Judul: Efek Penambahan Serat Selulosa Termodifikasi 3- Aminopropiltrietoksisilana (3-APTES) Terhadap Sifat Mekanik Poliasam Laktat.
Abstrak: Poliasam laktat (PLA) merupakan salah satu polimer yang kegunaannya terbatas karena kelemahan yang dimilikinya, seperti mudah patah, serta laju kristalisasi dan sifat termal yang rendah. Penambahan serat selulosa pada PLA dapat meningkatkan kekuatan dan modulusnya. Oleh karena itu serat selulosa dimodifikasi menggunakan 3-aminopropiltrietoksisilana (3-APTES) untuk meningkatkan interaksi permukaan antara matriks poliasam laktat (PLA) dan penguat (selulosa). Serat selulosa diperoleh dari hasil pemucatan menggunakan NaClO2, CH3COOH, dan KOH yang selanjutnya ditambah 3-APTES dengan konsentrasi2% dan 5%. Serat selulosa tanpa modifikasi dan yang termodifikasi kemudian diidentifikasi menggunakan spektroskopi inframerah. Hasil spektroskopi inframerah ditandai dengan puncak baru pada bilangan gelombang 1549.35 cm-1. Selulosa yang telah dimodifikasi dibuat menjadi komposit dengan PLA untuk diuji nilai perpanjangan putus, nilai modulus elastisitas, dan kuat tariknya. Hasil pengujian mekanik pada komposit PLA-selulosa menunjukkan bahwa tambahan 3-APTES belum bisa menguatkan nilai perpanjangan putus, modulus elastisitas, dan kuat tarik dari komposit yang dihasilkan.
Keyword: 3-aminopropiltrietoksisilana, komposit, modifikasi, PLA, selulosa

Judul: Penguatan Sifat Mekanis Komposit Poliasam Laktat dan Selulosa Mikrofibril Terasetilasi-Terlaktilasi
Abstrak: The composites based on polylactic acid (PLA) reinforced with 10% modified microfibrillated cellulose (MFC) has been succesfully prepared. Modification of MFC was needed to increase its compatibility with PLA in the composite formation. In this experiment, MFC was modified with partial acetylation (degree of substitution: 1) and further grafted with lactide monomers through ring-opening polymerization. The result of acetylation and grafting were verified by infrared spectra. Thermal characterization carried out using differential scanning calorimetry measurements showed that the presence of modified MFC increased the temperature of glass transition and accelerated the crystallization of PLA. In addition, mechanical properties measurements showed that the modified MFC formed percolation network and acted as a fillers within the PLA matrix. It was showed by enhancement in elongation at break (1.1% to 1.8%), tensile strength (14.9 MPa to 25.7 MPa), and modulus of elasticity (1.7 GPa to 2.1 GPa).
Keyword: polylactic acid., partial acetylation, microfibrillated cellulose, lactide grafting

Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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