A Askarizadeh - Islamic Azad University, Karaj Branch, Chemistry Department.
H Bouhendi - Iran Polymer and petrochemical Institute, Tehran, Iran.
M Ghiass - Iran Polymer and petrochemical Institute, Tehran, Iran.
G Bagheri - Islamic Azad University, Karaj Branch, Chemistry Department.

Aqueous non-soluble oils such as silicone oils mixed with the hydrophobic solid particles such as hydrophone silica particles are extensively used to destroy and prevent theformation of undesired foam in operation equipment. The chain length of the silicone oil used in the formulation ofdifferent types of antifoams play a major role in controllingthe form formation or the efficiency of the antifoam. Too short chain length of oil shows high efficiency but it hasadverse effect of exhaust process which decreases the effectiveness of antifoam, while oil with high molecular weight decreases the efficiency due to the high viscosity. In this work we study the effect of molecular weight of silicone oil on the antifoam efficiency and durability