Mixing Silica in Natural Rubber: The Impact of Surface Treatment and Mixing Parameters on Performance Properties, Throughput and Energy Usage

In previous work, it was demonstrated that PPG’s proprietary Agilon ^TM performance silica technology platform solves issues with compounding precipitated silica in natural rubber (NR).  This solution involved modifying the silica surface with a mercaptoorganometallic species and a non-coupling agent designed to increase interaction between polymer chains and the silica surface. Improvements in Mooney viscosity and microdispersion are easily observed as a result of the improved interaction.  In addition, improvements were seen in hysteresis (i.e. very low heat build up), tensile strength, abrasion resistance and tear strength. Furthermore, coupling agent related VOCs (volatile organic compounds) were eliminated and overall productivity improvements were indicated. In this paper, we focus on compounding of Agilon® 454 in natural rubber by exploring the influence of several variables. A model 100% NR compound was mixed using a range of tangential and intermeshing rotors at two different masterbatch dump temperatures in a 16 L KSBI internal mixer. In addition, we explore the impact of simplifying the mix sequence from 3 passes to 2 using Agilon 454 on each of the rotor and dump temperature combinations. Suggestions will be made on how to maximize the quality and performance of natural rubber composites made with Agilon® 454 based on rotor configuration and the collected mixing data.