Performance of Thermal-Oxidative Aging on the Structure and Properties of Ethylene Propylene Diene Monomer (EPDM) Vulcanizates

Abstract

A thermal-oxidative aging test at 120 °C was conducted on ethylene propylene diene monomer (EPDM) vulcanizates of the semi-efficient vulcanization system. The effect of thermal-oxidative aging on EPDM vulcanizates was systematically studied by curing kinetics, aging coefficient, crosslinking density, macroscopic physical properties, contact angle, Fourier Transform Infrared Spectrometer (FTIR), Thermogravimetric analysis (TGA) and thermal decomposition kinetics. The results show that the content of hydroxyl and carbonyl groups as well as the carbonyl index increased with increasing aging time, indicating that EPDM vulcanizates were gradually oxidized and degraded. As a result, the EPDM vulcanized rubber chains were crosslinked with limited conformational transformation and weakened flexibility. The thermogravimetric analysis demonstrates that the thermal degradation of EPDM vulcanizates had competitive reactions of crosslinking and degradation, and the thermal decomposition curve can be divided into three stages; meanwhile, the thermal stability of EPDM vulcanizates gradually decreased with increasing aging time. The introduction of antioxidants in the system can promote the crosslinking speed and reduce the crosslinking density of EPDM vulcanizates while inhibiting the surface thermal and oxygen aging reaction. This was attributed to the fact that the antioxidant can reduce the thermal degradation reaction level, but it is not conducive to the formation of a perfect crosslinking network structure and reduces the activation energy of thermal degradation of the main chain.

Study on flame retardancy of EPDM reinforced by ammonium polyphosphate

“…APP decomposition products such as metaphosphoric acid and polyphosphoric acid cannot combine with them to undergo dehydration and carbonization reactions. 28,29 Therefore, these substances migrate to the surface of the rubber material under the influence of pyrolysis gas. Together with the fumed silica in the material and the alumina formed by thermal decomposition, they gather on the surface of the carbonized layer, hindering the material exchange and energy exchange between the gas phase and the pyrolysis layer.…”

“…In an oxygen-rich environment, EPDM undergoes thermal oxidation reactions at high temperatures, and carboxyl and hydroxyl groups are formed on the carbon skeleton. 28 Substances such as metaphosphoric acid and polyphosphoric acid generated by thermal decomposition of APP can undergo dehydration and carbonization reactions with the hydroxyl groups on the carbon layer skeleton formed by the decomposition of EPDM to form a carbon layer. 29,30 During this process, phosphorus is enriched in the carbon layer.…”

“…APP decomposition products such as metaphosphoric acid and polyphosphoric acid cannot combine with them to undergo dehydration and carbonization reactions. 28,29 Therefore, these substances migrate to the surface of the rubber material under the inuence of pyrolysis gas.…”

Thermal Oxidative Aging and Service Life Prediction of Commercial Ethylene–Propylene–Diene Monomer Spacer Damping Composites for High–Voltage Transmission Lines

“…Consequently, the vulcanized EPDM chains underwent a limited conformational transformation. These irreversible changes, such as molecular chain breakage and crosslinking, affected the physical properties of EPDM materials, ultimately altering their hardness, strength, and loss factor [13]. Further investigations by Delor-Jestin et al demonstrated that during thermal oxidative aging of EPDM composites, the elongation at break decreased with increasing aging time, and the tensile strength decreased by 25% after 1000 h of aging.…”

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

“…The main purpose of any manufacturer is the extension of durability for their own products. This goal is achieved by means of several procedures: crosslinking [ 1 , 2 ], compounding [ 3 , 4 ], preparation of nanocomposites [ 5 , 6 ], and stabilization by antioxidants [ 7 , 8 ]. All of these procedures are based on the availability of polymer materials for molecular and morphologic reconstruction, starting from the recombination of fragments.…”