engleski

Local molecular dynamics in γ-irradiated natural rubber/zeolites composites

In order to improve the intrinsic properties of rubber and to get desirable mechanical properties, before the final production, rubber must be crosslinked and doped with filler which has the reinforcing role. Crosslinking is a process in which the rubber chain molecules form a tridimensional network structure. The most often used crosslinking agent is sulfur, while carbon black, because of its specific surface structure, is commonly used filler. Since the products made of rubber are subject to wear and aging, they must be regularly replaced by new ones. Considering their volume, they represent a huge environmental problem. A small part of the rubber waste is recycled and the rest is often burned. Burning leads to the production of ecologically harmful gases, mainly carbon and sulfur oxides. The main goal of this work was to apply the high energy γ-radiation, well-known inexpensive method for crosslinking polymer chains, in order to avoid the use of sulfur as crosslinking agent. By an application of γ-radiation on natural rubber/zeolites composites, crosslinking occurs by forming the C-C bonds that are more stable then C-S bonds formed when the natural rubber is crosslinked by sulfur. Additionally, zeolites, as ecologically acceptable materials, also known to act as flame retardant, were used as fillers. Mechanical properties of materials are highly influenced by chain dynamics. Therefore, this study was focused on the local molecular motions of poliisoprene chains in NR/zeolite composites. Electron spin resonance (ESR) – spin probe method was applied to investigate the motional behavior of matrix chain segments. Results obtained with γ-irradiated zeolite-filled rubber samples show a presence of relatively high amount of slow motions, indicating an important material reinforcement.

radiation crosslinking ; NR/zeolite composites ; molecular dynamics ; ESR – spin probe method

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