Preparation And Tanning Properties Of POSS/Polymer Composites

Chrome tanning agents are widely used because of their excellent properties.However,the chrome tanning method is facing enormous environmental pressure,so the development of less or no chrome tanning agent is imperative.Polyhedral oligomeric silsesquioxane?POSS?molecule and POSS/polymer composites have nano-cubic three-dimensional structure cavity.Its terminal or side chains contain a large number of active groups,such as amino,carboxyl,hydroxyl and sulfonic acid groups,which are similar to the structure of synthetic tanning agents commonly used in leather industry.They could combine with amino,hydroxyl and peptide groups in collagen fibers to form hydrogen bonds and valence bonds.Therefore,in this paper,POSS molecule and POSS/polymer composites containing carboxyl group and amino group were designed and synthesized,which were used in leather tanning and its tanning properties were studied.Specific research contents are as follows:Multi-carboxyl P?POSS-MAA?composite material was prepared by the free radicalpolymerizationofmethacrylicacid?MAA?and octavinyloctasilsesquioxane?POSS-Vi?which was obtained by hydrolysis and condensation of vinyl trimethoxysilane?A-171?.The structure of the polymer was characterized by Nuclear Magnetic Resonance?NMR?,Fourier Transform Infrared Spectroscopy?FT-IR?,X-Ray Diffraction?XRD?and Transmission Electron Microscope?TEM?,the results showed that P?POSS-MAA?composite was successfully obtained,and the POSS-Vi in P?POSS-MAA?composite was uniformly dispersed.It was indicated that the shrinkage temperature and thickening rate of the leather had improved.In addition,the chromium content in the waste solution was decrease when the P?POSS-MAA?composite combined with mass fraction 2.0%chromium was applied to the tanning process of goat acid skin.Meanwhile,when the content of the POSS-Vi was 6%in the P?POSS-MAA?composite,the shrinkage temperature?T_s?can reach up to 96.5?and the thickening rate can also increased to 36%after the leather pretanned with the P?POSS-MAA?composite combined with 2.0%chromium,and the chromium mass concentration in the waste solution can be decreased from 122mg/L to 41 mg/L compared with chrome tanning.The BOD₅/COD_Cr ratio was higher than 0.3,indicating that P?POSS-MAA?-2.0%chrome tanning wastewater had excellent biodegradability.The combination of P?POSS-MAA?composite and aluminium tanning agent applied to chrome-free tanning process,and the optimum tanning process was optimized.The results showed that as the dosage of P?POSS-MAA?composite material was 6.0%and the content of aluminium sulfate was 10.0%,the shrinkage temperature of could leather reached 73.5?,which was higher than that of single aluminum tanning.Compared with the traditional chrome tanning,the combined tanning leather has excellent whiteness,mechanical properties and thermal stability.Scanning electron microscope?SEM?and energy dispersive X-ray?EDX?spectroscopy analyses showed that collagen fibers have been dispersed and tanning agents were evenly distributed in collagen fibers.FT-IR results revealed that P?POSS-MAA?composites can enter into the collagen fibers of skin without destroying the triple helix structure of collagen,which was consistent with the XRD and molecular simulation?MS?result.Moreover,environmental impact assessment showed that the BOD₅/COD_Cr of the combination tanning wastewater was higher than 0.3,indicating its biodegradability was superior to the aluminum tanning and conventional tanning processes.The octa?aminopropylsilsesquioxane??POSS-NH₂?was synthesized from?-aminopropyltriethoxysilane by hydrolytic and condensation.The structure and morphology of products were characterized by ¹H-NMR,¹³C-NMR,FT-IR and TEM.A novel chrome-free tanning process based on combination tanning with cage-like octa?aminosilsesquioxane??POSS-NH₂?and tetrakis?hydroxymethyl?phosphonium sulfate?THPS?was proposed.The results showed that the T_s of THPS tanned leather was obviously increased with the introduction of POSS-NH₂,implying that POSS-NH₂ and THPS had synergistic tanning effect.The tanning process was optimized as 6.0%POSS-NH₂ combination with 2.5%THPS,endowing T_s of the leather reached above 83.0?and thickness rate was44.6%.FT-IR analysis showed that hydrogen bonds were formed between amino groups of POSS and the hydroxyl groups of collagen.The SEM-EDX and fluorescence tracing technique results revealed that POSS and THPS tanning agents penetrated and binded evenly in the leather matrix,thus promoting the weaving of collagen fibers into a tight network structure.