Effect of polyfunctional monomers on properties of radiation crosslinked EPDM/waste tire dust blend

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

This study presents the functional effects of BaTiO₃ powder loaded in ethylene-propylene-diene rubber (EPDM) in three concentrations: 0, 1, and 2.5 phr. The characterization of mechanical properties, oxidation strength, and biological vulnerability is achieved on these materials subjected to an accelerated degradation stimulated by their γ-irradiation at 50 and 100 kGy. The thermal performances of these materials are improved when the content of filler becomes higher. The results obtained by chemiluminescence, FTIR-ATR, and mechanical testing indicate that the loading of 2.5 phr is the most proper composition that resists for a long time after it is γ-irradiated at a high dose. If the oxidation starts at 176 °C in the pristine polymer, it becomes significant at 188 and 210 °C in the case of composites containing 1 and 2.5 phr of filler, respectively. The radiation treatment induces a significant stability improvement measured by the enlargement of temperature range by more than 1.5 times, which explains the durability growth for the radiation-processed studied composites. The extension of the stability period is also based on the interaction between degrading polymer substrate and particle surface in the composite richest in titanate fraction when the exposure is 100 kGy was analyzed. The mechanical testing as well as the FTIR investigation clearly delimits the positive effects of carbon black on the functionality of EPDM/BaTiO₃ composites. The contribution of carbon black is a defining feature of the studied composites based on the nucleation of the host matrix by which the polymer properties are effectively ameliorated.

Enhancing the physico-mechanical properties of ethylene propylene diene monomer rubber via ץ-radiation in the presence of bi-functional and tri-functional monomers

This study, uses two polyfunctional monomers (PFMs) namely ethylene glycol dimethacrylate (EGDMA) as a bifunctional monomer and trimethylolpropane triacrylate (TMPTA) as a trifunctional monomer were used as co-agents in irradiation crosslinking of Ethylene Propylene Diene Monomer Rubber (EPDM). The effect of concentration of each PFM and irradiation dose on the crosslinking density, gel content, swelling behavior in motor and brake oils, in addition to the mechanical and thermal stability properties of EPDM was investigated in detailed. The results showed a remarkable increase in the gel content, crosslinking density and mechanical properties as the concentration of PFMs increased from 1 to 5 phr (parts per hundred parts of rubber). The various blends of EPDM with the trifunctional monomer express the highest gel content and crosslinking density than those with the bifunctional monomer. The addition of 5 phr of TMPTA to EPDM causes a dramatic improvement in tensile strength (TS) of the prepared blend reached to 188% compared to neat EPDM at 50 kGy. At the same time, the maximum TS of the blend containing 5 phr of EGDMA achieved only 41% compared to neat EPDM at an irradiation dose of 100 kGy. The swelling of irradiated samples in brake oil revealed a stronger oil resistance than motor oil. For all irradiated samples, the oil uptake decreased with the irradiation dose up to 100 kGy. The EPDM samples containing 5 phr of TMPTA recorded the highest oil resistance at 100 kGy. The results also showed that the addition of PFMs and irradiation treatment of the various prepared blends improved the thermal stability of EPDM. Finally, neat EPDM and the blends containing 1 and 3 phr of EGDMA can be used as radiation dosimeters in the very high dose range (50–200 kGy).

Stability Efficiencies of POSS and Microalgae Extracts on the Durability of Ethylene-Propylene-Diene Monomer Based Hybrids

The EPDM (ethylene-propylene-diene monomer) hybrids with improved thermal and radiation strengths containing 1 and 5 phr of polyhedral oligomeric silsesquioxane (vinyl-POSS, Ov-POSS) and/or 2 phr of microalgae (Chlorella vulgaris (CV) and Spirulinaplatensis (SP)) powders were investigated in respect to their thermal stability after γ-irradiation. The material durability under accelerated degradation was qualified by chemiluminescence and gelation, which prove the contribution of inorganic filler and microalgae extracts on the increase of hybrid thermal stability, as well as the interaction between added components (POSS and CV or SP). The activation energies and the durabilities under accelerated degradation were calculated, indicating their suitable usage as appropriate materials in various applications. The reported results indicate the improvement effect of both microalgal powders on the oxidation strength, but the contribution of Spirulinaplatensis grabs attention on its efficient effects upon the prevention of degradation under accelerated aging conditions. The thermal performances of the tested EPDM based hybrids are remarkably ameliorated, if the certain formulation includes Ov-POSS (5 phr) and Spirulinaplatensis (2 phr), certifying its suitability for the pertinent applications.