We explain what plastic is, the types that exist and the various uses of this polymer. Also, its history and its properties.
What is plastic?
Plastic is the generic and common name given to a series of substances with similar molecular structure and physical-chemical characteristics, whose fundamental characteristic is to have elasticity and flexibility during a range of temperatures, thus allowing it to be molded and adapted to various shapes. This name comes from his eminent plasticitythat is, its ease in acquiring certain forms.
Most plastics are, specifically, synthetic and petroleum-derived materials obtained through polymerization processes, that is, synthesis processes of long chains of carbon atoms, which give rise to an organic substance that is malleable in hot and resistant to cold. There are also plastics that are not derived from petroleum, such as plastics derived from starch, cellulose, and certain bacteria.
This material is extremely versatile thanks to its lightness, pleasant touch and resistance to both biological and environmental degradation (except for prolonged exposure to UV rays in some cases).
These properties are difficult to achieve with other materials, and make plastic both a blessing and a problem, since while being the most useful and effective synthetic material in human history, it is also the main source of solid pollution on the planet (trash). Luckily, plastic is recyclable, although its production is much cheaper and easier than its reuse.
When subjected to direct heat, most plastics release gases rich in dioxins and furans, carcinogenic hydrocarbons and compounds capable of suffocating living beings, in addition to causing tremendous atmospheric damage.
See also: Fiber optics
Types of plastic
There are various ways of classifying plastics, such as:
- According to the origin of the monomers that compose it
- Natural Monomers come from natural substances such as rubber, cellulose and casein (protein present in milk). For example: cellophane and rubber.
- Artificial The monomers come from synthetic substances, mainly derived from petroleum. For example: polyethylene.
- According to their reaction to heat
- Thermoplastics When heated they acquire a liquid consistency and when cooled they acquire a vitreous (glass-like) state. This type of plastic can be heated and molded, and then it can be reheated several times and change its shape back. For example: polyethylene and rubber.
- Thermostable When they are heated, molded and cooled to take a certain shape, it is then impossible to reheat them to melt them again. That is why they are said to be rigid or thermohard. For example: Bakelite and polyesters.
- Elastomers. Also called “rubbers”, they are polymers with high elasticity. If a deforming force is applied to them, they have a high capacity to recover their original shape when said force is removed. For example: neoprene.
- According to its molecular structure
- Amorphous Their molecules are disorganized and do not tend to form any ordered structure, which is why they leave large spaces between their particles for light to penetrate, thus achieving transparent plastics. For example: atactic polystyrene.
- Crystallizable They tend to form rigid crystals that are resistant to deformation. Depending on the cooling rate of a polymer, its crystallinity can be increased or decreased. If it cools quickly, its crystallinity decreases, and if it cools slowly, its crystallinity increases. In the case of amorphous plastics, they will not have any level of crystallinity, regardless of the rate at which they cool. For example: polypropylene is a crystallizable plastic.
- Semi-crystallizable They have intermediate characteristics between amorphous and crystallizable, since they have disordered areas and other ordered ones. The passage of light through them will depend on their thickness. For example: low-density polyethylene.
Uses of plastic
The applications of plastic are virtually endless: from spare parts for electronic, electrical and industrial devices, such as insulators, protectors, covers, shock absorbers, etc., to components in the construction sector such as pipes, waterproofing, insulating materials, glass, etc.
Another very common use of plastic is in the manufacture of tools, toys, packaging, furniture, containers, dividers, fasteners and, above all, bags.
History of plastic
The invention of plastic revolutionized human industry forever. Initially It was developed in the late 19th century as a substitute for ivory to create billiard balls, by the American John Weasley Hyatt, who was able to synthesize a celluloid by dissolving vegetable cellulose in camphor and ethanol.
Years later, in 1909, Leo Hendrik Baekeland created a polymer from phenol and formaldehyde, which was the first synthetic plastic in history, still known as “Bakelite”.
This is considered the beginning of the “plastic era” that peaked in the 20th century, when the exploration of plastic resins began and their subsequent application to practically all fields of industry.
Ten years later, In 1919, the macromolecular composition of plastic was discovered thanks to the studies of the German Hermann Staudinger.
Plastic properties
Plastics are sets of organic macromolecules, generally of synthetic origin, mostly waterproof, resistant, diamagnetic and good acoustic, electrical and thermal insulators, although they are not very resistant to very high temperatures in their entirety.
In addition, they are not very dense, economical to manufacture, easy to work and shape. Once cooled and shaped, they are resistant to corrosion and many chemicals except organic solvents (such as thinnerdiluent whose name comes from English).
Furthermore, most plastics are not biodegradable although there is currently experimentation in that direction, they are not easy to recycle, which makes them an important source of pollution that lasts over time.
