Novel natural rubber composites based on silver nanoparticles and carbon nanotubes hybrid filler

Hybrid filler of carbon nanotubes (CNT) and silver nanoparticles (AgNP) was prepared and then mixed with natural rubber (NR) with CNT:AgNP ratio = 100:1. The AgNP was first synthesized by reacting silver nitrate with sodium citrate as a reducing agent in an aqueous solution. Then, the UV-vis spectrometry and transmission emission microscopy were used to follow the reaction forming AgNP and the optimum reaction time was found at about 20 minutes. The latex mixing of NR and CNT-AgNP hybrid filler was eventually performed. It was also found that the CNT-AgNP hybrid filler enhanced various properties of the NR composites, including torque difference, storage modulus, and initial modulus (from temperature scanning stress relaxation test) as compared to the conventional NR-CNT composite. Furthermore, higher electrical conductivity with comparatively low percolation threshold of the hybrid composites was found as compared to the NR-CNT composite. This might be due to decoration of AgNP particles on CNT surfaces or between CNT bundles caused hindering CNT agglomeration and facilitating electron tunneling. Also, CNT network formation the NR hybrid composite was stronger than in the NR-CNT composite. Furthermore, strong infinite CNT network formation increased thermal diffusion in the NR-CNT/AgNP hybrid composite.