Effects of surfactants on the physical properties of silicate binders and the mechanical properties of silicate-bonded foundry sand cores.

In the foundry industry, casting sand cores require high and low peak and residual strengths, respectively, to achieve comprehensive optimal mechanical performance. The peak and residual strengths of sand cores are positively related, highlighting the criticality of balancing them. Thus, an innovative approach comprising the incorporation of anionic surfactants into the silicate binder was introduced to balance both factors. Additionally, the investigation of the effects of the anionic surfactants on the physical properties of the silicate binder, including its colloidal stability, surface tension and adhesion, revealed that four different anionic surfactants reduced the surface tension and adhesion of the silicate binders and reduced the residual strength of the silicate-bonded sand cores. Among them, 0.10 wt% lauryl ether phosphate reduced the surface tension and adhesion of the adhesive by 49.64 and 112 mN/m, respectively, and reduced the residual strength of the sand core by 0.035 MPa. However, increasing the dosage did not further reduce the residual strength of the sand core, although it continued to reduce its peak strength. Therefore, during silicate binder modification with anionic surfactants, the dosage of the anionic surfactant must be kept at ≤0.10 wt%, as this dosage exerted the most comprehensive optimal modification effect, which was attributable to the adsorption of anionic polymers onto the surface of the silicate aggregates. This adsorption weakened the network structure of the silicate aggregates and imparted the sand cores with appropriate mechanical properties during casting. [ABSTRACT FROM AUTHOR]