Judul: Properties of Inner Part of Oil Palm (Elaeis guineensis Jacq.) Trunk Compregnated by Methylene Diphenyl Diisocyanate and Its Application as Blockboard
Abstrak: Inner part of oil palm (Elaeis guineensis Jacq.) trunk (IOPT) is still not optimally utilized. The IOPT can be used as raw material for wood and composite products such as blockboards to increase its added value. However, the IOPT has low density, strength, and dimensional stability. The physical and mechanical properties of the IOPT can be improved by wood modification techniques such as densification, impregnation, and compregnation. Densification has drawbacks such as the occurring of a spring-back so that the modification results are not fixed. Meanwhile, impregnation is a technique of filling wood voids with thermosetting resin to increase density. The combination of impregnation and densification is called compregnation. Compregnation has a lower spring-back than densification due to the presence of impregnants. So far, the impregnants used in the impregnation or compregnation techniques are formaldehyde-based resins which are not environmentally friendly. Therefore, research on impregnation using materials that are more environmentally friendly is important. This study aims to improve the properties of IOPT through impregnation, densification, and compregnation methods and its application as a blockboard core. The research was divided into three stages, that is (1) determination of methylene diphenyl diisocyanate (MDI) concentration as an impregnant in the IOPT (2) determination of the optimum compression ratio in the densification and compregnation of IOPT, and (3) characterization of physical and mechanical properties of blockboard with a compregnated IOPT as a core. The impregnation of IOPT was carried out by the vacuum-pressing method. The impregnation process was initiated with a 7.6 MPa vacuum process for 15 minutes. Impregnation using MDI resin with concentrations of 10% and 20% were carried out at a pressure of 1.2 MPa for 60 minutes. Densification with a target thickness of 1.5 cm and compression ratios of 20% and 30% was carried out using hot pressing at a temperature of 150 °C and a pressure of 8 MPa for 30 minutes. Compregnation is carried out by a combination of impregnation and densification as described above. The physical and mechanical properties of the modified IOPT were carried out according to the ASTM D 143-2000 standard. The resistance of the MDI impregnated IOPT against subterranean termites was tested based on the SNI 7207-2014 standard. The blockboards were made from the compregnated IOPT as the core and the mangium wood (Acacia mangium Willd.) veneer as the face layers. Total blockboards layers are three and seven layers. The IOPT and mangium wood veneers were glued with MDI resin with a spread rate of 200 g·m-2 and hot- pressed at 100 °C and a pressure of 0.5 MPa for 4 minutes for three-ply blockboard and 8 minutes for seven-ply blockboard. Physical and mechanical properties of blockboards were tested based on Japanese Industrial Standard (JIS) A 5908-2003 and Japanese Agricultural Standard (JAS) 232-2003. The results showed that the impregnation using MDI improved the physical and mechanical properties of the IOPT at the bottom, middle, and top parts. The increase in the physical and mechanical properties of the IOPT was higher by increasing MDI concentration. The MDI impregnated IOPT had a higher density values and a lower
Keyword: blockboard, compregnation, inner part of oil palm trunk, methylene diphenyl diisocyanate

Judul: Quality enhancement of the inner part of oil palm trunk by close system compression method and by phenol formaldehyde compregnation
Abstrak: Improvement of physical and mechanical properties of oil palm trunk could be done by close system compression (CSC) and by compregnation with fenol formaldehida. The aims of these researches were to determine the maximum compression level by studying the density distribution and stress-strain curves of oil palm trunk, to evaluated the fixation of the inner part of oil palm trunk by close system compression, heat treatment and steam treatment, to measured the physical, mechanical, anatomical and chemical of densified oil palm trunk by CSC, and to evaluated the physical and mechanical of phenol formaldehyde (PF)- densified of oil palm trunk. The results showed that density of oil palm trunk was around 0.23-0.74 g/cm3. The density at the outer part was higher, and then decreasing toward the center of trunk. The stress-strain curves showed that water saturated and wet conditions were easier to compress than that of air dry condition. The compression level increased from the outer part to the center. The maximum compression levels of the center park were 67% in air dry condition and 72-73% in wet and water saturated conditions from their initial thickness. Fixation of the trunk by steam treatment method was achieved at 170 oC for 30 min, by CSC at 180 oC for 30 min, while by heat treatment was not yet fixed even at 200 oC for 180 min. Compression by CSC results in the improvement of the physical and mechanical properties of the inner part of oil palm trunk. The density, MOR, MOE and compression parallel to grain of densified-oil palm trunk were improved 3.33-90%, 14.31-192.81%, 43.22-192.74% and 18.93- 123.20%, from the initial samples (control), respectively. The chemical components especially holocellulose was decreased with the increasing of temperature and time of compression, but the other components (lignin, alfa cellulose, extractive by hot water and by alcohol-benzene) were increased. Then, PF compregnation results in the improvement of the physical and mechanical of the inner part of oil palm trunk. The density, MOR, MOE and compression parallel to grain of PF-densified oil palm trunk were improved 94.12–176.47%, 191.7–309.5%, 108.2–287.5%, and 83.72–191.75%, from the initial samples (control), respectively. The last, the inner part of oil palm trunk after treating by CSC and by compregnation PF is suitable for furniture material.
Keyword: Oil Palm Trunk, Close System Compression Method, phenol formaldehyde, physical and mechanical properties

Judul: Analisis kestabilan model infeksi virus leukemia feline
Abstrak: Virus leukemia foline adalah virus penyebab kanker darah dan kerusakan swnsum tulang pada kucing. Virus ini menyebar secara pidemi melalui air liur dan lendir hidung lewat interaksi antarkucing. Penyebaran virus leukemia feline ini digarnbarkan dengan suatu model matematis yang memuat sejumlah persarnaan diferensial biasa non linear yang didasarkan pada prinsip-prinsip epidemi standar (Murray, 1989). Model ini mendeskripsikan penyebaran virus lellkelllia feline dalarn suatu populasi konstan yang dihubungkan dengan waktu.
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