INFLUENCE OF THE NATURE AND FORMULATION OF STYRENE-BUTADIENE RUBBER ON THE EFFECTS PRODUCED BY SURFACE-TREATMENT WITH TRICHLOROISOCYANURIC ACID

The nature and formulation of two synthetic sulfur-vulcanized styrene- butadiene rubbers affected the extent, but not the nature, of the surf ace modification produced by halogenation with different amounts (1-7 wt%) of trichloroisocyanuric acid (TCI) solutions in ethyl acetate. R1 rubber had a low oil and plasticizer content, whereas R2 rubber conta ined a smaller amount of styrene than R1, and a relatively significant amount of oil and plasticizer. Chlorination of the rubbers decreased their tensile strength (more markedly in R2) without noticeable change s in elongation at break, and heterogeneities and cracks were created on the rubber surface (mainly in R2). The surface modifications were n ot influenced by the manner in which the post-chlorination agent was r emoved (air or vacuum). Chlorination with TCI created C-Cl, C-O, and C OO- moieties on the rubber surface which were responsible for its enha nced acid-base contribution to the surface energy. The extent of chlor ination was more extensive in R1 (the rubber with a smaller butadiene content). The surface modification was less effective for R2, due to i ts noticeable amount of oil and plasticizer. On the other hand, when t he chlorination was carried out with 7 wt% TCI, removal of the excess of the post-chlorination agent in vacuum prevented the formation of we ak boundary layers (due to isocyanuric acid + mechanically damaged sur face) in the treated surfaces. The nature and formulation of the rubbe r determined the thickness of the weak boundary layer (thinner in R1). On the other hand, a relatively deep penetration (at least 10 nm) of the chlorination agent into the rubber bulk was produced.