STUDY ON THE SURFACE AND INTERFACE CONTRO L OF VULCANIZATES .2. EFFECT OF MOLDS ON THE SURFACE FREE-ENERGY AND FRICTION COEFFICIENT OF VULCANIZATES

The surface formation of vulcanizates starts from the wetting of uncur ed rubber compounds to the surface molds. The surface free energy of v ulcanizates obtained was estimated from surface-chemical study; the en ergy determined reflected the surface free energy of the molds. This e stimation was demonstrated to be reasonable by the comparison of surfa ce free energies of molds used and vulcanizates obtained. Molds of hig h surface free energy gave polar vulcanizate surfaces with high surfac e energy and those of low surface free energy gave non-polar vulcaniza te surfaces when rubber molecules consisted of polar and non polar gro ups. The friction coefficient of vulcanizates was also discussed as re lated to the surface free energy of vulcanizates. The relation between surface free energy and friction coefficient of vulcanizates was inve stigated. The friction coefficient of vulcanizates increased with surf ace free energy in vulcanizates when the surface free energy of scratc hing rods is higher than that of vulcanizates.