Influence of the particle size on the viscoelastic glass transition of silica-filled polystyrene

The effects of the filler particle size and volume fraction on the viscoelastic glass-transition temperature of filled polymers were investigated with polystyrene containing silica nanoparticles. The samples were prepared by a solution-mixing method to obtain a better dispersion of silica particles. Dynamic rheometry was used to study the viscoelastic behavior of these materials in the melt state. The addition of silica particles broadened the elastic modulus and increased its magnitude in the glass-transition region. Also, the magnitude of the loss modulus and loss tangent peaks decreased. These phenomena were intensified by a reduction of the silica particle size, which increased filler-filler interactions. Furthermore, with a reduction in the size of the silica particles, the glass-transition temperature of the filled polymer increased simultaneously with an increase in the interfacial layer volume fraction, which was related to an increase in the total surface area of the silica particles.