Elucidation of the principle of microwave rubber vulcanization based on dielectric parameters and vulcanization of tire rubber by variable frequency microwave

Abstract

AbstractThe microwave vulcanization of tire rubber was investigated by monitoring the dielectric properties of the rubber polymer and other components of the formulation (including carbon filler, antioxidant, and vulcanization agents) as functions of frequency and temperature. The effect of the vulcanization reaction on the dielectric properties during heating was also assessed. The physical interaction between the crosslinked structure and the carbon black significantly favors the responsiveness to microwaves during the vulcanization reaction. Based on these basic data, microwave irradiation conditions were determined, and model tire samples were microwave vulcanized in a PTFE mold. It has achieved a shorter time of heating and 65% energy saving, but on the other hand, it has become clear that the vulcanization produces very poor physical quality compared to vulcanization by electric furnace heating. To solve this problem, we performed microwave irradiation using variable frequency microwave (VFM; 5.85 ~ 6.65 GHz) using glass fiber on polyetherketoneketone (PEEK/GF) mold. In VFM, compared to conventional fixed frequency microwave (FFM), successfully synthesized high‐quality tire rubber because it showed 4.2, 1.1, 2.0, 1.2, and 1.8 times higher values in terms of cross‐linking density value, hardness value, tensile strength, elongation at break, and 200% modulus, respectively.