Definitions [3]
Define thermosetting polymers with two examples of them.
Thermosetting polymers are cross-linked or heavily branched polymers which get hardened during the molding process. These plastics cannot be softened again on heating. Examples of thermosetting plastics include bakelite, urea-formaldehyde resins.
Define rubber.
Polymers which are elastic in nature are called rubber.
Answer the following in one sentence.
Define the term: Vulcanization
The process by which a network of cross-links is introduced into an elastomer is called vulcanization.
Key Points
Key Points: Classification of Polymers> Based on Source or Origin
- Polymers are classified based on their source or origin into three types: natural, semi-synthetic, and synthetic polymers.
- Natural polymers are obtained from plants and animals, such as cellulose, starch, proteins, cotton, and silk.
- Semi-synthetic polymers are chemically modified forms of natural polymers, e.g., cellulose acetate and cellulose nitrate (rayon).
- Synthetic polymers are man-made and prepared in laboratories by polymerisation, such as nylon, polythene, Teflon, and Bakelite.
- Synthetic polymers are further used to make fibres, rubbers, and plastics, which have wide industrial applications.
Key Points: Classification of Polymers> Based on Structure
- Polymers can be classified based on structure into linear, branched, and cross-linked (network) polymers.
- Linear polymers have long, straight chains of monomers joined in a line; e.g., HDPE, PVC, polystyrene.
- Branched polymers have a main chain with side branches of different lengths; e.g., LDPE, polypropylene.
- Cross-linked (network) polymers have chains connected by strong covalent bonds, forming a 3D network structure.
- Cross-linked polymers are hard and rigid due to strong bonding; common examples include Bakelite and melamine.
Key Points: Classification of Polymers> Based on Mode of Polymerisation
- Polymers are classified based on the mode of polymerisation into addition (chain growth), condensation (step growth), and ring-opening polymerisation.
- Addition polymerisation involves repeated addition of monomers (with double/triple bonds) without loss of small molecules; e.g., Teflon, PAN.
- Condensation polymerisation occurs between bi-functional or polyfunctional monomers with elimination of small molecules like water or alcohol; e.g., Nylon, Terylene.
- Ring-opening polymerisation involves polymerisation of cyclic monomers to form long chains, usually without elimination of small molecules; e.g., caprolactam.
Key Points: Classification of Polymers> Based on Intermolecular Forces
- Polymers can be classified based on intermolecular forces into elastomers, fibres, thermoplastics, and thermosetting polymers.
- Elastomers have the weakest intermolecular forces, making them flexible and elastic; e.g., natural rubber, Buna-S.
- Fibres have strong intermolecular forces (like hydrogen bonding), giving them high tensile strength; e.g., Nylon-6, Terylene, PAN.
- Thermoplastics have weak van der Waals forces, so they can be softened and reshaped on heating; e.g., polythene, polystyrene.
- Thermosetting polymers have strong cross-linked structures, making them hard and rigid; e.g., Bakelite, melamine.
Strength order: Elastomers < Thermoplastics < Fibres < Thermosetting polymers.
Key Points: Classification of Polymers> Based on Biodegradability
Polymers are classified as biodegradable or non-biodegradable based on their biodegradability.
1. Biodegradable Polymers
- Meaning: Polymers that decompose by microorganisms or enzymes.
- Nature: Environment-friendly, as they break down naturally.
- Examples: PHBV, Nylon-2–Nylon-6.
- Special point: PHBV is a copolymer used in packaging, medical devices, and drug delivery.
- Use: Helps reduce environmental pollution.
2. Non-Biodegradable Polymers
- Meaning: Polymers that do not decompose by microorganisms.
- Nature: Persist in the environment for a long time.
- Examples: Polythene (LDPE, HDPE), Teflon, Nylon-6,6, PAN.
- Use: Widely used in plastics, fibres, containers, insulation, etc.
- Disadvantage: Causes environmental pollution due to slow decomposition.
Key Points: Some Important Polymers
| Polymer | Monomer(s) | Uses |
|---|---|---|
| Natural Rubber (Polyisoprene) | Isoprene (2-methyl-1,3-butadiene) | Exhibits elastic property |
| Neoprene | Chloroprene (2-chloro-1,3-butadiene) | Conveyer belts |
| Buna-S | 1,3-Butadiene + Styrene | Bubblegums, tyres |
| Buna-N | 1,3-Butadiene + Acrylonitrile | Rubber belts, shoe soles, O-rings, gaskets |
| Polypropene | Propene | Ropes, toys, pipes, fibres |
| Polystyrene | Styrene | Insulator, wrapping material, toys, radio & TV cabinets |
| PVC | Vinyl chloride | Rain coats, handbags, vinyl flooring, water pipes |
| Glyptal | Ethylene glycol + Phthalic acid | Paints and lacquers |
| Bakelite | Phenol + Formaldehyde | Combs, phonograph records, electrical switches, wooden planks |
| Nylon 6,6 | Adipic acid + Hexamethylenediamine | Fabrics, ropes, tyre cords |
| Nylon 6 | ε-Caprolactam | Fabrics, ropes |
| Terylene / Dacron | Ethylene glycol + Terephthalic acid | Fibres, safety belts, tents |
| Melamine-formaldehyde | Melamine + Formaldehyde | Unbreakable crockery |
| Urea-formaldehyde resin | Urea + Formaldehyde | Unbreakable cups, laminated sheets |
Important Questions [28]
- Write the names of monomers used for getting the following polymer: Teflon
- Write the Names and Structures of the Monomers of the Following Polymers: (I) Terylene (Ii) Bakelite (Iii) Buna-s
- Write the Names and Structures of the Monomers of the Following Polymers: Polyvinyl Chloride
- Write the Name of Monomers Used for Getting the Following Polymers : Bakelite
- Write a Chemical Reaction to Show that the Open Structure of D-glucose Contains the Following : Straight Chain
- Write the Names and Structures of the Monomers of the Following Polymers: Buna-s
- Write the Names and Structures of the Monomers of the Following Polymers: Dacron
- Write the Names and Structures of the Monomers of the Following Polymers: Buna-n
- Shyam Went to a Grocery Shop to Purchase Some Food Items. the Shopkeeper Packed All the Items in Polythene Bags and Gave Them to Shyam Write the Values (At Least Two) Shown by Shyam and and Write One Structural Difference Between Low-density Polyethene and High-density Polyethene and What is a Biodegradable Polymer? Give an Example.
- Write the names of monomers used for getting the following polymer: Neoprene
- Arrange the Following Polymers in Increasing Order of Their Intermolecular Forces:
- What is the Role of T-butyl Peroxide in the Polymerization of Ethene?
- Write the Mechanism of Free Radical Polymerization of Ethene.
- Which of the Following is a Natural Polymer ? Buna-S, Proteins, PVC
- Which of the Following is a Fibre? Nylon, Neoprene, PVC
- Write the names and structure of the monomers of the following polymers: Nylon-6, 6
- What is the significance of number of 6,6 in the polymer nylon-6,6?
- Write the Structures of Monomers Used the Following Polymers: Nylon-6, 6
- Is a Homopolymer Or Copolymer? Give Reason
- What is the Role of Sulphur in the Vulcanization of Rubber?
- Write Names and Chemical Formulae of Monomers Used in Preparing Buna-n.
- Write the structure of the monomer used in the following polymer:Buna-S
- What is the Role of Sulphur in the Vulcanisation of Rubber?
- After the Ban on Plastic Bags, Students of a School Decided to Make People Aware of the Harmful Effects of Plastic Bags on the Environment and Yamuna River
- Write the Structures of Monomers Used the Following Polymers: Glyptal
- Write the Structures of the Monomers Used for Getting the Following Polymers Melamine – Formaldehyde Polymer
- Write the Monomers of the Following Polymer :
- Based on Molecular Forces, What Type of Polymer is Neoprene?
Concepts [15]
- Introduction to Polymers
- Classification of Polymers> Based on Source or Origin
- Classification of Polymers> Based on Structure
- Classification of Polymers> Based on Mode of Polymerisation
- Classification of Polymers> Based on Intermolecular Forces
- Classification of Polymers Based on Growth Polymerisation
- Types of Polymerisation Reactions - Addition Polymerisation or Chain Growth Polymerisation
- Types of Polymerisation Reactions - Condensation Polymerisation Or Step Growth Polymerisation
- Types of Polymerisation Reactions - Copolymerisation
- Types of Polymerisation Reactions - Rubber
- Molecular Mass of Polymers
- Classification of Polymers> Based on Biodegradability
- Polymers of Commercial Importance
- Some Important Polymers
- Polymers Numericals
