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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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Presentation Transcript
slide1

UNIT OPERASI

UNTUK

MEMPROSES POLIMER

slide2

POLYMER PROCESSING

POLYMER END PRODUCT

articles of desired shapes

PELLET / POWDER

slide3

POLYMER PROCESSING

Pemilihanbahanbaku

Pemilihanteknikproses

ekonomis

slide4

EXTRUSION

Extrude = mendorongkeluar

Extrusionadalahsuatuteknikpemrosesanuntukmengubah material termoplastikbentukbubukataubutiranmenjadilelehan (continuous uniform melt), danmendoronglelehantersebutmelaluishaping die yang terletakdiujungakhirmesin.

Bentukprodukakhir yang dihasilkantergantungpadabentukdie orifice yang dilaluilelehanpolimer.

slide6

Single-screw extruder terdiridari 5 komponen:

Drive system/sistempenggerak

Feed system/sistemumpan

Screw/Barrel system

Head/Die system

Instrumentation & Control System

slide8

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.
slide9

hopper

FEED SYSTEM

throat

DIAGRAM SKEMATIK FEED SYSTEM DARI SINGLE-SCREW EXTRUDER

slide11

Screw merupakanbagian yang bergerak, danberfungsiuntuk:

  • Memompa/memindahkan
  • memanaskan
  • mencampur
  • menekan

Screw berputardidalambarreldengandaya yang di-pasokoleh motor penggerak.

slide12

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.

slide13

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.

slide14

Metering/pump section

Bagianiniberfungsimenjagalajualirtetapkonstan, danmembangkitkantekananuntukmenekanlelehanpolimermelaluibagianakhirdari extruder dankeluarmelaluidie.

slide15

BARREL

Diagram skematik screw dan barrel

slide16

Barrelmerupakansilinder yang membentangdarifeed throat sampaiujungscrew.

  • Ujung akhirbarreldisebutkepala/head.
  • Permukaanbagiandalambarreldilapisibahan yang sangatkeras, sepertitungsten-carbide alloy.
  • Lapisaninimengurangiterjadinyaabrasibarreldanmemperpanjangumurbarrel.
slide17

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.
slide18

HEAD/DIE SYSTEM

Diagram skematikdie head danmandrel

slide19

Die merupakan “otak” darioperasi extrusion.

  • Head/die system menerimalelehanpolimerdari screw danmembentuknyamenjadibentukakhir yang diinginkansebelumdidinginkan.
  • Biasanyadigunakan nozzle dan/atau adaptor untukmengarahkanaliranlelehandaribarrel exit kedie entrance.
slide20

APLIKASI

  • Resin yang diprosesdenganteknik extrusion:
  • Kebanyakanjenistermoplastikseperti
  • PE (polyethylene),
  • PP (polypropylene),
  • PVC (poly vinyl chloride),
  • ABS (acrylonitrile–butadiene–styrene)
  • PS (poly styrene)
slide21

Produk:

Pipeand tubing

Sheet and cast film

Coating

Fiber

Blown film

Profile

slide22

1. Pipe and tubing

Pipadan tube banyakdigunakanuntukpipa air, sepertiuntukrumahtangga, rumahsakit, danirigasi.

Produkinidibuatdenganmenggunakandie yang berbentuk annulus.

slide23

Sheet and cast film

Sheet : tebal > 0,001 in

Film : tebal < 0,001 in

Produkinibanyakdigunakan, mulaidaricellotapesampai diaper.

slide24

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.

slide25

Fiber

Fiber digunakanuntuktekstil (pakaiandankarpet) dantalipancing.

slide26

Blown film

Blown film extrusion merupakanteknik yang paling banyakdigunakan.

Contohproduk: tasbelanja, kantongsampah.

slide27

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.

slide28

Injection molding melakukan 3 fungsi:

Melelehkanplastiksehinggadapatdialirkandenganbantuantekanan.

Menginjeksikanlelehanplastikkedalamcetakan.

Memeganglelehanplastikdalamcetakandinginsementaralelehantersebutmengeras, kemudianmengeluarkanplastiktersebut.

slide29

Polimer yang biasadiprosesdengan molding:

Polyethylene, polypropylene, dan polystyrene untukpembuatan container, mainan, dandperalatanrumahtangga.

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.

slide31

BAGIAN-BAGIAN INJECTION MOLDING:

Injection unit

Plasticizing screw

Heating cylinder

Clamp

slide32

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.
slide34

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.
slide35

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.
slide36

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.
slide38

Mold/cetakanterdiridari 2 bagian, yaitucavitydancore.

Cavitymemberibentukluar, sedangcorememberibentukdalam.

Kebanyakan mold dirancanguntukpenggunaan yang lama, sehinggadibuatdaribaja.

Agar bentukproduktetapkonsisten, maka material cetakanharustahanausdankorosi.

slide40

FIBER SPINNER

Prosespembuatan fiber meliputi extrusion cairanpolimerdalambentukfilamenkecildanpanjang, yang akanmengerasdandigulung.

Jikabahanbakunyaberupalarutanpolimer, makasolvenharusdiuapkandenganbantuan gas panas (proseskering) ataukoagulasi (prosesbasah).

slide41

Gear pump drive

Gear pump

Hopper

Extruder

Spinneret

Insulated isothermal oven

Diagram skematik melt-spinning apparatus