Preparation of Low-Surface-Energy SSBR@FA Hybrid Fillers via Solution Mechanochemical Approach and Its Enhancement in Mechanical Strength on the Modified FA/SBR Composites

Owing to the substantial polarity difference and weak interfacial interaction, the large-scale application of fly ash (FA) in rubber materials still faces substantial challenges. To solve this issue, this study prepared a modified hybrid SSBR@FA filler through a solution mechanochemical reaction between solution-polymerized styrene-butadiene rubber (SSBR) and FA in a lab planetary ball mill. Fourier transform infrared spectroscopy (FTIR) and energy-dispersive spectroscopy (EDS) analyses demonstrated the in situ grafting-neutralization between the carboxyl in the SSBR chains and metal oxides in FA. Transmission electron microscopy (TEM) showed that surface-grafted SSBR formed a rubber-constrained layer on FA particle surfaces, which can reduce their surface energy and improve the wettability between FA and SBR matrix. Compared with the SBR vulcanizate, the mechanical properties, thermal conductivity, and flame-retardant properties of the SBR/SSBR@FA vulcanizates were obviously improved. This was because of the uniform distribution of FA and the improved interfacial interaction between FA and the rubber matrix. For example, the tensile strength, tear strength, and elongation at break increased by 66.3%, 52.9%, and 17.7%, respectively. This easy, efficient, and environmentally modified method for FA was expected offer a practical and creative solution for its application in rubber manufacturing.