Thermal Analysis and Identification of Potential Fire-proof Energy Building Material Based on Artificial Leather

Artificial leather fire-proof materials have obtained a good market due to stable production quality and low production price. Three kinds of artificial leather materials(polyvinyl chloride artificial leather(PVC), polyurethane artificial leather(PU) and polyurethane/polyvinyl chloride artificial leather(PU/PVC)) have been investigated, and then seven analysis methods were introduced to identify the materials. Thermo-gravimetric analysis indicated the materials had fine thermal stability. Fire-proof testing revealed the artificial leather materials had good flame retardancy, which could improve the applicability of fire-proof building materials. Tearing examination results indicated that there was a clear distinction between PVC and PU. The PU displayed significant differences compared with PVC or PVC/PU through pH indicator to observe the color of the pyrolysis gas aqueous solution. The dissolution tests results showed that cyclohexanone, dichloromethane and dimethylformamide(DMF) were efficient solvents that could be used for identifying PVC, PU and PU/PVC. The ATR-FTIR, a way to provide the high discriminating ability for identifying artificial leathers, indicated that the artificial leathers had different infrared characteristic peaks. In addition, the main compositive materials of the artificial leathers could be inferred by the relative contents analysis of N and Cl in artificial leathers.

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.

Characteristics of natural biopolymers and their derivative as sorbents for chromium adsorption:a review

Chromium is widely used in industry,and improper disposal of wastewater and industrial residues containing excessive chromium can contaminate water and soil,endangering both environmental and human health.Natural biopolymers and their derivatives have been investigated for removal of chromium(Cr)from wastewater.Cellulose,lignin,tannin,chitin,chitosan,and polypeptides are abundant in nature,and have high potential as adsorbents due to their easy access,low cost,and the recyclability of the captured heavy metals.In order to improve their mechanical strength,recyclability,specific surface area,binding site number,and adsorption rate as adsorbents,native materials have also been modified.This review discusses the source of chromium contamination and the main species of interest,as well as their toxicity.The structures of the aforementioned biopolymers were analyzed,and the adsorption mechanism of chromium and the main influencing factors on this process are discussed.The modification methods of various adsorbents and their adsorption effects on chromium are also detailed,and the developmental direction of research on the use of biopolymer adsorption remediation to control chromium contamination is discussed.

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.

An exploration of enhancing thermal stability of leather by hydrophilicity regulation:effect of hydrophilicity of phenolic syntan

Effect of retanning on the thermal stability of leather is eliciting increasing attention. However, the relationship between the hydrophilicity of retanning agents and the heat resistance of leather and the corresponding mechanism remain unclear. Herein, phenolic formaldehyde syntans (PFSs) were selected as models to explore the effect of the hydrophilicity of retanning agents on the thermal stability of retanned leather. The thermal stability of leather was closely correlated to the hydrophilic group content (sulfonation degree) of PFSs. As the sulfonation degree increased, the water absorption rate of PFSs and their retanned leathers decreased, whereas the thermal stability of leather increased. Molecular dynamics simulation results proved that the introduction of PFSs could reduce the binding ability of collagen molecules with water and thus decreased the water molecules around the PFS-treated collagen. These results may provide guidance for the tanners to select retanning agents reasonably to improve the thermal stability of leather.

Advances on the modification and biomedical applications of acellular dermal matrices

Acellular dermal matrix(ADM)is derived from natural skin by removing the entire epidermis and the cell components of dermis,but retaining the collagen components of dermis.It can be used as a therapeutic alternative to“gold standard”tissue grafts and has been widely used in many surgical fields,since it possesses affluent predominant physicochemical and biological characteristics that have attracted the attention of researchers.Herein,the basic science of biologics with a focus on ADMs is comprehensively described,the modification principles and technologies of ADM are discussed,and the characteristics of ADMs and the evidence behind their use for a variety of reconstructive and prosthetic purposes are reviewed.In addition,the advances in biomedical applications of ADMs and the common indications for use in reconstructing and repairing wounds,maintaining homeostasis in the filling of a tissue defect,guiding tissue regeneration,and delivering cells via grafts in surgical applications are thoroughly analyzed.This review expectedly promotes and inspires the emergence of natural raw collagen-based materials as an advanced substitute biomaterial to autologous tissue transplantation.

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.

Interaction between retanning agents and wet white tanned by a novel bimetal complex tanning agent

A promising and practical chrome-free tanning system has been developed based on a novel Al–Zr bimetal complex tanning agent.However,to achieve satisfactory resultant leather,the retanning process that is compatible with this emerging tannage needs to be investigated systematically.This paper aims to explore the interaction between the bimetal complex tanned wet white and retanning agents.The isoelectric point(pI)of wet white was 7.2,which was nearly the same as wet blue.The electropositivity of wet white was even higher than that of wet blue during post-tanning processes,resulting in higher uptake rate of retanning agents.The distribution of various retanning agents in wet white was analyzed by pI measurement of layered leather and fluorescent tracing technique.The retanning agents were unevenly distributed throughout the cross-section,which might be an important restriction factor in obtaining satisfactory organoleptic properties of the crust leather.This fact is mainly due to the strong electrostatic interaction between anionic retanning agents and wet white.Applying a high dosage of multiple retanning agents in a proper sequence of addition benefited the full penetration of retanning agents in leather matrix and thus improved the organoleptic properties of crust leather.This work provides guidance for optimizing retanning process of the wet white leather.

Does weight loss affect the center of pressure of children with obesity: a follow-up study

Background:Children with obesity were found to show the greater postural instability compared to the normal-weighted children.However,it’s still unclear if their altered postural control ability would recover towards normal pat-tern after weight loss.The purpose of this study was to investigate the effect of weight loss on the center of pressure(COP)for obese children.Method:Totally 147 children were conducted a follow-up study in three years.A total number of 22 participants aged 7-13 years were recruited for their remission of obesity problem after 36 months.Their dynamic plantar pressure data were collected by Footscan pressure plate.The normalized time of four sub-phases,displacements and velocities of COP in anterior-posterior(AP)and medial-lateral(ML)directions were calculated to perform the Kolmogorov-Smirnov test and paired sample t test for statistical analyses.Results:After weight loss,children’s normalized time of forefoot contact phase(FFCP)increased significantly,and their duration of flat foot phase(FFP)decreased significantly.They also exhibited the more medial and posterior ori-entated COP path after weight loss.In ML-direction,the COP displacement during FFP and FFPOP increased,and the COP velocity during FFPOP increased.In AP-direction,COP velocity during FFP and FFPOP increased.Conclusions:The findings indicated that weight loss would have effects on the COP characteristics and postural stability for obese children.COP trajectory can provide essential information for evaluating foot function.The findings may be useful for obese children,medical staff,and healthcare physician.

Factors affecting mass transfer of protease in pelt during enzymatic bating process

Bating pelt with protease is an important process,which removes unwanted non-collagenous proteins from the pelt and moderately disperse hide collagen network.However,the grain surface,may be excessively hydrolyzed during bating due to the longer retention time of protease in the grain than in the middle layer caused by the low mass transfer rate of protease in pelt.Here,the effects of protease dosage,common auxiliaries and molecular weight of protease on protease transfer during bating were investigated so that we can find the key points to avoid excessive collagen damage,particularly in the grain.Observably,increasing protease dosage led to faster protease transfer and softer leather,but along with more considerable grain damage.Using penetrating agent JFC(fatty alcohol-polyoxyethylene ether)and ammonium sulfate enhanced protease transfer and simultaneously alleviated collagen damage due to the decrease in interfacial tension and electrostatic attraction between protease and pelt,respectively.Additionally,proteases with lower molecular weight transferred faster in pelt,which suggests that a potential strategy to solve the conflict between the mass transfer and the reaction of protease in pelt might be to produce/employ smaller bating proteases.