Preparation and Characterization of Acrylonitrile-Butadiene Rubber/Ferric Sulfate Coordination Crosslinking Composites

Acrylonitrile-butadiene rubber (NBR) filled with Ferric (Ⅲ) Sulfate (Fe₂(SO₄)₃) particles were prepared by planetary ball-mill method and the average size of Fe₂(SO₄)₃ particles decreased from 10.23 μm to 1.13 μm. Electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) indicated that the coordination reaction occurred between nitrile groups (-CN) of NBR and ferric ions (Fe³⁺) of Fe₂(SO₄)₃. Scanning electron microscope (SEM) indicated that a layer of "creases" appeared around the Fe₂(SO₄)₃ and NBR after hot pressing, which was due to the coordination effect between Fe₂(SO₄)₃ particles and NBR matrix. This phenomenon resulted in the enhancement of compatibility of the interface. The glass transition temperature (T_g) and crosslinking density of composites increased with the rise of Fe₂(SO₄)₃ content. The comprehensive mechanical properties of composite filled with 15 phr (parts per hundred of rubber) Fe₂(SO₄)₃ were the best. The tensile strength of composite filled with 15 phr Fe₂(SO₄)₃ increased by 12.8 times compared with that of pure NBR. Although the coordination ability of Fe₂(SO₄)₃ was limited, non-coordination Fe₂(SO₄)₃ particles had the effect of physical enhancement of NBR when the loading of Fe₂(SO₄)₃ rose to 30 phr. The tensile strength of composite filled with 30 phr Fe₂(SO₄)₃ was about 1.41 times larger than that of composite filled with 15 phr Fe₂(SO₄)₃ while elongation at break decreased only a little. The crosslinking density, tensile strength, hardness, rebound resilience, tension fatigue factor and ageing-resistant performance of composite filled with 15 phr Fe₂(SO₄)₃ prepared by planetary ball-mill method were better than those of composite prepared by dry method, which indicated that the solution ball-mill method was better than the traditional dry method. However, the energy consumption of planetary ball-mill method was higher than that of dry method. It is an important research direction in the future to reduce the energy consumption of planetary ball-mill method.