Bottle making

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Before the Bottle is Made Before a plastic bottle can be manufactured, the PET must be made. PET is a polymer that is made from petroleum hydrocarbons. It comes from a reaction between terephthalic acide and ethylene glycol. The process to make PET is called polymerization. Making the Bottle The process to make PET bottles is called stretch blow molding. PET pellets are injection-molded in a thin-walled plastic tube. The tube is then cooled and cut into shorter lengths. Each length of tube is i
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  Before the Bottle is Made Before a plastic bottle can be manufactured, the PET must be made. PET is a polymer that is made from petroleum hydrocarbons. It comes from a reaction between terephthalicacide and ethylene glycol. The process to make PET is called polymerization. Making the Bottle The process to make PET bottles is called stretch blow molding. PET pellets areinjection-molded in a thin-walled plastic tube. The tube is then cooled and cut intoshorter lengths. Each length of tube is inserted into a mold that is shaped like the bottlethe manufacturer wants to create. A steel rod is inserted into the tube and blows outhighly pressurized air. This pushes the plastic and PET against the inner sides of themold. Under this high pressure and high temperature, the molecules in the PET polarize,in essence, crystallize, which give the bottle its strength. The consistent pressure alsoensures a uniform thickness to the PET. The bottle bottom is made from a separate moldduring the process and attached later. Finishing the Bottle The mold is then cooled quickly to keep any of the PET from flowing inside themold. The bottle is then removed from the mold and trimmed to remove and PETthat leaked through cracks in the mold. The bottles are then packaged and sent tothe company that ordered them. Lids and labels are made in an entirely separate process.--------------------------------------------------------------------------------------------------- BLOWN FILM PROCESS Blown film extrusion is the process by which most commodity andspecialized plastic films are made for the packaging industry. The film blowing process basically consists of a extruding atube of molten thermoplastic andcontinuously inflating it to severaltimes initial diameter, to form a thintubular product that can be useddirectly, or slit to form a flat film. The Process Plastic melt is extruded through anannular slit die, usually vertically, to  form a thin walled tube. Air is introduced via a hole in the centre of the die to blow up thetube like aballoon. Mounted on top of the die, a high-speed air ring blows onto the hotfilm to cool it. The tube of film then continues upwards, continually cooling, until it passes through nip rolls where the tube is flattened to create what is known as a ' lay-flat'tube of film. This lay-flat or collapsed tube is then taken back down the extrusion ' tower'via more rollers. On higher output lines, the air inside the bubble is also exchanged. Thisis known as IBS (Internal Bubble Cooling).The lay-flat film is then either kept as such or the edges of the lay-flat are slit off to produce two flat film sheets and wound up onto reels. If kept as lay-flat, the tube of filmis made into bags by sealing across the width of film and cutting or perforating to makeeach bag. This is done either in line with the blown film process or at a later stage.Typically, the expansion ratio between die and blown tube of film would be 1.5 to 4times the die diameter. The drawdown between the melt wall thickness and the cooledfilm thickness occurs in both radial and longitudinal directions and is easily controlled bychanging the volume of air inside the bubble and by altering the haul off speed. Thisgives blown film a better balance of properties than traditional cast or extruded filmwhich is drawn down along the extrusion direction only. materials: Polyethylenes (HDPE, LDPE and LLDPE) are the most common resins in use, but a widevariety of other materials can be used as blends with these resins or as single layers in amulti-layer film structure. these include pp, pa, evoh. In some cases, these materials donot gel together, so a multi-layer film would delaminate. To overcome this, small layersof special adhesive resins are used in between. These are known as “tie layers”. advantages: ã Produce tubing (both flat and gussetted) in a single operation ã Regulation of film width and thichness by control of the volume of air in the bubble, the output of the extruder and the speed of the haul-off  ã Eliminate end effects such as edge bead trim and non uniform temperature that canresult from flat die film extrusion ã capability of biaxial orientation (allowing uniformity of mechanical properties) ã Very high productivity ã Permits the combination of a number of different materials and properties applications: Blown film can be used either in tube form (e.g. for plastic bags and sacks) or the tubecan be slit to form a sheet.Typical applications include Industry packaging (e.g. shrink film, stretch film, bag film or container liners), Consumer packaging (e.g. packaging film for frozen products, shrink film for transport packaging, food wrap film, packaging bags, or form, fill and seal packaging film), Laminating film (e.g. laminating of aluminium or paper used for    packaging for example milk or coffee), Barrier film (e.g. film made of raw materials suchas polyamides and EVOH acting as an aroma or oxygen barrier used for packaging food,e. g. cold meats and cheese), films for the packaging of medical products, Agriculturalfilm (e.g. greenhouse film, crop forcing film, silage film, silage stretch film).
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