Plastics

Plastics

A generic term for chemically produced resinous materials. It is used to describe a product of synthetic origin which is capable of being shaped at some stage of its manufacture but is not rubber, wood, leather or metal.

Resin

This is a basic ingredient of plastic. It is combined with fillers, stabilizers, plasticizers, pigments, and other components to form plastics.

Fillers

These are added to impart a certain characteristic property, such as durability or heat resistance to plastic. Some fillers, called extenders, may be added to decrease the amount of relatively expensive plastic required and to increase the mass of the product.

Stabilizers

Component of plastic which gives protection against degradation pf the plastic resulting from exposure to environmental conditions such as ultraviolet rays and even oxygen.

Plasticizers

This component of plastic is mixed with the resin to increase flexibility, resiliency, and impact resistance. The addition of plasticizers lends the required flexibility to sheet so that it can be rolled without cracking.

Casting and Molding and Forming

Two methods of fabrication of plastic.

Casting and Molding

Requires that the plastic material should be fluid, either in a hot molten state, or as a liquid at or about room temperature.

Liquid Casting

This casting method uses syrupy or liquid plastic
resins that are poured into molds and are cured by heating or by chemical reaction. Casting produces sheets, rods, and special shapes.

Low pressure molding

It is used to shape plastic that has to be reinforced. The liquid resins are mixed with mats or fibers of such materials as glass or asbestos, and the resulting substance is molded at a low pressure.

Slush and Rotational Molding

uses plastisols and plastigels which are combinations of resins and other ingredients in paste or liquid form or in a gel. The plastic is put into a mold and left to set until a layer is formed on the surface of the mold. When the desired thickness is reached, the unsolidified plastic is poured off, and the layer left to finish hardening.

Injection Molding

It is a method of shaping plastic in which the plastic is fed from a hopper into a heating chamber where it is softened to a fluid state. The plastic fluid is pushed at a high pressure through a nozzle at the end of the chamber into a cool, closed mold. Here the plastic cools and becomes a solid shape. Then the mold is opened and the finished item is ejected. Injection molding is the principal process for forming thermoplastic materials.

Compression Molding

It is a technique of producing shaped plastic which the resin granules or powders are placed in an open mold and are subjected to heat and pressure after the mold is closed. This converts the plastic into a liquid, and as it cools it becomes solid, finished form. This method is commonly used for thermosetting plastics.

Transfer Molding

it is a type of compression molding. The resin is heated in one chamber and then transferred by force into a cavity of a heated, closed mold.

Forming

It is the fabrication of a plastic that is in a solid state.

Sheet Forming

It is used to shape thermoplastic materials. A sheet of plastic is heated above the temperature of its softening
point. It is placed over a mold and shaped by the application of pressure from mechanical or hydraulic force, from preheated compressed air, or from vacuum techniques.

Extrusion

It is a process in which the softened plastic is forced through a die to produce rods, tubing, and cross-sectional shapes in long, lengths. It may be used with most thermoplastic and some thermosetting plastics.

Powder Molding

It involves the fusing of plastic powder under heat and pressure until it takes on the shape of the surface of a mold.

Plastic Coloring

Generally added during the chemical processing so that it becomes an integral part of the plastic material.

Polishing

This is done after fabrication. This is accomplished both manually and mechanically with mild abrasives and water.

Thermoplastic and Thermosetting

Major divisions of plastics

Thermoplastic

Becomes soft with sufficient heat and hardens again when cooled, no matter how often the process is repeated. They require the addition of plasticizers to
increase their flexibility. Generally offer higher impact strength, easier processing, and better adaptability to complex designs.

Acrylonitrile Butadiene Styrene (ABS)

A type of thermoplastic that is very tough, but not brittle, and is resistant to chemicals and to impact. It exhibits high gloss, low shrinkage, and good dimensional stability. Widely used in injection molding of appliances, furniture and automotive parts. Examples of this are Lego bricks, bottle caps, pipes and connectors.

Acrylic

Also known as polymethyl methocrylate; a thermoplastic. It has the clarity of glass, good weatherability, surface hardness and chemical resistance, but are not abrasion resistant. It is lightweight and colorfast and does not yellow with age. Luxite and Plexiglass are popular trade names.

Fluorocarbon/Fluoroplastics

It is a type of thermoplastic. It has high thermal ability, excellent resistance to chemical attack, low coefficient of friction, good electrical properties, excellent wear resistance and practically no moisture absorption.

Polycarbonate

A polymer offering outstanding impact strength, dimensional stability under varying humidity or temperature, heat resistance, weather resistance, and clarity. It is injection molded in order to produced shaped parts needed.

Polystyrene

This thermoplastic is inexpensive and easy to process.
They are noted for their sparkling clarity, hardness, and extreme ease of processing. They are non-water absorbent, brittle, and having a wide range of colors.

Vinyls

A large group of plastics, including polyvinyl chloride (PVC) and polyvinyl butyral (PVB) It is used in interiors for the floor coverings, window blinds, upholstery materials, and wall coverings that are largely made of vinyl.

Thermosetting

Sometimes called thermocuring plastics, these are plastics that are set into permanent shapes when heated during forming. Once they are set, they cannot be remolded.

Alkyds

It has a rapid cure cycle and good mold flow characteristics, which allow them to be molded into relatively complicated shapes. Most prevalent use in commercial interiors is a paint coating.

Epoxy

This is a type of thermosetting plastic; Its resins react or hardens to form an exceptionally durable plastic. They are known to have superior adhesive qualities and excellent resistance to chemicals and corrosion. Epoxy ester coatings are often used in floor and gymnasium finishes. Powder coating, based on heat cured epoxy resins, are increasingly popular as metal furniture finishes.

Melamine or Urea

Hard, durable, clear and dimensionally stable, these quite similar plastics are resistant to stains, chemicals, electrical potential and heat. These surfaces are difficult to scratch or cut, and they do not yellow with age. Melamine for laminates, molded dishes, countertops. Urea for baked enamels.

Phenolic

It is strong, durable, and both electrical and heat resistant. It is limited to dark colors.

Polyester

Most commonly used plastic in large glass-fiber reinforced translucent panels that are strong, rigid and impact resistant, thus forming fiberglass.

Silicone

These known for their stability through a
wide range of temperatures, ultraviolet radiation, and harsh weather. They are used in commercial interior applications as water repellant fabric finishes and joint sealants.

Urethane

It is also called as polyurethane. It is available in multitudes of forms with an extensive variety of physical properties. It is widely used as a building insulation material, seat cushions, and bed mattresses.