Study On The Modification Synthesis Mechanism,Bonding Mechanism And Curing Mechanism Of Animal Glue Binder

With the continuous development of foundry industry in our country,the consumption of casting binder is gradually increasing yearly.Therefore,it is very important to develop an environmentally friendly and biodegradable binder.Animal glue is one of environmental friendly binders,which is non-toxic,biodegradable and water soluble.In this paper,the animal glue was modified by a modification and a new binder for foundry,which has high bond strength.The synthesis mechanism,the bonding properties and the hardening mechanism were studied systematically,furthermore,the regeneration of animal glue used sand is also studied.First,the composition and molecular composition of animal bone glue are systematically analyzed.The determined results show that the animal glue is mainly composed of four elements:C,H,N and O,as well as its molecular structure is mainly composed of peptide chain,and contains amino group?-NH₂?and carboxyl group?-COOH?.The relative molecular mass distribution of animal glue is relatively wide,mainly in the20000Da-100000Da.It mainly contains 20 types of amino acids,such as glycine,proline,etc.And the total amino acid content is 8633.10nmol/mg.However,the viscosity of animal bone glue is large,the fluidity is poor,and the strength is low.It is necessary to improve the bond strength and fluidity of animal glue by modified,and make it liquid at room temperature.The hydrolysis principle of animal bone glue has been analyzed and discussed.The hydrolysis process parameters of animal bone glue is optimized.The most effective hydrolysis process is the following.The amount of anhydrous sodium carbonate is 3 wt%to animal glue,water to binder ratio was 140:100?mass ratio?,and the hydrolysis reaction should be performed at 50°?for a reaction time of 60 min.The viscosity of the binder is580mPa·s.Moreover,the molecular weight and viscosity are reduced,and the number of active groups are increased after hydrolysis process.According to the affection on the tensile strength of sand,the optimum resluts has been achieved by the experiments of orthogonal design about the amount of acrylic acid and furfuryl alcohol to form a steady binder system with high strength.The proportion of above factors is as followed:the acrylic acid:ammonium peroxydisulfate:furfuryl alcohol:animal glue=14:3:10:100?mass ratio?.The synthetic reaction should be performed at 80°C for a reaction time of 100 min.After modification,the viscosity is 1000mPa·s,the original strength is 2.69 MPa?180?×15min?and final strengh is 2.55 MPa.Furthermore,the structure,elemental composition,relative molecular weight,crystallization and thermal stability of the modified animal glue were characterized by Fourier transform infrared spectroscopy?FT-IR?,Nuclear magnetic resonance?¹H-NMR?,Raman spectrometer,Gel permeation chromatograph?GPC?and Thermogravimetric analysis?TG?.The characterization results show that the structure of the modified binder is changed by graft copolymerization and esterification cross-linking reaction.The improvement of thermostability,bond strength and hydrophilic performance for modified animal glue binder is more than that of the unmodified binder.Then,the hardening mechanism and bonding mechanism of animal glue binder sand are analyzed theoretically.The heating hardening of animal glue sand is mainly the process of molecular dehydration polycondensation of binder.The chemical reaction occurs between active groups such as amino,carboxyl and hydroxyl groups in the animal glue to remove water and contact closely.There are some spatial net structures formed by the intermolecular condensation of binder molecules,as the result of improving strength.Micorwave hardening is mainly a process of rapid removal of water under microwave irradiation to establish strengh.When animal glue sand is blown into CO₂ gas,it can remove water from binder molecules by reaction of calcium hydroxide with CO₂,and Ca²⁺can also have coordination reaction with the binder,it can be closely connected with binder to improve the bond strength.The adhesion of animal glue binder and silica sand,which is a complex physical and chemical reaction.In order to reveal the physical chemical reaction between binder and sand surface,the bonding characteristics are analyzed.The contact angle,viscosity and surface tension of binder were measured and analyzed.The contact angle of modified binder is40.158?and compared with unmodified binder,the decrease is 55.08%.The surface tension of the modified binder is 36.000mN/m,it compared with unmodified binder,the decrease is54.34%.This indicates that the wettability of the modified binder on sand is better,and it is easier to infiltrate sand.From Scanning electron microscopy?SEM?,it is found that the modified binder has more“adhesive bridge”.The more“adhesive bridge”increase adhesive forces between sand and binder.In order to reduce the environmental pollution caused by waste foundry sand,three regeneration methods were studied.The regeneration of animal glue used sand is analyzed by mechanical regeneration,thermal regeneration and wet scrubbing regeneration.Results show that three regeneration methods can effectively remove the residual binder film on the surface.Furthermore,the mechanical regeneration is more suitable for animal glue wasted sand.Finally,the research has been carried out on the modified animal glue binder industrial production and some performance index of modified animal glue binder sand have been tested.The cured modified binder has been used successfully for making aluminium-alloy with clean surface and no porosity.The economic analysis shows that the cost of the modified animal glue binder is lower and can meet the requirement of the foundry production,and it has space for popularization and application.