The Effect of Organoclay on Curing Characteristic, Mechanical Properties, Swelling and Morphology of Natural Rubber/Organoclay Nanocomposites M. Irfan Fathurrohman,* 1 Bambang Soegijono, 2 Emil Budianto, 2 Saeful Rohman, 3 Arief Ramadhan 1 Summary: Rubber nanocomposites based on the natural rubber (NR) and organically modified montmorillonite (OMMT) were prepared by melt intercalation technique using a laboratory open mill followed by compression molding. Organically modified organoclays with different d-spacing were added to the natural rubber matrix to examine the influence of d-spacing of organoclay on morphology, curing characteristic and mechanical property of nanocomposite. The character- izations were carried out by means of X-ray diffraction, scanning electron, atomic force microscopy and moving die rheometer. The results show that melt mixing by an open mill is an effective method for dispersing OMMT throughout the natural rubber matrix especially for organoclay cloisite 15A whose d-spacing is high and well dispersed in natural rubber matrix. The hardness and stresses at low strain of NR/organoclay nanocomposites slightly increased with increasing d-spacing of organoclay, but elongation at break decreased. The swelling behavior of NR/ organoclay nanocomposite improved with increasing d-spacing of organoclay. Keywords: nanocomposite; natural rubber; organoclay Introduction Natural rubber (NR) is one of the materials from natural resources that have interest- ing physical properties due to its ability to crystallize under stretching. In order to enhance the mechanical properties of the rubber products, compounders are always adding the filler in the rubber compound. Carbon black (CB) is the most important reinforcing agent used in rubber industry. Because of its origin from petroleum, carbon black causes pollution and gives the rubber black color. Since researchers from Toyota Central Research Laboratories introduced polya- mide organoclay nanocomposites, its makes another researcher interest to study about organoclay nanocomposite based on the other polymer including rubber. Mechanical properties of NR with 10 part hundred rubber (phr) organoclay are comparable to the compound with 40 phr carbon black and the organoclay improve the strength of the NR without hardly any reduction in the elasticity of the material. [1] Sun et al. [2] prepared organomodified montmorillonite by solid-state method and its nanocompo- sites with natural rubber. The results showed that the nanocomposites consisting of solid- state organomodified mont-morillonite improved the mechanical properties and aging resistance properties of NR. [2] The addition of very small amount of pristine clays revealed a significant improvement of the physical properties of the NR based nanocomposites. [3] Kim et al. [4] prepared 1 Indonesian Rubber Research Institute, Jl. Salak No. 1, Bogor 16151, Indonesia Fax: (þ62-251) 8324047; E-mail: irfan@puslitkaret.co.id 2 Materials Science Graduate Program, University of Indonesia, Jl. Salemba no. 4, Jakarta, Indonesia 3 Centre of Polymer Technology, Puspiptek Serpong, Tangerang Selatan, Indonesia Macromol. Symp. 2015, 353, 62–69 DOI: 10.1002/masy.201550308 62 | © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com