Polymers are substances made up of very large molecules called macromolecules, which are made up of many repeating units linked together called monomers.
The synthetic polymers are polymers simply artificially synthesized in a laboratory or in a chemical plant, using different types of monomers and catalysts.
In simple terms, synthetic polymers are all industrial plastic materials. The first to be synthesized was Bakelite, and today there are hundreds of them made up of different types of monomers and with very particular physical and chemical properties.
Some were originally produced from coal and its derivatives, but today they are mainly synthesized from oil . In fact, they represent one of the most important products in the entire petrochemical industry.
They are usually very chemically inert
Many synthetic polymers are saturated hydrocarbons, which are very little reactive. In fact, they do not usually react with strong acids such as nitric or sulfuric acid, nor with strong bases, nor with oxidizing agents such as potassium permanganate.
Most are insoluble in water but soluble in polar solvents
This is because most synthetic polymers are nonpolar organic compounds . Furthermore, the large size of macromolecules makes them more difficult to dissolve in any solvent, but some nonpolar organic solvents such as carbon tetrachloride or cyclohexane are capable of dissolving them.
Most are combustible organic compounds
Since the vast majority of synthetic polymers are organic compounds, then they can undergo the combustion reaction. That is, they can burn in the presence of oxygen.
Most do not conduct electricity
This is because, for the most part, they do not have delocalized electrons that can move back and forth in the presence of a voltage difference. In fact, most of the electrical insulating materials in common use are made of synthetic polymers.
They are bad thermal conductors
Just as they are poor electrical conductors, they are also poor conductors of heat.
They are usually amorphous solids
It often happens that the molecules that make up a polymer are not all the same, and they are also extremely long. This makes it very difficult to form ordered crystalline structures so they often form amorphous solids.
They can have very varied mechanical properties
In terms of mechanical properties, polymers can be synthesized for almost any need:
- Some are very hard while others are very soft.
- Some are elastic and flexible while others are rigid.
- There are synthetic polymers that are highly resistant to stress while others break easily when subjected to stress.
- Some are usually very resistant to impact and some are not.
They have relatively low melting points
Compared to many other substances, the melting points of polymers are low. However, most of them do not have a defined melting point. Instead, they have a temperature at which they go from a crystalline state to an amorphous solid, which is called the glass transition temperature.
They are not very dense
The lack of order in the structure of solid plastics makes the polymer molecules occupy more volume than they could occupy, which makes them not very dense. Many of them are even less dense than water.
They are not biodegradable
Due to their low chemical reactivity, synthetic polymers do not spontaneously decompose in the environment, and very few microorganisms are capable of degrading them. For this reason, they tend to last for many years in the environment.
Synthetic Polymer Applications
Synthetic polymers have endless applications in all fields:
- In the textile industry: synthetic fibers such as nylon and polyester, as well as many others, are made from synthetic polymers.
- In the construction industry: Almost all water pipes, electrical conduits, electrical switches, and electrical wiring insulation used in construction are made of plastics or synthetic polymers.
- In the food industry: thanks to their low chemical reactivity and their impermeability to water and gases, plastics are used in all types of food packaging such as water bottles and soft drinks, among others.
- Medical Applications: Synthetic polymers are found in all types of medical instruments, as well as in drug packaging, different types of prosthetics, and more.
- Applications in electronics: most of the circuits that are part of all our electronic devices are built on a plate or matrix made of a synthetic polymer.
- In manufacturing and prototyping: synthetic polymers are the basis of all products manufactured by the plastics industry and in 3D printing manufacturing.
Types of synthetic polymers
Synthetic polymers are very varied and there are different ways to classify them. The most important are:
According to its structure
- Linear: Linear synthetic polymers consist of long chains of monomers joined one after another without the appearance of branching.
- Branched: unlike linear ones, these polymers have long central chains, but they also have other shorter side chains that form branches.
- Cross-linked: These synthetic polymers consist of linear or branched polymers in which the main chains are linked together by means of other shorter chains giving rise to a network.
According to the monomers used
- Homopolymers: are those formed by a single type of monomer, as in the case of polyethylene.
- Copolymers: They are polymers of only 2 different monomers. An example is styrene-butadiene rubber (SBR).
- Heteropolymers: are those formed by more than two different monomers. An example is acrylonitrile-butadiene-styrene (ABS) plastic.
According to its physical properties
- Thermoplastics: they are those that can be heated until melted and cooled again while maintaining their properties.
- Thermosetting: they are those that, when heated, are transformed into harder and more resistant polymers by the formation of new bonds between the chains.
- Elastomers: they are elastic polymers such as silicones.
According to the type of bond between the monomers
- Polyolefins: are formed by the union of unsaturated hydrocarbons such as ethylene.
- Polyesters: They are those in which the monomers are linked by means of the condensation between an acid and an alcohol.
- Polyethers: In these cases the monomers are linked through an oxygen atom.
- Polyamides: Monomers are linked by condensation between an acid and an amine.
- Acrylic polymers: They are a family of polymers derived from acrylic acid and its esters.
- Vinyl polymers: they are similar to polyolefins but with substituents such as chlorine or fluorine.
- Polyurethanes: they are polymers derived from isocyanates.
Examples of synthetic polymers
- Bakelite: the first synthetic polymer. It is a thermosetting polymer.
- Polyethylene (PE): It is the most produced and used polymer worldwide.
- Polypropylene (PP): used in industrial fibers, plastic bags and food containers.
- Polystyrene (PE): is the preferred material for plastic cutlery.
- Polyvinyl Chloride (PCV or PVC) – Used in pipes, fabrics, bottles, and vinyl flooring.
- Nylon: it is a polyamide that is used in elastic fabrics.
- Teflon or polytetrafluoroethylene (PTFE): It is a very popular non-stick material.
- Thermoplastic Polyurethane (TPU): is a soft synthetic polymer similar to natural rubber.