• International Journal of Technology (IJTech)
  • Vol 11, No 4 (2020)

Curing Characteristics and Physical Properties of Natural Rubber Composites Using Modified Clay Filler

Abu Hasan, Martha Aznury, Indah Purnamasari, Maykel Manawan, Chandra Liza

Corresponding email: abu_hasan@polsri.ac.id

Cite this article as:
Hasan, A., Aznury, M., Purnamasari, I., Manawan, M., Liza, C., 2020. Curing Characteristics and Physical Properties of Natural Rubber Composites Using Modified Clay Filler. International Journal of Technology. Volume 11(4), pp. 830-841

Abu Hasan Department of Chemical Engineering, Politeknik Negeri Sriwijaya, Jl. Srijaya Negara Bukit Besar Palembang 30139, Indonesia
Martha Aznury Department of Chemical Engineering, Politeknik Negeri Sriwijaya, Jl. Srijaya Negara Bukit Besar Palembang 30139, Indonesia
Indah Purnamasari Department of Chemical Engineering, Politeknik Negeri Sriwijaya, Jl. Srijaya Negara Bukit Besar Palembang 30139, Indonesia
Maykel Manawan Department of Mechanical Engineering, Politeknik Negeri Jakarta, Jl. Margonda Raya, Depok 16424, Indonesia
Chandra Liza Center for Polymer Technology, Agency for the Assessment and Application Technology (BPPT), Puspiptek Office area, Building 460, Serpong, Banten 15311, Indonesia
Email to Corresponding Author


The differences in the curing characteristics and physical properties of natural rubber samples using clay and modified clay as fillers were studied. After the clay was modified with dodecylamine, the rubber milling process was conducted at a temperature of 65–70oC to obtain the natural rubber compound. The content of clay and modified clay in the natural rubber was approximately 15 phr. A curing test at 150oC was performed, and then the physical properties were tested. The results of the physical properties test showed a significant increase in the tensile strength, from 16.3 to 25 MPa, a change in hardness from 43 to 54 Shore A, a change in modulus of 300% from 1.6 to 4.6 MPa, a change in tear strength from 29.3 to 40.2 kN/m, and a change in compression set from 25.75% to 30.57% due to the use of modified clay compared to the sample with unmodified clay. However, some physical properties—such as elongation at break, from 720% to 600%—decreased dramatically. Smax increased sharply, from 7.05 to 11.45 kg-cm, while optimum cure and scorch time decreased sharply, from 11.23 to 6.43 minutes and from 6.35 to 2.38 minutes, respectively. FTIR and XRD analyses showed evidence of clay modification. Similarly, the AFM and SEM analyses of clay surfaces and the dispersion of the clay in the rubber showed that the dispersion of the modified clay in the rubber was better than that of unmodified clay. The TA/DTA analysis also supported the above explanation, particularly for the changes in curing characteristics and physical properties.

Clay; Dodecylamine; Modified clay; Natural rubber; Reinforcement


 Global warming has become an increasingly serious problem in recent years, motivating a strong worldwide effort to address its causes and ameliorate their effects. The origins of global warming include the production of CO2 from human activities, particularly from burning fossils fuels such as oil, coal, and natural gas to provide energy for motor vehicles, heat sources, and power plants. Other sources of CO2 emissions are forest fires, forest burning, and land clearing for both plantation land and agricultural land. In particular, forest fires cause greater emissions than forest burning and land clearing, and the burnt areas are much larger due to the long dry-season. Similarly, in the cement manufacturing industry, CO2 is produced from the calcination of limestone, which is the main raw material in cement production. Despite efforts to reduce CO2 from cement plants, a significant reduction in CO2 emissions has not been achieved to date. The production of CO2 by the carbon black manufacturing industry, where carbon black is used as a filler in rubber, is another important source of CO2 emissions. Carbon black is produced using the thermal decomposition method or the partial combustion method, using oil or natural gas as raw material.

Among its other applications, carbon black is used for making rubber compounds in the vehicle tire industry. The role of carbon black is still very dominant in rubber compound manufacturing because carbon black can provide significant reinforcement effects and can reduce the amount of rubber used. While silica is an alternative material to carbon black that can also act as a reinforcement in rubber compounds, its reinforcement effect is inferior to that of carbon black. As reported by Hasan et al. (2019), local clay includes a fairly large amount of silica, which means that the nature of local clay is fairly similar to the nature of silica. Therefore, it is important to use local clay as a filler. Although the effect of clay as a filler has a smaller reinforcing effect on vulcanized rubber compared to the use of carbon black fillers, clay surface modification is needed to increase compatibility with the rubber matrix.

Local clay containing 50.83–75.29% silica is a common silica source in nature (Hasan et al., 2019) that is five times more common than coal. Therefore, this clay is an interesting possible filler material in rubber compounds. The type of clay in this study is kaolin clay, as described in Figure 8. The use of clay as a rubber filler has been studied by many researchers, including Goodman and Riley (2012), Ismail and Mathialagan (2011), Lalikova et al. (2011), Ruamcharoen et al. (2014), Szustakiewicz et al. (2013), Zhang et al. (2012), and Zhang et al. (2010, 2014), and modified clay has also been widely examined—for example, in the work by Ambre et al. (2008), Jagtap et al. (2013), Kord et al. (2017), Ogbebor et al. (2015a, 2015b), Peter et al. (2016), Puglia et al. (2016), Saritha et al. (2012), Sheikh et al. (2017), Sreelekshmi et al. (2016, 2017), Sukumar and Menon (2008), and Yahaya et al. (2009). Most of the types of clay used by researchers are kaolin clay, in addition to bentonite and montmorillonite clay.

A wide variety of chemicals have been used by researchers to modify clay, such as the metal chlorides used by Lalikova et al. (2011), the fatty acid salt used by Zhang et al. (2014), the hydrazine hydrate used by Sukumar and Menon (2008), the dimethyl, benzyl, dehydrogenated tallow, and quarternary ammonium used by Saritha et al. (2012), the 3-mercaptoprophyltrimethoxysilane used by Sheikh et al. (2017), the hexamethylenediamine used by Sreelekshmi et al. (2017), the dimethyldioctadecylammonium and bis(4-hydroxybuthyl)methyldioctadecylammonium used by Nam et al. (2004), and the octadecylamine used by Praveen et al. (2009), Nigam et al. (2012), and Manchado et al. (2003). In general, this clay modification aims to increase the adsorption on the clay surface so that the clay can function better as a filler. An increase in surface adsorption is carried out not only on the clay but also on the adsorbent (Wilson and Mahmud, 2015; Anuar et al., 2019; Kusrini et al., 2019). Here, clay also functions as an adsorbent for rubber molecules on its surface.

Therefore, this study aims to compare the curing characteristics and physical properties of natural rubber composites using clay and dodecylamine-modified clay as the fillers. The modified clay was analyzed by FTIR spectroscopy and X-ray diffraction while the natural rubber compounds were examined by TA/DTA and SEM. The surface of vulcanized natural rubber was analyzed by AFM.


Modified clay has a better effect on the curing characteristics and physical properties of natural rubber than unmodified clay. The vulcanized rubber stiffness, due to an increased vulcanization reaction in the natural rubber, leads to changes in the physical properties of the natural rubber. An analysis of FTIR spectra shows that the clay has been modified with dodecylamine. These results agree with the XRD analysis results that indicate a change in the dimensions of the clay crystal. SEM and AFM images provide consistent information about the filler dispersion in the natural rubber. Modified clay dispersion is better than that of unmodified clay, and this finding supports the explanation of the different physical properties of the obtained vulcanized natural rubber. TA/DTA thermal stability analyses show that natural rubber compounds that use modified clay as the filler are more stable than those using only unmodified clay filler.


    This work was supported by the Directorate General of Strengthening Research and Development, Ministries of Research, and Higher Education, Republic of Indonesia, with the scheme of Higher Education Applied Research under contract number 153/SP2H/LT/DRPM/2019, dated March 11, 2019.


 Ambre, A., Jagtap, R., Dewangan, B., 2008. ABS Nanocomposites Containing Modified ClayJournal of Reinforced Plastics and Composites, Volume 28(3), pp. 343–352

Anuar, F.I., Hadibarata, T., Muryanto, M., Yuniarto, A., Priyandoko, D., Sari, A.A., 2019. Innovative Chemically Modified Biosorbent for Removal of Procion Red. International Journal of Technology, Volume 10(4), pp. 776–786

Assad, J.N., El-Nashar, D.E., Mansour, S.H., 2014. Effect of Modified Clay and Mg(OH)2 on the Properties of Ethylene Propylene Diene Monomer/Silicon Rubber Nanocomposites. InProceedings of the Institution of Mechanical Engineers Part N Journal of Nanoengineering and Nanosystems, Volume 229(3), pp. 121–130

Goodman, H., Riley, A., 2012. Clay Mineral Products and Their Use in Rubber Compositions. United States: Imerys Minerals Limited, Par Cornwall (GB). Patent US8183316B2

Hasan, A., Kalsum, L., Yerizam, M., Junaidi, R., Taufik, M., Aznury, M., Fatria, F., 2019. Potential of Clay in Coal Mining of Tanjung Enim Area as a Filler on Rubber Compound. In: Proceeding of 2nd Forum in Research, Science, and Technology. Palembang, Indonesia, IOP Conference. Series: Journal of Physics, Volume 1167(2019), 012042, IOP Publishing

Ismail H., Mathialagan M., 2011. Curing Characteristics, Morphological, Tensile and Thermal Properties of Bentonite-Filled Ethylene-Propylene-Diene Monomer (EPDM) Composites. Polymer-Plastics Technology and Engineering, Volume 50(14), pp. 1421–1428

Jagtap, S.B., Rao, V.S., Ratna, D., 2013. Preparation of Flexible Epoxy/Clay Nanocomposites: Effect of Preparation Method, Clay Modifier and Matrix Ductility. Journal of Reinforced Plastics and Composites, Volume 32(3), pp. 183–196

Kord, B., Ravanfar, P., Ayrilmis, N., 2017. Influence of Organically Modified Nanoclay on Thermal and Combustion Properties of Bagasse Reinforced HDPE Nanocomposites. Journal of Polymers and the Environment, Volume 25(4), pp. 1198–1207

Kusrini, E., Putra, N., Siswahyu, A., Tristatini, D., Prihandini, W.W., Alhamid, M.I., Yulizar, Y., Usman, A., 2019. Effects of Sequence Preparation of Titanium Dioxide–water Nanofluid using Cetyltrimethylammonium Bromide Surfactant and TiO2 Nanoparticles for Enhancement of Thermal Conductivity. International Journal of Technology, Volume 10(7), pp. 1453–1464

Lalikova, S., Pajtasova, M., Chromc?kova, M., Liska, M., Sutinska, V., Olsovsky, M., Ondrusova, D., Mojumdar, S.C., 2011. Investigation of Natural Rubber Composites with Addition of Montmorillonite Fillers using Thermal Analysis. Journal of Thermal Analysis and Calorimetry, Volume 104, pp. 969–973

Manchado, M.A.L., Arroyo, M., Herrero, B., Biagiotti, J., 2003. Vulcanization Kinetics of Natural Rubber–Organoclay NanocompositesJournal of Applied Polymer Science, Volume 89(1), pp. 1–15

Nam, P.H., Fujimori, A., Masuko, T., 2004. Flocculation Characteristics of Organo-modified Clay Particles in Poly(L-lactide)/Montmorillonite Hybrid Systems. e-Polymers, Volume 4(1), pp. 1–7

Nigam, V., Soni, H., Saroop, M., Verma, G.L., Bhattacharya, A.S., Setua, D.K., 2012. Thermal, Morphological, and X-Ray Study of Polymer-Clay Nanocomposites. Journal of Applied Polymer Science, Volume 124(4), pp. 3236–3244

Ogbebor, O.J., Oikiemen, F.E., Ogbeifun, D.E., Okwo, U.N., 2015a. Organomodified Kaolin as Filler for Natural Rubber. Chemical Industry & Chemical Engineering QuarterlyVolume 21(4), pp. 477–484

Ogbebor, O.J., Oikiemen, F.E., Ogbeifun, D.E., Okwo, U.N., 2015b. Preparation and Properties of Organokaolin Natural Rubber Latex Vulcanizate. Advance in Materials, Volume 4(4), pp. 75–79

Peter, R., Sreelekshmi, R.V., Menon, A.R.R., 2016. Cetyltrimethyl Ammonium Bromide Modified Kaolin as a Reinforcing Filler for Natural Rubber. Journal of Polymers and the Environment, Volume 26(1), pp. 39–47

Praveen, S., Chattopadhyay, P.K., Albert, P., Dalvi, V.G., Chakraborty, B.C., Chattopadhyay, S., 2009. Synergistic Effect of Carbon Black and Nanoclay Fillers in Styrene Butadiene Rubber Matrix: Development of Dual Structure. Composites Part A: Applied Science and Manufacturing, Volume 40(3), pp. 309–316

Puglia, D., Fortunati, E., D’Amico, D.A., Miri, V., Stoclet, G., Manfredi, L.B., Cyras, V.P., Kenny, J.M., 2016. Influence of Processing Conditions on Morphological, Thermal and Degradative Behavior of Nanocomposites based on Plasticized Poly(3-Hydroxybutyrate) and Organo-Modified Clay. Journal of Polymers and the Environment, Volume 24(1), pp. 12–22

Ruamcharoen, J., Ratana, T., Ruamcharoen, P., 2014. Bentonite as a Reinforcing and Compatibilizing Filler for Natural Rubber and Polystyrene Blends in Latex Stage. Polymer Engineering and Science, Volume 54(6), pp. 1436–1443

Saritha, A., Joseph, K., Thomas, S., Muraleekrishnan, R., 2012. The Role of Surfactant Type and Modifier Concentration in Tailoring the Properties of Chlorobutyl Rubber/Organo Clay Nanocomposites. Journal of Applied Polymer Science, Volume 124, pp. 4590–4597

Sheikh, S.H., Yin, X., Ansyarifar, A., Yendall, K., 2017. The Potential of Kaolin as a Reinforcing Filler for Rubber Composites with New Sulfur Cure Systems. Journal of Reinforced Plastic and Composites, Volume 36(16), pp. 1132–1145

Sukumar, R., Menon, A.R.R., 2008. Organomodified Kaolin as a Reinforcing Filler for Natural Rubber. Journal of Applied Polymer Science, Volume 107(6), pp. 3476–3483

Suresha, B., Devarajaiah, R.M., Pasang, T., Ranganathaiah, C., 2013. Investigation of Organo-Modified Montmorillonite Loading Effect on the Abrasion Resistance of Hybrid CompositesMaterials and Design, Volume 47, pp. 750–758

Sreelekshmi, R.V., Brahmakumar, M., Sudha, J.D., Menon, A.R.R., 2017. Studies on Natural Rubber Containing Kaolin Modified with Hexamethylenediamine Derivative of Phosphorylated Cashew Nut Shell Liquid Prepolymer. Applied Clay Science, Volume 141, pp. 171–179

Sreelekshmi, R.V., Sudha, J.D., Menon, A.R.R., 2016. Novel Organomodified Kaolin/Silica Hybrid Fillers in Natural Rubber and Its Blend with Polybutadiene Rubber. Polymer Bulletin, Volume 74(3), pp. 783–801

Szustakiewicz, K., Cichy, B., Gazinska, M., Piglowski, J., 2013. Comparative Study on Flame, Thermal, and Mechanical Properties of HDPE/Clay Nanocomposites with MPP or APP. Journal of Reinforced Plastics and Composites, Volume 32(14), pp. 1005–1017

Wilson, L.D., Mahmud, S.T., 2015. The Adsorption Properties of Surface-modified Mesoporous Silica Materials with ?-Cylodextrin. International Journal of Technology, Volume 6(4), pp. 533–545

Yahaya, L.E., Adebowale, K.O., Menon, A.R.R., 2009. Mechanical Properties of Organomodified Kaolin/Natural Rubber Vulcanizates. Applied Clay Science, Volume 46(3), pp. 283–288

Zhang, Q., Zhang, Y., Wang, Y., 2012. Mechanical and Thermal Properties of Kaolin/Natural Rubber Nanocomposites Prepared by the Conventional Two-Roll Mill Method. Applied Mechanics and Materials, Volume 164, pp. 142–145

Zhang, Y., Liu, Q., Zhang, Q., Lu, Y., 2010. Gas Barrier Properties of Natural Rubber/Kaolin Composites Prepared by Melt Blending. Applied Clay Science, Volume 50(2), pp. 255–259

Zhang, Y., Zhang, Q., Liu, Q., Cheng, H., Frost, R.L., 2014. Thermal Stability of Styrene Butadiene         Rubber (SBR) Composites Filled with Kaolinite/Silica Hybrid Filler. Journal of Thermal Analysis and         Calorimetry, Volume 115, pp. 1013–1020