Preparation And Application Of Dispersible Nano-SiO₂-GO/polymer Nanocomposite Tanning Agents

Chrome tanning is one of the traditional tanning methods in leather industry.However,thetoxicity and the environmental pollution caused by chrome tanning are becoming more and more prominent.No-chromium in tanning leather is the fundamental method to solve chromium pollution and the shortage of chromium resources.Therefore,the chrome-free or less-chrome tanning has become one of the research hotspots in the global leather industry.At present,most researchers still focus on the development of conventional tanning agents and improvement of application processes.However,it is difficult to satisfy the requirement of good performance of leather by using the traditional tanning methods.In order to solve these problems,the tanning process and new technologies are constantly converted and applied in the traditional leather industry.Moreover,the nanotechnologies and nanomaterials are expected to partially or completely substitute for chrome tanning.The key actions of chrome-free tanning are to improve the stability of crosslinking structuresbetween tanning agents and leather protein fiber as well as the filling effects of leather.In this work,the surface-functionalized spherical nano-SiO₂ was compounded with the graphene oxide by chemical bonding to prepare SiO₂-GO nanocomposites.The new nanocomposite tanning agents were prepared by combining SiO₂-GO with polymer matrix.In the process of leather tanning,the spherical nano-SiO₂ and graphene oxide nanosheets can play a synergistic tanning effect,which leads to high-density crosslinking structures between collagen fibers and tanning agent moleculars.The application of the nanocomposite tanning agents in leather significantly improves the stability and mechanical properties of the tanned leather and endows the leather excellent filling performance.Moreover,the tanned leather not only feels soft,plump and elastic but also has antistatic property as well as flame retardant characteristics.1.Firstly,the modified Hummers method was used to prepare graphite oxide with graphite powder.Then the graphite oxide was treated with ultrasonic treatment to produce graphene oxide?GO?and graphene was obtained by using a green reducing agent.The graphene nanosheets were compounded with acrylic resin tanning agents and polyurethane respectively.The results show that the water resistance of polyurethane can be improved with the addition of the graphene.2.The nano-SiO₂ was prepared with tetraethyl silicate?TEOS?,polyvinyl alcohol?PVA?and polyethylene glycol?PEG?as surface-modifiers.The polyol surface-modified nano-SiO₂ and graphene oxide were compounded in aqueous solution by chemical bonding.The obtained samples were analyzed by FT-IR,XRD,Raman,SEM and TEM.The results showed that the SiO₂ nanoparticles were modified by polyol successfully loaded on the graphene oxide nanosheets by covalent bonding.The PVA-SiO₂-GO and PEG-SiO₂-GO were compounded with maleic anhydride-acrylic acid polymer successfully.The nanocomposite tanning agents were applied in the tanning leather and significantly improved the thickening increase and a series of physical and mechanical properties.Moreover,the heat-stability of the tanned leather were improved.3.Firstly,the Fe₃O₄@SiO₂ core-shell nanoparticles were prepared.Then the nanoparticles were modified by acrylamide containing tanning functional groups and the hydrophilic Fe₃O₄@AMSiO₂core-shell nanoparticles were obtained.Finally,Fe₃O₄@AMSiO₂-GO nanocomposites were prepared by electrostatic interaction and compounded with maleic anhydride-acrylic acid polymer.The Fe₃O₄@AMSiO₂-GO/polyer nanocomposite tanning agents were applied to tan the leather.The application results showed that the nanocomposite tanning agents in the tanning process significantly improved the the heat-stability of the tanned leather due to the introduction of Fe₃O₄ nanoparticles in leather.They play synergistic flame retardant effects with the addition of graphene oxide,which endows the leather excellent flame retardant performance.