Superior Strong and Tough Epoxy Composite Enhanced by Novel Hyperbranched Polysiloxane with Hydroxy-Terminated and Epoxy-Terminated Groups

Abstract

Achieving both superior mechanical properties and thermal stability in epoxy resins remains a significant challenge. We designed a novel hyperbranched polysiloxane (HBPSi) containing specific epoxy and hydroxyl end groups as a toughening agent for epoxy resins to overcome the incompatibility of the toughening agent with the resin. Remarkably, a small amount of epoxy group-capped HBPSi not only enhanced the mechanical properties of the epoxy resins (DGEBA) but also increased its glass transition temperature. Compared with pure epoxy resin, the resin containing 3 wt% HBPSi not only has improved toughness, but also has significantly increased elongation at break and impact strength by 80.0% and 163.7%. It is worth noting that the improvement of toughness is not at the expense of mechanical strength and glass transition temperature. On the contrary, the mechanical strength and T_g of polysiloxane increased slightly with the introduction of end epoxide hyperbranched polysiloxane. In addition, SEM and DMA results show that HBPSi has good compatibility with epoxy resin. The above results show that the synthesized HBPSi can effectively improve the mechanical properties and thermal stability of epoxy resin, and broaden the application range of epoxy resin.

Keywords

hyperbranched polysiloxane / epoxy resins / toughening / strength

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