Judul: Produksi Kantong Plastik Komposit dari Tepung Ubi Kayu dan LLDPE
Abstrak: Composites plastic is plastic which made from synthetic polymer and biopolymer blends with the addition some additives. The purpose of this study was to produce composites plastic bags from linear low density polyethylene (LLDPE) resin and cassava flour with the addition of additives such as water and glycerol as plasticizer and palm fatty acid distillate (PFAD) as compatibilizer. The results showed that the best formulation for the production of plastic bags is LLDPE and cassava flour ratio 7:3 with the addition of glycerol 30% and PFAD 5%. This formulation produced composites plastic which has specific gravity 0.916 and melt flow index 4.45 gram/10 min. Composites plastic film has thickness 250 micron and the texture of its surface is relative smooth. Tensile strength and elongation value of composites plastic film at each orientation is 3.71 MPa and 396.18% for machine direction, 3.06 MPa and 126.29% for transverse direction, and 3.11 MPa and 137.06% for heat sealing. The value of whiteness index, yellowness index and opacity of composites plastic film is 6.36, 16.28 and 18.13.
Keyword: PFAD, LLDPE, glycerol, cassava flour, composites, plastic bag

Judul: Produksi Plastik Komposit Dari Tepung Ubi Kayu dan Linear Low Density Polyethylene (LLDPE)
Abstrak: The mixing of cassava flour with linear low density polyethylene is one solution to reducing the environmental problem caused by plastics waste. The objectives of this study was to produce plastic composite from cassava flour and LLDPE resins. Composite plastic was made with addition of glycerol as plasticizer and stearic acid as compatibilizer. Thermoplastic cassava flour was made by mixing glycerol by 30 and 40%. Plastic composites was made with plasticised cassava flour and LLDPE resins ratio at 20:80 and 30:70 with the addition of stearic acid by 5 and 7%. The analysis showed that stearic acid at 5 and 7%, respectively had melt flow index of 4.13 and 4.69 g/10 min. Composite pellets with plasticised cassava flour and LLDPE resins ratio at 20:80 and 30:70 each has a specific gravity of 0.916 and 0.941 g/cm3. The best mechanical properties obtained from the formulation with cassava flour and resins at 20:80 with a glycerol concentration of 40% and 5% stearic acid. Plastics from this formulation have md tensile strength of 5.62 MPa and md elongation at 594.27%. Plastic film composite with 40% glycerol has more opaque colors than plastic film composite with 30% glycerol.
Keyword: cassava flour, composite plastic, stearic acid

Judul: Pengaruh vaksinasi terhadap dinamika populasi pada model SIR (Susceptible-Infected-Recovered)
Abstrak: SIR model can be used to model the spread of diseases in a closed population based on certain assumptions. In this research, the SIR model is formulated by including the factor of vaccination. As the result, the model has been shown to have two equilibrium points, i.e. disease free and endemic equilibrium. A simulation study is carried out to illustrate the model. The results show that some equilibrium points are asymptotically stable. Moreover, a minimum level of vaccination has been defined. For the vaccination level less than the minimum level, increase in the vaccination level results in decrease of the proportion of infected individuals in the corresponding equilibrium point. On the other hand, for the vaccination level greater than the minimum level, increase in the vaccination level results in decrease the proportion of susceptible individuals in the corresponding equilibrium point. Furthermore, when vaccination level is greater than the minimum level, it is found that the time needed for the disease to extinct is shorter.
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