Effect of Calcium Copper Titanate (CaCu3Ti4O12) addition on the properties of epoxidised natural Rubber 25 (ENR-25) composite

High dielectric constant material plays a vital role in miniaturising many electronic devices. CaCu3Ti4O12 (CCTO) has always been remark as very high dielectric constant ceramic (100,000) at room temperature and nearly independent within a wide frequency range from 1 Hz to 1 MHz, whereas a polymer has low dielectric properties but possesses excellent flexibility. Unfortunately, the forming process of ceramic into the desired shape requires pressing and sintering process, and these will limit the control for the complex shapes. To solve this problem, the excellent properties of ceramic and polymer combined to become composite material. In this study, CCTO ceramic powder was blended with a group of polymer rubber, which is Epoxidised Natural Rubber (ENR). The CCTO powder is initially synthesised using solid-state reaction followed by compounding formulation of ENR-25 with CCTO (0, 20, 40, 60, 80, 100 and 120 phr) in a Brabender. Small blocks of the composite were cast to ~2 mm of mould thickness and hot compressed to remove air bubble. Samples were characterised for mechanical, electrical, microstructural and thermal properties. Mechanical testing of the composite show an increase in tensile strength from 5.91 to 16.46 MPa, but after 40 phr content, the magnitude of tensile strength gradually decreased with increasing filler loading from 13.63 to 6.49 MPa. While, both of hardness and density of composite show an increasing with increasing of filler loading which is from 30.5 to 44.7 Shore A for hardness and 0.98 to 1.70 g/cm3 for density. Meanwhile, LCR meter shows an increasing CCTO content can improve the dielectric constant from 6.134 to 12.114 at 75 kHz and dielectric loss is decreasing from 0.136 to 0.125 at 5.01 MHz. The microstructure of the composite also showed the crystal of CCTO immersed in the ENR-25 with good surface contact and the surface morphology show that filler content from 60 phr and onwards has many pores and agglomeration of CCTO particles, which reduce its mechanical strength. Its thermal behaviour of glass transition temperature is shift to the left as increasing filler loading, which improve its thermal behaviours. In conclusion, the most excellent filler content that exhibits excellent properties is 40 phr of CCTO filler loading.