Jumat, 25 Desember 2009

MENGENAL PLASTIK

Pengenalan Plastik secara umum diakui oleh Pemerintah

Banyak sekali plastik yang beredar di masyarakat saat ini, berbagai jenis plastik digunakan berbagai macam fungsinya akan tetapi sebagian besar produksi plastik tersebut mempunyai proses yang hampir sama (yaitu sederhana dan mudah) akan tetapi bagi kita yang belum tahu sama sekali sangat susah.

Berikut aneka ragam plastik (biasa dipakai sehari-hari) antara lain :

1. PET /PETE
PET (Polyethylene Terephthalate) adalah polimer jernih dan kuat dengan sifat-sifat penahan gas dan kelembaban. Kemampuan plastik PET untuk menampung karbon dioksida (karbonasi) membuatnya sangat ideal untuk digunakan sebagai botol-botol minuman ringan (bersoda / terkarbonasi). Selain itu plastik PET juga sering digunakan sebagai botol air minum kemasan.dan dapat digunakan sebagai kemasan stand up pouch kemasan reffil isi ulang.

2. HDPE/HD/MD
HDPE (High Density Polyethylene), merupakan bahan plastik yang bewarna putih susu atau putih bersih. Digunakan untuk kantong tissue, botol detergent dan minyak, dan plastik anti panas, pipa plastik.shopping bag dan kantong plastik yang cocok untuk kantung sayur makanan yang berkuah karena fleksibel dengan kekuatan tinggi.

3. PVC
PVC (Poly Vinly Chlorine), merupakan bahan plastik yang dipergunakan untuk packing botol minyak, daging, pipa air dan jendela plastik.




4. LDPE/LLDLLDPE (Low Linier Density Poly Ethylene) dikenal sebutan PE saja, merupakan bahan plastik yang digunakan sebagai packing minuman atau barang-cairan, seperti es batu, syrup, maupun minuman lainnya.
LDPE (Low Density Polyethylene), merupakan bahan plastik yang digunakan untuk pelapis kaleng. Plastik pembungkus makanan supaya tetap hangat (food wrapping). Kantong grocery, bungkus roti, tas plastik fleksibel dengan kekuatan remas.

5. PP/OPP
PP (Polypropylene), merupakan bahan plastik yang digunakan untuk dipakai pada packing makanan kering / snack. sedotan, kantong obat, penutup, cup, tas, botol, dsb.
OPP (Oriented Polystyrene), sangat bening, kurang tahan panas. Digunakan untuk mempacking roti & snack, t-shirt, jackets, baju. untuk Menambah keindahan dan penampilan product .
Plastik Mika berbahan campuran antara bahan PP/PE/PVC biasanya digunakan untuk album, taplak meja, sampul, bungkus dll.dan dijual dalam kemasan roll.

6. POLYSTYRENE/STYROFOAM
Polystyrene (PS) bersifat berubah bentuk & berbunyi. Bahan plastik yang digunakan untuk gabus (styrofoam, cup, box, tray daging, tempat telur)
Lunchbox Polystyrene, merupakan bahan plastik yang digunakan untuk packing makanan ringan, nasi, dll


Data diatas disadur dari sumber http://www.distributorplastik.com/

Rabu, 23 Desember 2009

PRINSIP-PRINSIP EXTRUSION

Latar Belakang
Extrusi pada thermo plastik adalah proses pada material sampai mencapai meleleh akibat panas dari luar / panas gesekan dan yang kemudian dialirkan ke die oleh screw yang kemudian dibuat produk sesuai bentuk yang diinginkan. Proses ekstrusi adalah proses kontinyu yang menghasilkan beberapa produk sperti, Film plastik, tali rafia, pipa, peletan, lembaran plastik, fiber, filamen, selubung kabel dan beberapa produk dapat juga dibentuk.

Extruder
Ada yang dimaksut extruder adalah mesin yang terdiri dari Hopper, Barrel/screw dan Die. Berikut gambaran extruder yang sering ada saat ini.

Gambar Komponen Extruder

Hopper
Semua extruder pasti mempunyai masukan untuk bahan biji/pellet plastik yang melalui lubang yang nantinya mengalir dalam dinding dinding extruder tsb, hopper biasanya terbuat dari lembaran baja atau stainless steel yang berbentuk untuk menampung sejumlah bahan pelet plastik untuk stock beberapa jam pemrosesan. Hopper ada yang disediakan pemanas awal jika diperlukan proses pellet yang memerlukan pemanasan awal sebelum pellet memasuki extruder.

Screw
Screw adalah jantungnya extruder, screw mengalirkan polimer yang telah meleleh ke kepala die setelah mengalami proses pencampuran dan homogenisasi pada lelehan polimer tersebut

w = Flight Width (~ 0.1 D) W = Pitch (1.0D)
H = Flight Diameter (HF ~ 0.1D) δ = Flight Tip/Barrel Clearance (0.001C)
HF/Hm = Comprission Rasio (2-4) Φ = Helix Angle (17.70)

Gambar Parameter Screw

Ada beberapa pertimbangan dalam mendesign sebuah screw untuk jenis material tertentu, yang paling penting adalah Depth of Chanel (kedalaman kanal). Mesikipun screw itu mempunyai fungsi sama secara umum, alangkah baiknya merancang disesuaikan dengan tipe material yang dipakai untuk mendapatkan hasil yang terbaik. Jadi untuk contoh optimal proses screw bahn PVC, kemudian diikuti screw untuk bahan PP/PE

Screw PVC
Karena kita ketahui PVC adalah material yang tidak stabil dalam keadaan panas, maka untuk proses ini memerlukan screw dengan kedalaman chanel yang lebih, sedikit bahkan tidak ada zona metering sama sekali, bahan dilapisi dengan hard chrom, ujung screw berbentuk kerucut menhindari material tertahan. Diameter scrw bervariasi antara 30mm s/d 140mm. L/D rasio berfariasi antara 18 - 22 untuk singgle screw dan 16 - 18 untuk double/twin screw. Compresion rasio bervariasi antra 1.5 -2.2 : 1 baik untuk screw singgle maupun twin. Venting(lubang) pada extruder di pakai untuk menghilangkan uap/gas.

Screw PP/PE
Screw PP/PE hampir sama, tetapi screw ini di desain dengan chanel yang dangkal, compressi tiba-tiba dan zona matering yang lebih panjang. L/D rasio bervariasi 24:1 s/d 33:1, diameter screw 20mm s/d 250mm, compresi rasio 2.5 s/d 3.1


Type Screw Barrier (2 ulir)
Pada kasus-kasus tertentu atau permintaan design khusus, screw tidak dapat menyelesaikan proses leleh secara sempurna. Jadi dalam kasus tertentu extruser berisi material plastik yang belum leleh, ini dapat di cegah dengan membuat screw ulir kedua (barrier) pada kanal (lihat gambar). Barier ini dapat memotong dan memaksa hanya plastik yang leleh bisa lewat. Jadi design barrier ini memastikan lelehan plastis komplit /selesai pada extruder

ada bebrapa jenis yang berbeda screw barrier yang ada dipasaran saat ini. Adalah seperti contoh dibawah dimana mempunyai karakteristik sendiri sendiri.
1. Maillefer / Uniroyal
2. Hartig
3. Bar I dan Bar II

Kepala Mixing
Daerah metering pada screw standar tidak membunyai pencampuran yang baik. Aliran lapisan-lapisan halus plastik berjalan secara tetap pada dalam screw. Sehingga jiga ada lapisan yang tidak sama tidak akan bercampur dengan baik, kepala Mixer dibuat pada secrew agar dapat mencapur antar lapisan tersebut sehingga lebih merata dan homogen.
Pin Mixer (Dupon Mixer) adalah sample mixer yang menggunakan pin dengan gesekan rendah, alat ini mudah di pasang pada screw yang ada untuk meningkatkan performance dari screw

Dupon Mixer

Type lain dari Mixer adalah Maddock (Union Carbide) dam Egan, mixer jenis ini beroperasi pada lelehan material dengan gaya gesek tinggi sehingga dapat lebih sempurna percampurannya. Mixer maddock cara kerja operasi seperti screw type barrier, putarannya mengakibatkan material bergerak maju dan tertekan sehingga membantu material lebih homogen.
Maddock Mixer

Egan Mixer

Breaker Plate /Screen Park(saringan)
Breker Plate dengan saringan dimasukkan kedalam adapter, yang mana menghubungkan antara ujung extruder dan pangkal die. Peralatan ini mempunyai beberapa fungsi sebgai berikut
Meredam puteran rotasinal lelehan dan dirubah menjadi searah
Memperbaiki homogenisasi dengan memecah dan menggabungkan lagi
Memperbaiki mixing dengan meningkatnya tekanan balik
Menghilangkan kotoran dan materil tidak leleh.
Saringan dibuat beberapa lapis dan tiap lapis mempunyai perbedaan mesh, saringan paling kasar sebagai penopang diletakkan menghadap breker plate kemudian ke yang paling halus terakhir
Dies
Variasi type dies digunakan untuk proses bahan PVC atau PP/PE. Ini bisa berbentuk Flat atau model lingkaran. Tyope dies dapat dilihat sebagai berikut.

Dies PVC
PVC adalah bahan panas tidak stabil, maka die untuk PVC harus memiliki alur yang sempurna. Spiral mandrel pada die berguna untuk membagi lelehan merata dan membantu lebih homogen sehingga aliran menjadi lebih halus merata ke luar dies

Mandrel untuk bahan PVC

Dies PP/PE
Untuk memroses bahan PP/PE die menggunakan spiral seperti gambar. Plastik leleh mengalir dari lubang masuk ke putraan spiral pada die. Dari gambar tersebut ini jelas bahwa kedalam antara sepiral dan dinding betambah seiring bertambahnya material dalam die itu sendiri, sebagi hasilnya penyebaran diseluruh die lebih merata sehingga mudah untuk di adjust ketebalan dari tabung / balon.
Peralatan tambahan
Ketika produk keluar dalam bentuk lelehan (spt. Film, sheet, Pipa, Fiber dll) keluar dari dies ini didinginkan oleh air/udara/rol dingin dam kemudian dipotong menjadi barang jadi dengan berbagai teknik. Dalam berapa proses seperti BOPP, tali rafia, fiber dll, setelah pendinginan awal kemudian akan dipanaskan kembali melalui oven pemanas dan kemudian di lemaskan untuk memperoleh sifat mekanik dan sifat optik lebih baik. Bebrapa peralatan pendinginan dan pemanasan sbb
Variasi Dies untuk perbedaan die gap untuk aplikasi PE/PP/PVC

Sumber : Product Aplication dan Research center (mumbai)
Polimer extrusien 4th adition (Rowendal)

METODE PEMBUATAN FILM PLASTIK

EXTRUSION FILM

There are fundamentally two different methods of extruding film, namely ,blow extrusion and slit die extrusion. The former method produces tubular film, which may be gussetted or lay-flat while the latter result is flat film. If desired, lay-out film can be slit to give flat film. The equipment for film extrusion consists of an extruder, fitted with a suitable die equipment to cool the molten film, haul-off machinery and a wind-up unit. Blow extrusion and slit die extrusion vary in the design of die used and in the type of cooling the haul-off and wind-up equipment is also different. The design and operation for the extruder up to the die is the same for both methods, however, and will be briefly described here before considering the different types of film manufacture. The basic extrusion process is designed to convert, continuously, a thermoplastics material into a particular form, in this case film. The basic sequence of events is as follows:
1. Plasticization of the raw material in granule or powder form.
2. Metering for the plasticised product through a die which converts it to the required form (i.e. tubular or flat).
3. Solidification into the required form.
4. Winding into reels.

Processes (1) and (2) are carried out in the extruder, whilst (3) and (4) are ancillary processes.
A typically extruder is shown in figure 1 and consists essentially of an Archimedean screw which revolves within a close fitting, heated barrel. The plastics granules are fed through a hopper mounted at one end of the barrel and carried forward along the barrel by the action of the screw. As the granules move along the screw, they are melted by contact with the heated walls of the barrel, and by the heat generated by friction.


Fig. 1. SCHEME FOR A TYPICAL SINGLE-SCREW EXTRUDER (L/D = 20) SHOWN EXTRUDING PIPE

The screw then forces the molten plastic through the die which determines its final form,. The most important component of the extruder is the screw are used for extruding different polymers. Extruder screws are characterised by their length to diameter ratio(commonly written as L/D ratio) and their compresison ratios. The compression ratio is the ratio of the volume of one flight of the screw at the hopper end to the volume of one flight at the die end. L/D ratios most commonly used for single screw extruders are between about 15:1 to 30:1, while compression ratios can vary from 2:1 to 4:1. An extruder screws is usually divided into three sectors, namely, feed, compression and metering. The feed section transports the material from under the hopper mouth to the hotter portion of the barrel. The compression section is that section where the diminishing depth of thread causes a volume compression of the melting granules. The main effect of this is an increase in the shearing action on the molten polymer due to the relative motion of the screw surface with respect to the barrel wall. This improves the mixing and also leads to an increase in frictional heat and a more uniform heat distribution throughout the melt. The function of the final section of the screw is to homogenize the melt further, meter it uniformly through the die and smooth out pulsations.
Just prior to the die is fitted a breaker plate supporting screen pack consisting of a number of fine or coarse mesh gauges. The screen pack filters out any contamination which might be present in the raw material. This is particularly important in the case of thin film extrusion where even the smallest of contaminating particles could cause holes or even breaks in the film. The screen pack also increases the back pressure in the extruder and this improves the mixing and homogenisation of the melt.
The above description has been based on a single screw extruder but multi-screw models are also available giving more positive transport of the molten polymer and more efficient mixing.

Fig. 2 : BLOWN FILM EXTRUSION

A typical set-up for blown film extrusion is shown in figure-2. In this instance the molten polymer from the extruder enters the die from the side but entry can also be effected from the bottom of the die. Once in the die, the molten polymer is made to flow round a mandrel and emerges through a ring shaped die opening, in the form of a tube. The tube is expanded into a bubble of the required diameter by an air pressure maintained through the centre of the mandrel. The expansion of the bubble is accompanied by a corresponding reduction in thickness. Extrusion of the tube is usually upwards but it can be extruded downwards, or even sideways, the bubble pressure is maintained by pinch rolls at one end and by the die at the other. It is important that the pressure of the air is kept constant in order to ensure uniform thickness and width of film. Other factors that effect film thickness are extruder output, haul-off speed and temperatures of the die and along the barrel. These must also be strictly controlled.
As with any extrusion process, film blowing becomes more economical as speeds are increased. The limiting factor here is the rate at which the tubular extrudate can be cooled. Cooling is usually achieved by blowing air against the outside surface of the bubble. Under constant air flow conditions an increase in extrusion speed result in a higher 'frost' line (the line where solidification of the extrudate commences) and this leads to bubble instability. Increasing the air flow gives more rapid cooling and lowers the 'frost' its application because too high a velocity of the air stream will distort the bubble. Various designs of air cooling rings have been worked out in order to produce improved cooling without these attendant difficulties and one such design (designed and patented by shell) is shown in figure.3. It consists of a conically shaped ring provided with three air slits, the airstreams from which are so directed and regulated that the space between the bubble and the ring decreases gradually towards the top of the ring. This gives improved cooling by increasing the speed of the air stream. The design also results in a zone of under-pressure at the top of the ring and this greatly improves the bubble stability. Blown film extrusion is an extremely complex subject and there are many problems associated with the production of good quality film. Among the many defects which can occur are variations in film thickness, surface defects such as 'orange peel', 'apple sauce' of 'fish eyes', low tensile strength, low impact strength, hazy film, blocking and wrinkling. Wrinkling is a particularly annoying problems because it can be costly, leading to scrapping of a roll of film, and because it can arise from such a wide variety of causes that it is likely to occur even in the best regulated extrusion shop. If the film is too cold when it reaches the pinch rolls, for instance it will be stiff and this may cause crimping at the nip and wrinkling. One way of raising the film, temperature at the nip rolls is to raise the melt temperature but this can lead to other troubles such 'as blocking. In fact, this is illustrative of the whole subject of film blowing inasmuch as compromises are often necessary to achieve the best balance of properties. Wrinkling can also be caused by the die gap being out of adjustment. This causes variations in film thickness and can lead to uneven pull at the pinch rolls. Another cause of wrinkling may be surging from the extruder or air currents in the extruder shop. Both of these factors can cause wobbling of the film bubble and thus wrinkling at the wind-up stage.

Fig. 3. SHELL COOLING RING

The film bubble may be established by supporting it with horizontal stationary guides or the whole extruder may be protected from stray air currents by a film curtain. Other causes include non-alignment of the guide roll and the pinch rolls, or non-uniformity of pressure across the face of the pinch rolls.
Among the surface defects mentioned earlier, 'fish eyes' are due to imperfect mixing in the extruder or to contamination. Both of these factors are controlled by the screen pack which not only screens out contaminating particles but improves homogeneity by increasing the back pressure in the extruder. 'Orange peel' or 'apple sauce' are also surface defects caused by inhomogeneity of the molten polymer.
Since low density polyethylene forms by far the greatest percentage of all film made, it will be useful to consider the influence of the various polymer parameters such as metal flow index and molecular weight on the film properties. Impact strength, for instance, increases with molecular weight (i.e. decreasing melt index and with decreasing density. Heavy duty sacks, for instance, are normally made from polyethylene grades having densities between 0.916 and 0.922 g/cm3 and melt indices between 0.2 and 0.5. For thinner technical film as used in building applications or waterproof lining of ponds, higher melt indices have to be used because of the difficulty of drawing down very viscous melts to thin film. Melt indices of between 1 and 2.5 are more useful, therefore, and impact strengths are less than for heavy duty sacks. Clarity is, however, improved. Where a good balance of properties is required as in the medium clarity/medium impact grades, slightly higher densities are used (0.920 to 0,925 g/cm3) and the melt index is varied between 0.75 and 2.5. For high clarity, a high density and a high melt index are required since increases in both these properties cause an increase in see-through clarity, a decrease in haze and an increase in gloss. High clarity film will, of course, have a relatively poor impact strength because of the high melt index and such film should not be used for packaging heavy items.

SLIT DIE EXTRUSION (FLAT FILM EXTRUSION)
In flat film extrusion the molten polymer is extruded through a slit die and thence into a quenching water bath or on to a chilled roller. In either case the essence of the process in rapid cooling of the extruded film and cooling is, therefore, applied within a very short distance of the die lips (usually between 25 and 65 mm,). This short distance is also dictated by the necessity to reduce 'necking' of the film web, with consequent loss of width. In the chill roll casting method, the melt is extruded onto a chromium plated roller, cored for water cooling. The rapid cooling leads to the formation of small crystallites and this gives a clearer film.

Fig. 4 : FILM CASTING (SLIT-DIE EXTRUSION)

Where the quench bath method is used, the water temperature should be kept constant for best results. At constant extrusion temperature, lower quench temperatures, improve slip and antiblocking properties while higher quench temperatures give film that is easier to wind without wrinkles and with better physical properties.

Fig. 5 : CROSS-SECTION OF MANIFOLD-TYPE DIE FOR FILM

Slit-dies for flat film are wide in comparison with the diameter of the extruder head and this means that the flow path to the extreme edges of the die is longer than to the centre. Flow compensation is usually obtained by a manifold die, a cross-section of which is shown in figure. 5. It consists of lateral channel (or manifold) of such a diameter that the low resistance is small compared with that offered by the die lips. The manifold can only be efficient in its task of flow compensation if the viscosity of the melt is fairly low so that higher temperatures are necessary for flat film extrusion. This limits the use of the manifold die to materials of good thermal stability while another consequence of the higher extrusion temperature is the necessity for a heavier screen pack in order to maintain satisfactory back pressures. The inside surface of flat die has to be precision machined and well polished since the slightest surface imperfection will result in striations or variations in gauge.

COMPARISON OF BLOW AND CAST FILM PROCESSES
Some of the advantages of the tubular film process are as follows:
the mechanical properties of the film are generally better than those of cast film. The width of lay flat film is easily adjustable and there are no losses due to edge trimming. This latter is necessary for flat film because of the thickening of the film edge due to necking-in. Lay flat film is more easily converted into bags since it is only necessary to seal one end of a cut length to make the bag.
The cost for making wide blown film is much lower than for wide cast film because the cost of chill rollers increases rapidly with width due to the difficulty of precision grinding longer rollers.
A tubular film die is more compact and is cheaper than a slit-die producing film of comparable width. The tubular process is easier and more flexible to operate. These advantages must be balanced against the advantages of the slit-die process which are as follows:
Very high outputs can be obtained by slit-die extrusion units. Slit-die film normally has superior optical properties but it should be noted that special rapid cooling processes have been developed for tubular film, particularly in the case of polypropylene film. One example, the shell Tubular Quench Process, will be described in more detail later. Thickness variation is usually less with slit-die extruded film.
WATER COOLED POLYPROPYLENE FILM

Among the advantages of the air-cooled tubular process mentioned above were cheapness, case of conversion into bags and flexibility of operation. These factors have been largely responsible for the large scale penetration of low density polypropylene film into packaging markets. Polypropylene cannot be processed on the same equipment since the rate of cooling is inadequate to prevent the formation of large ' spherulites' (crystalline aggregates) in the film. This leads to the production of a brittle film having a matt, opaque appearance. Clear polypropylene film can be produced by chill roll casting techniques but the equipment is expensive and is not normally economic at outputs below about 600 tons per annum. This has greatly hindered its penetration of the clear film packaging market. Techniques of water cooling tubular polypropylene film, however, have opened up ways of producing clear film, with greater toughness and at no greater cost than cast polypropylene film. Among the different techniques commercially available is sheil's. Tubular Quench (TQ Process) which involves downward extrusion of a tubular extrudate from an annular die followed by rapid cooling on water-covered converging boards.
Fig. 6. EQUIPMENT SETTING FOR T-Q FILM EXTRUSION

At the same time the tubular extrudate is inflated with air in the normal way to give film of the required lay flat width and thickness. The water film that runs down the converging boards shock cools the film and causes rapid crystallite formation and hence the formation of small spherulites with a consequent increase in clarity. The layout of the TQ Process is shown schematically in figure. 6. As with polyethylene, the blow up ratio influences the balance of molecular orientation between machine and transverse directions and this affects film impact strength, tensile strength and tear strength in the usual manner. The properties of TQ polypropylene film are similar to those of the cast film. However, the ability to vary the blow up ratio allows a measure of control over the molecular orientation and this in turn can result in an improvement in mechanical properties compared with cast where the orientation is essentially all in the machine direction of the film. The degree of orientation in the TQ process is still low compared with that of true biaxially oriented film and TQ film does not compete with it in properties. The production of biaxially oriented film will be dealt with later but a comparison of polypropylene film produced by chill roll casting, the TQ Process and bixial orientation is given in table 1.


The TQ process is particularly valuable for outputs of film below the economic output of a cast film line (up to about 600 tonnes per annum). Costs are much lower and benefit from the great flexibility of the blown film process and the absence of edge trim waste. Another process is the Dow-Taga process. In this the blown film goes through a hollow ring where it is coated with a film of water which flows from the ring and on to the film before it is collapsed. Different sizes of rings must be used to match changes in blow up ratios whereas with the TQ process, no changes in equipment are needed when making different diameters of tubular film. In a third process, developed by Kokoku Rayon and Pulp Co. Ltd. In Japan (now the Kohjin Co. Ltd.), the tube of polypropylene film, after it comes out of the die, is passed over a mandrel that extends down into a water bath. After cooling, the film comes out of the bath, still in tubular form. It is then dried and the tube collapsed between a set of rolls.

Selasa, 22 Desember 2009

PLASTIK SAMPAH

PLASTIK SAMPAH WARNA HITAM
biasanya dipakai khusus buat sampah (atau diisi sampah)
bukan/jangan untuk pembungkus bahan makanan karena
berbahaya beracun!! tersedia ukuran sedang dan besar sekali,
biasanya dipakai di rumah makan, hotel dan rumah sakit
yang dipakai sekali pakai saja.......langsung dibuang



Gbr. 1 pak beriisi 1 kg kantong sampah

Gbr 2. Tumpukan Kantong sampah siap di kemas/karung






Senin, 21 Desember 2009

JUAL VS MOTOR BEKAS

JUAL VS MOTOR BEKAS PABRIK GUE
yaitu motor 3 fase menggunakan VS (variable speed) dimana kecepatan diatur dengan control tersebut. tersedia banyak sekali mulai dari 1 HP sampai 75 HP, motor ini bekas digunakan di mesin extrussion, tetapi telah di upgrade ke motor induksi biasa. VS motor ini masih bekerja dengan baik dan disimpan di gudang tidak tahu sampai kapan hee heee. makanya dicariin yang mau pakai silahkan tawarr


Gbr: VS motor yang paling besar + controlnya

Berbagai ukuran tersedia

Vs Control
Berminat kontak
YM = novri_ariyanto2002