Impact of formulation and processing parameters on mechanical properties of magadiite/elastomer composites.

摘要

This work seeks a better understanding of mechanical reinforcement and energy dissipation in elastomer composites containing the layered silicate magadiite (MGD, Na2Si14O29˙nH2O). We characterized the elastomer's accessibility into MGD interlayer spaces and studied the factors that influence the composite mechanical properties. We also compare the mechanical reinforcement of MGD with montmorillonite (MMT, a layered aluminosilicate clay mineral), which is widely used as filler in other kinds of nanocomposites. The study explores the grafting chemistry, vulcanization, and reinforcement mechanism in MGD/elastomer composites, which may help us to formulate the platelet/elastomer composites with superior mechanical properties and performance in the future. We continued previous work in our group on the influence of organosilane pre-functionalization on MGD reinforcement. Various organosilane-functionlized MGD (OS-MGD) were reacted with squalene (SQ), a small molecule model for natural rubber. For OS-MGD with larger initial interlayer spacing, more SQ entered the interlayer space. For OS-MGD with smaller initial interlayer spacing, SQ was excluded from intercalation. By calculating the composition based on TGA and EA results, we studied the MGD grafting chemistry and quantified the SQ accessibility into the MGD interlayer space. Then, we explored various factors that influence the mechanical reinforcement of composites consisting of MGD dispersed in styrene-butadiene rubber (SBR), such as the interlayer spacing, various mixing times, the addition of silane coupling agents, different sulfur sources, the presence of surfactant, and varying elastomer chemistry. Rationalizing the relationship between those factors and composite mechanical properties provides a deeper understanding of the reinforcement mechanism and energy dissipation in MGD/SBR composites. Finally, we compare the mechanical reinforcement of MGD and MMT in SBR composites directly. Based on XRD results, MMT was speculated to be partially exfoliated after compounding with SBR prepolymer, resulting in greater mechanical reinforcement and higher crosslink density for MMT/SBR composites compared to MGD/SBR composites. This work helps us to understand and formulate elastomer composites containing other members of these two mineral families in the future.