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 Campuran Tapioka-Onggok Termoplastis dengan Compatibilized Polietilen
Abstrak: One of alternative solution for plastic disposal problem is by developing biodegradable plastic. The typical drawbacks of starch-based plastic is inferior of its physico-mechanical properties. In order to improve the physico-mechanical properties and compatibility of blending system, tapioca-casava bagasse was modified into thermoplastic tapioca-casava bagasse blends while polyethylene was compatibilized by addition maleic anhydride. The aim of this research was to produce composite plastic from thermoplastic tapioca-casava bagasse blends and compatibilized polyethylene (compt-HDPE, compt-LDPE and compt-LLDPE). This research investigated the effect of fiber content in formulating the tapioca-casava bagasse blends, as 5, 10, 15 and 20%; glycerol (as plasticizer) concentration, as 30, 35 and 40% to the mechanical, thermal, biodegradability and surface morphological properties of composite plastics. The result showed that fiber contents in blends tapioca-casava bagasse up to 15% can improve physico-mechanical properties (tensile stress at yield, tensile stress at break and thermal properties) but addition of glycerol more than 30% can decrease mechanical composite plastic properties especially for HDPE. Introduction of thermoplastic tapioca-casava bagasse in polyethylene composite plastic generally can decrease physico-mechanical properties plastic. Synthetic polymer that suitable with thermoplastic blends tapioca-casava bagasse was compt-HDPE. The best result gained from 40% thermoplastic blends with HDPE, 15% of fiber and 30% of glycerol contents. Biodegradability test showed that composite plastic can be degraded, but only natural component such as starch and fiber was degraded.
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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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