The Acquisition or Manufacture of Plastic

Plastic is considered an organic polymer material (consisting of giant organic molecules) that can be formed to achieve a desired shape by extrusion, casting or spinning. The molecules can be naturally occurring, such as cellulose, wax, and natural or synthetic rubber, or synthetic, such as polyethylene and nylon.

 

The manufacture of plastics involves four basic steps: obtaining raw materials, synthesizing the basic polymers, converting the polymer into an industrially usable product, and molding or forming the plastic into its final form.

Originally, most plastics were made from plant resins, such as cellulose (cotton), furfural (from oat husk), seed oils and starch derivatives, or coal. Milk casein was also one of the plant materials used. Even though the production of nylon was originally based on coal, air and water, and nylon 11 was made from castor beans, the majority of plastics today are made from petroleum derivatives. Oil-based raw materials are cheap and plentiful. However, given that world oil supplies are limited, other sources of raw materials such as coal gasification are being investigated.

 

In bulk polymerization, only the monomer is polymerized, usually in a liquid or gas phase, but also in a solid state. In a solution polymerization, an emulsion is formed that produces coagulates. Interface polymerization is where monomers are dissolved in two immiscible liquids and the polymerization takes place at the interaction between the two.

 

Chemical additives are often used to achieve a particular property. For example, antioxidants protect the polymer from chemical degradation caused by oxygen or ozone. In a similar way, stabilizers protect from the elements. Plasticizers produce a more flexible polymer, lubricants reduce friction, and pigments give color to plastics. Some flame retardants and antistatic additives are also used. Many plastics are manufactured in the form of composite material, which involves the addition of a reinforcing material (usually fiberglass or carbon) to the plastic resin matrix. Composite materials have the strength and stability of metals, but generally are lighter. Plastic foams, made of plastic and gas, provide a large mass but are very light.

The techniques used to obtain the final shape and finishing of plastics depend on three factors: time, temperature and formation. The nature of many of these processes is cyclical, although some may be classified as continuous or semi continuous.

 

One of the most common operations is extrusion. An extruder is a device that pumps plastic into a mold with the desired shape. The extrusion machine also performs other operations such as blow molding or injection molding.

 

Other processes used include compression molding, in which the pressure forces the plastic to take a concrete form, and transfer molding, in which a piston introduces the pressurized molten plastic into a mold. Calendering is another technique by which plastic sheets are formed. Some plastics, especially those with a high temperature resistance, require special manufacturing processes.

 

Química PLEDCA is a company dedicated to the manufacture and marketing of industrial chemical additives of excellent quality for specific uses in the plastics industry, and in emulsions, cosmetics, automotive finishes, welding, etc.

 

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