Introduction of Polymers
➧ Modern life cannot be imagined without polymers. In order to manage our daily life in a simple and easy way, the importance of polymers is immense. If we take a closer look, we can see that most of the items used in our daily life are made of polymers. For example Brush, plastic cups, plastic bags, buckets, toys, synthetic cloth, and tyres, electrical insulating materials etc. Even the proteins in our body are polymers. All these materials are made with different types of polymers. So, in this chapter we will be discussing different types of polymers.
What are Polymers?
➧A Polymer is a combination of many repeating subunits.
➧The polymers are giant molecules with high molecular masses (103 -107u)
➧These repeating subunits are called ‘monomers’.
➧ The word ‘polymer’ derived from two Greek words, Poly – means ‘many’ and ‘Mer’ – means ‘unit or part’.
➧ For example the monomer ethylene gets linked with many other ethylene molecules to form polyethylene, or large number of vinyl chloride molecules combine to form polyvinyl chloride.
Common classifications of polymers
➧ Based on some special features (like source, structure) the following are some of the common classifications of polymers.
❖ Classification Based on Source.
❖ Classification Based on Structure of Polymers
❖ Classification Based on Mode of Polymerisation
❖ Classification Based on Molecular Forces
❒ Classification of Polymers Based on Source
➥ there are three subcategories –
- 1. Natural polymers
- 2. Semi-synthetic polymers
- 3. Synthetic polymers
➧ Natural polymers
- Natural polymers are the most common types of polymers.
- These are found in humans and animals.
- Examples – Resins and Rubber, Starch and Cellulose (found in Plants), Proteins (found in Animals) .
➧ Semi-Synthetic polymers
- Semi-Synthetic polymers produced artificially in labs by the modification in natural polymers.
- Example – Cellulose acetate (rayon) and cellulose nitrate, both are Cellulose derivatives
➧ Synthetic polymers
- Synthetic polymers artificially produced by humans.
- Due to high demand these are produced commercially by industries.
- Example: – Plastic (polythene), Nylon 6, 6, Synthetic rubbers (Buna – S)
Classification of Polymers based on Structure of Polymers
➥ Polymers based on Structure subdivided into three categories –
- Linear polymers
- Branched chain polymers
- Cross linked or Network polymers
➧ Linear polymers
- Monomers are united together to form a long straight chains.
- High melting and boiling points, high density and high tensile strength. (Due to well packed structure)
- Example: – High density polythene, Polyvinyl chloride (PVC), Nylon.
- This types of polymer used to make bottles, Buckets, PVC pipes.
➧ Branched chain polymers
- Linear chains having some branches.
- Low density, low melting points.
- They are not well packed due to formation of branches.
- Low melting and boiling points, low density and low tensile strength. (Due to formation of branches, they are loosely tied)
- Example: – Low density polythene (LDPE).
- Low density polythene is used to manufacturing plastic bags, dispensing bottles, tubing, wash bottles.
➧ Cross linked or Network polymers
- Network polymer formed by bi-functional and tri-functional monomers.
- The monomers are linked together by strong covalent bonds.
- A three-dimensional network formed by the monomers of the cross linked polymers.
- Example: – Bakelite, Melamine.
- Bakelite widely used in manufacturing of electrical insulating materials.
- Melamine is primarily used in manufacturing of floor tile, kitchen wares. And fabrics..
❒ Classification of Polymers based on Mode of Polymerisation
- On the basis of mode of polymerization the polymers can also be classified into two subgroups.
- Addition polymers
- Condensation polymers
➧ Addition polymers
- This polymer formed by Simple repeated addition of monomeric units. (Molecules of single monomer)
- Addition polymerization reaction never produced any by-products (e.g water)
- The monomaric unit is unsaturated or possessing double bonds.
- Additional polymer is non biodegradable and resistant to acids.
- Example:- Polythene, polypropene.
➧ Condensation polymers
- This polymer formed by Simple repeated addition of two different monomaric units. (Molecule of two different monomer)
- The condensation reaction produced by products (usually water)
- The monomaric unit contain reactive functional groups attend of the molecules.
- Carboxylic acid and alcohol arethe two functional groups.
- Biodegradable and can be hydrolyzed by acids.
- Example:- nylon 6, Terylene (Dacron), Nylon 6, 6
❒ Classification of polymers based on Molecular Force
➧ Mechanical properties of polymers depend on the intermolecular force of the polymer.
➧ Some of the mechanical properties are elasticity, toughness,tensile strength
➧ These mechanical properties are governed by intermolecular forces like…..
◘ 1. Van der Waals forces
◘ 2. Hydrogen bonds present in the polymer.
♦ based on intermolecular forces present in the polymer, the polymers are classified into four sub categories.
◘ 1. Elastomers
◘ 2. Fibres
◘ 3. Thermoplastic polymers
◘ 4. Thermosetting polymers
➧ Elastomers or Rubber
- Weakest intermolecular force (vanderwaal force) of attraction between molecules.
- Due to this weakest force the polymer can be stretched by applying some force and when the force ids released the polymer returns its original shape.
- Example: – Buna-S, Buna-N, Neoprene.
- Strong molecular forces (like hydrogen bonding) .
- High tensile strength and high modulus.
- Example: – Polyamides (nylon 6, 6), Polyesters (Terylene)
➧ Thermoplastic polymers
- Long chain linear or slightly branched molecules.
- It becomes soft on heating and hard on cooling.
- It’s intermolecular forces of attraction intermediate between elastomers and fibres.
- Weak intermolecular forces of attraction due to Weak Vander Waals force
- Thermoplastic polymer prepared by the addition polymerization reaction.
- Low molecular weights.
- Soluble in organic solvents.
- Example: – Polystyrene, Polythene, Polyvinyls.
➧ Thermosetting polymers
- Heavily branched, cross linked polymer.
- Also known as thermo set.
- Also called rigid temperature polymers.
- Thermosetting polymer prepared by condensation polymerization reaction.
- Cannot be softened by heating.
- Strong intermolecular force of attraction due to strong covalent bonds.
- These are hard, strong, more brittle and cannot be reused,
- Thermosetting polymers are doing not soften on heating.
- High molecular weights.
- Insoluble in organic solvents.
- Examples: – Polyester, Epoxy-resin, Urea-formaldehyde, Melamine.
Classification of Polymers Infographics
List of Polymers ,Monomers and Uses
|♦ Polypropylene||• Propane||• Manufacturing of Ropes, Toys, Pipes, Fibres|
|♦ Polystyrene||• Styrene||• Insulator
• Wrapping material
• Manufacture of Toys
• Manufacture of Radio and
/ Dacron or terylene
|• Ethylene glycol
• Terephthalic acid
|• Used in blending with cotton and wool fibres
• Glass reinforcing materials in safety helmets
|♦ Polyvinyl chloride
|• Vinyl chloride||• Manufacture of rain coats,
hand bags, vinyl flooring, water pipes
|♦ Glyptal.||• Ethylene glycol
• Phthalic acid
|• Manufacture of Paints and Lacquers|
|♦ Urea-formaldehyde Resin||• Urea
|• For making Unbreakable cups and Laminated Sheets.|
|♦ Bakelite||• Phenol
|• Making combs
• Electrical switches
• Handles of Utensils
• Computer discs
|♦ Poly β-hydroxybutyrate
– co-β-hydroxy valerate
|• 3-hydroxybutanoic acid
• 3 – hydroxypentanoic acid
|• Used in packaging of
|♦ Buna – N||•1, 3 – butadiene
|• Used in making oil seals, Tank lining|
|♦ Neoprene||• Chloroprene.||• Used for manufacturing Conveyor belts
Gaskets and Hoses.
|♦ Melamine||• Melamine
|• Manufacturing of unbreakable crockery|
|• Tetrafluoroethene||• Used in making oil seals and
gaskets , non – stick surface coated utensils
|• Acrylonitrile||• Making commercial fibres as orlon or acrilan|
|♦ Nylon 6||• Caprolactum||• Manufacture of tyre cords, fabrics and ropes|
|♦ Nylon 6,6||• Hexamethylenediamine
• Adipic acid
|• Used in making sheets, bristles
for brushes and in textile industry
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