Viscoelastic behavior of glass‐bead filled crosslinked polymers in the dry and swollen states

Stress relaxation and moduli of elasticity of the composite system crosslinked poly(2‐hydroxyethyl methacrylate) (PHEMA)–glass beads were studied dry and swollen in water to equilibrium state over the temperature range 5–170°C. The moduli of the composites in the dry state increased with increasing filler concentration, while those of the composites measured in the swollen state up to the volume concentration of the filler v ≅ 0.15 decreased. In this respect the composites behaved as porous systems, i.e., as polymers with macroscopic defects. This effect was explained as a consequence of weak filler–matrix interaction. The results were compared with the existing theories of moduli of the composite materials.