Judul: Pengaruh Suhu Penyimpanan Terhadap Sifat Fisik dan Mekanik Kemasan Plastik Retai
Abstrak: Retail plastisc are commonly used for food and non-food packaging. Retail plastics that used for packaging of fresh product should have good physical and mechanical properties in order to keep the quality of the product. Mechanical properties of plastic packaging are seen from tensile strength and elongation percentage, while physical properties are seen from water vapour permeability and morphology surface. Plastic retail that has good mechanical properties is HDPE and HDPE perforated. Biodegradable plastic has low mechanical and physical properties because of a mixture of tapioca starch. The effect of storage temperatures are reduced the mechanical properties of HDPE and HDPE perforated, especially in low-temperature storages. While storage temperatures does not affect the mechanical properties of biodegradable plastic significantly. Based on morphology surfaces, storage in low temperature will change the surface of biodegradable plastic. Its seen from the increasing number and shape of the granules of starch on the surface of the plastic. Water vapor permeability of HDPE and HDPE perforated increased during the time of storage, while the biodegradable plastic showed a decreased.
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Judul: Rekayasa proses produksi bioplastik berbahan baku pati termoplastik dan polietilen
Abstrak: Plastics have been used widely for packaging materials. However, plastic wastes can pollute environment because of its persistency to be biodegraded by microorganisms. Efforts have been conducted to develop environmental friendly plastic from renewable resources. Problems encountered in the manufacture of bioplastic are poor physical-mechanical properties and incompatibility between hydrophilic/polar and hydrophobic/non-polar materials. The modification of raw materials and use of compatibilizer can be applied to improve the compatibility between the two material blends. The purpose of this study is to develop a process of manufacturing bioplastic by modifying the raw material characteristics and the use of compatibilizer. This study consisted of three steps, namely preparation of thermoplastic starch, preparation of maleic anhydride (MA) grafted with LLDPE/HDPE (LLDPE-g-MA/HDPE-g-MA) and manufacturing process of bioplastic. Thermoplastic was prepared by mixing distilled water and glycerol with tapioca, and then allowed to aging for 8 days to a mixture of distilled water and glycerol can be absorbed completely into raw materials (tapioca). Grafting of maleic anhydride with LLDPE/HDPE (LLDPE-g-MA and HDPE-g-MA) was carried out in a twin screw extruder. There were three levels of maleic anhidride concentration namely 2.5%, 5%, 7.5% (w/w) and dicumyl peroxide 0.1% (w/w polymer) used in this experiment. After mixing LLDPE-g-MA and HDPE-g-MA compatibilizer with thermoplastic starch (TPS), the resulting mixtures were then extrudered with LLDPE/HDPE. Four ratios between LLDPE/HDPE and TPS were investigated namely 0:100; 20:80; 40:60; and 60:40. The plastic properties observed included melt flow rate, density, thermal, mechanical, barrier, and degradation properties. The results showed that increasing thermoplastic starch content decreased melt flow rate, melting temperature, mechanical, oxygen transmition rate properties and increased density, water vapor transmition rate and its biodegradability. The presence of LLDPE-g-MA/HDPE-g-MA compatibilizer resulted in better physical and mechanical properties of bioplastic. The compatibilizer improved surface adhesion and decreased surface tension between TPS and LLDPE/HDPE matrix. The best formulation for wrapping applications was the LLDPE-TPS with 40% of TPS and 5% MA with 6,96% of grafting degree, whereas that for plastic bag applications was HDPE-TPS with 30% of TPS and 7,5% MA with 3,21% of grafting degree. Stability tests of bioplastic TPS-LLDPE and TPS-HDPE for packaging applications at room and low temperature showed no significant changes in the mechanical properties, permeability, and morphology, and therefore the product has the ability to maintain mechanical properties at low temperature.
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Judul: Mitochondrial DNA Gene Organization and Phylogenetic Relationship of Naja siamensis
Abstrak: Naja siamensis is one of Asiatic cobra in the Family of Elapidae, known as a cryptic snake. It has many morphological variations that lead to misidentification. Misidentification can cause the wrong concept in developing antivenom types due to high snakebite cases occur in Thailand. Thus, an accurate species identification using a molecular approach is crucially required. Mitochondrial DNA has been used widely in snake molecular studies. These studies were aimed to determine the arrangement of the N. siamensis partial mitochondrial genes using reptile-oriented primers and to reveal the phylogenetic relationship among other species of Asian cobra. DNA extraction was carried out based on the standard DNA salting-out protocol and was conducted by bioinformatics analysis using BLASTn and MEGA 6 software. Gene annotation was performed against N. kaouthia complete genome. A total of 3121 bp of N. siamensis mtDNA genes were sequenced consisting of partial of six regions: 16S rRNA, ND1, tRNA-Ile, CRII region, tRNA-Leu, tRNA-Gln, and COI genes. The mtDNA gene organization of N. siamensis was predicted to has a similar pattern with the common Elapidae mtDNA gene organization. This study showed that there is a monophyletic form in Naja genus and N. kaouthia is the closest species with N. siamensis based on partial 16S rRNA and ND1 gene.
Keyword: 16S rRNA, Elapidae, ND1, phylogenetic relationship