COMPOUNDING AND TESTING OF 3 MODIFIED ELASTOMERS TO BE USED AS PARENTERAL STOPPERS

Tetramethylthiouram disulphide (1) is known as a vulcanizing agent, al one or with mercaptobenzothiazole (2) in the presence of a small quant ity of sulphur. Different concentrations of 1 were added to natural cr epe and to bromobutyl rubber mixes [0.5-3 parts per hundred (phr) part s of rubber at curing temperatures of 140-160 degrees C]. It was found that the addition of 2 parts of 1 to each one of the two elastomers a t a curing temperature of 150 degrees C results in good physico-mechan ical and swelling properties. When the vulcanizing system 2 phr 1/0.1 phr 2 was used, a delay in the cure time (T-c90) and an increase in th e scorch time (T-s2) was obtained. The effect of blending natural and bromobutyl rubber mixes in different percentages showed that increasin g the percent of natural rubber in the blends to 40 phr raises the cur e time and improved the physico-mechanical and swelling properties. Th e best percentage was found to be 30 natural/70 bromobutyl. Three form ulations of natural, bromobutyl and their blend rubber were used as pa renteral stoppers. The results of aging, indicates that the three elas tomers posses good heat resistance and antioxidant characteristics and are suitable for sterilization. The suitability tests, performed acco rding to the international standards (rubber stoppers intended for use as parenteral stoppers), proved that the three elastomers have suitab le limits of physico-mechanical and chemical properties.