The Types of plastics Can be classified according to their nature - natural and synthetic - and according to their internal structure - thermoplastics, PVC, polystyrene... -.
Plastics are compounds that are made up of large molecules called polymers. They consist of very strong structures, which allow molding by heat and pressure.
In this way, any material containing an organic substance with a high molecular weight and solid in its final state is defined as plastic. In addition, it is a material that must have undergone some manufacturing process such as casting, pressing, rolling, molding, stretching, among others for final finishing.
Plastic was the first synthetic material invented by man. However, not all plastics are of synthetic origin, as there are also of natural origin. In fact, this is the first classification that can be made of plastic.
But this material also has another categorization, which is by its internal structure. In this case, there are three basic types that are thermoplastics, thermosets and elastomers. And these in turn are divided into other types that we will see below.
By its nature
Natural
Natural plastics are those that are obtained directly from the raw material such as latex, milk casein and cellulose. That is, they are plastic substances that for their production do not require a laboratory process. This is because they are formed by natural compounds whose origin is animal and vegetable.
But although in this case materials are used that are extracted from natural substances, they also require a chemical transformation to modify their molecular components so that they obtain the desired plastic characteristics. Among them are cellulose acetate, synthetic rubbers, casein plastics, methyl cellulose, ethylcellulose, gum esters, cellulose nitrate and lignite plastics.
Synthetics
These are man made plastics. They are substances that are obtained from chemical reactions that involve two or more elements also chemical. This type of plastic is mainly derived from petroleum, coal and natural gas.
Within synthetic plastics are acrylic resins, fluoroplastics, phenols, hydrocarbon resins, polyamines, melamines, polyesters, polystyrenes, polyester (epoxy), polyethylene, polypropylene, polyurethane, polyvinylchlorides and vinyl polyacetates.
Due to its internal structure
Thermoplastics
This type of plastic is formed by chains of linear, branched or non-branched polymers. Among the properties of thermoplastics is that they are deformed by heat and solidify on cooling. This means that they can be melted and processed again and again without any alterations. They have very varied mechanical properties, so they can be from rigid and brittle to elastic and flexible.
The most used methods for its manufacture with the injection, blowing, extrusion and termoformado. On the other hand, the maximum temperature at which they can be exposed can not exceed 150 ° C. Thermoplastics are the type of plastic most used today and can be seen in boxes, bottles, bags, etc.
PVC (polyvinyl chloride)
It is one of the most versatile plastic materials. It is a very stable plastic, resistant, waterproof and durable. In addition, it softens and deforms at low temperatures and has a great resistance to corrosive liquids.
On the other hand, sunlight usually affects the point that causes it to change color. Usually used for water pipes, gloves, insulation tubes, linings, waterproof suits, shoe soles, hoses, windows, doors, etc.
Polystyrene
This is a hard and brittle material. It is shock resistant and is a good acoustic and thermal insulation. A peculiarity of this plastic is that it can be colored. It has two presentations: hard and expanded.
The hard polystyrene is transparent and can be colored with a pigment. It is usually used for clear films for wrapping and food packaging. In the case of the expanded, it is a spongy and soft material. This is usually used in packaging as well as in packaging and insulation.
Polyethylene
This type of plastic can be soft or rigid. It all depends on its density. It has good chemical and electrical resistance, is flexible and waterproof. And it can also be pigmented.
Polyethylene can be of three types: high, medium and low density. The high density is rigid and very resistant. It is colorless, odorless and non-toxic. It is often used for packaging of various types, for flexible pipes, garbage containers, textiles, among many others.
The medium density is identified by its yellow color and is used in underground natural gas pipelines. And in the case of low density, it is a more flexible and soft plastic than the high density. It can be transparent and opaque and is also a good insulation material. It is usually used in the manufacture of glasses, bags, sacks, plates, insulation for electric conductors, toys, etc.
Polypropylene
It is an opaque color material that has a high resistance to heat (it softens to 150 ° C), to the blows, as well as to the corrosive products.
Because it has low density, it can bend easily and is also capable of withstanding multiple twists. It is often used to make pipes for hot fluids, cases, appliances, furniture, packaging, toys, among others.
Methacrylate (plexiglass)
This plastic, also known as plexiglass, is rigid and tenacious. It has excellent chemical resistance and various weather conditions. Unlike PVC, its color is not affected by sunlight. In addition, it is easily molded and has a good dielectric behavior.
On the other hand, thanks to being polished easily, is often used in decorative objects. For being transparent or translucent and for its resistance becomes a good substitute for glass. It is used in the manufacture of light panels, goggles, aircraft windows, signs, watches, optical parts, among others.
Polycarbonate
It is an easy plastic to mold and thermoform. It is very resistant to impacts but also to heat. It has good dimensional stability and thermal conductivity. The sunlight makes it change color slightly. In addition, it is self-extinguishing and has a high dielectric strength. It also has excellent electrical insulation properties.
It is usually used in exterior glass and as safety glass. It is also used for transparent and translucent roofs for skylights and domes. It is also used in advertising for ads.
Teflon (fluorocarbon)
It is a polyethylene-like polymer. It has a high molecular weight which is formed by fluorine and carbon, which are tightly bound. That is why it is inert. It is a slip and non-stick material that has a high thermal resistance, as well as hydrocarbons, acids and bases and almost any chemical substance. It is also resistant to radiation.
Its other chemical properties include its high permeability to gases and liquids. On the other hand, it is a material that in the flames does not produce smell, does not release gases or deform. It is used in cooking utensils such as pans, among others.
Cellophane
This is a naturally occurring polymer that is derived from cellulose. It is characterized by a thin film, flexible, shiny, transparent and resistant to tensile stress, but very easy to cut. When cellophane has not been treated it is semipermeable and is usually used in some scientific procedures.
This material is made by the dissolution of fibers of cotton, hemp or wood. From this process a viscous solution is obtained which is subjected to an extrusion process to be subsequently bathed by an acid. Cellophane is used as wrapping gifts, food, in the manufacture of adhesive tapes, to produce semipermeable membranes and even as a coating.
Polyamide
Also known as PA or nylon, it is a translucent material and shiny, resistant, waterproof and flexible. It can withstand both friction and wear and chemical agents. It can be presented in two forms: rigid and fiber.
In the first case it is used in the manufacture of transmission parts of movements like screws, pieces of machinery, tools, wheels of all type, among others. In the second case (fiber) is used in the textile industry and in the rope for the manufacture of fabrics, ropes, stockings, toothbrushes, among other flexible elements.
Thermosets
This is a type of plastic that is only soft when heated for the first time. Which means that although it breaks down with heat, this is just before it melts. Once they have been molded and cooled, they can not be softened by heat. It is a compact and hard material, but also fragile.
The thermosets undergo a so-called set-up chemical transformation. Through this process, the polymers are interlaced permanently, so it remains rigid. Prior to the setting, this material usually has a liquid texture, pasty or solid. The fact that they can not melt again means that they can not be recycled by the application of heat.
Polyurethane
It is a plastic material that is produced from the chemical reaction between two liquid components that are the polyol and the isocyanate. This process involves catalysts, additives, fillers and foaming agents. Depending on the composition of the mixture of these two elements polyurethanes with different properties are obtained.
They can have a semi-rigid, rigid, flexible and spongy structure. They can also be elastic and adherent. It is a material resistant to acids and solvents, it also withstands heat well. It is also waterproof and allows thermal insulation. It is a plastic of industrial use that is usually used as foam for mattresses and seats, thermal and acoustic insulation, friction wheels, sponges, etc.
Phenolic resins
Also known as phenoplasts or bakelites. It is a hard material and at the same time fragile. It is dark, shiny and metallic in appearance. It includes fibers that are resistant to shock and asbestos to make it a heat resistant. In addition, it has insulating properties, so it is used in the manufacture of electronic and electrical elements.
Melamine
This material has properties similar to Bakelite. It is a lightweight, hard plastic and very resistant to shocks. Besides that can be colored, it has refractory qualities that make it suitable for domestic use. It has no odor or taste and is used as a thermal insulation.
This type of plastic is very important in the manufacture of laminates, but also in dinnerware, parts of household appliances, decorative items, furniture, food containers, acoustic and thermal insulation, among others.
Polyester
Also known as polyester resin, it is a rigid but fragile material. It improves the mechanical and resistance properties when reinforced with carbon fiber. It is usually used in the manufacture of synthetic textile fibers, since they do not wrinkle and do not shrink. They also have the ability to dry quickly.
Elastomers
This plastic is characterized by its great elasticity, due to its low hardness and its adhesion. These are substances formed by linear macromolecules, which are linked by bridges. These form a network that can stretch and contract. It is possible to say that structurally the elastomers are in the middle of thermoplastics and thermosets.
This type of material does not withstand heat well and degrade to medium temperatures. This eliminates the possibility of heat recycling. In addition, they are resistant to oils and fats, as well as to ozone.
Natural rubber
This is a type of plastic of natural origin since it is obtained from latex. Specifically the latex coagulation of several trees. It is an elastic and very resistant substance that presents as a translucent, yellowish or colorless mass. Usually used for thermal or electrical insulation.
Synthetic rubber
This type of plastic is derived from petroleum. They are macromolecular substances with elastic properties, a material very resistant to chemical agents. Like natural rubber, it is made up of long flexible chains. And usually used for the manufacture of tires, pipes, hoses, pavement, steering wheels, gloves, mattresses, etc.
Neoprene
Neoprene is a type of artificial rubber that is obtained by means of chemical processes with treated hydrocarbons. This material has an insulating property, is hard, resistant and waterproof. It is used for the manufacture of suits and even suits for firemen.
References
- Garavito, J. (undated). Plastics Protocol. Course of Manufacturing Processes. Edition 2007-2. Colombian School of Engineering. Colombia. Web: www.escuelaing.edu.co.
- Beltrán, M; Marcilla, A. (undated). Polymer Technology. Topic 2. Types of plastics, additives and blends. Web: iq.ua.es.
- Manjarrez, A. (2015). Natural Plastics and Derivatives. Web: prezi.com.
- Sosa, A. (undated). Plastics: materials to the measure. Web: www.cientec.or.cr.