Application of Cationic Waterborne Polyurethane as Impregnation Material for Microfiber Synthetic Leather Base

A cationic waterborne polyurethane(CWPU) was synthesized and utilized as impregnation material for manufacturing microfiber synthetic leather base,in an attempt to decrease environmental pollution associated with organic solvents and improve simulation degree relative to genuine leather.The alkali resistance of the CWPU and four manufacture methods were investigated.Meanwhile,the dyeing properties of the microfiber synthetic leather base were studied.It was found that the CWPU displayed enough alkali resistance to endure the alkali deweighting process for microfiber synthetic leather base manufacture.In terms of bending length,bending rigidity,compression elasticity ratio and specific compression elasticity ratio of the resulting base,coagulating the impregnated CWPU with sodium hydroxide before steam treatment was the optimal method.The extent of fiber splitting and the handle of the base from this method were both similar to conventional base filled with solvent-based polyurethane(SPU).The dyeing properties of the microfiber synthetic leather base filled with CWPU were also found superior to the one filled with either anionic waterborne polyurethane(AWPU) or SPU.

A Novel Approach to Clean Tanning Technology

Traditional chrome tanning technology is still widely used today. In this technology, chrome shaving as well as chrome contained effluent in tanning and retanning processes is a big issue in the industry. Wet white tanning technology has been gaining in importance in recent years, but in general, the comprehensive performance of chrome-free tanned leather is not comparable with that of chrome tanned leather. In the present work, chrome-free tanning and chrome tanning are combined in a reversed procedure, which produces leather with chrome tanned leather quality without chrome tanned leather waste problems. In this procedure, a special amphoteric organic compound, no pickle, no salt chrome-free tanning agent TWT was used to tan delimed hides （no pickle） making wet white with shrinking temperature at 80-85 ~C. Then, new method called reversed tanning further process the wet white into chrome-tanned crust. In this reversed method, retanning, fatliquoring and coloring processes were carried out before chrome tanning. This technology eliminates chrome waste issue in tanning, shaving, post tanning processes. The chrome contained effluent is only concentrated in the last chrome tanning process. The leather made with this technology has complete conventional chrome-tanned leather quality. In this way, chrome leather quality without chrome waste problems was achieved. So, it is a new clean tanning technology.

Thickness Method for Measuring Hair Density of Rex Rabbit

[Objective] The paper was to characterize hair density by changes in hair thickness under certain pressure.[Method] Tile effects of weight of thickness tester and wafer urea at the hottom of presser foot on measurement results were studied, and the optimal measuring weight and wafer diameter was determined. The measurement results of hair thickness under the ahove condition were compared with the results of manual counting. Meanwhile, the effects of hair length and hair fineness on hair density were analyzed.[Result] The hair density obtained by manual count- ing had consistent change trend with the hair thickness measured under certain conditions. If the length and fineness of hairs were introduced for modification, the correlation between hair thickness and hair density would be better. There were little changes in hair length and finelless of rex rabbit, and their effects on hair thickness could be ignored under general condition. [Conclusion] It is completely feasible to characterize hair den- sity of rex rabbit by hair thickness under pressure.

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.

3D bioprinting of collagen-based materials for oral medicine

Oral diseases have emerged as one of the leading public health challenges globally.Although the existing clinical modalities for restoration of dental tissue loss and craniomaxillofacial injuries can achieve satisfactory therapeutic results,they cannot fully restore the original complex anatomical structure and physiological function of the tissue.3D printing of biological tissues has gained growing interest in the field of oral medicine with the ability to control the bioink component and printing structure for spatially heterogeneous repairing constructs,holding enormous promise for the precise treatment of oral disease.Particularly,collagen-based materials have been recognized as promising biogenic bioinks for the regeneration of several tissues with high cell-activating and biocompatible properties.In this review,we summarize 3D printing methods for collagen-based biomaterials and their mechanisms.Additionally,we highlight the animal sources of collagen and their characteristics,as well as the methods of collagen extraction.Furthermore,this review provides an overview of the 3D bioprinting technology for the regeneration of the pulpal nerve and blood vessels,cartilage,and periodontal tissue.We envision that this technique opens up immense opportunities over the conventional ones,with high replicability and customized function,which can ultimately promote effective oral tissue regeneration.

Wearable synthetic leather-based high-performance X-ray shielding materials enabled by the plant polyphenol-and hierarchical structure-facilitated dispersion

Effective protection against X-ray is the premise of utilizing the X-ray,thus it is critical to develop novel X-ray shielding materials with both low density and high X-ray attenuation efficiency.As the even distribution of high-Z element components is of great significance for increasing the attenuation efficiency of X-ray shielding materials,in this study,the microfiber membrane(MFM),a type of synthetic leather featuring hierarchical structure was chosen to provide large surface area for the dispersion of rare earth(RE)element.Meanwhile,plant polyphenol was utilized to achieve the stable loading and uniform dispersion of the Ce or Er into MFM.Benefiting from the assistance of polyphenol and hierarchical structure of MFM,the even dispersion of RE element was successfully realized.The resultant shielding materials displayed approximately 10%superior X-ray attenuation efficiency compared to that without polyphenol,and an averagely 9%increment in X-ray attenuation efficiency than that without hierarchical structure.Moreover,the obtained composite with a thickness of 2.8 mm displayed superior X-ray shielding performance compared to 0.25 mm lead sheet in 16-83 keV and retained an ultralow density of 1.4 g cm^(-3).Our research results would shed new light on the manufacture of high-performance X-ray shielding materials with excellent X-ray shielding performance.

Multi-functional epoxides cross-linked collagen sponges for tissue engineering scaffolds

With the efficient cross-linking abilities and the flexible regulation abilities to the performances of cross-linked products,the multi-functional aliphatic epoxides were once widely used to cross-link the collagen-based materials in the last century.In present work,the multi-functional epoxides were used to construct and cross-link collagen sponges for tissue engineering scaffolds,which was hoped to board the theoretical system of epoxides and explore their potentials for modern applications.The bi-to tetra-functional epoxides were used to cross-link collagen solutions and establish the gel-like precursors,then using freeze-drying to form the final sponges.The SEM observed that the sponges had shown regular porous structures with a wide range of pore sizes from 160 to 440μm.The sponges had presented the resistance to enzymatic degradation,shape-remaining ability,and reversible compressibility in aqueous environments,which all could be regulated through the functionalities of epoxides.The regulation abilities of multi-functional epoxides on the performances of sponges had been mainly achieved through the cross-linking degrees that the higherfunctionality of epoxides would bring higher cross-linking degree.Such higher cross-linking degrees could enhance the elastic behaviors of gel-like precursors,and improve the compressive strengths and thermal stabilities of sponges.Nevertheless,the multi-functional epoxides had barely affected the safety of collagen sponges at the cellular level according to the results of CCK8 assay and the SEM and CLSM images of L929 fibroblasts cultured on the cross-sections of sponges.

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-sullfited 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 fatiiliquors,helped reduce the environmental burdens in leather manufacturing.

Adsorptive Recovery of Uranium from Nuclear Fuel Industrial Wastewater by Titanium Loaded Collagen Fiber

Effective recovery of UO2+2 from wastewater is essential for nuclear fuel industry and related industries.In this study,a novel adsorbent was prepared by loading titanium(Ti4+) onto collagen fiber(TICF),and its physical and chemical properties as well as adsorption to UO2+2 in nuclear fuel industrial wastewater were investigated.It is found that TICF can effectively recover UO2+2 from the wastewater with excellent adsorption capacity.The adsorption capacity is 0.62 mmol·g-1 at 303 K and pH 5.0 when the initial concentration of UO2+2 is 1.50 mmol·L-1.The adsorption isotherms can be described by the Langmuir equation and the adsorption capacity increases with temperature.The effect of co-existed F on the adsorption capacity for UO2+2 is significant,which can be eliminated by adding aluminum ions as complexing agent,while the other co-existed ions in the solutions,including HCO-3,Cl-,NO-3,Ca2+,Mg2+ and Cu2+,have little effect on the adsorption capacity for UO2+2.The saturated TICF after UO2+2 adsorption can be regenerated by using 0.2 mol·L-1 nitrate(HNO-3) as desorption agent,and the TICF can be reused at least three times.Thus the TICF is a new and effective adsorbent for the recovery of UO2+2 from the wastewater.

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,Crystal Structure and Antimicrobial Activity of a New Ternary Copper(Ⅱ) Complex with p-Chlorophenoxyacetic Acid and 2-Amino Benzothiazole

A novel ternary complex of Cu（pcpa）2（aben）2 （pcpa=p-chlorophenoxyacetic acid anion,aben=2-amino benzothiazole） was synthesized by the reaction of copper acetate,2-amino benzothiazole and p-chlorophenoxyacetic acid.Elemental analysis,IR,UV and X-ray single-crystal diffraction were carried out to determine the composition and crystal structure.The crystal crystalli-zes in the monoclinic system,space group C2/c with a=25.795（4）,b=7.384（3）,c =17.741（6）,β=107.47（2）°,C30H24Cl2CuN4O6S2,Mr=735.09,V=3223.2（18） 3,Z=4,Dc=1.515 Mg/m3,λ（MoKα）=0.71073 ,μ=1.022 mm-1,F（000）=1500,the final R=0.0464 and wR=0.1244.A total of 3218 unique reflections were collected,of which 2228 with I 〉 2σ（I） were observed.The Cu（II） atom is four-coordinated with two carboxylate oxygen atoms of the two pcpa ligands and two nitrogen atoms in thiazole rings of two aben ligands.The analysis of crystal structure shows intermolecular and intramolecular hydrogen bonds between amino-nitrogen atoms of the two aben ligands and carboxylate oxygen atoms of the two pcpa ligands.The antimicrobial properties of the title complex and its two free ligands were tested against representative bacterial and fungal strains.Results show that the antibacterial activity of the complex is less than or equal to that of 2-amino benzothiazole,but for yeasts and moulds,it exhibits excellent inhibitory effect better than that of its two free ligands.

Progress and mechanism of breaking glycoconjugates by glycosidases in skin for promoting unhairing and fiber opening-up in leather manufacture.A review

The glycoconjugates,herein glyco-proteins,existing in animal skins are closely related to the effectiveness of unhairing and fiber opening-up.Glycosidases have been used in leather making processes to reduce pollutants and improve leather quality.But the selection of glycosidases is still blind because the related mechanisms are not well understood yet.Hence,the animal skin structures and glycoconjugates components,the advances in the methods and mechanisms of removing glycoconjugates related to unhairing and fiber opening-up in leather manufacture,the kinds,compositions,structures and functions of typical glycoconjugates in skin are summarized.Then the approaches to destroy them,possible glycosidases suitable for leather making and their acting sites are analyzed based on the recognition of glycoconjugates in skin and the specificities of glycosidases toward substrates.It is expected to provide useful information for the optimization of glycosidases and the development of new enzymes and the cleaner technologies of unhairing and opening up fiber bundles assisted by glycosidases.

Effects of bactericide-protease interactions on the protease-assisted soaking performance

Protease-assisted soaking has received increasing attention in recent years.However,few reports have elaborated on the effect of bactericides,which are used to protect raw hides from microbial damage in the soaking process,on the performance of protease-assisted soaking.Here we investigate the effects of three bactericides,namely,2-methyl-4-isothiazolin-3-one(MIT),sodium propyl 4-hydroxybenzoate(SPHB)and cetyl trimethyl ammonium bromide(CTAB),on the catalytic activity of protease.MIT and SPHB have little effect on the proteolytic activity,whilst CTAB has a negative effect.Fluorescence spectroscopy,synchronous fluorescence spectroscopy,molecular docking and molecular dynamics simulation were used to analyse the bactericide-protease interaction.The data reveal that MIT and SPHB are bound to the non-catalytic sites of protease,whilst CTAB affects the catalytic triad of protease.Furthermore,the protease and bactericides were used alone,simultaneously and sequentially in the soaking process,and their soaking performances were evaluated.The evaluation shows that the use of protease increases the microorganisms in the soaking float,and MIT exhibits the best bactericidal effect.The simultaneous use of protease and MIT effectively inhibits bacteria and scarcely affects the removal of unstructured proteins from hides and the attack on epidermis by protease.These findings contribute to a better understanding of the scientific use of protease with other auxiliaries in soaking.

Essential role of isoelectric point of skin/leather in leather processing

Leather,made from animal hide or skin,is mainly com-posed of collagen.Collagen is a type of fibrous protein.The basic amino acid residues(lysine,arginine and histi-dine)and acidic amino acid residues(glutamic acid and aspartic acid)of the protein confer zwitterionic character to collagen,making the protein positively or negatively charged at different pH values.The pH at which the net charge of collagen becomes zero is defined as isoelectric point(IEP,the value is labeled as pI).

Biomass derived oligosaccharides for potential leather tanning

The global demand for renewable and affordable feed-stocks,combined with the worldwide targets for reduc-ing carbon emissions,is the driving force behind a breakthrough in resource revolution and GreenTech innovations[1].Owing to the vast reserves and short growing cycle,utilizing lignocellulosic biomass as an alternative to petroleum and environmentally friendly feedstock to furnish bioenergy and biomaterials is key to building a more sustainable future.Lignocellulose mainly contains three biopolymers,i.e.,cellulose,hemicellulose and lignin.Over the centuries,utilization of lignocellu-lose has crossed its possible molecular scale ranging from 101 m,as the original matrix,to 10-10 m,as a mono-meric molecule.

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.

Self-driven directional dehydration enabled eco-friendly manufacture of chrome-free leather

Manufacture of eco-friendly chrome-free leather is of great significance for realizing sustainable development of leather industry.Conventional tanning theory believes that it is impossible to convert raw hide to leather without the utilization of cross-linking agent(e.g.,chrome salts)among collagen fibers in raw hide.Here,we developed a brand-new leather manufacture strategy that relied on the composite dehydration media enabled self-driven directional dehydration mechanism to accomplish chrome-free leather manufacture for the first time,rather than followed the classic cross-linking mechanism that has been obeyed for more than one century in leather industry.We demonstrated that the essence of leather making is to regulate the water content in raw hide rather than to form cross-linkage among collagen fibers.The composite dehydration media comprised of anhydrous ethanol and molecular sieves(3A activated zeolite powder)successfully guaranteed continuous self-driven directional dehydration of raw hide by establishing stable water concentration gradient between raw hide and ethanol,which significantly increased the dispersity of collagen fibers in raw hide(with the water content reduced from 56.07%to 5.20%),thus obtaining chrome-free leather that is more ecological than chrome-tanned leather due to the elimination of any tanning agent.The as-prepared chrome-free leather exhibited outstanding tear force(174.86 N),tensile strength(24.56 N mm−2),elongation at break(53.28%)and dry-thermal stability,superior to chrome-tanned leather.Notably,the used compos-ite dehydration media was recyclable for chrome-free leather manufacture,therefore facilitating an environmentally benign leather manufacture process.Our investigations are expected to open up a new conceptual leather making strategy that is applicable for realizing substantial manufacture of eco-friendly leather.

A salt-induced tackifying polymer for enhancing oil recovery in highsalinity reservoirs:Synthesis,evaluation,and mechanism

Polymerflooding is an effective method widely applied for enhancing oil recovery(EOR)by reducing the mobility ratio between theinjected water and crude oil.However,traditional polymers encounter challenges in high salinity reservoirs due to their salt sensitivity.Toovercome this challenge,we synthesized a zwitterion polymer(PAMNS)with salt-induced tackifying property through copolymerization ofacrylamide and a zwitterion monomer,methylacrylamide propyl-N,N-dimethylbutylsulfonate(NS).NS monomer is obtained from thereaction between 1,4-butanesultone and dimethylamino propyl methylacrylamide.In this study,the rheological properties,salt responsiveness,and EOR efficiency of PAMNS were evaluated.Results demonstrate that PAMNS exhibits desirable salt-induced tackifyingcharacteristics,with viscosity increasing up to 2.4 times as the NaCl concentration reaches a salinity of 30×10^(4)mg L^(-1).Furthermore,highvalence ions possess a much stronger effect on enhancing viscosity,manifested as Mg^(2+)>Ca^(2+)>Na^(+).Molecular dynamics simulations(MD)andfluid dynamics experiment results demonstrate that PAMNS molecules exhibit a more stretched state and enhanced intermolecularassociations in high-salinity environments.It is because of the salt-induced tackifying,PAMNS demonstrates superior performance inpolymerflooding experiments under salinity ranges from 5×10^(4)mg L^(-1)to 20×10^(4)mg L^(-1),leading to 10.38–19.83%higher EOR thantraditional polymers.

A collagen-based electrolyte-locked separator enables capacitor to have high safety and ionic conductivity

The conventional liquid electrolytes(LEs) have a high level of ionic conductivity;however, they often suffer from the poor processability and safety risks of potential leakage. Although solid-state electrolytes(SSEs) can solve these inherent problems of LEs, the ionic conductivity of most SSEs is several magnitudes lower than these of LEs. Herein, we report a novel strategy by building liquid ion-transport channels in a solid framework and prepared an electrolyte-locked separator(ELS) using a collagen fiber membrane(CFm). The liquid electrolyte was primarily infiltrated in the smaller voids of CFm, and its ionic conductivity could attain to 9.0×10-3 S cm-1 when the electrolyte absorption(EA) reached up to 112.0%. After centrifuging treatment, the electrolyte retentions(ER) and ionic conductivities of ELS were 108.93% and 8.37×10-3 S cm-1, respectively, which were much higher than those of commercial cellulose separator(CS), exerting excellent liquid-locking performances. In particular, the electrical double-layer capacitors(EDLC) assembled by ELS or CS were characterized and exhibited similar electrochemical performance,demonstrating the satisfactory ability and applicability of ELS for commercial use. In addition, the ELSbased EDLC exhibited favorable flexibility with relative lower loss of capacitance under different angles of bending.

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.