The Contribution of BaTiO₃ to the Stability Improvement of Ethylene-Propylene-Diene Rubber: Part II-Doped Filler

The thermal and radiation stabilities of the formulations based on ethylene-propylene-diene rubber (EPDM), which contain barium titanate (BaTiO₃) doped with lanthanum and cerium oxides, were investigated by chemiluminescence and mechanical testing. The contributions of these doped fillers are related to the surface interaction between the structural defects (doping atoms, i.e., lanthanum and cerium) implanted in the filler lattice and the molecular fragments formed during the progress of degradation. These composite materials present extended durabilities with respect to the references; the oxidation periods are a minimum of three times longer than the corresponding times for pristine polymers. This behavior is associated with the scavenging activity of dopants. Mechanical testing has demonstrated the contributions of doped filler to the improvement of tensile strength and elongation at break by the restructuration of the polymer phase. Scanning electron microscopy images revealed the densification of materials in the presence of doped barium titanates. All the investigations constitute valid proof for the qualification of BaTiO₃ doped with Ce as the more efficient stabilizer compared to the same inorganic filler doped with La.