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Abstract
The effects of electron beam irradiation on the properties of ethylene propylene diene monomer (EPDM)/butyl rubber composites in presence of a polyfunctional monomer were investigated by means of differential scanning calorimetry (DSC), thermal analysis, scanning electron microscopy (SEM), attenuated total reflection absorption infrared spectroscopy (ATR-IR), and mechanical and surface energy measurements. The samples were exposed over a wide range of irradiation doses (20–150 kGy). The EPDM matrix was modified with butyl rubber, chlorobutyl rubber, and bromobutyl rubber. The gel content and crosslink density were found to increase with the electron beam irradiation dose. The values of the hardness and modulus increased gradually with the irradiation dose, while the tensile strength and elongation at break decreased with increasing irradiation dose. The EPDM/butyl rubber composites presented a higher thermal stability compared to the initial EPDM sample. The incorporation of butyl rubbers into the EPDM matrix led to an increase in material hydrophobicity. A similar trend was observed when the irradiation dose increased. The greatest change in the surface free energy and the contact angles occurs at an irradiation dose of 20 kGy. The Charlesby–Pinner plots prove the tendency to crosslinking as the irradiation dose increases.
Highlights
Polymerization of ethylene, propylene, and a nonconjugated diene results in obtaining ethylene propylene diene monomer (EPDM) rubber having a saturated polymer backbone and a very low content of unsaturation in the side groups
To improve some physical and mechanical characteristics of EPDM rubber and to obtain different technical goods with particular properties, EPDM can be associated with other elastomers, such as butyl rubber (IIR) or halobutyls (chlorobutyl rubber (Cl–IIR) and bromobutyl rubber (Br–IIR))
Butyl rubber has a low gas and moisture permeability, good weathering resistance, excellent resistance to oxygen and ozone attack, and chemical stability to a great number of organic and inorganic media, but it has a limited resistance to thermal ageing
Summary
Polymerization of ethylene, propylene, and a nonconjugated diene results in obtaining ethylene propylene diene monomer (EPDM) rubber having a saturated polymer backbone and a very low content of unsaturation in the side groups. EPDM exhibits excellent thermal stability and high resistance to heat, ozone, radiation temperature, ageing, etc. Due to its nonpolar character, EPDM has superior electric resistivity, particular retention properties (even after ageing), and high resistance against polar solvents such as water, acids, alkalies, ketones, or alcohols [3,4]. Butyl rubber has a low gas and moisture permeability, good weathering resistance, excellent resistance to oxygen and ozone attack, and chemical stability to a great number of organic and inorganic media, but it has a limited resistance to thermal ageing. Chlorobutyl rubbers present a low gas and moisture permeability, good resistance to weathering and hydrocarbon solvents, and high thermal stability [5,8]
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