Chemically Modified Oil Palm Ash-Filled Natural Rubber Composites and its Properties Zhong Xian Ooi, Hanafi Ismail, Azhar Abu Bakar Division of Polymer Engineering, School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia Chemically modified Oil Palm Ash (OPA)-filled natural rubber composites were prepared by modifying the functional group of OPA with cetyltrimethylammonium bromide (CTAB) prior to compounding by using labora- tory conventional laboratory-sized two-roll mills. The functional groups of CTAB-modified OPA were ana- lyzed by using Fourier Transform Infrared (FTIR) and compared with those of non-modified ones. The CTAB- modified OPA-filled NR composites showed shorter scorch time and cure time as compared to those of non-modified OPA, which was attributed to the new functional groups occurred. The tensile test results showed that the OPA-filled NR composites with CTAB modification exhibit improvement in tensile strength, tensile modulus, and hardness but lower elongation at break as compared to nonmodified ones. The tensile fractured surface of modified OPA filled NR compo- sites revealed the well embedded and better distribu- tion of CTAB-modified OPA in NR matrix. The toluene uptake was also found to be lower for the modified OPA-filled NR composites and showed better rubber– filler interaction; it further showed that surface modifi- cation with CTAB could compatibilize the OPA particles and NR matrix. POLYM. COMPOS., 00:000–000, 2013. V C 2013 Society of Plastics Engineers INTRODUCTION Oil palm cultivation increased rapidly since 1960s under the government’s agricultural diversification pro- gramme and currently the cultivation of oil palm has a coverage of 4.49 million hectares of land in Malaysia [1]. According to Suhaily et al. [2], only 10% of the total oil palm biomass is utilized, whereas the remainder is con- sidered as waste and underutilized. In Malaysia, millions tonnes of solid waste i.e. empty fruit bunch, palm press fiber, palm kernel shell, and etc. are produced annually [3] and tend to increase every year because of palm oil extraction activities. Presently, those solid wastes are used as an alternative fuel in oil palm mill plants for steam generation. However, this alternative method is not solving the solid waste problem as it produces another by-product known as oil palm ash (OPA). This issue gains the researchers’ concern and interest to utilize the OPA by transforming it into a sustainable and high-value added product. In the previous work [4], the OPA had been utilized and it was found that the incorporation of OPA could rein- forced the natural rubber by improving the tensile strength (16%) and elongation at break (7.4%) but this only suits at very low filler loading. Generally, the OPA showed the unique surface characteristics, i.e. irregular shaped particle with porous structure and rough surface [5], which introdu- ces better physical interaction between filler surface and rubber matrix [6]. One of the major drawbacks of using OPA is its hydrophilic nature that causes agglomeration and poor dispersion during compounding. To improve the mechanical properties of OPA-filled nat- ural rubber composites, the filler modifications may be applied to alter the surface characteristics of the OPA in terms of extensity, intensity, and geometry factors and these were taken into account to affect the performance of natu- ral rubber composites when filled with modified OPA. In this paper, the cetyltrimethylammonium bromide (CTAB) solution was utilized as media modification in which alky- lammonium ion (cationic surfactant) of CTAB [7] would induce the electrostatic interaction with hydrophilic OPA and thereby absorb onto the OPA surface as well as modify the surface characteristic of the OPA filler. The aim of this paper is to further improve the tensile properties of natural rubber composites by minimising the polarity gap and reducing the micro voids within natural rubber and CTAB- modified OPA. The swelling of the composites was also measured to understand the rubber-filler interaction. EXPERIMENTAL DETAILS Materials Natural rubber grade SMR L was used as the matrix, which was purchased from Zarm Scientific & Supplies Correspondence to: H. Ismail; e-mail: hanafi@eng.usm.my DOI 10.1002/pc.22712 Published online in Wiley Online Library (wileyonlinelibrary.com). V C 2013 Society of Plastics Engineers POLYMER COMPOSITES—2013