Molibdenum disulfida merupakan aditif gemuk yang terkenal karena memiliki sifat ketahanan aus yang sangat baik. Ukuran partikel memengaruhi kinerja aditif, dimana semakin kecil ukuran partikel akan memberikan sifat ketahanan aus yang semakin baik. Namun diperlukan biaya yang semakin besar untuk memperoleh partikel berukuran kecil. Oleh karena itu, dibutuhkan penelitian terkait kombinasi ukuran partikel aditif molibdenum disulfida terhadap efektivitas kerja pelumasan gemuk untuk memaksimalkan efisiensi biaya yang diperlukan. Pembuatan gemuk dilakukan melalui reaksi saponifikasi minyak sawit sebagai bahan dasar dengan asam 12-hidroksi stearat, kalsium hidroksida, dan asam asetat sebagai pengental. Hasil bio-gemuk kalsium kompleks NLGI 2 selanjutnya dicampur dengan bubuk aditif molibdenum disulfida 1% b/b. Ukuran partikel aditif divariasikan menjadi 5 μm (Mb), 2 μm (Mk), dan 100 nm (N). Selain itu, dilakukan variasi kombinasi dua ukuran meliputi Mb+Mk, Mb+N, Mk+N, serta kombinasi tiga ukuran dengan komposisi berbeda. Partikel dikarakterisasi ukurannya menggunakan TEM dan PSA. Sedangkan gemuk dikaraktersasi menggunakan uji penetrasi, dropping point, dan four-ball. Hasil penelitian menunjukkan bahwa penambahan aditif molibdenum disulfida dapat mencegah keausan. Selanjutnya, kombinasi tiga ukuran terbukti efektif dalam meningkatkan performa anti-wear, diikuti dengan kombinasi dua dan satu ukuran, dimana hasil paling optimum yaitu dengan komposisi 1:1:1. Namun, penambahan aditif tidak memengaruhi tingkat penetrasi dan dropping point.
Molybdenum disulfide is a grease additive known for its excellent anti-wear properties. Its performance is affected by particle size, where the smaller the particle will provide better anti-wear performance. In consequence, higher costs are needed. Therefore, research is needed on the particle size combination of molybdenum disulfide particles on tribological performance to achieve cost efficient grease. The grease is made through the saponification reaction of palm oil as base material with 12-hydroxystearic acid, calcium hydroxide, and acetic acid as thickener. The resulting NLGI 2 calcium complex bio-grease was then mixed with 1% w/w molybdenum disulfide powder. The additive particle size was varied into 5 μm (Mb), 2 μm (Mk), and 100 nm (N). Various combinations of two sizes were also carried out, while three sizes were varied by its compositions. Particles were characterized using TEM and PSA, meanwhile bio-grease using penetration, drop point, and four ball tests. The results showed that the addition of molybdenum disulfide could prevent wear. Furthermore, combination of three sizes was proven to be effective in increasing anti-wear performance, followed by combination of two and one size, with optimal results of 1:1:1. However, the addition of additives did not affect the penetration rate and drop point. |
