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"High Density Polyethylene (HDPE) merupakan salah satu jenis termoplastik dimana rantai panjang yang disusun secara berulang dari struktur [ CH2 CH2 ]n . HDPE banyak diproses dengan menggunakan teknologi Ekstrusi, Injection Molding dan lain-lain. Dalam penelitian ini dilakukan pengujian dengan proses Extrusion single screw dengan menggunakan material HDPE murni dengan penambahan blowing agent yang bervariasi yaitu 0,00%; 0,05%; 0,10%; 0,15%; 0,20%; 0,25% dengan variasi temperatur die 150º, 155°, 160º, 165°, 170º, 175°. Selanjutnya pada sampel dilakukan pengujian dengan mengukur densitas, tensile strength dan elongation. Karakterisisasi pada sampel dilakukan dengan SEM (Scanning Electron Microscope) dan TGA (Thermal Gravimetry Analysis). Penelitian ini menghasilkan suatu penambahan blowing agent yang sesuai dengan parameter proses optimum dan sifat mekanik yang terbaik yaitu komposisi blowing agent 0,25% dengan temperatur die 155 °C yang meghasilkan sampel dengan densitas sebesar 0,9460 g/cc, tensile strength sebesar 10,085 Mpa ( ASTM D638–98 ) dan Elongation 232.62% ( ASTM D638-98 ). Dibandingkan dengan HDPE murni, maka penambahan blowing agent 0,25% menghasilkan penurunan densitas sebesar 0.9420%.

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High Density Polyethylene (HDPE) is one of thermoplastic consist of long repeated [CH2 CH2 ]n branch on its molecule structure. HDPE is already worldwide produced in many process such as extrusion; injection molding, and many other. During this experiment material pure HDPE with various blowing agent from 0,00%; 0,05%; 0,101%; 0,20%; 0,25% and various die temperature from 150°; 160°; 165°; 170°; 175o were extruded by extrusion single screw. Each sampel had been tested to determine its density; tensile strength and elongation. Sampel characterization was defined by SEM (Scanning Electron Microscope) and TGA (Thermal Gravimetry Analysis). The optimum condition was be achieved at die temperature 155°C and blowing agent additional 0.25% where density is 0,9460 g /cc; tensile strength 10,.085Mpa and elongation 232,62%. Compare to pure HDPE using blowing agent 0.25% can reduced density 0,9420%."

"Latar Belakang: Pempek merupakan makanan khas kota Palembang yang biasanya dikonsumsi bersama dengan larutan cuka pempek. Larutan cuka pempek mengandung asam asetat, ion klor dan fluor yang dapat menyebabkan kekasaran permukaan pada bahan basis gigi tiruan. Tujuan: Menganalisis pengaruh larutan cuka pempek terhadap kekasaran permukaan basis gigi tiruan resin akrilik heatcured, nilon termoplastik, dan cobalt-chromium alloy. Metode: Spesimen plat resin akrilik heat-cured dan nilon termoplastik berukuran 15 x 10 x 1 mm sedangkan spesimen cobalt-chromium alloy berbentuk silinder dengan diameter 7,7 mm dan tinggi 17,5 mm. Masing-masing kelompok spesimen berjumlah 10 buah. Setiap spesimen direndam dalam larutan cuka pempek pada suhu 37oC selama 4 hari. Kekasaran permukaan diukur dengan menggunakan Profilometer sebelum dan sesudah dilakukan perendaman. Hasil: Dari hasil uji statistik (p<0,05), menunjukkan bahwa terjadi perubahan kekasaran permukaan yang bermakna pada spesimen plat resin akrilik heat-cured, nilon termoplastik, dan cobalt-chromium alloy setelah perendaman dalam larutan cuka pempek selama 4 hari. Kesimpulan: Larutan cuka pempek mempengaruhi kekasaran permukaan pada plat resin akrilik heat-cured, nilon termoplastik dan cobalt-chromium alloy setelah perendaman selama 4 hari. Perubahan kekasaran permukaan terbesar terjadi pada plat nilon termoplastik sedangkan perubahan kekasaran permukaan terkecil terjadi pada cobalt-chromium alloy.

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Background: Fishcake is a typical food of Palembang city that is usually eaten with fishcake vinegar. Fishcake vinegar contains of acetic acid, chlorine and fluorine ion which cause surface roughness on the denture base material.

Objective: To analyze the effect of fishcake vinegar in surface roughness of heatcured acrylic resin, nylon thermoplastic, and cobalt-chromium alloy.

Method: Specimen plate of heat-cured acrylic resin and nylon thermoplastic was made in form of 15 x 10 x 1 mm, while the specimen cobalt-chromium alloy was used in cylinder form with a diameter of 7.7 mm and a height of 17.5 mm. Each group of specimens consist of 10 pieces. Each specimen was immersed in fishcake vinegar at 37°C for 4 days. Surface roughness was measured using a profilometer before and after immersion.

Result: Statistical analysis (p<0,05) showed that there is a significant change in surface roughness of heat-cured acrylic resin, nylon thermoplastic, and cobalt-chromium alloy after immersion in fishcake vinegar for 4 days.

Conclusions: Fishcake vinegar affects the surface roughness of heat-cured acrylic resin, nylon thermoplastic and cobalt-chromium alloy after immersion for 4 days. The highest surface roughness changes occured in thermoplastic nylon while the lowest surface roughness changes occured in cobalt-chromium alloy."

"[ABSTRAKSifat karet alam dapat ditingkatkan melalui modifikasi kimiawi secara reaksikopolimerisasi cangkok emulsi karet alam terdeproteinisasi (DPNR) denganmonomer vinil (MV) tunggal maupun paduannya menggunakan inisiatorammonium peroksidisulfat dan surfaktan sodium dodesil sulfat menghasilkankaret alam termoplastik (TPNR). Reaksi dijalankan secara eksitu pada suhu 65ºCselama 5 jam dilanjutkan pada 70ºC selama 1 jam dengan teknik batch padaberbagai komposisi DPNR terhadap MV dan rasio paduan MV (stirena (ST)terhadap metil metakrilat (MMA)). Hasil penelitian secara umum menunjukkanbahwa TPNR yang disintesis dari DPNR dengan paduan MV menggabungkansifat unggul TPNR yang diperoleh dari hasil reaksi DPNR dengan MV tunggal.Komposisi DPNR terhadap MV sebesar 60 : 40 dengan rasio ST terhadap MMAsebesar 2 : 1 ditetapkan sebagai kondisi teroptimum dalam reaksi kopolimerisasicangkok emulsi pembentukan TPNR.

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ABSTRACTNatural rubber properties can be improved by chemical modification suchemulsion graft copolymerization of deproteinized natural rubber (DPNR) witheither single or combination of vinyl monomers (MV) by using ammoniumperoxydisulfate as initiator and sodium dodecyl sulfate as surfactant to producethermoplastic natural rubber (TPNR). The reaction was run at 65ºC for 5 hourscontinued at 70ºC for an hour by exitu ? batch procedure at various proportion ofDPNR to single MV and combination of MV ratio (styrene (ST) to metylmethacrylate (MMA)). Generally, the result showed that TPNR synthesized fromDPNR and combination of MV integrated the prior properties of TPNRsynthesized from DPNR and single MV. The proportion of DPNR to MV as 60 :40 and ratio of ST to MMA as 2 : 1 were regarded as the best condition onemulsion graft copolymerization in the formation of TPNR., Natural rubber properties can be improved by chemical modification suchemulsion graft copolymerization of deproteinized natural rubber (DPNR) witheither single or combination of vinyl monomers (MV) by using ammoniumperoxydisulfate as initiator and sodium dodecyl sulfate as surfactant to producethermoplastic natural rubber (TPNR). The reaction was run at 65ºC for 5 hourscontinued at 70ºC for an hour by exitu – batch procedure at various proportion ofDPNR to single MV and combination of MV ratio (styrene (ST) to metylmethacrylate (MMA)). Generally, the result showed that TPNR synthesized fromDPNR and combination of MV integrated the prior properties of TPNRsynthesized from DPNR and single MV. The proportion of DPNR to MV as 60 :40 and ratio of ST to MMA as 2 : 1 were regarded as the best condition onemulsion graft copolymerization in the formation of TPNR.]"