Preparation Of Nano-composite Fibers And Products Using Aldehyde-tanning Waste Leather Shavings As Raw Materials

The utilization rate of raw materials in the tanning industry is low,and a large amount of waste leather shavings will be generated in the tanned raw material skins during the shaving process.The main component of waste leather shavings is type I collagen fiber,which is an excellent biomass material.The cost of handling waste leather shavings as waste material is always expensive,and the existing recycling methods are relatively extensive and the added value is low,which is a common problem in the leather industry.Therefore,there is an urgent need to develop processes and products that utilize waste leather shavings in a resourceful,refined,and high-value manner.In this paper,aldehyde-tanned waste leather scraps are used as raw materials to prepare aldehyde-tanned waste leather powder and extract skin collagen fibers.Skin fiber leather is prepared by compounding the prepared aldehyde-tanned waste leather powder and water-based polyurethane,and skin fiber sponge material as pressure-sensitive electronic skin is prepared by using the extracted skin collagen fiber and carboxylated multi-wall carbon nanotubes.The main research contents and conclusions are as follows:1.The aldehyde-tanning waste leather scraps were analyzed and tested,which mainly contain carbon,hydrogen,oxygen,nitrogen,sulfur,and other elements like amide bonds,amino groups,and carboxyl groups.The free glutaraldehyde content is 1.17 mg/g.30-40 mesh,40-80 mesh,80-100 mesh,100-200 mesh aldehyde tanning waste leather powder was prepared by using plant fiber crusher by controlling the crushing time.Using citric acid,under the condition of pH=2 at 40?,the swelling time was adjusted,and collagen fibers with diameters of 10 ?m,5 ?m,2 ?m,and 100 nm were extracted.2.Compound the prepared aldehyde-tanned waste leather powder with water-based polyurethane,and optimize the formula and process parameters to prepare skin fiber leather with good mechanical properties and breathability.With aldehyde-tanned waste leather powder mass fraction of 20%,mesh range of 30-40 mesh,skin fiber extract mass fraction of 4%,TG enzyme addition amount of 4%,under the environment of Citric acid-sodium citrate buffer solution at 50?,pH=6,skin fiber leather with a tensile strength of 17.34 kPa,an elongation at break of 18.42%and a water vapor transmission rate of 231.51 mg·10 cm-2·24 h-1 was obtained.Compared with the polyurethane without leather powder,the water vapor transmission rate was increased by 40.42%.3.Compound the extracted skin collagen fibers with carboxylated multi-wall carbon nanotubes(c-MWCNTs),the composite skin collagen fiber sponge material was prepared by vacuum freeze-drying technology and made into electronic skin.The main factors influencing the compressive elastic modulus were cleared by orthogonal experiment method.With the c-MWCNTs mass fraction of 8%,the c-MWCNTs composite skin collagen fiber sponge density of 0.8g·cm-3,and the collagen fiber extraction time of 8h,the average sensitivity of the prepared pressure-sensitive electronic skin at 10-20 kPa is 0.037 kPa-1,the water vapor transmission rate is 287.32 mg·10 cm-2·24 h-1,and the degradation period is about 50 days in lmol/L NaOH ethanol solution.The pressure-sensitive sensor assembled by the prepared pressure-sensitive electronic skin and the Bluetooth signal conversion module can make a synchronous response to the periodic application and removal of excitation.In this study,aldehyde-tanned leather scraps were studied from different scales:from the centimeter scale to the micrometer scale by crushing,and then to the nanometer scale by swelling.On the micrometer scale,aldehyde-tanned waste leather powder was used as a raw material to produce skin fiber leather that can be used as an instep material,using biological enzymes.On the nanometer scale,pressure sensitive electronic skin was prepared by mining the natural multi-layer structure of skin collagen and skin bionics.To a certain extent,it has realized the resource,refinement and high-value utilization of aldehyde-tanned waste leather shavings,solved the pain points of aldehyde-tanned waste leather shavings processing in the leather industry,and promoted the sustainable development of the leather ecological industry.