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

Abstract

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.

Stability Qualification of Resins/Metallic Oxide Composites for Surface Oxidative Protection

“…The thermal performances of these materials are based on their resistance, whose activation energies are around 70-75 kJ mol −1 [55]. The involvement of oxide filler in the stabilization of polymers against oxidation is characterized by the surface interaction, where the generated free fragments are scavenged by the superficial traps [2,56]. After the initiation of oxidative degradation, the propagation stage may be influenced by the blending filler, which withdraws reactive radicals from the oxidation chains [40].…”

“…The addition of metallic oxides in the structure of polymer composites determines the increased material stability in most of the cases [1][2][3][4]. The general overview on the issued papers presenting the improved properties of polymer composite is rather focused on the functional properties, because the majority of assessments principally depict the contributions of fillers to efficient applications [5][6][7][8].…”

“…The composites containing metallic oxides present good resistance against burning due to their intumescent capacity for the limitation of fire propagation [13]. The main contributions of oxide fillers included in polymer materials are differentiated by the dissimilarity of electronic densities between the metallic atoms, as well as the high electronegativity of oxygen that makes the formation of gaps with an electronic deficit possible [2].…”

“…The presence of oxides in the compositions of polymer-based materials is a determining factor for modifications in long-term stability. While some inorganic fillers like oxides or clays extend the durability ranges [2,37,38], other compounds behave as pro-oxidants [39]. However, the nanocomposites with specific fillers have peculiar commitments, which are related to the extension of application ranges under different energetic stressing conditions (nuclear engineering, transports, aircraft, pipe sealing).…”