Sustainable metal-free leather manufacture via synergistic effects of triazine derivative and vegetable tannins

Restrictions on heavy metals,especially chromium,have encouraged alternative tanning systems that can reduce environmental and human health risks from conventional chrome-based tanning.In this work,metal-free combination tanning was developed by using vegetable tannins and a triazine-based syntan containing active chlorine groups(SACC).Specifically,the relationship between leather performance(e.g.,hydrothermal stability and organoleptic properties)and technical protocols(e.g.,types and dose of tannins)was systematically established.The optimized protocol involving a unique procedure(i.e.,10%SACC pre-tanning,shaving,and 25%wattle tanning)endowed the leather with high shrinkage temperature(~92℃)and met the Chinese standards for shoe upper leather(QB/T 1873-2010).Our method not only produces zero chrome-containing solid wastes,but also uses~75%less tannin for leather manufacture.The excellent leather performance was ascribed to the synergistic effects,where SACC and wattle diffused into collagen fibrils and may bind to collagen via covalent,hydrogen and ionic bonding,locking the hierarchical structure of collagen from microfibrils to fiber bundles.Moreover,we summarized these findings and proposed a diffusion-binding-locking mechanism,providing new insights for current tanning theory.Together with the biodegradable spent tanning liquor,this approach will underpin the development of sustainable leather manufacture.

Anionic surfactant sulfate dodecyl sodium (SDS)-induced thermodynamics and conformational changes of collagen by ultrasensitive microcalorimetry

In this communication,sulfate dodecyl sodium(SDS)-induced thermodynamics and conformational changes of collagen were studied.We used ultrasensitive differential scanning calorimetry(US-DSC)to directly monitor the thermal transition of collagen in the presence of SDS.The results show that SDS affects the conformation and thermal stability of collagen very differently depending on its concentrations.At C SDS≤0.05mM,the enhanced thermal stability of collagen indicates the stabilizing effect by SDS.However,a further increase of SDS leads to the denaturation of collagen,verifying the well-known ability of SDS to unfold proteins.This striking difference in thermodynamics and conformational changes of collagen caused by SDS concentrations can be explained in terms of their interactions.With increasing SDS,the binding of SDS to collagen can be dominated by electrostatic interaction shifting to hydrophobic interaction,and the latter plays a key role in loosening and unfolding the triple-helix structure of collagen.The important finding in the present study is the stabilizing effect of SDS on collagen molecules at extreme low concentration.

A facile preparation of a novel nonleaching antimicrobial waterborne polyurethane leather coating functionalized by quaternary phosphonium salt

The aim of this research is to develop a novel non-leaching antimicrobial waterborne polyurethane(WPU)leather coating material with covalently attached quaternary phosphonium salt(QPS).The structure of the QPS-bearing WPU has been identified,and their thermal stability,mechanical property,and antimicrobial performance have been investigated.The results reveal that the incorporation of QPS slightly reduces the thermal stability of WPU material but would not affects its usability as leather coating.Despite the presence of hydrophobic benzene in QPS structure,the strong hydration of its cationic groups leads to the increased surface contact angle(SCA)and water absorption rate(WAR)of the films,suggesting that the water resistance of the films needs to be improved for the purpose of leather coatings.Antibacterial tests demonstrate that when the QPS content is 20 wt%,QPS-bearing WPU shows effective antimicrobial activity against bacteria.The WPU containing QPS prepared in this study is a non-leaching antimicrobial material and has great potential application as leather coating.

Life cycle assessment and leather production

Leather industry is facing new trends on production and consumption patterns due to society concerns.Circular economy is proposing a transition from the current economic model to a more sustainable one,in which waste is designed out and resources will be reused and recycled as long as possible.In this transition,Life Cycle Assessment(LCA)is an important tool to help decision-making.In the present review,39 English-written peer-reviewed papers related to LCA and leather have been found,30 of which were published in the last 6 years,meaning LCA is nowadays an important subject.Papers are presented within 4 types,focused on:1)the whole leather production process,2)a single step in the production process(e.g,new technologies for unhairing),3)waste treatment and recycling,and 4)life cycle thinking with ideas on long-term strategies for leather industries.As discussed in the literature review,leather industry has important challenges to address:increasing sustainability and transparency on the supply chain,and strengthening the beauty of leather.Taking up these challenges from a life cycle perspective will help leather industry flourish in the coming future.

Pickering aqueous foam templating:a promising strategy to fabricate porous waterborne polyurethane coatings

Waterborne polyurethane(WPU)has been widely used as coatings in industrial fields ranging from wood,real/synthetic leather,and textiles,because it exhibits versatile performance,excellent eco-friendliness,and superior film-forming property.In terms of wearable products,compact WPU coatings often cause discomfort due to the intrinsic poor vapor transmission.