Plastics

INTRODUCTION TO PLASTICS

A material that contains as an essential ingredient one or more organic polymeric substances of large molecular weight, is solid in its finished state, and, at some stage in its manufacture or processing into finished articles, can be shaped by flow. It smells similar like new polyethylene plastic bags. This smell hints either to a sort of smooth plastic coating or is caused when the very fresh latex was sealed into a smelly plastic bag.

MAIN TYPES OF PLASTICS

There are many different types of plastics made every day, but these are the seven main types of plastic:

1. Polyethylene Terephthalate (PETE)

Polyethylene terephthalate is a plastic resin of the polyester family that is used to make beverage, food and other liquid containers. It is also one of the most important raw materials used in man-made fibers. It may exist both as an amorphous (transparent) and as a semi-crystalline (opaque and white) material.

Uses of PETE

PETE can be semi-rigid to rigid, depending on its thickness, and is very lightweight. It makes a good gas and fair moisture barrier, as well as a barrier to alcohol (requires additional "Barrier" treatment) and solvents. It is strong and impact-resistant. It is naturally colorless and transparent.

When filled with glass particles or fibers, it becomes significantly stiffer and more durable. This glass-filled plastic, in a semi-crystalline formulation, is sold under the tradename Rynite.

2. High-density Polyethylene (HDPE)

High-density polyethylene (HDPE) is a polyethylene thermoplastic made from takes 1.75 kilograms of petroleum (in terms of energy and raw materials) to make one kilogram of HDPE.

Uses of HDPE

High Density Polyethylene (HDPE) is used for many packaging applications because it provides excellent moisture barrier properties and chemical resistance. However, HDPE, like all types of polyethylene, is

limited to those food packaging applications that do not require an oxygen or CO2 barrier. In film form, HDPE is used in snack food packages and cereal box liners; in blow-molded bottle form, for milk and non-carbonated beverage bottles; and in injection-molded tub form, for packaging margarine, whipped toppings and deli foods. Because HDPE has good chemical resistance, it is used for packaging many household as well as industrial chemicals such as detergents, bleach and acids. General uses of HDPE include injection-molded beverage cases, bread trays as well as films for grocery sacks and bottles for beverages and household chemicals.

3. Polyvinyl chloride(PVC)

Polyvinyl chloride commonly abbreviated PVC, is a widely-used plastic. In terms of revenue generated, it is one of the most valuable products of the chemical industry. Globally, over 50% of PVC manufactured is used in construction. As a building material, PVC is cheap and easy to assemble. In recent years, PVC has been replacing traditional building materials such as wood, concrete and clay in many areas. Despite appearing to be an ideal building material, concerns have been raised about the costs of PVC to the natural environment and human health.

Uses of PVC

Polyvinyl Chloride (PVC) has excellent transparency, chemical resistance, long term stability, good weatherability and stable electrical properties.

Vinyl products can be broadly divided into rigid and flexible materials. Rigid applications are concentrated in construction markets, which include pipe and fittings, siding, carpet backing and windows. PVC's has resistance to most chemicals, imperviousness to attack by bacteria or micro-organisms, corrosion resistance and strength. Flexible vinyl is used in wire and cable sheathing, insulation, film and sheet, floor coverings, synthetic leather products, coatings, blood bags and medical tubing.

4. Low Density Polyethylene (LDPE)

Low-density polyethylene (LDPE) is a thermoplastic made from oil. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerisation. Its manufacture employs the same method today.

Uses

Low Density Polyethylene (LDPE) is predominantly used in film applications due to its toughness, flexibility and transparency.

LDPE has a low melting point making it popular for use in applications where heat sealing is necessary. Typically, LDPE is used to manufacture flexible films such as those used for dry cleaned garment bags and produce bags. LDPE is also used to manufacture some flexible lids and bottles, and it is widely used in wire and cable applications for its stable electrical properties and processing characteristics.

Production of Plastics

1) Making