Study On Factors Influence Appearance Stability And Properties Of No-Bake Furan Resin And New Curing Agent

No-bake furan resin as a binder in foundry practice exhibited excellent properties of high strength, good collapsibility, low viscosity,acid or alkali and organic solvent resistance, simple synthetic process and low production costs was widely used in foundry. However, there were still many problems in production practice of furan resin to be solved, mainly are that:(1)furan resin appeared turbid, layered, precipitation in the process of synthesis and placement, affecting the appearance and stability, that not only make people have a negative impression but cause trouble to production and use; (2)The content of free acid of curing agent is high and the curing rate is slow, more important is the shortage of row materials, so the production costs is very high. To solve the above problems, experiments were done as follow:(1)The molar ratio of formaldehyde-to-urea (F/U) and pH values, reaction temperature, reaction time in addition and condensation stage in the preparation process of furan resin were studied by orthogonal experiment, the mainly factor which have an effect on appearance of furan resin were found, a optimized craft was obtained primarily. (2)The molar ratio of formaldehyde-to-urea (nF1/nU1) in addition stage, pH values, reaction temperature, reaction time in addition and condensation stage and the way of adding alcohol and vacuum dehydration in the preparation process of furan resin are deeply studied by single factor experiment. The relationship between process conditions with the properties of resin such as the appearance of furan resin, the content of free formaldehyde, the viscosity of resin and the tensile strength of sand mold was found. The micro-structure of products in different reaction steps or made under different processing conditions were investigated by IR, the reason that lead to the furan resin appeared turbid, layered, precipitation was analyzed by comparing the difference of the micro-structure of the products. (3)The synthetic conditions of sulfuric acid ester curing agent were explored, a new curing agent was prepared through comparing of the performance and cost which not only can meet the production requirements but has a low cost. The effect of different curing agent on thermal stability of furan resin were compared by the Thermo Gravimetric Analyzer.