BahruddinHelwani, ZuchraSaktiani, LiliYanuarSatoso,Rahmat2014-02-142014-02-142014-02-14wahyu sari yenihttps://repository.unri.ac.id/handle/123456789/5587Palm oil fly ash (POFA) as solid waste produced from crude palm oil industries consist of quite high of silica (more than 50% w/w). This study aimed to compare the properties and morphology of thermoset natural rubber (TNR) with POFA, silica, carbon black (CB), and mixture of POFA-CB fillers. The filler content used is 30 phr (per hundred rubbers). The process of making the compound was conducted by using a roll mill at room temperature and a maximum roll rotational speed of 20 rpm. Zinc oxide 5 phr, stearic acid 2 phr, mercaptodibenzothiazyldisulfide (MBTS) 0.6 phr, and Sulfur of 3 phr were used as curative agents. Trimethylquinone (TMQ) 1 phr was used as an antioxidant. Commercial minarex 2.5 phr was used as a plasticizer. Vulcanization process was carried out at a temperature of 150 °C and a pressure of 50 kg/cm^ using a hot press. Morphology was observed using a scanning electron microscope (SEM). Measurement of tensile properties was carried out using universal testing machine (UTM) according to ASTM D412-06a standard. The results indicated that the use of POFA as a filler could potentially produce TNR with quite good morphology, tensile properties and water absorption properties. A mixture of POFA-CB with a mass ratio of 50/50 (w/w) produced the thermoset with the value of 18.5 MPa of tensile strength, 1600% of elongation at break, and 1.2 MPa of elastic modulusencarbon blacktensile propertiesmorphologynatural rubberpalm oil fly ashUR-Scientific Work Lecturer