H-NMR analyses. And the structure of keratin-BG and PCL-keratin-BG composite scaffolds were studied and compared by the FTIR and XRD characterization, which indicated the successful preparation of the PCL-keratin-BG composite scaffold. In addition, the SEM observation, and contact angle and water absorption rate measurements demonstrated that the PCL-keratin-BG composite scaffold has interconnected porous structure, appropriate pore size and good hydrophilicity, which is helpful to cell adhesion, differentiation and prolifera-tion. Importantly, compression experiments showed that, when compared with the keratin-BG composite scaffold, the PCL-keratin-BG composite scaffold increased greatly from 0.91 ± 0.06 MPa and 7.25 ± 1.7 MPa to 1.58 ± 0.21 MPa and 14.14 ± 1.95 MPa, respectively, which suggesting the strong reinforcement of polycaprolactone. In addition, the biomineralization experiment and MTT assay indicated that the PCL-keratin-BG scaffold has good mineralization abil-ity and no-cytotoxicity, which can promote cell adhesion, proliferation and growth. Therefore, the results suggested that the PCL-keratin-BG composite scaffold has the potential as a candidate for application in bone regeneration field.

Chitosan based antibacterial composite materials for leather industry: a review

Chitosan is an amorphous translucent substance with a structural unit similar to the polysaccharide structure of the extracellular matrix,It has good antibacterial,biocompatible,and degradable properties.It has important application value in leather,water treatment,medicine,food and other fields,so chitosan and its modified products have received widespread attention.This article reviewed the preparation methods of chitosan-based antibacterial composites in recent years,including chitosan/collagen,chitosan/graphene,chitosan/tannic acid,and chitosan/polyethylene glycol composite materials,elaborates their modification methods and antibacterial mechanism were reviewed in detail,and its applications in the leather industry as antibacterial auxiliaries and water treatment antibacterial adsorption materials were discussed.Finally,the future development and challenges of chitosan-based composite materials in the leather industry were forecasted.

Preparation of aerogel and its application progress in coatings: a mini overview

Aerogels are predominantly mesoporous,extremely lightweight,low density(∼0.003 g/cm 3)and thermally insulat-ing materials.Over the years,aerogels have gained increasing attention due to their extraordinary properties(light,heat,sound,electricity and force)and application potentials in varieties of fields.Several studies have been carried out regarding aerogel preparation and its applications in coatings on different substrates.In this review,an overview of aerogels preparation and their application progress in coatings of most common substrates is presented.Attention is paid to aerogel coatings of textiles,leather,and substrates other than leather and textiles for special functionali-ties that could address the application progress in coatings.This review will help to inspire scientists and engineers towards novel aerogel materials and technologies to boost the industrial fabrication of flexible advanced materials.

Tanning capacityof Tessmannia burttii extracts:thepotentialeco-friendlytanning agents fortheleatherindustry

In the present study,the tannins from stem and root barks of Tessmannia burttii Harms(Caesalpiniaceae),a plant species abundantly growing in Tanzania and other parts of Africa,were investigated for their suitability in hides tanning.Tannin powder was extracted at selected temperatures(30,50 and 80°C)and the influence of each temperature on the crosslinking capacity was evaluated.The interaction mechanism between hide powder collagen and the tannins was studied by Differential Scanning Calorimetry(DSC),trinitrobenzensulfonic(TNBS)acid assay and amino acid hydrolysis methods.Extraction temperatures showed low influence on crosslinking capacity of the tannins.However,extract obtained at 50°C exhibited best performance in terms of gap size between T onset and T peak.The stem bark extract yield was higher than that from the root bark,but both were within the recommended ranges.The tannin content(61%)of T.burttii stem bark extract was above recommended value(10%),whereas its total phenolic content and total flavonoic content were found to be above that of commercial Acacia mearnsii tannin.The study of cross-linking parameters as a function of pH showed cross-linking to occur via a covalent mechanism at the basic amino groups.However,the bonds were not resistant to acid hydrolysis.The observed interaction mechanism indicated that tannins from stem and root barks of T.burttii belong to the condensed tannin,similar to A.mearnsii(black wattle),a commercial tannin source that was used in this study as a reference.Findings from this study depict that T.burttii extracts are auspicious eco-friendly alternative source of vegetable tannins to overcome the use of chromium salts in the leather industry.

Wrapping collagen-based nanoparticle with macrophage membrane for treating multidrug-resistant bacterial infection

Nowadays,multidrug-resistant(MDR)bacterial infectious diseases has become a thorny issue in the healthcare field.Owning to its intrinsic merits,photodynamic therapy(PDT)shows tremendous strengths in fighting against MDR bacterial infections.However,most photodynamic nanoplatforms exhibit unsatisfactory targeting efficiency towards bacteria and infection site,which may compromise the bactericidal effect of PDT.Herein,we firstly reported a bacteria-targeted collagen-based nanoparticle,named Ce6/Col/MM,for treating methicillin-resistant Staphylococ-cus aureus(MRSA)-infected wound.Ce6/Col/MM was fabricated by wrapping chlorin e6(Ce6)-loaded collagen-based nanoparticles with macrophage membrane(MM),showing excellent photodynamic activity and good biocompat-ibility.In vitro studies demonstrated that Ce6/Col/MM could target to bacteria and then exhibit prominent antibacterial capacity against planktonic MRSA under light irradiation.Furthermore,the treatment of MRSA-infected wound in mice with Ce6/Col/MM plus light illumination resulted in potent bacterial inactivation and accelerated wound healing,accompanied by favorable histological compatibility.Collectively,Ce6/Col/MM with superior targeting ability towards bacteria,effective photodynamic antibacterial potency and minimal safety concerns,might be a powerful bactericidal nanoagent for treating infections caused by MDR bacteria。

Evaluation and improvement of the oxidative stability of leather fatliquors

Fatliquor oxidation may give leather unpleasant odor,and excessive amounts of Cr(VI)and volatile organic com-pounds.The accurate evaluation and improvement of the oxidative stability of fatliquors are of great significance to high-quality leather manufacturing.We proposed a set of practical methods for evaluating the oxidative stability of fatliquors on the basis of oxidation induction time,change in iodine value(∆IV),and change in acid value(∆AV)under accelerated oxidation conditions(at 100°C with 10 L/h of air).Oxidation induction time is a highly sensitive marker for quantifying the oxidative stability of fatliquors,and∆IV and∆AV that are low cost and easy to operate are useful in evaluating the oxidative stability of fatliquors when the oxidation induction time is less than 22 h.The number of double bonds in fatliquors is an important factor affecting oxidative stability.The sulfation modification of fatliquors that greatly reduces double bonds and the addition of antioxidants,especially butylated hydroxyanisole and butylated hydroxytoluene,markedly improve oxidative stability of fatliquors.

Facile and scalable preparation of ZIF-67 decorated cotton fibers as recoverable and efficient adsorbents for removal of malachite green

Recently,metal–organic frameworks(MOFs)have received considerable attention as highly efficient adsorbents for dye wastewater remediation.However,the immobilization of MOFs on the substrate surfaces to fabricate easy recy-clable adsorbents via a facile route is still a challenge.In this work,ZIF-67/cotton fibers as adsorbents for dye removal were prepared in a large-scale using a simple coordination replication method.The successful fabrication of the ZIF-67/cotton fibers was confirmed by FTIR,XRD,XPS,SEM and BET analysis,respectively.As expected,the as-prepared ZIF-67/cotton fibers exhibited high adsorption capacity of 3787 mg/g towards malachite green(MG).Meanwhile,the adsorption kinetics and isotherm obeyed the pseudo-second-order kinetics and Langmuir model,respectively.Moreover,its removal efficiency towards MG was not significantly influenced by the pH and ionic strength of aque-ous solution.Most importantly,the ZIF-67/cotton fibers can remove MG from synthetic effluents,and it can be easily regenerated without filtration or centrifugation processes,with the regeneration efficiency remaining over 90%even after 10 cycles.Additionally,the ZIF-67/cotton fibers presented excellent antimicrobial performance against E.coli and S.aureus.Hence,the distinctive features of the as-prepared ZIF-67/cotton fibers make it promisingly applicable for the colored wastewater treatment.

Leather for flexible multifunctional bio-based materials: a review

Nowadays, diverse leather usage conditions and increasing demands from consumers challenge the leather industry. Traditional leather manufacturing is facing long-term challenges, including low-value threshold, confined applica-tion fields, and environmental issues. Leather inherits all the biomimetic properties of natural skin such as flexibility, sanitation, cold resistance, biocompatibility, biodegradability, and other cross-domain functions, achieving unre-mitting attention in multi-functional bio-based materials. Series of researches have been devoted to creating and developing leather-based flexible multi-functional bio-materials, including antibacterial leather, conductive leather, flame-retardant leather, self-cleaning leather, aromatic leather, and electromagnetic shielding leather. In this review, we provide a comprehensive overview of the commonly used leather-based functional materials. Furthermore, the possible challenges for the development of functional leathers are proposed, and expected development directions of leather-based functional materials are discussed. This review may promote and inspire the emerging preparation and applications of leather for flexible functional bio-based materials.