Polymers are macromolecules made up of smaller units, the monomers. Monomers are linked together through covalent bonds.
The term polymer is derived from the Greek, poly "many" and mere "parts".
You mere are the repeating units in a polymer. O monomer is the molecule consisting of a single mere and the polymer it consists of several meres.
Polymerization is the name given to the polymer formation reaction. The degree of polymerization refers to the number of mers in a polymer chain.
Human history is related to the use of natural polymers such as leather, wool, cotton and wood. Currently, many utensils used in everyday life are produced from synthetic polymers.
Types of Polymers
There are several classifications for polymers, the main ones are as follows:
Classification regarding the number of monomers:
homopolymer is the polymer derived from only one type of monomer.
Copolymer is polymer derived from two or more types of monomers.
Classification by nature:
Natural Polymers
Natural polymers or biopolymers are those that occur in nature.
Examples of natural polymers are rubber, polysaccharides (starch, cellulose and glycogen) and proteins.
Synthetic Polymers
Synthetic or artificial polymers are produced in the laboratory, in general, from products derived from Petroleum.
Examples of synthetic polymers are: polymethyl methacrylate (acrylic), polystyrene, polyvinyl chloride (PVC), polyethylene and polypropylene.
From synthetic polymers it is possible to manufacture plastic bags, hydraulic pipes, civil construction materials, glues, Styrofoam, paint, chewing gum, tires, plastic packaging, Teflon and silicone.
PVC materials
Classification as to the method of obtaining:
Addition Polymers
These are polymers obtained by successive addition of monomers. Examples are polysaccharides, formed by monosaccharide monomers and proteins, formed by amino acid monomers.
Condensing Polymers
These are polymers obtained by adding two different monomers with the elimination of a water, alcohol or acid molecule during polymerization.
Rearrangement Polymers
It is the polymers resulting from the reaction between monomers that undergo rearrangement in their chemical structures during the polymerization reaction.
Classification regarding mechanical behavior
Elastomers or Rubbers
Elastomers can be natural or synthetic. Its main feature is its high elasticity.
Natural rubber is obtained from the rubber tree Hevea brasiliensis, through cuts in your torso. With this, a white liquid, latex, is obtained.
Rubber tree latex extraction
Synthetic rubbers are formed by adding two types of monomers (Copolymer). They are more resistant and used commercially for the production of hoses, belts and sealing articles.
Plastics
Plastics are formed by combining various monomers. Generally, petroleum is used as a raw material for the production of plastics.
Natural or synthetic plastics can be divided into thermosets and thermoplastics.
You thermoset or thermosets are those that, by heating, assume a three-dimensional structure, becoming insoluble and infusible. After that, they are unable to return to their original form. They give rise to rigid and durable structures like car parts. Some examples are: polyurethane, polyethylene, polystyrene and polyester.
You thermoplastics they are those that allow fusion by heating and solidification by cooling, this enables their treatment and molding repeatedly, as long as they are reheated. They are easily malleable and used for film, fiber and packaging production. Thermoplastics are recyclable.
Fibers
Fibers can be natural or synthetic. The production of artificial fibers consists of the chemical transformation of natural raw materials.
In nature, fibers can be obtained from animal hair, such as silkworm silk, or from stems, seeds, leaves and fruits, such as cotton and flax. Synthetic fibers are represented by polyester, polyamide, acrylic, polypropylene and aramids.
Biodegradable Polymers
Biodegradable polymers are materials that degrade into carbon dioxide, water and biomass as a result of the action of living organisms or enzymes. Under favorable conditions of biodegradation, they can be completely degraded within weeks.
Biodegradable polymers can be natural or synthetic. They can be derived from the following sources:
- Renewable sources of vegetable origin such as corn, cellulose, potatoes, sugar cane;
- Synthesized by bacteria;
- Derived from animal sources such as chitin, chitosan or proteins;
- Obtained from fossil sources such as oil.
Biodegradable polymers are used to produce food packaging, bags, agricultural products and consumer products.
Through the biodegradation process, they avoid the accumulation of garbage and, consequently, pollution, fitting into the concept of sustainability.
