Imagine a day without touching some plastic!
Did people use to brush their teeth before choosing
red, blue, or purple plastic toothbrushes but do you really want a metal or
wooden one? Milk and shampoo were sold in glass bottles, and there was no
problem if you didn't drop and break any of them.
We cannot imagine our daily life without the use
of plastics. A human being from toe to head and till dawn to dusk is everywhere
very much involved with plastics products. Forty years ago, anything made of
plastic was considered “cheap”. This is undoubtedly a lie today when plastic is
used in thousands of products ranging from computers, auto parts, and large
medical equipment to toys, kitchen utensils, sports equipment, and even
clothing. And the plastics industry continues to develop rapidly.
What are plastics?
Students may be surprised to learn that before
the first synthetic plastics were made, gutta-percha, shellac, and animal horns
were all-natural materials used as plastic components. Gutta-perch is obtained
from the clusters of certain trees, and shellac is obtained from the secretions
of small-sized scaly insects. However, before using the horn, it must be
"plasticized" or softened by boiling in water or soaking in an
alkaline solution.
The first synthetic plastic plant material was
made from cellulose. In 1869, John Wesley Hayatt, an American painter and
inventor, discovered that cellulose nitrate could be used as an inexpensive
substitute for ivory. The mixture can be plasticized with the addition of
camphor. Celluloid, as this new material was called, became the only
commercially important plastic for 30 years. It includes a glasses frame, comb,
billiard ball, shirt collar, buttons, dentures, and photographic film.
In 1951, two young research chemists from the
Philips Petroleum Company in Bartlesville, Oklahoma, discovered something that
revolutionized the world of plastics. Today, the plastics they discovered -
polypropylene and polythene - are used to produce thousands of plastic products
around the world.
Petroleum to Plastics
The technological road from oil field to finished plastic product
has numerous fascinating side trips. Here’s the route took in the
petroleum-to-plastics process:
1. Petroleum is drilled and transported to a
refinery.
2. Crude oil and natural gas are refined into
ethane, propane, hundreds of other petrochemical products, and, of course, fuel
for your car.
3. Ethane and propane are "broken"
into ethylene and propylene, utilizing high-temperature heaters.
4. Catalyst is combined with ethylene or
propylene in a reactor, resulting in “fluff,” a powdered material (polymer)
resembling laundry detergent.
5. Fluff is joined with added substances in a
consistent blender.
6. Polymer is taken care of to an extruder
where it is liquefied.
7. The melted plastic is
cooled and then fed to a pelletizer which cuts the product into small granules.
8. Pallets are sent to
customers.
9. Customers make
plastic by processes like extrusion, injection molding, blow molding, etc.
Plastics Processing Methods
Extrusion molding - the main process used in the formation of plastics. A heated plastic compound is continuously pressed through a forming mold made into the desired shape in a forced form (e.g., holding a toothpaste out of a tube, producing a long, usually narrow unbroken product). The formed plastic is cooled under blown air or in a water bath and hardened in a moving belt. Rods, tubes, pipes, slinkies ©, and thin films and sheets (such as food wrappers) are extruded then coiled or cut to desired lengths. Plastic fibers are made using an extrusion process. The liquid resin is cut through thousands of tiny holes known as rows to create fine threads that are woven of plastic cloth.
Injection molding: This is the second most utilized process in plastic molding. In a semi-liquid state, the warmed plastic compound is immediately set when poured into a mold under high pressure. The mold is then opened and the part is exposed. This cycle can be repeated the same number of times as important and is particularly reasonable for large scale manufacturing strategies.
Injection molding is used for a variety of plastic products, ranging from small glasses and toys to objects weighing 30 pounds or more.
Blow Molding - Pressure Straight bottles or two-gallon milk bottles are used directly or indirectly to form empty objects. In the direct blow mold welding method, a heated and partially formed plastic is molded into a mold. The air is molded, forcing it to expand in the shape of a mold. In the indirect method, a plastic sheet or a special shape is heated and then clamped between a dye and Akana. Air pressure is applied between the plastic and the cover and the material.
AUTHOR-M.ZAMAN(RASEL)
How are plastics made and What are plastics?){kind=link}
0 Comments