Judul: Pembuatan dan Karakterisasi Film Biodegradabel dari Kitosan/PLA (Poly Lactic Acid) dengan Pemlastis Polietilen Glikol (PEG)
Abstrak: Plastic has many advantages such as good mechanical and barrier characteristics, cheap, easy to form, and flexible in application, so it becomes the most used material as food packaging. Unfortunately, plastic waste is difficult to be degraded in nature, therefore polluting the environment. Moreover, global warming issue has driven to create an eco-friendly packaging such as biodegradable plastics made from renewable resources. The objective of this research was to develop biodegradable plastic made from chitosan and poly(lactic acid) (PLA) with the addition of poly (ethylene glycol) (PEG) as plasticizer. The main goal of these blends is to improve the water vapor barrier of chitosan by blending with PLA and to improve the elasticity of chitosan/PLA blended films. The obtained films were characterized in terms of physicochemical and mechanical properties including water activity (aw), thickness, tensile strength, elongation at break, and water vapour permeability (WVP). Moreover, Scanning Electronic Microscopy (SEM) and Differential Scanning Calorimetry (DSC) were used to confirm the miscibility of PLA and chitosan. Films of chitosan/PLA blends had aw values range from 0.71 until 0.76. Generally, the blend films prepared with lactic acid as chitosan solvent were thicker than those prepared with acetic acid as chitosan solvent. The same phenomenon was observed in addition of PEG, where films containing PEG as plasticizer were thicker than those without PEG. The tensile strength and elongation at break of the obtained films decreased with the addition of PLA and PEG. It appeared that the obtained films produced with lactic acid as solvent and with the addition of PEG were more elastic than those produced with acetic acid as chitosan solvent and without the addition of PEG. In term of barrier properties, the WVP value of film chitosan/PLA ranged from 111.8 to 208.9 gr/m2/day for films prepared with lactic acid as chitosan solvent and from 233.3 to 358.15 gr/m2/day for films prepared with acetic acid as solvent. Furthermore, the observation on microstructure of the chitosan/PLA composite films, conducted with SEM, has revealed that PLA particles have been well distributed in chitosan matrix. However, the average diametre of PLA particles was in the range of 2 – 3 m, therefore this blending was categorized as microcomposites.
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Judul: Characterization and Biodegradation of Polyblend (Styrofoam-Starch) with Polylactid acid (PLA) as Biocompatizer.
Abstrak: Styrofoam is a kind of polystyrene which can not be naturally decomposed. The increasing amount of using styrofoam causes environment pollution. In facing this problem, modification of recyclable styrofoam is needed to produce degradable plastic. Starch can be a solution because it is a polymer that can be biologically decomposed. The mixture of starch to the styrofoam composite creates biodegradable plastic. Unfortunately, various polarity of styrofoam and starch is difficult to mixed homogenously, so we need polylactic acid (PLA) as the biocompatizer. Styrofoam and starch of four different concentrations of PLA, 5, 10, 15, and 20%. Film with the highest homogeneity was given by 80:20 concentration of styrofoam and starch combination with 20 % of PLA addition. The more PLA, the more homogenous of film we got. Film with the highest homogeneity produced substantial weight reduction which about 10%. The film that has been produced was amorphous since it had wide melting point, 155 °C to 185 °C. Infrared spectrum film showed the existence of C-O ester on 1184 cm-1 region. Ester functional group indicated that the film could be biodegraded. The infrared spectrum of the film did not show new functional groups, so we concluded that the film was a product of physical mixture between styrofoam and starch.
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Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular