Study on mechanical property of epoxy composite filled with nano-sized calcium carbonate particles

Epoxy resin (EP) is used widely nowadays as a structural, adhesive and electronic material due to exhibiting high strength, high elastic modulus, high insulation etc. [1]. However, EP may show limitations, especially over-fragility in application, so other constituents have to be added to improve its performance. Methods of toughening EP has long been sought, and one of the most common methods is the incorporation into EP of a dispersed rubbery elastomer, which can enhance impact strenght of EP at the expense of weakening rigidity and heat-resistance of the matrix as well as raising cost [2]. Calcium carbonate is considered as a suitable substitute for rubbery elastomer in EP matrix because it demonstrates high rigidity and may overcome the shortcomings of rubbery elastomer if incorporated well into the EP matrix. Traditionally, micron-sized calcium carbonate is added into polymers for the purpose of reducing formulation cost of the polymer-based composites. Nevertheless, micron-sized calcium carbonate may have negative impact on the mechnical performance of polymers. It was reported that mechanical properties of polymers could be otherwise improved by adding nano-sized fillers. Generally, mechanical behaviors of particulate-filled polymers, which have a very complex dependence on the interfacial bonding between the filler and the matrix, are influenced strongly by factors such as size, content and shape of the filler. Of these fillers, nano-sized calcium carbonate (nano-CaCO3) particles have attracted considerable attention and play effective role in many composite systems [3]. This work reports an investigation of the influence of nano-CaCO3 on the mechanical properties fo EP composite. Nano-CaCO3 employed in this experiment, with a cubic shape and an average diameter of 40 nm (Fig. 1), was synthesized by the reactive precipitation reaction method under high gravity environment. Detailed methodology and basic theory about the preparation of nano-CaCO3 by this method can be found in the reference [4]. The dispersion degree of the filler in the matrix will significantly influence the properties of composite. However, it is very difficult to disperse nano-sized particles in a high viscous polymer matrix. Generl method is to introduce a high shearing force to the mixture in order to intermix the fillers with the matrix [5].