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UNIT OPERASI UNTUK MEMPROSES POLIMER

UNIT OPERASI UNTUK MEMPROSES POLIMER. POLYMER PROCESSING. POLYMER END PRODUCT. articles of desired shapes. PELLET / POWDER. POLYMER PROCESSING. Pemilihan bahan baku. Pemilihan teknik proses. ekonomis. EXTRUSION. Extrude = mendorong keluar

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UNIT OPERASI UNTUK MEMPROSES POLIMER

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  1. UNIT OPERASI UNTUK MEMPROSES POLIMER

  2. POLYMER PROCESSING POLYMER END PRODUCT articles of desired shapes PELLET / POWDER

  3. POLYMER PROCESSING Pemilihanbahanbaku Pemilihanteknikproses ekonomis

  4. EXTRUSION Extrude = mendorongkeluar Extrusionadalahsuatuteknikpemrosesanuntukmengubah material termoplastikbentukbubukataubutiranmenjadilelehan (continuous uniform melt), danmendoronglelehantersebutmelaluishaping die yang terletakdiujungakhirmesin. Bentukprodukakhir yang dihasilkantergantungpadabentukdie orifice yang dilaluilelehanpolimer.

  5. EXTRUDER

  6. Single-screw extruder terdiridari 5 komponen: Drive system/sistempenggerak Feed system/sistemumpan Screw/Barrel system Head/Die system Instrumentation & Control System

  7. DIAGRAM SKEMATIK SINGLE-SCREW EXTRUDER

  8. DRIVE SYSTEM • Motor • Motor berfungsimenggerakkan screw, berdayabesarkarenaharusmendoronglelehanpolimer yang sangatkentalmelalui die/orifice yang berukurankecil. • Speed reducer • Speed reducer berfungsimenurunkan rpm motor denganfaktor 12 : 1. Jikaputaran screw terlalutinggi, makatemperaturlelehanpolimerakannaikdankemungkinanakanterdegradasi. Denganturunnya rpm, makaakandidapat torsi screw lebihbesar, daninidiperlukanuntukmendoronglelehanpolimer yang sangatkental.

  9. hopper FEED SYSTEM throat DIAGRAM SKEMATIK FEED SYSTEM DARI SINGLE-SCREW EXTRUDER

  10. SCREW/BARREL SYSTEM

  11. Screw merupakanbagian yang bergerak, danberfungsiuntuk: • Memompa/memindahkan • memanaskan • mencampur • menekan Screw berputardidalambarreldengandaya yang di-pasokoleh motor penggerak.

  12. KARAKTERISTIK GEOMETRI SCREW COMPRESSION RATIO Nilai CR berkisarantara 2 : 1 sampai 4 : 1 L/D RATIO Nilai L/D Ratio berkisarantara 18 : 1 sampai 32 : 1, dan yang paling umumdigunakanadalah 24 : 1.

  13. Screw dibagimenjadi 3 zona: Feed section(L = 1 – 10 D) Bagianiniberfungsimengambil resin dibawah hopper danmeneruskannyake barrel yang dilengkapidenganpemanasluar, sehingga resin mulaimeleleh. Transition/compression section(L = 5 D) Bagianinimengkompakkanpolimerumpanuntukmenghilangkankantongudara. Bagianinimengubah resin menjadilelehan yang mengalirkontinyu. Gaya gesekantara resin, dinding barrel, dan screw yang berputarmerupakansumberenergiuntukmeleleh-kan resin.

  14. Metering/pump section Bagianiniberfungsimenjagalajualirtetapkonstan, danmembangkitkantekananuntukmenekanlelehanpolimermelaluibagianakhirdari extruder dankeluarmelaluidie.

  15. BARREL Diagram skematik screw dan barrel

  16. Barrelmerupakansilinder yang membentangdarifeed throat sampaiujungscrew. • Ujung akhirbarreldisebutkepala/head. • Permukaanbagiandalambarreldilapisibahan yang sangatkeras, sepertitungsten-carbide alloy. • Lapisaninimengurangiterjadinyaabrasibarreldanmemperpanjangumurbarrel.

  17. Clearance/jarakantaraujung flight dengandinding barrel biasanya 0,1% dari diameter screw. • Jika clearance terlalubesar, makaakanmengurangikapasitas screw untukmelelehkandanmemompa. • Jika clearance terlalukecil, makaakanmenyebabkandinding barrel ataupun flight mengalamiabrasi.

  18. HEAD/DIE SYSTEM Diagram skematikdie head danmandrel

  19. Die merupakan “otak” darioperasi extrusion. • Head/die system menerimalelehanpolimerdari screw danmembentuknyamenjadibentukakhir yang diinginkansebelumdidinginkan. • Biasanyadigunakan nozzle dan/atau adaptor untukmengarahkanaliranlelehandaribarrel exit kedie entrance.

  20. APLIKASI • Resin yang diprosesdenganteknik extrusion: • Kebanyakanjenistermoplastikseperti • PE (polyethylene), • PP (polypropylene), • PVC (poly vinyl chloride), • ABS (acrylonitrile–butadiene–styrene) • PS (poly styrene)

  21. Produk: Pipeand tubing Sheet and cast film Coating Fiber Blown film Profile

  22. 1. Pipe and tubing Pipadan tube banyakdigunakanuntukpipa air, sepertiuntukrumahtangga, rumahsakit, danirigasi. Produkinidibuatdenganmenggunakandie yang berbentuk annulus.

  23. Sheet and cast film Sheet : tebal > 0,001 in Film : tebal < 0,001 in Produkinibanyakdigunakan, mulaidaricellotapesampai diaper.

  24. Coating Ada 2 jenis coating: substrate coating dan wire coating. Substrate coating biasanyaberbentukdatar, sepertilembaranpolimer. Contoh: untuk cover buku. Wire coating diperlukandalamproduksi extension cord, kabellistrik, dankabeltelepon.

  25. Fiber Fiber digunakanuntuktekstil (pakaiandankarpet) dantalipancing.

  26. Blown film Blown film extrusion merupakanteknik yang paling banyakdigunakan. Contohproduk: tasbelanja, kantongsampah.

  27. INJECTION MOLDING Injection molding merupakansalahsatuteknikprosesuntukmengubah material termoplastikdantermo-setting daribentuk pellet dan powder menjadiberbagaimacambentuk. Contohproduk injection modling: garpu, sendok, keyboard komputer, casing TV, casing kalkulator, telepon, dll.

  28. Injection molding melakukan 3 fungsi: Melelehkanplastiksehinggadapatdialirkandenganbantuantekanan. Menginjeksikanlelehanplastikkedalamcetakan. Memeganglelehanplastikdalamcetakandinginsementaralelehantersebutmengeras, kemudianmengeluarkanplastiktersebut.

  29. Polimer yang biasadiprosesdengan molding: Polyethylene, polypropylene, dan polystyrene untukpembuatan container, mainan, danperalatanrumahtangga. Polyesteruntuk gear, bearing, konektor, switch, dan socket listrik, perlengkapanrumah, peganganpintu. Nylonsuntukperalatan yang digunakanpadatemperaturtinggisepertibagiantangki radiator mobildanuntuk anti korosi, Acetalsuntuk gear, bearing, impeller, faucet, dan fitting pipa. Polymethylmethacrylateuntuklensadandpelindungsinarmatahari, Polycarbonatesdan ABS untukperalatanrumahdanmobil.

  30. Major parts of a typical injection-molding machine

  31. BAGIAN-BAGIAN INJECTION MOLDING: Injection unit Plasticizing screw Heating cylinder Clamp

  32. INJECTION UNIT • The injection unit essentially has two functions: • melt the pellet or powder and then • inject the melt into the mold. • It consists of • the hopper, a device for feeding process material; • a heated cylinder or chamber where the material is melted; and • a device for injecting the molten material into the mold.

  33. Schematic diagram of a plunger-type injection molding machine

  34. A measured volume of the plastic material is delivered into the heated cylinder from the hopper while the ram is retracted. • At the beginning of the injection cycle, the plunger pushes forward and forces the material through the heated cylinder compacting it tightly behind and over the centrally located spreader or torpedo. • The material is melted by heat convection and conduction. The sustained forward motion of the plunger forces the melt through the nozzle of the cylinder into the mold.

  35. In the plunger-type machine, material flow in the cylinder is essentially laminar. • Consequently there is hardly any mixing in this system and, as such, large temperature gradients exist in the melt, and color blending is thus problematic. • Also, as a result of the friction between the cold resin pellets in the neighborhood of the hopper and the barrel walls, a considerable loss of pressure, up to 80% of the total ram pressure, occurs. • This necessitates long injection time. As indicated above, the resin is melted by heat conduction from the walls of the cylinder and the resin itself.

  36. Since plastics are poor heat conductors, high cylinder temperatures are required to achieve fast resin plasticization. • This can result in the degradation of the material. • To avoid such possible material deterioration, the heating of the cylinder is limited, and this also limits the plasticizing capacity of plunger-type injection machines.

  37. Reciprocating-screw machine

  38. Mold/cetakanterdiridari 2 bagian, yaitucavitydancore. Cavitymemberibentukluar, sedangcorememberibentukdalam. Kebanyakan mold dirancanguntukpenggunaan yang lama, sehinggadibuatdaribaja. Agar bentukproduktetapkonsisten, maka material cetakanharustahanausdankorosi.

  39. Cetakan/mold sederhanauntukmencetakgelasbesar/tumbler

  40. FIBER SPINNER Prosespembuatan fiber meliputi extrusion cairanpolimerdalambentukfilamenkecildanpanjang, yang akanmengerasdandigulung. Jikabahanbakunyaberupalarutanpolimer, makasolvenharusdiuapkandenganbantuan gas panas (proseskering) ataukoagulasi (prosesbasah).

  41. Gear pump drive Gear pump Hopper Extruder Spinneret Insulated isothermal oven Diagram skematik melt-spinning apparatus

  42. (a) Spinneret used for fiber spinning; (b) a simple capillary

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