ORIGINAL PAPER Effects of magnetically modified natural zeolite addition on the crosslink density, mechanical, morphological, and damping properties of SIR 20 natural rubber reinforced with nanosilica compounds Riri Murniati 1 & Handika Dany Rahmayanti 1 & Fisca Dian Utami 1 & Adi Cifriadi 2 & Ferry Iskandar 1 & Mikrajuddin Abdullah 1 Received: 23 May 2019 /Accepted: 10 January 2020 # The Polymer Society, Taipei 2020 Abstract We investigated the effect of magnetically modified natural zeolite on the mechanical and damping properties of natural rubber- nanosilica compounds. We used natural rubber SIR 20 technical specified rubber (TSR) reinforced with a nanosilica filler. The results showed that using zeolite modified with magnetite and titanate coupling agent (TCA), which are alternative coupling agents to replace silane coupling agents, and amorphous silica as the filler in natural rubber TSR SIR 20 compounds enhanced the mechanical properties of the TSR vulcanization products. The relationships among the crosslink density, mechanical properties and damping properties were also explored. We also identified that an improvement in the properties resulted from a modification of the white oil softener and filler comprising the zeolite-nanosilica-magnetic blends. The results of magnetically modified zeolite showed that the crosslink density, mechanical properties and damping properties increased significantly. The damping ratio in the sample comprising Si + Fe + Z with or without the white oil softener was higher than that of the other samples herein (ζ > 0.03). Based on this result, a reinforced nanosilica filler with magnetically modified zeolite has the potential to replace carbon black and is applicable to damping devices. Keywords Zeolite . Crosslink density . Mechanical properties . Damping . Nanosilica Introduction Commonly used fillers in the rubber industry are synthetic silica [1], fly ash (FA) [2], rice husk ash (RHA) [3], oil palm ash (OPA) [4], bagasse fiber ash (BFA) [5], cellulose fiber [6], coconut shell powder (CSP) [7], and lignin [8]. However, carbon black (CB) is widely used as a filler and light stabilizer for elastomers due to its better reinforcing properties. However, the production of CB causes pollution as it is pre- pared from petroleum feedstock, and it always colors rubber products black. CB dust can also go into the lungs through breathing and causes many physical and psychological problems [9]. Coal tar is the main raw material of the CB industry, and its price has increased significantly in recent years. Therefore, it is necessary to search for alternative rein- forcing agents as substitutes for the CB in rubber compounds. Inorganic mineral fillers, such as silica [10–12], have been applied to make rubber composites, but there are few reports about the application of modified zeolite [13–16] to develop rubber composites. Also, there have been no reports regarding the simultaneous application of magnetic materials, such as magnetite and natural zeolites, to improve the strength of com- posite containing silica as a reinforcing agent. In general, a silica-reinforced rubber has a poorer modulus than a CB-reinforced rubber [17]. However, silica provides a unique combination of tear strength, abrasion resistance, age resistance, adhesion properties, and reduces the accumulation of heat [18]. Silica has been proven to be a better filler choice for high-performance tires than carbon black since the intro- duction of the “green tire” by Michelin in 1992 [19]. Actually, silica can also provide better wet traction than carbon black, combined with a decreased rolling resistance [20]. However, * Mikrajuddin Abdullah mikrajuddin@gmail.com 1 Department of Physics, Bandung Institute of Technology, Jl. Ganesha 10, Bandung 40132, Indonesia 2 Indonesian Rubber Research Institute, Jl. Salak 1, Bogor 16151, Indonesia Journal of Polymer Research (2020) 27:37 https://doi.org/10.1007/s10965-020-2013-0