Judul: Wettability and Bonding Quality of Paints on Ten Tropical Woods Species
Abstrak: Surface properties of wood such as surface roughness, wettability and surface free energy (SFE) are important properties influencing further manufacturing process such as finishing or adhesive strength characteristics. The aim of this research was to determine surface properties such as surface roughness, SFE, and wettability of ten tropical woods and its effect to their bonding quality of paints. The woods tested in this study were fast-growing teak Biotrop variation, afrika, sungkai, mindi, merbau, durian, lamtoro, pulai, acacia and kempas. Wood surfaces were divided into unsanded and sanded using abrasive paper of 120 grits. SFE values were calculated based on the Rabel method. Wettability were measured by based on the contact angle between liquid paint and wood surface using sessile drop method and (S/G) model was used to evaluate the wettability of the surface coatings on the wood. Bonding quality of paints were measured using cross-cut test based on the ASTM 3359-02 standard. The results indicated that sanding decrease the surface roughness presented by Ra (arithmetical mean roughness), wettability and SFE of wood but produce higher equilibrium contact angle. Higher K-Value indicates higher wettability and bonding quality of paints. Afrika had greater wettability of acrylic and alkyd paints than the other wood species. Cross-cut tests showed that bonding quality of paints on ten wood species tend to decreased as the surface became smoother. The oil-based alkyd paint was more wettable and generates better bonding quality compared to the water-based acrylic paint.
Keyword: cat akrilik dan alkid, daya lekat, energi bebas permukaan, kekasaran permukaan, keterbasahan

Judul: The effectivity of surface coating in teak and pine for exterior use
Abstrak: Penelitian ini dilakukan untuk mengetahui efektivitas lapisan pelindung berupa water repellent (WR), bahan pengawet dan cat serta kombinasi ketiga bahan tersebut pada kayu jati berdaur panjang, jati berdaur pendek dan pinus melalui uji pemaparan terhadap cuaca selama 24 minggu. Contoh uji berupa papan berukuran 30 cm x 15 cm x 2 cm berkadar air 12±3% dengan pola penampang yang berbeda diampelas kemudian diukur tingkat kekasarannya (Ra) menggunakan roughness tester TR200. WR, bahan pengawet, cat dan kombinasinya masing-masing dilaburkan pada permukaan contoh uji dengan berat labor 100 gr/m2. Pengujian keterbasahan dilakukan dengan pengukuran sudut kontak (contact angle) antara tetesan bahan pelindung dan permukaan contoh uji menggunakan Motic Images Plus (MIP) versi 2.0. Nilai sudut kontak statis ditentukan menggunakan program PROC NLIN dari SAS 9.1.3 Portable. Contoh uji kemudian dipaparkan di areal terbuka selama 24 minggu. Setiap dua minggu sekali kondisi permukaan contoh uji dievaluasi dengan merujuk kepada ASTM D 3274-95 (evaluasi kerusakan lapisan pelindung akibat serangan mikroba), ASTM D 660-93 (evaluasi pengelupasan lapisan pelindung) dan ASTM D 661-93 (evaluasi keretakan lapisan pelindung)., The purpose of this research was to determine the effects of surface conditions on the adhesion strength of coating agents on teak and pine boards. Wood samples of 30 (L) x 15 (W) x 2 (T) cm were sanded before measurement of surface roughness (Ra) using roughness tester TR200. Water repellents (WR), preservatives, paint and it’s combinations were coated on the surface of the wood samples. Wettability was calculated by measuring the contact angle between the coatings droplet and the surface of the wood samples using Motic Images Plus (MIP) version 2.0. Static contact angles were determined by using segmented regression model in PROC NLIN of the SAS 9.1.3 Portable program
Keyword: adhesion strength, paint, surface roughness, water repellent, weathering

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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