Although many manufacturers are familiar with the term polymer, it’s easy to lose track of the basics of familiar terms.
What then is a polymer? How do you know what you can call a polymer?
In this article, we’ll expand on what a polymer is, its features, classifications, and examples.
What Is a Polymer?
The word polymer comes from a Greek term that translates to “many parts.” A polymer is a term used for large chemical compounds with several subunits. These subunits are also known as monomers, and they are linked to each other in long recurring chains. Sometimes, too, polymers may be made up of one type of monomer or different kinds.
As you already know, polymers are not only restricted to materials used in manufacturing. Polymers, as per their definition, can be found anywhere and everywhere. A strand of hair, ball of nylon fibre, and polypropylene are all examples of polymers.
Features of Polymers
Some characteristic features of polymers are:
- They are usually elastic, so they can stretch
- Polymers can stretch beyond themselves in the presence of a load. However, they can go back to their normal size if the load is removed, and they don’t reach their elastic
- Polymers have different strengths. Some can be so weak that they have the strength of a liquid, while others have the strength close to a solid metal
- Synthetic polymers are, to an extent, resistant to degradation
- Natural polymers are mostly fragile and easily broken down
- Some polymers are soluble in organic solvents such as chloroform, acetone, alcohols, etc.
- Most polymers are hydrophobic. That is, they don’t mix with water
- Polymers range from highly amorphous to highly crystalline
- Polymers are best for as insulators as they do not conduct electricity
Classification of Polymers
Different types of polymers are available. To capture these different types of polymers, polymers are classified based on their varying qualities. These classifications are explained below.
1. Classification Based on Source
Based on this classification, there are two main types of polymers: natural and synthetic polymers. There’s also a third group known as semi-synthetic polymers.
Natural Polymers
As the name implies, these groups of polymers are naturally occurring. You can find them in either plants or animals. Common examples include rubber (obtained from plants), starch, and cellulose.
Of all the naturally occurring polymers, cellulose is the most common type. It’s found in the cell walls of plants. Oftentimes, this cellulose is used to produce paper and clothing materials.
Man-Made/Synthetic Polymers
They are made from scratch in laboratories, and they constitute the most common plastics in the world.
Synthetic polymers have a variety of characteristics too. While some are flexible and easy to work with, others are rigid.
Examples include nylon, polyethylene, PVC, and polystyrene.
Semi-Synthetic Polymer
This type of polymer is still naturally occurring. However, they’ve gone through several kinds of chemical changes to amplify their strengths in certain areas. Common examples of this type of polymer are cellulose nitrate and cellulose acetate.
2. Classification Based on Their Reaction to Heat
Based on this characteristic, polymers are of two types: thermoplastics and thermosets.
Thermosets
When you place thermoset polymers in heat, it solidifies into a shape (if you use a mold). That is, thermosets do not melt or change into liquid before they re-solidify. This happens because the solidification process of thermoset polymers involves the formation of a special type of bond that holds the subunits in place.
Thermoset polymers are not easy to reshape or straight after you cure them. However, they are relatively more resistant to heat, chemicals, and corrosion. They also have improved mechanical stability.
Examples of thermoset polymers are silicones, phenolics, epoxies, etc.
Thermoplastics
Thermoplastics are a type of polymers that are solid at room temperature. However, when they are subjected to heat, they melt and become soft. Thermoplastics have a reversible curing process. They can be recycled easily too.
Thermoplastic polymers are flexible, and you can reshape them with ease. They are also fairly resistant to chemicals. However, thermoplastics melt at temperatures higher and lower temperatures due to the weaker bonds between the molecules. An excellent example of thermoset is polyvinyl chloride.
3. Classification of Polymers Based on the Structure of the Monomer Chain
Based on the structure of the chains of the subunits, polymers may be:
Linear Polymers
Here, the linking bonds of the polymers are long and straight (Think of the normal chains you know). Polyvinyl chloride (PVC) is an example of linear polymers. Because they are linear, they are used to make straight products like pipes, electric cables, and so on.
Branched-chain Polymers
Sometimes, these straight polymeric chains may give out some branches at different points. The resultant type of polymer is now called branched-chain polymer. An excellent example is polythene.
Cross-Linked Polymers
These polymers have interlinked and multifunctional monomers. The bonds in cross-linked polymers are covalent bonds, hence they have better strength in comparison to other polymers in this class. Good examples are bakelite and melamine.
4. Classification Based on the Type of Polymerization
Based on the type of polymerization they undergo to become polymers, polymers may either be:
Addition Polymerization
In this type of polymer formation, several small monomeric subunits come together to form a larger polymer. With every newly introduced monomer, the length of the chain “grows.”
Examples of polymers formed by additional polymerization include polymerizing ethane in the presence of peroxides to produce polythane, Teflon, polyvinyl chloride, and so on.
Condensation Polymerization
During this process of polymerization, smaller linking molecules like H2O, CO, and NH3 are gotten rid of. The result is a condensed form of polymer.
Organic chemical compounds with functional groups like diamines and dicarboxylic acids are more likely to form polymers via this process.
Examples of polymers formed with this method of polymerization include nylon -6, 6, polyester, etc.
Copolymerization
In co-polymerization, different types of monomers join to form the polymer. BUNA–S and other synthetic rubbers are formed with this process.
5. Classification Based on Monomeric Units
Depending on the type of monomeric subunits present, a polymer may either be:
Homomer
Here, there’s a single type of monomeric subunit throughout the entire polymer. An example of a homomer is polyethylene.
Heteropolymer or Co-Polymer
Heteropolymers have more than one type of monomeric subunits. E g, nylon -6, 6
6. Classification Based on Molecular Forces
They are either elastomers or fibers
Elastomers
Elastomers are flexible and elastic solids polymers. They have weak bonds, hence, the increased flexibility of the polymers. E.g, natural rubber, silicone rubber, etc.
Fibers
These are tough polymers with high tensile strength. The binding force between them is stronger. E.g., Nylon -6, 6.
7. Classification Based on Biodegradability
There are two classes of biodegradable polymers:
Bioplastics
This type of polymer is made from renewable raw materials. The chemical compounds of bioplastics are made by microbes such as bacteria or genetically modified plants. As a result, they’re easy to recycle.
Biodegradable With Industrial Processing
These types of polymers are petrochemicals with biodegradable additives. The polymers are designed with additives that enhance their biodegradability, so they are broken down upon industrial processing.
Common Examples of Polymers Used In Manufacturing Processes
Some of the very common types of polymers used in manufacturing processes include:
Nylons
Nylons are tough and chemically resistant polymers. They are made of fibres, and the surface of nylon is slippery.
There are different types of nylon polymers available for different kinds of manufacturing procedures. These different types of nylon sheets have varying manufacturing methods and molecular weights, yet they’re all polymers. Nylons are often used as ropes, clothing, webbing, and, to a small extent, insulation materials.
Latex rubbers
These are polymers obtained from the sap of some plants. They harden when exposed to air. Upon improvements, they can be used for a variety of purposes, including as insulation materials, etc.
Starches
Starches are polymers that have poor tensile strength and are unstable with heat. Upon improvement, purification, and additives, they are used to make PLA and PLA+.
Cellulose
Cellulose is a popular naturally occurring polymer with a tough and rigid structure. They are used to make clothing materials and ropes, or in other places where strength is necessary.
Polyethylenes
These are branching polymers made solely of a single subunit– ethylene gas. Polythenes are of different grades and molecular weights. They can range from low-density materials to ultra-high molecular weight materials. They are used to make food containers and pipes in some machines.
Polyesters
Polyesters are amorphous materials that are similar to nylons. They are among the most used man-made polymers, and they are used to make clothing materials, ropes, and fibers.
Silicone
Silicone is mostly made as two-part, thermoset polymers that undergo a catalytic reaction when mixed.
Epoxy Resins
These are polymers formed by copolymerization. It’s used for making decorations, machine parts, or other situations where great strength is needed.
Polystyrene
Polystyrene is also globally appreciated for its unique properties. It can be expanded by foaming with refrigerant gas to make a fragile but shock-resistant insulating material.
Polypropylene
Polypropylene is a type of thermoset polymer with a single monomeric propylene. It’s used in places where strength and flexibility are required. They are available as polypropylene sheets and may be used to make food packages, ropes, fiber decors, etc.
Other examples of polymers include:
Polyethylene terephthalate (PET)
Acrylonitrile Butadiene Styrene (ABS)
Polycarbonate (PC)
Polysulfone
Conclusion
Knowing what a polymer is is important especially if you are into manufacturing, as studying them is important for your profit and reputation. The different qualities of these polymers will greatly influence the quality of your customer products, so knowing the polymers is vital.
