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: Infeksi leucocytozoon Smithi (Laveran dan Lucet, 1905) pada kalkun
Abstrak: Leucocytozoon smithi adalah parasit darah yang menyebabkan leucocytozoonosis pada kalkun, dan termasuk dalam genus Leucocytozoon yang perkembangan skizogoninya terja- di dalam sel-sel endotel dan sel-sel parenkhim hati, jan- tung, ginjal dan organ-organ lain dari unggas. Genus ini menghasilkan skizon yang besar. Gametogoninya terjadi di dalam sel-sel darah dan sel yang terinfeksi dapat berubah bentuk dan mengambil bentuk kumparan. Parasit ini tidak menghasilkan pigmen dan ditularkan oleh lalat penghisap darah dari genus Simulium. Infeksi kalkun terjadi pada saat sporozoit masuk ke dalam peredaran darah dan selanjutnya masuk ke dalam sel- sel parenkhim hati. Siklus hidupnya mirip dengan siklus hidup L. simondi seperti yang diuraikan di bawah ini. Skizogoni yang terjadi di dalam hati menghasilkan skizon hepatik. Skizon hepatik dewasa menghasilkan merozoit dan sinsitia. Merozoit dari skizon hepatik memasuki eritroblas dan eritrosit dan membentuk gametosit bulat, sedangkan sinsitianya dapat masuk ke dalam sel-sel RES dan kemudian membentuk megaloskizon. Megaloskizon dewasa menghasilkan merozoit yang kemudian masuk ke dalam limfosit dan leukosit lain membentuk gametosit memanjang. Gametositgametosit ini akan menjadi makrogametosit dan mikrogametosit. Perkembangan parasit dalam tubuh vektor (Simulium), segera dimulai setelah vektor menghisap darah kalkun yang mengandung gametosit ini. Dalam tubuh vektor ini akan ter- jadi pembuahan makrogamet oleh mikrogamet (tahap gametogoni). Dari pembuahan ini dihasilkan zigot yang bergerak (ookinet). Ookinet akan masuk dinding usus vektor untuk memulai tahap sporogoni yang menghasilkan sporozoit. Sporozoit ini akan menuju ke kelenjar ludah dan dari sini dapat dipindahkan lagi ke tubuh kalkun pada saat vektor menghisap darah. Vektor untuk L. smithi adalah S. occidentale, S. nigroparvum, S. slossonae, S. nigritarse. L. smithi berbahaya, terutama bagi kalkun-kalkun muda. Mortalitasnya dapat mencapai 90 persen. Gejala klinis yang ditimbulkannya antara lain anorexia, lemas dan cenderung untuk duduk, kekurusan dan kelemahan, sesak nafas dan in- koordinasi dan terjungkal terlihat pada stadium akhir dan selanjutnya kalkun mengalami coma kemudian mati…dst
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