Optimization of Animal-Glue Binders for Casting Applications

In typical metal foundry applications,sand casting is still the most used technology.The related binder plays a very important role as its performances can directly influence the quality of castings.Among many binders,glues of animal origin have attracted much attention in recent years due to their reduced environmental impact.How-ever,they display some drawbacks such as the tendency to coagulate easily at room temperature and a relatively low strength.In this study,a novel gas-hardening casting binder was prepared using an animal glue and anhy-drous potassium carbonate as a hydrolyzing agent to avoid undesired agglomeration.Moreover,sodium pyropho-sphate and furfuryl alcohol were exploited as modifiers to obtain a binder with a high compressive strength.The best modification conditions,determined by means of an orthogonal design matrix approach,were 4 g of Na2CO3,sodium pyrophosphate,furfuryl alcohol and animal glue with a ratio of 4:12:100,at 85°C and with a duration of 115 min,respectively.The viscosity of the mixture obtained under these optimized conditions was 1250 mPa⋅s.The compressive strength of the binder,hardened by CO_(2) gas,was 4.00 MPa.Its gas evolution at 850°C was 15 ml⋅g-1,and its residual strength after 10 min calculation at 800°C was 0.01 MPa,which is high enough to meet the requirement of core-making in foundry.Moreover,after hydrolysis and further modification,animal glue and modifiers displayed a grafting reaction and an esterification reaction,respectively,which made the adhesive network denser and improved its thermal stability.