SULFONATION OF POLYMER SURFACES .2. CHEMICAL-CHANGES ON POLYPROPYLENEAND POLYSTYRENE SURFACES AFTER GAS-PHASE SULFONATION

This study investigates the chemical changes effected on the surface o f polypropylene and polystyrene as a result of sulfonation using an SO 3-air mixture (1% SO3 v/v). Polypropylene is a purely aliphatic system and is characterized by the tertiary carbon which it has on its backb one. On the other hand, polystyrene is characterized by an aromatic ri ng on its backbone. Different surface analytical techniques (XPS, FTIR -ATR, and contact angle measurements) were used to quantify the change s. It was concluded that the formation of sulfonic acids was the main chemical change which occurred on the surfaces of polypropylene and po lystyrene. Besides sulfonic acids, there was an indication of several side reactions occurring in the case of polypropylene while polystyren e did not show any such side reactions. The surfaces of both polymers reached a state of treatment saturation (similar to 6.5% for polypropy lene and 7% for polystyrene). Sulfonation of polypropylene beyond the saturation limit led to degradation, as manifested by a highly sulfona ted layer of polypropylene which sloughed off during neutralization. H owever, intense sulfonation of polystyrene did not show any conspicuou s degradation.