Glass-polymer melt hybrids. I: Viscoelastic properties of novel affordable organic-inorganic polymer hybrids

A novel class of organic-inorganic polymer hybrids was developed by melt-blending up to 50 (v/v) % [about 83 (w/w) %] tin-based polyphosphate glass (Pglass) and low-density polyethylene (LDPE) in conventional plastics processing equipment. The liquid- and solid-state rheology of the polymer hybrids was studied under oscillatory shear flow and deformation to understand the behavior of these materials and to accelerate efforts to melt process the Pglass with organic polymers. All the materials were found to be linearly viscoelastic: in the range of temperature and frequencies examined and their viscoelastic functions increased with increasing Pglass concentration. The Pglass significantly enhanced the shear-thinning characteristics of the Pglass-LDPE hybrid, indicating the presence of nonlinear chemical and physical interactions between the hybrid components. Morphological examination of the materials by scanning electron microscopy revealed interesting evolution of microstructure of the Pglass phase from droplets (or round beads) to elongated and interpenetrating network structures as the glass concentration was increased in the Pglass-LDPE hybrids. Melt viscosities of the materials were well described by a simple power-law equation and a Maxwellian (Hookean) model with three relaxation times. Time-temperature superpositioning (TTS) of the complex viscosity versus frequency data was excellent at 170 degreesC < T < 220 degreesC and the temperature dependencies of the shift factors conformed excellently well to predictions from an Arrhenius-type relation, enabling calculation of the flow-activation energies (25-285 kJ/mol) for the materials. The beneficial function of the Pglass in the hybrid system was significantly enhanced by pre-treating the glass with coupling agents prior to incorporating them into the Pglass-LDPE hybrids.