Surface modification of fly ash - characterisation and evaluation as reinforcing filler in polyisoprene

Fly ash, used in conjunction with bis(triethoxysilylpropyl)tetrasulghane (T ESPT) as coupling agent, has been investigated as a reinforcing filler for polyisoprene compounds. The TESPT adsorption isotherm on silica showed that in forming a monolayer, the molecule assumes an inverted U conformation on the surface. With silica, half a monolayer of TESPT gave the maximum bound rubber formation. Fly ash particles were modified by acid and base treatme nt and characterised by electron microscopy and surface area determination. Little bound rubber formed on any of the modified Ay ash particles, the gr een strength of compounds with 30 phr filler was poor, and limited reinforc ement was obtained only with the acid-base modified material. This filler h ad a large surface area (146 m(2) g(-1)), but even for this filler, TESPT a ddition led to little bound rubber formation, possibly because of the lack of hydroxy groups on the surface. PRC/1512 (C) 1999 IoM Communications Ltd.