PHOSPHORYLATED CNSL PREPOLYMER AS A FOUNDRY-SAND CORE BINDER

The performance of phosphorylated cashew-nut shell liquid prepolymer ( PCNSL) as a core binder in foundry applications is studied. Moulding p roperties such as strength and permeability and casting characteristic s such as surface quality of castings, core-metal reactions, core coll apsibility and anti-damping behaviour are analysed. PCNSL gave superio r performance in all these factors when compared to other system of bi nders such as sodium silicate. Studies based on LR spectra and SEM on the nature of bonding between sand and PCNSL indicate involvement most ly of physical and mechanical interactions rather than chemical bondin g. The formation (during casting) of higher content of char (due to th e presence of phosphate group in the resin) with open porous structure as revealed by SEM is thought to give better collapsibility to the sy stem.