How is Plastic Made?

Also referred to as polymers, plastic was initially manufactured from naturally occurring materials like horns of animals, shellac (from secretions of minuscule scale insects), and gutta-percha (from sap of trees).

It was only in 1869 that the first synthetic plastic was prepared from the natural plant material; cellulose. An American printer and inventor called Wesley Hyatt discovered that cellulose nitrate could be plasticized by adding camphor.

The first commercially acclaimed, synthetic plastic material developed was called celluloid. This plastic found its applications in scores of areas like combs, dentures, eyeglass frames, etc.

The revolutionizing discovery in the field of plastic took place in 1951, when two young research chemists happened to discover polypropylene and polyethylene. This discovery paved the way for the myriads of plastic products we're familiar with today.

To prepare plastic from petroleum, petroleum is first drilled and transported to a refinery. At the refinery, the petroleum is made to go through a refining process along with natural gas.

Ethane, propane, and scores of other petrochemical products are produced as a result of the refining process. Next, the ethane and propane formed are further broken down using a furnace with high temperature. Ethylene and propylene are formed after this process.

In a reactor, the ethylene and propylene formed is combined along with a catalyst to form a powdery substance. This powdery compound formed bears semblance to washing powder, however, is the plastic polymer. In a continuous blender, some additives are combined with the polymer, and then fed to an extruder, where it enters the molten state.

The molten plastic is allowed to cool and then fed into a pelletizer, which further divides the polymer into tiny pellets. The pellets formed are the final plastic pellets, which are then shipped across to various customers.

Manufacturers of combs, plastic bottles, dentures, plastic utensils, etc., purchase these pellets and then use them to prepare various products via different processes like extrusion molding, calendering, film blowing, injection molding, blow molding, rotational molding, casting, etc.

It's wonderful that plastic can be prepared from petroleum, however, it takes a lot of petroleum to make it. To prevent a great resource like petroleum from getting exhausted, various efforts are being taken.

In December 2009, an Ithaca, New York-based company, Novomer, Inc. announced its commencement of commercializing the company's polypropylene carbonate (PPC) materials by using a combination of carbon dioxide and petroleum.

Their effort has been co-funded by New York State Energy Research and Development Authority. The idea is to add carbon dioxide, so as to reduce the need for petroleum by half.

A company named Spectragraphics Label Systems has been making labels for over 25 years. They were using petroleum to make the plastic required for their labels, however, they came up with a way to make plastic from edible corn.

They made use of the carbohydrate sugars present in the corn to form a type of plastic called polylactide polymer. This plastic manufactured by them bears the trademark, 'NatureWorks'. Quite a remarkable invention, isn't it!

Discovery of corn plastic has reduced our dependence on exhaustible petroleum. Corn kernels are milled and dextrose is added to it in the milled form, which is then allowed to ferment and produce polylactide polymer (PLA) and lactic acid as by-products. PLA is then created into pellets, which can be further processed to make plastic products.

However, the next question that arises is, 'why hasn't corn taken over the plastic industry?' One reason is that corn plastic cannot be heated beyond 114°C without melting. This is why PLA cannot overtake plastic made from petroleum.