Structure, Types and Characteristics of Polymers
The simplest way to understand the term polymer is a beneficial chemical made of many repeating units. A polymer can be a 3-dimensional (3D) network Imagine of a repeating unit joined together left and right, back and front, up and down or it is a 2-dimensional (2D) network Imagine of the repeating units linked together right, left, down, and up in a sheet or a 1-dimensional (1D) network Imagine of a repeating unit-linked right and left in a chain. Each unit that repeats is the “-Mer” or has a fundamental unit with “polymer” meaning multiple repeating units. The unit which is repeating is often made of hydrogen and carbon and sometimes nitrogen, oxygen, fluorine, sulfur, chlorine, silicon, and phosphorus. This forms a chain, many links or “-mers” are chemically attached or polymerized together. Linking infinite strips of construction paper together to create paper garlands or attached together hundreds of paper clips to make chains, or stringing beads helps you to visualize the polymers. Polymers can occur naturally and can be made to serve particular needs. The polymers that can be manufactured can be 3-dimensional (3D) systems that do not go once formed. Such networks are called Thermoset polymers. Epoxy resins which are used in 2-part adhesives are thermoset plastics. These manufactured polymers can also be a 1-dimensional chain that can be melted. These chains are Thermoplastic polymers and can also be called Linear polymers. The Cups, Plastic bottles, Films, and fibers are Thermoplastic plastics.
Polymers are found in nature. The ultimate natural polymers are deoxyribonucleic acid i.e., DNA, and ribonucleic acid i.e., RNA that explain life. Hair, Spider silk, and horn are the protein polymers. A Starch can be a polymer as it has cellulose in wood. We use rubber tree latex and cellulose as raw materials to make fabricated polymeric rubber and plastics. The very first synthetic manufactured plastic was Bakelite, in the year 1909 for telephone casing and electrical components. The first produced polymeric fiber was Rayon, from cellulose, in the year 1910. Nylon was invented in the year 1935 while trying synthetic spider silk.
Structures of Polymers:
Many general classes of polymers are formed of hydrocarbons, hydrogen, and compounds of carbon. The polymers are exactly made of carbon atoms bonded together, one to the next, into large chains that are called the backbone of the polymer. We can attach one or more other atoms to each carbon atom in the backbone chain. There are polymers that have only carbon and hydrogen atoms. Polyethylene, polybutylene, polystyrene, polypropylene, and polymethyl pentene are examples of these polymers. Polyvinyl chloride (PVC) has a chlorine atom attached to all the carbon backbone. The Teflon has fluorine attached to all the carbon backbone.
Other commonly produced polymers have backbones that have elements other than carbon. Nylons contain nitrogen atoms in the repeated unit of the backbone. Polycarbonates and Polyesters contain an oxygen atom in the backbone. There are also a few polymers that, alternatively of having a carbon backbone, have phosphorus or silicon backbone. These are recognized inorganic polymers.
Different Types of Polymers:
Polyvinyl chloride (PVC) is said to be a plastic polymer that is made of monomer vinyl chloride.
The urea-formaldehyde resin is not transparent in nature the plastic is obtained by heating formaldehyde and urea.
Glyptal is actually made up of monomers ethylene glycol and phthalic acid.
Bakelite can also be called poly-oxy-benzyl-methyl englycol anhydride, which is a plastic that is made up of monomers phenol and aldehyde.
Classification of Polymers
1. Source-Based Classification
Let's look at the first classification of polymers based on their source of origin.
Natural Polymers
The easiest method to categorize polymers is by their origin. Natural polymers arise naturally and can be found in natural sources such as plants and animals. Proteins (which have the same structure in humans and animals), Cellulose and Starch (which are present in plants), and Rubber are all common examples (which are harvested from the latex of a plant).
Synthetic Polymers
Synthetic polymers are polymers that can be created or synthesized in a lab by humans. These are manufactured commercially for human consumption. Polyethene (a mass-made plastic used in packaging) and Nylon Fibers are two examples of commercially created polymers that we utilize daily (commonly used in our clothes, ropes, etc.)
Semi-Synthetic Polymers
These polymers are polymers created in a lab by artificially altering natural polymers. These commercially essential polymers are created through a chemical reaction (in a controlled environment). Examples are vulcanized Rubber which is created by crosslinking sulphur to the polymer chains in Natural Rubber, cellulose acetate (rayon), and other materials.
2. Polymer Classification Based on the Structure
Polymers can be classified into three categories based on their structure:
Linear Polymers
These polymers have a structure that resembles a long straight chain with identical links connecting them. These are made up of monomers that are bonded together to form a lengthy chain. These polymers have a higher melting point and density than others. PVC is a good illustration of this (Poly-vinyl chloride). This polymer is commonly used in the manufacture of electrical cables and pipes.
Branch Chain Polymers
These types of polymers have the structure of branches sprouting at random places from a single linear chain, as the name implies. Monomers combine to form a long straight chain with branching chains of various lengths. The polymers are not tightly packed together as a result of their branches. They have a low melting point and density: plastic bags and general-purpose containers made of low-density polyethene (LDPE).
Crosslinked or Network Polymers:
Monomers are joined together to form a three-dimensional network in this type of polymer. Because they are made up of bivalent or trivalent molecules, the monomers have strong covalent bonds. These polymers are brittle and difficult to work with. Examples are bakelite (used in electrical insulators), Melamine, and other similar materials.
3. The Following Variables Can be Used to Control When Producing a Polymer:
The monomer polymerized or can be called the monomers copolymerized.
The reagent that is used to initiate the polymerization reaction.
We can identify an amount of the reagent that can be used to crosslink the polymer chains.
Identify the temperature and pressure at which the polymerization happens.
In which the solvent the monomer is polymerized.
The method in which the polymer is collected can produce either a more or less random alignment of the polymer chains or a fabric in which the chains are aligned in a particular direction.
When you change one or more of these parameters can affect the Linearity of this polymer, its average molecular weight, the tactic of side chains on the polymer backbone, and the density of the product.
Characteristics:
Polymers are very resistant to chemicals. Consider all the cleaning fluids in your house that are packaged in plastic. Reading the warning labels that explain what happens when the chemical comes in contact with eyes or skin or is ingested will indicate the need for chemical resistance in the plastic packaging. While solvents simply dissolve some plastics, other plastics produce safe, non-breakable packages for aggressive solvents.
Polymers act equally as electrical and thermal insulators. A walk by your house will strengthen this concept, as you consider all the cords, appliances, electrical outlets and wiring that are made or covered with polymeric materials. Thermal resistance is visible in the kitchen with pan and pot handles made of polymers, the coffee pot handles, the foam core of freezers and refrigerators, microwave cookware, insulated cups, and coolers. The thermal undergarments that many skiers wear are made of polypropylene and the fiberfill in winter jackets is acrylic and polyester.
The polymers are very light in mass with important degrees of power. Consider the range of applications, from toys to the frame construction of place locations, or from feeble nylon fiber in pantyhose to Kevlar, which have been used in bulletproof vests. Some polymers float on water while others sink immediately. Still, while being compared to the weight of stone, concrete, steel, copper, or aluminum, all plastics are lightweight substances.
The polymers can be prepared in different ways. Extrusion delivers thin fibers or heavy pipes or films or food bottles. Injection shaping can produce very complex parts or large car body panels. Plastics can be made into drums or be mixed with solvents to become adhesives or paints. Elastomers and some plastics extend and are very flexible. Some plastics are extended in processing to take their shape, such as soft drink bottles. Other polymers can be foamed like polystyrene polyurethane and polyethylene.
Polymers are substances with a seemingly endless range of features and colors. Polymers have many original properties that can be further improved by a deep range of additives to increase their uses and applications. Polymers can be used to mimic cotton, silk, and wool fibers; porcelain and marble; and aluminum and zinc. Polymers can also make possible products that do not easily come from the natural world, such as clean clear sheets and flexible films.
The Uses of Polymers
Polypropene has a broad range of usage in industries such as stationery, textiles, packaging, plastics, aircraft, construction, rope, toys, etc.
Polystyrene is one of the most common plastics that is actively used in the packaging industry. Disposable glasses, bottles, toys, containers, trays, plates, tv cabinets, and lids are some of the dairy products used by us that are made up of polystyrene. It can also be used as an insulator.
The very important use of polyvinyl chloride is the manufacture of sewage pipes. It can also be used as an insulator in electric cables.
Polyvinyl chloride is used in furniture and clothing and has recently become famous for the construction of doors and windows. It can be used in vinyl flooring.
Urea-formaldehyde resins are used for making molds, adhesives, laminated sheets, unbreakable containers, etc.
Glyptal is used for making paints, coating metals, and lacquers.
Bakelite is used for making electrical appliances such as switches, kitchen products, toys, jewelry, firearms, insulators, computer discs, etc.
FAQs on Uses of Polymers
1. What is a polymer in simple terms?
A polymer is a large molecule, or macromolecule, composed of many repeating smaller units called monomers. Imagine a long chain made by linking hundreds of paper clips together; each paper clip is a monomer, and the entire chain is the polymer. These long chains give polymers their unique and useful properties.
2. What are the main uses of common polymers like Polyethene and PVC?
Polyethene and Polyvinyl Chloride (PVC) are two of the most widely used synthetic polymers with distinct applications:
- Polyethene (or Polyethylene): Primarily used for packaging. Low-Density Polyethene (LDPE) is used for plastic bags and films, while High-Density Polyethene (HDPE) is used for more rigid items like bottles, pipes, and toys.
- Polyvinyl Chloride (PVC): Known for its durability and resistance to water and chemicals. It is widely used for making pipes, window frames, flooring, electrical cable insulation, and imitation leather.
3. How are polymers classified based on their source of origin?
Polymers are classified into three main types based on their source, as per the CBSE syllabus:
- Natural Polymers: These are found in plants and animals. Examples include proteins (like silk, wool, hair), cellulose (in wood and paper), starch, and natural rubber.
- Synthetic Polymers: These are man-made polymers synthesised in laboratories. Examples include Nylon, Polyethene, Polystyrene, and PVC.
- Semi-synthetic Polymers: These are derived from natural polymers by performing chemical modifications. A common example is cellulose acetate (rayon), which is made from cellulose.
4. What is the difference between thermosetting plastics and thermoplastics?
The key difference lies in how they respond to heat. Thermoplastics are polymers that can be melted by heating and solidified by cooling, a process that can be repeated multiple times without significant chemical change (e.g., Polyethene). In contrast, thermosetting plastics become permanently hard and rigid when heated. They form extensive cross-links between chains, creating a 3D structure that cannot be reshaped or melted again (e.g., Bakelite).
5. What are some important uses of Bakelite and Glyptal?
Bakelite and Glyptal are important thermosetting polymers with specific industrial uses:
- Bakelite: As one of the first synthetic plastics, it is known for its heat resistance and electrical insulating properties. It is used to make electrical switches, plugs, handles for cookware, and telephone casings.
- Glyptal: This is a polyester resin used primarily in the manufacturing of paints, lacquers, and other surface coatings due to its strong adhesive properties.
6. How does the structure of a polymer affect its properties and uses?
The arrangement of monomer chains significantly impacts a polymer's physical properties. This is a key concept in understanding their application:
- Linear Polymers: Have long, straight chains that can be packed closely together, resulting in high density, high tensile strength, and high melting points. HDPE is an example.
- Branched-chain Polymers: Have a main linear chain with smaller side branches. These branches prevent close packing, leading to lower density, lower tensile strength, and lower melting points. LDPE is a prime example.
- Cross-linked Polymers: Contain strong covalent bonds connecting different polymer chains, forming a rigid 3D network. This makes them hard, rigid, and brittle, like Bakelite.
7. Why are polymers considered excellent insulators for heat and electricity?
Polymers are effective insulators primarily due to their molecular structure. The electrons in the covalent bonds that make up the polymer backbone are held tightly and are not free to move, which prevents the flow of electric current. For thermal insulation, the long, entangled chains of polymers hinder the efficient transfer of vibrational energy (heat) from one part of the material to another.
8. What are some examples of natural polymers we encounter in daily life?
We use and interact with many natural polymers every day. Some common examples include:
- Starch: A polymer of glucose, found in foods like potatoes, rice, and corn.
- Cellulose: The main component of plant cell walls, it forms the basis of wood, paper, and cotton fabrics.
- Proteins: These are polymers of amino acids. Examples include keratin (in hair and nails) and silk (from silkworms).
- Natural Rubber: A polymer of isoprene, harvested from the latex of rubber trees and used for tyres and elastic materials.
9. Beyond rigid plastics, what are other forms that polymers can take and their uses?
Polymers exist in several forms beyond common plastics, each with specialised uses:
- Fibres: These are thread-like polymers with high tensile strength, used in textiles and ropes. Examples include Nylon and Polyester.
- Elastomers: These are rubber-like polymers that can be stretched and then return to their original shape. Examples include Neoprene (used in wetsuits) and Buna-S (used in tyres).
- Resins: These are often liquid polymers that can be cured to form a hard, durable solid. Epoxy resins are a common example, used as strong adhesives and coatings.
10. What makes a polymer biodegradable, and why aren't all polymers designed this way?
A polymer's biodegradability depends on its chemical structure. Polymers like PHBV (Poly β-hydroxybutyrate-co-β-hydroxy valerate) have chemical bonds, such as ester linkages, that can be broken down by enzymes from microorganisms. In contrast, most common synthetic polymers like Polyethene have extremely strong and stable carbon-carbon backbones that are resistant to microbial attack. While desirable for reducing waste, not all polymers are designed to be biodegradable because their primary application often requires long-term durability and resistance to environmental degradation, such as in construction materials, medical implants, or car parts.
