STRUCTURAL ARREST AND THERMODYNAMIC SCALING INFILLER-REINFORCED POLYMERS

摘要

The role of small silica particles on the stiffness and glass transition dynamics of polyvinylacetate (PVAc) wasexamined for filler volume fraction (φ) from 0 to 0.28. Whereas the influences of bound polymer and a strain-dependentfiller network were clearly noted in the shear properties, the only effect of filler on the bulk modulus was the reductionin deformable polymer. The calorimetric glass transition of PVAc and its dependence on cooling rate were unaltered bythe presence of the silica, in agreement with previous dielectric relaxation results. In contrast to the temperature depend-ence of the segmental dynamics, which was independent of φ, the effect of volume on segmental relaxation was ampli-fied by the addition of silica. This resulted in larger values for the thermodynamic scaling exponent (γ), which alsoincreased sharply at the filler concentration corresponding to the development of a percolated filler network.