Manufacturing Process Of Plastic Bottles

PLASTIC BOTTLESA plastic bottle is a container constructed of plastic, with a neck that is narrower than its body and an opening at the top. The mouth of the bottle is normally sealed with a plastic bottle cap. Plastic bottles are typically used to store liquids such as water, soft drinks, cooking oil, medicine, shampoo, milk, and ink.

RAWMATERIALS USED1) High Density Poly Ethylene (HDPE)2) Poly Propylene (PP)1) High Density Poly Ethylene (HDPE)Plastic bottles manufactured from HDPE will be:· Less durable· More opaqueBest used for (packing of):· Food products· TabletsColours are added to HDPE to increase non-transparencyand strength of the plastic products.2) Poly Propylene (PP)Plastic bottles manufactured from PP will be:· Transparent· Clear· Durable· FlexibleBest for carrying liquid products

3) polyethylene terephthalate(PET)

What is PET?The most-common plastic bottle you see nowadays is the soda bottle. It is made from polyethylene terephthalate, also known as PET. PET is used for 14 percent of all plastic containers and 43 percent of soda bottles. It was developed in 1941, but it wasn't used for soda bottles until the 1970s.

Before the Bottle is MadeBefore 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 BottleThe 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 inserted into a mold that is shaped like the bottle the manufacturer wants to create. A steel rod is inserted into the tube and blows out highly pressurized air. This pushes the plastic and PET against the inner sides of the mold. 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 also ensures a uniform thickness to the PET. The bottle bottom is made from a separate mold during the process and attached later.

Finishing the BottleThe mold is then cooled quickly to keep any of the PET from flowing inside the mold. The bottle is then removed from the mold and trimmed to remove and PET that leaked through cracks in the mold. The bottles are then packaged and sent to the company that ordered them. Lids and labels are made in an entirely separate process.

MANUFACTURING PROCESS OF PLASTIC BOTTLES

Polymerization

Before the bottles can be made, the PET itself must be manufactured, or polymerized. In polymerization, smaller molecules are combined to form larger substances.

INJECTION MACHINE :

Injection molding is the most commonly used manufacturing process for the fabrication of plastic parts.

A wide variety of products are manufactured using injection molding, which vary greatly in their size, complexity, and application.

The injection molding process requires the use of an injection molding machine, raw plastic material, and a mold.

The plastic is melted in the injection molding machine and then injected into the mold, where it cools and solidifies into the final part.

The Injection machine works some what similar to the blow mould machine. Two main differences to be noted among the two are:

Air is not blown to expand the plastic. Instead of the movement of the screws in the heater, there is a horizontal push of the

plastic in it. Usually the bottle caps are manufactured in this process (machine).

Machine for injection moulding

BLOW MOULDING MACHINE:

A Blow Moulding Machine is usually used to manufacture the body of a plastic bottle or the bottom part of the plastic bottle.

It has a mould with a pre-carved shape within the cavity so as to get the desired shape of the bottle.

The machine also blows air into the plastic material so as to expand the interior of the bottle or in other words to obtain interior space.

The opening where the raw materials are introduced is called the Hopper.

From there the materials pass through a barrel called the Heater. As the name itself suggests, here the raw materials are heated, but at different stages and at different temperatures, gradually from lower temperatures to higher temperatures. The screws are contained in the heater.

They help in the easy movement of the raw materials. Then the liquid (or the semi liquid) flows into the mould, where the plastic is moulded to the desired shape

After it is moulded, air is blown into the plastic. Now the plastic bottle is ready. In this way the base of the bottle is ready.

Extrusion Blow Moulding

In Extrusion blow moulding ,plastic is melted and extruded into a hollow tube (a parison)

The process begins with the conventional downward extrusion of a tube.

When the tube reaches the desired length the mould is closed catching and holding the neck end open and pinching the bottom end closed.

Then a blow-pin is inserted into the neck end of the hot tube to form the threaded opening and inflate the tube inside the mold cavity.

When the mould is completely cooled it is opened to eject the bottle and the excess plastic is trimmed from the neck and bottom areas.

Stretch Blow Moulding

The main applications of stretch blow moulding includes jars, bottles, and similar containers because it produces items of excellent visual and dimensional quality compared to extrusion blow moulding.

The process first requires the plastic to be injection moulded into a 'preform' with the finished necks (threads) of the bottles on one end.

The preform is then heated above its glass transition temperature and blown, using high pressure air, into

bottles using metal blow molds. At the same time the preform is stretched with a core rod to fill inside of the mould.

PREFORM

QUALITY CONTROL TESTING

Samples are regularly tested in quality control testing

They measure thickness & performs compression testing to measure it’s strength

They verify it’s dimensions & capacity

The resistance to the vaccum pressure are also evaluated

PROGRAMMING LOGIC CONTROL (PLC)

A plastic industry or any industry for that matter can not run with a single machine.

Even a small scale concern with a single manufacturing outlet will have at least 2 to 5 machines for manufacturing its products.

Hence, it is necessary to co-ordinate the functioning of the machines and to program them for the process of manufacturing or production.

This is bought about by the PROGRAM LOGIC CONTROL (or PLC).

Recycling

PET is the most extensively recycled plastic.

With the rapid acceptance of PET bottles in the marketplace, PET began to fill up landfills, which creates environmental problems.

PET can be and is recycable. The plastic can be remelted and mixed with unused PET to create new bottles.

Anupama Aparna Kripna Nijina Nimisha Ebin Sidharth