V. Thammathadanukul et al., COMPARISON OF RUBBER REINFORCEMENT USING VARIOUS SURFACE-MODIFIED PRECIPITATED SILICAS, Journal of applied polymer science, 59(11), 1996, pp. 1741-1750
The reinforcement of a natural rubber compound by various surface-modi
fied precipitated silicas was compared. Compound physical properties w
ere determined for two silicas differing in surface area and were used
as controls to evaluate these silicas after surface modification by u
sing either a bifunctional organosilane coupling agent (gamma-mercapto
propyl-trimethoxysilane) or a new surface modification process. This n
ew process is based on the in situ polymerization of organic monomers
solubilized inside surfactant bilayers that are adsorbed onto the sili
ca surface to afford silicas modified with styrene-butadiene and styre
ne-isoprene copolymers. Both surface modification processes afford mat
erials that dramatically increase the compound cure rate, thereby sign
ificantly reducing T-90 cure times, while also improving tensile prope
rties, tear strength, abrasion resistance, and compression set of the
cured compound. The silane-modified silica gives a higher flex-crackin
g resistance than do the silicas modified by the in situ polymerizatio
n of organic monomers, whereas these latter silicas significantly incr
ease rebound resilience and offer greater overall improvements in rubb
er compound performance. The rubber compound physical properties obtai
ned using the modified, higher surface area Hi-Sil(R) 255 silica are g
enerally improved relative to those obtained using the modified Hi-Sil
(R) 233 silica. (C) 1996 John Wiley & Sons, Inc.