| Casein,as one of the four major finishing agents widely used in leather industry,the casein film has the advantages of strong adhesion,high temperature resistance,easy polishing and good sanitary properties,casein contains a variety of amino acids coupled with strong hygroscopicity,which provides conditions for bacteria growth and reproduction,causing it is highly susceptible to bacterial erosion.On the other hand,the finishing agent is always affected by the external environment,and cratches and microcracks will inevitably appear on the surface of the leather coatings,so that the mechanical properties and protection of the coating will be damaged largely,which limits its further application.In order to solve this problem,we creatively prepared zeolitic imidazolate framework-8(ZIF8)with casein as the template,regulated the size and morphology of ZIF-8 through the template,while giving casein excellent antibacterial properties,and then loading hydrophobic silicone oil in the system and adjusting the film formation conditions to give the film superior hydrophobic and self-healing properties.Finally,casein-based composite emulsion was applied to leather finishing to make leather have good antibacterial,hydrophobic and self-healing properties and improved the added value of the products.The main research contents are as follows:(1)Firstly,CA-CPL@ZIF-8 was obtained by in situ growth ZIF-8 using CACPL micelles as the template.The structure and morphology of CA-CPL@ZIF-8 were optimized by changing parameters such as type and size of template,usage of CA-CPL,reaction time and temperature.The chemical structure and micromorphology of the samples were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM)and N2 adsorption-desorption.The results showed that the CA-CPL@ZIF-8 with complete crystal structure was successfully grown by turning the size of the template,the size of CA-CPL@ZIF8 was about 200 nm,with high specific surface area micropore structure(specific surface area was 1128 m2/g,pore size was about 2.70 nm).Casein-based CACPL@ZIF-8 composite emulsion and film were prepared by compounding CACPL@ZIF-8 with casein emulsion.When the usage of CA-CPL@ZIF-8 was 0.8%,the composite emulsion had outstanding antibacterial properties(Winh=10 mm for S.aureus),and the composite film had fine mechanical properties(tensile strength and elongation at break increased to 1.63 MPa and 107.85%,respectively).(2)Based on the preparation of CA-CPL@ZIF-8,SO@CA-CPL@ZIF-8 was successfully prepared by further introducing silicone oil(SO).The effects of the usage of CA-CPL and SO on the morphology and size of SO@CA-CPL@ZIF-8 were investigated by single factor experiments.The results indicated that SO@CA-CPL@ZIF-8 was rhombohedral dodecahedron with size of about 300 nm,with high specific surface area microporous structure(specific surface area was 1078 m2/g,pore diameter about 2.21 nm)and had superior thermal stability.Then SO@CA-CPL@ZIF-8 nanoparticles were introduced into casein emulsion to prepare composite emulsion and film.The composite film had certain hydrophobicity,and had pH response property(water contact angle was raised to 107.80 in acidic environment after 24 h).Appropriate amount of deionized water let casein-based film has a certain self-healing performance,and the self-healing efficiency about mechanical property was up to 80%.(3)In order to further explore the application properties of the prepared CACPL@ZIF-8 and SO@CA-CPL@ZIF-8 nanoparticles,then casein-based composite emulsion was applied to leather finishing.The results manifested that the introduction of nano-particles endowing the leather great antibacterial,selfhealing and pH response hydrophobicity(water contact angle of leather surface was reached to 110.3° under acidic environment).At the same time,the mechanical and sanitary properties of leather were improved. |
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