화학공학소재연구정보센터
Journal of Applied Polymer Science, Vol.109, No.1, 424-433, 2008
Silica-reinforced natural rubber prepared by the sol-gel process of ethoxysilanes in rubber latex
Silica-reinforced natural rubber (NR) composite was prepared by using tetraethoxysilane (TEOS) as a precursor to generate silica particles inside the rubber. The silica was generated in situ by the sol-gel process of TEOS that was mixed directly into commercial-graded NR latex having 60% dry rubber content and 0.7% ammonia. The conversions of TEOS to silica inside the rubber were ranging from 90 to 97%. The silica particles dispersed evenly without extensive aggregation with sizes between 100 and 500 nm, as determined by scanning electron microscopy (SEM). An experimental design methodology, namely "two-level factorial design," was used to evaluate the influence of the amounts of TEOS, ammonia, and gelation time on the tensile modulus, tensile strength, and tear strength of the vulcanizates. The mechanical properties were significantly affected by the amount of TEOS added into the latex. Ammonia in the amount of 0.7% (w/w) present in the commercial latex was found to be sufficient for the conversion reaction of TEOS to silica. Bis-(3-triethoxysilylpropyl)tetrasulfide or TESPT, a coupling agent regularly used in rubber industry, was also added with TEOS to prepare the silica-filled composite. The presence of TESPT resulted in an increase of the mechanical properties and the rate of sulfur cure. (c) 2008 Wiley Periodicals, Inc.