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Types of Plastics


Acetals     Acrylics     Amino Resins      Cellulosics     Phenolics     Polyamides     Polyesters     Polyolefins    Polyurethanes     Styrenes    Vinyls

Acetals

Acetals are engineering-type thermoplastics.  The acetal homopolymer is polyoxymethylene, in which methyl groups are linked together by an oxygen atom.

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Mechanical and Chemical Properties

Acetals are highly crystalline.  They are rigid, resilient, tough, and strong.  They do not easily become brittle, even with long-term exposure to unfavorable conditions and high temperatures. Acetals cannot be dissolved by organic solvents, however they have limited resistance to strong acids and oxidizing chemicals.  Acetals absorb minimal amounts of moisture, a characteristic which enhances their high flammability.

Applications

Acetals are used in hardware components such as gears and bearings.  They are also found in pumps, valves, screws, bottles, fans, paint sprayers, shower heads, tool handles, and dishes.

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Acrylics

Acrylics are synthetic plastics, prepared from acrylic acids.  They are polymers of the esters of acrylic acid.

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Mechanical and Chemical Properties

While acrylics are clear and transmit light exceptionally well, they are also easily coloured.  They can be found in all shades, including fluorescents.  Their surface lustre is outstanding.  Despite the fact that they have a low softening point, acrylics are weather resistant and hard.  Acrylics have low moisture absorbtivity and high scratch resistance.  They are susceptible to damage by certain chemicals such as gasoline and cleaning fluids, however they will withstand non-oxidizing acids and household alkalies.  Acrylic plastics are slow burning and burn with little smoke or toxicity.

Applications

Acrylics are excellent as lens material.  They are used in binoculars, cameras, and eye glasses. Acrylics are also used in stop lights and car headlights.  Lighting fixtures, dishes, floor waxes, carpets, piano keys, beverage dispensers, and skylights all contain acrylic plastics.

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Amino Resins

Amino resins consist of melamine formaldehydes and urea formaldehydes. The molecular structure of urea formaldehyde is shown below.

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Mechanical and Chemical Properties

Amino plastics are hard, scratch and stain resistant, moldable, thermally resistant, and come in a variety of transluscent and opaque colours.  While they are fairly strong, they are not unbreakable.  They are resistant to solvents such as cleaning fluids, gasoline, and oils.  Aminos will not burn or soften, even in open flame.

Applications

Amino resins are used in molding powders.  Molded products of amino plastics include switch cover plates, buttons, electric mixer housings, radio cabinets, coffee makers, and door knobs. Aminos are also extremely useful as adhesives, especially in the woods industry, and as laminated lay-ups for kitchen counters.  Finally, aminos are also employed as surface coatings on paper and fabric.

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Cellulosics

"Cellulosics" is the general term for a group of plastics which are derived from cellulose, a natural occuring fibre which is obtained from wood pulp.  The five principle cellulose plastics are:

The molecular structure of cellulose is shown below:

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Various chemical groups are substituted for the hydroxy groups in glucose, with each substitution resulting in the production of one of these five plastics.  

Mechanical and Chemical Properties

While each of the five cellulosics have unique properties, certain characteristics are common to all of these plastics.  They are among the toughest of all the plastics, and are moderately heat resistant.  They have lustrous surfaces and can be found in opaque, transluscent, and transparent forms.  All cellulosics are soluble in some hydrocarbons and decompose in strong acids. Cellulose plastics are available in a wide variety of colours.

Applications

Cellulosics are used in shoe heels, eyeglass frames, toothbrush handles, pen and pencil barrels, piano keys, beads, toys, fisherperson's floats and tackle, cutlery handles, combs and steering wheels.

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Phenolics

Phenolics are synthetic resins, produced by the condensation of phenol with formaldehyde in  the presence of a base.  The generic phenolic structure is shown below.

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Various chemical groups are substituted for the hydroxy groups in glucose, with each substitution resulting in the production of one of these five plastics.  

Mechanical and Chemical Properties

Phenolics are hard, rigid, heat resistant, and brittle.  Fillers are used in order to improve their toughness.  They have excellent insulating properties and are heat resistant to 260°C. They are chemically inert to most common solvents and weak acids.  They absorb very little moisture.  Fillers are widely used in the manufacture of phenolics in order to achieve certain desired charactertics as appropriate for the application of the plastic. 

Applications

Phenolics may be used in their liquid form in laminating of veneers, fabrics, and paper.  Phenolics are also used in distributor caps, brake linings, pulleys, washing machines, detergent dispensers, telephones, salad bowls, ash trays, croquet balls, and roof panels.

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Polyamides

Polyamides are plastics whose structural units are linked by amide groupings.  The most common type of polyamide is nylon.

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Mechanical and Chemical Properties

Polyamides are naturally beige or off-white, but they can be manufactured to be transparent. Polyamides can be easily molded.  They are hard and brittle and resistant to abrasion, shrinkage and heat. Certains polyamides are especially flexible and impervious to impact.  Polyamides are resistant to deterioration by alkalies, petroleum products, and organic solvents.  Hot phenol, formaldehydes, ultraviolet light and mineral acids destroy polyamides.  Most polyamides are self-extinguishing in the event of fire.    

Applications   

Polyamides are used in small bearings, speedometer gears, windshield wipers, water hose nozzels, football helmets, racehorse shoes, inks, clothing, parachute fabrics, rainwear, and cellophane. 

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Polyesters 

Polyesters are formed either by a reaction between a dibasic acid and a dihydroxy alcohol or by the polymerization of a hydroxy carboxylic acid.  

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Mechanical and Chemical Properties   

Polyesters are naturally clear and colourless, however they can be coloured and filled according to specifications.  Polyesters do not show wear with exposure to poor weather conditions.  They are highly resistant to chemical deterioration, withstanding most solvents, acids, and salts. Polyesters are strong and tough and range from rigid to flexible.  They are also resistant to heat damage and can be made to be self-extinguishing.

Applications 

The dominant uses for polyesters are in laminating and molding.  Boat hulls, automobiles, and aircraft bodies all contain polyesters.  Polyesters are also found in wash tubs, luggage, hammer handles, costume jewlery, and fan blades.

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Polyolefins

Polyolefins are unsaturated hydrocarbons extracted from petroleum or natural gas.  The structure shown below is that of a simple, straight-chain polyolefin, however polyolefins can also be found with varying degrees of carbon chain branching.  

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Mechanical and Chemical Properties

The properties of the polyolefins depend in large part on the length and branching of their carbon chains.  Short chains make brittle, waxy plastics.  Longer chains produce a very tough plastic. As the density of a polyolefin increases, so do its softening temperature, gloss, and grease resistance.  As the density of a polyolefin decreases, so do its crack-resistance and its permeability.  Most polyolefins are resistant to attack by acids, bases, and salts.  Oxidizing agents, solvents, and hydrocarbons can destroy this group of plastics.  Uncoloured polyolefins are more susceptible to damage by weathering in the presence of oxygen and sunlight. Polyolefins are slow burning.

Applications

Polyolefins are used in pipe fittings, packaging films, surgical implants, wire insulation, beverage cases, trash-can liners, produce bags, canteens, and rug backing for automotive flooring.

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Polyurethanes

Polyurethanes are produced by reacting diisocyanates with glycols.  The molecular structure of polyurethane is shown below.

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Mechanical and Chemical Properties

Polyurethanes are naturally amber in colour.  They are easily stretched; a property which has earned them the nickname 'elastomers'.  Polyurethanes are scratch, tear, and shock resistant. They are very tough but have good cushioning properties.  Polyurethanes are not easily damaged by chemicals including solvents, acids, and oils.

Applications

Polyurethanes are found in tires, gaskets, bumpers, and synthetic leather.  More foamy varieties of polyurethane are used in refrigerator insulation, sponges, furniture cushioning, and life jackets.

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Styrenes

Styrene plastics are made by the polymerization of styrenes.  Its carbon chain is long, linear, and amorphous.

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Mechanical and Chemical Properties

Styrenes are smooth, clear, odourless, and tasteless.  They can be found in a wide range of colours.  They melt over a wide range of temperatures and pressures, allowing for terrific molding possibilities.  They demonstrate terrific insulating properties.  Styrenes are hard and brittle and show poor resistance to chemical treatments.  Styrenes are limited in their amount of liquid absorption.  Butadiene fillers increase the impact resistance of styrenes, making them much more versatile in their range of uses.  Styrenes burn slowly.   

Applications

Styrenes are widely used in disposable products including picnic utensils and food containers. They are also found in automobile interior parts, model airplane and car kits, jewelery, clock cases, place mats, envelope windows, ice buckets, and egg cartons.

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Vinyls

Vinyl plastics are formed by the polymerization of chemical compounds containing the group CH2=CH—. 

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Mechanical and Chemical Properties

Vinyls are strong, with excellent resistance to damage caused by water and chemical wearing. However, they are ruined by prolonged exposure to sunlight. They are available in a wide variety of colours.  Vinyls range from being hard and rigid to soft and flexible.  Vinyls are self-extinguishing.

Applications

Vinyls are used in automobile seat covers, shower curtains, raincoats, bottles, visors, shoe soles, garden hoses, and mannequins.

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