Judul: Kopolimer karet alam-stirena iradiasi sebagai aditif viscosity index improver dalam minyak lumas
Abstrak: Aditif viscosity index improver berfungsi untuk menstabilkan viskositas minyak lumas terhadap perubahan suhu telah dibuat berdasarkan proses kopolimerisasi lateks karet alam dengan stirena. Proses ini menggunakan iradiasi sinar gamma dari 60Co. Tujuan penelitian ini untuk mendapatkan konsentrasi aditif peningkat indeks kekentalan terbaik dari kopolimer lateks karet alam-stirena dalam minyak lumas skala laboratorium yang dalam penelitian lebih lanjut diharapkan dapat ditingkatkan menjadi skala komersil. Dosis radiasi diambil dari penelitian terdahulu sebesar 30 kGy. Produk yang dihasilkan berbentuk kopolimer karet alam stirena dengan konsentrasi 50, 100, dan 200 psk (perseratus bagian bobot karet) yang selanjutnya digiling, dicacah, dan dilarutkan dalam xilena dengan konsentrasi sekitar 20% w/v sebagai aditif. Larutan kental ini dilarutkan lagi ke dalam beberapa bahan baku minyak lumas untuk dilihat kelarutannya secara kualitatif. Bahan baku minyak lumas yang terbaik melarutkan aditif dipilih sebagai bahan baku utama. Dalam studi ini dicoba membuat formulasi sederhana dengan mencampur aditif dengan bahan baku minyak utama dengan komposisi 2.5% dan 1% v/v, kemudian diperiksa nilai indeks viskositasnya. Minyak lumas A, B, dan C yang beredar saat ini sebagai pembanding nilai indeks viskositas. Hasil pemeriksaan menunjukan bahwa aditif larut baik dalam bahan baku minyak lumas HVI (high viscosity index) 650. Minyak lumas berupa aditif 1% v/v kopolimer karet alam stirena 200 psk dalam HVI 650 dapat meningkatkan indeks viskositas dari 93 menjadi 110. Sementara itu, indeks viskositas minyak lumas komersial adalah 125-135.
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Judul: Pemanfaatan Kopolimer Cangkok Karet Alam dan Stirena sebagai Aditif Peningkat Indeks Viskositas Minyak Lumas
Abstrak: Thermoplastic elastomer which is produced from graft copolymerization of styrene onto natural rubber can be used as lubricant additive. This additive has a function as index viscosity improver. Index viscosity is one of the important aspect to classify the lubricant quality since it has an influence on temperature stability of the lubricant oil. Graft copolymerization by free radical mechanism on emulsion polymerization v technique was conducted at ratio 85:15, ammonium peroxidisulfate as initiator, and sodium dodecyl sulfate as surfactant at 65oC for 7 hours. The graft copolymer was creeped and soaked into acetone to separate the homopolymer of styrene. The pure graft copolymer was dried and masticated. The pure graft copolymer was made into main solution by dissolving on xylene at 20% concentration. The main solution was added on base oil (HVI 60 and HVI 650) at concentration of 1%, 3% and 5%. The result showed that the grafting efficiency was 56.48%. The base oil HVI 60 and HVI 650 has initial index viscosity as 100 and 92, respectively. Further after the addition of graft copolymer the index viscosity was increased to 181, 185, 186 and 141, 143, 145, respectively. The other characterizations include ash content 0.01%, Mg content as 0.003%, density 0.86 g/ml and 0.89 g/ml, and pH 5. Thus the grafted copolymer of natural rubber and styrene can be used as index viscosity improver at concentration 5%.
Keyword: Bogor Agricultural University (IPB), viscosity index, thermoplastic elastomer, lubricating oil, graft copolymerization

Judul: Studi sistematika  Oreophryne Boettger, 1895Sulawesi (Anura: Microhylidae)
Abstrak: The cross frogs, genus Oreophryne Boettger, 1895 are most diverse in the mainland of New Guinea and adjacent islands, to the Wallacea region in the Moluccas, Sulawesi, and the Lesser Sunda Islands, even marginally to the Oriental region in Bali and to the southern Philippine Islands. In Sulawesi, this taxon consists of three species but has rarely been reported since their original descriptions and remained unstudied in both taxonomical work and molecular study. This research aims to evaluate the taxonomic status of the cross frogs in Sulawesi based on morphology and estimate the phylogenetic using the 16S rRNA gene. The phylogenetic tree was reconstructed under Maximum Likelihood (ML) and Bayesian Inference (BI) analyses. We used the specimens of Sulawesian Oreophryne which were stored at the Museum Zoologicum Bogoriense (MZB). A total of about 19 morphological characters were measured by a digital caliper and ocular micrometer to the nearest 0.01 mm. The phylogenetic tree shows that the three nominal species of Oreophryne from Sulawesi are clearly clustered. Correspondingly, the phylogenetic analysis supports the recognition of a new taxon, Oreophryne sp. However, the phylogenetic relationships between Oreophryne within Wallacea remain unresolved. Consequently, further systematic analysis along with additional sequences from the type locality is necessary to clarify the interspecific relationship among this region. We examined the morphology of 50 voucher specimens of Sulawesian Oreophryne. The validity of O. celebensis, O. variabilis, and O. zimmeri was confirmed in this study, but still the latter remains to be established. The three nominal species examined here were not collected from the type locality, so additional specimens, either in the type locality, new locations, or in other areas on this island are needed to evaluate the taxonomic status of these species deeply. Moreover, the unnamed species from the highland of the Mekongga mountains differ morphologically and genetically from all previously described Sulawesian Oreophryne. This distinct species will increase the number of cross frogs in Sulawesi to four species, all of which are endemic.
Keyword: frog, morphology, Oreophryne, phylogenetic, Sulawesi, systematics