Vol.:(0123456789) 1 3 Iranian Polymer Journal https://doi.org/10.1007/s13726-018-0643-4 ORIGINAL RESEARCH Sepiolite hybridized commercial fllers, and their efects on curing process, mechanical properties, thermal stability, and fammability of ethylene propylene diene monomer rubber composites Nurul Aizan Mohd Zaini 1,2  · Hanaf Ismail 1  · Arjulizan Rusli 1 Received: 9 January 2018 / Accepted: 8 July 2018 © Iran Polymer and Petrochemical Institute 2018 Abstract Ethylene propylene diene monomer rubber (EPDM)-based composites containing sepiolite (sep) hybridized with calcium carbonate (CaCO 3 ), silica (Sil) or carbon black (CB) were prepared on a two-roll mill. The infuence of fllers’ contents on the curing, mechanical, thermal and fammability of the composites was investigated. In comparison with EPDM/sep at 30 parts per hundred rubbers (phr) as a control composite, EPDM/sep/CB composites exhibited an outstanding improvement in tensile strength followed by EPDM/sep/Sil and EPDM/sep/CaCO 3 composites. EPDM/sep/CB displayed the highest thermal stability and also improved fammability resistance. In addition, a higher amount of carbon black gave higher tensile strength. The results were infuenced by the ability of CB to disperse well and form protective layers acting as mass transport barri- ers in the matrix. The feld emission scanning electron microscopy analyses proved better dispersion of CB in the matrix. The presence of protective layers on the surface of samples consequently improved the thermal properties of the EPDM composites. The mechanism of formation of char protective layer in hybrid EPDM composites was also investigated based on morphological observations of char residues. According to this work, Sil and CB were able to hybrid with sep, while sep could be a potential substitution of CaCO 3 in the EPDM composites. Keywords Sepiolite · Hybrid fller · Tensile properties · Thermal stability · Flammability Introduction Rubber plays an exceptional role in industry due to its remarkably high elasticity. However, rubber is usually a soft material with weak mechanical properties; therefore, the addition of reinforcing fllers such as carbon black and silica is one of the main important criteria [1, 2]. Mean- while, calcium carbonate is a non-reinforcing fller which has been used in rubber composites since ages. Carbon black ofers great strengthening efects such as tensile and tear strength, modulus, hardness and abrasion resistance to rubber composites. But, its production consumes large amounts of fossil fuels. Its production process pollutes the environment and releases large amounts of heat and waste gases as well as the end product being darker in colour [3, 4], which is limited to only certain applications such as tyres. On the other hand, silica is an inorganic (petroleum-independent) fller that ofers an outstanding reinforcement efect and low cost, but has poor dispersion due to the abundant of hydroxyl groups on the polar silica surface, as well as, a lot of energy is consumed in its pro- duction [5, 6]. Whereas, calcium carbonate is an inorganic powder which is generally supplied as agglomerates and in the processing the agglomerates are broken and dispersed into primary particles. Large amounts of particle–particle interactions may result in inhomogeneous distribution of fller in the polymer matrix, and consequently, decrease of tensile properties of the rubber composites [7]. The drawbacks of commercial rubber fllers might be overcome with new fller systems, guaranteeing good dispersion and Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13726-018-0643-4) contains supplementary material, which is available to authorized users. * Hanaf Ismail ihanaf@usm.my 1 School of Materials and Mineral Resources, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia 2 On Study Leave from Faculty of Applied Sciences, Universiti Teknologi Mara Perlis, 02600 Arau, Perlis, Malaysia