Polymers and Their Classification
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Which of the following is NOT an advantage of liquid crystal polymers?

  • High cost (correct)
  • Excellent insulating properties
  • Inherent flame retardancy
  • Very low melt viscosity

Liquid crystal polymers have very high water absorption rates.

False (B)

What application of liquid crystal polymers helps eliminate static build-ups in electrical signals?

Electrical connectors

Liquid crystal polymers can withstand temperatures up to ________ °C.

<p>280</p> Signup and view all the answers

Match the following applications of liquid crystal polymers with their descriptions:

<p>Electrical connectors = Eliminate static build-ups in signals Vascular catheter reinforcement = Important for MRI scans Surgical instruments = Withstands radiation and sterilization Cookware coatings = Resistant to high temperatures and dishwashers</p> Signup and view all the answers

Which of the following is an example of a synthetic polymer?

<p>Nylons (C)</p> Signup and view all the answers

Natural polymers are exclusively synthetic in nature.

<p>False (B)</p> Signup and view all the answers

What is the process of converting monomers into polymers called?

<p>Polymerization</p> Signup and view all the answers

A ____ is a repeating unit that composes a polymer.

<p>monomer</p> Signup and view all the answers

Match the following types of polymers with their characteristics:

<p>Linear Polymers = Long and straight chains Branched-chain Polymers = Linear chains with branches Cross-linked Polymers = Chains connected by covalent bonds Homo-polymers = Comprising only one type of monomer</p> Signup and view all the answers

Which of the following is a characteristic of branched-chain polymers?

<p>They have linear chains with branches. (D)</p> Signup and view all the answers

Co-polymers consist of more than one type of monomer.

<p>True (A)</p> Signup and view all the answers

Give an example of a cross-linked polymer.

<p>Bakelite</p> Signup and view all the answers

Which of the following types of polyethene has a lower density?

<p>Low Density Polyethene (LDPE) (B)</p> Signup and view all the answers

Addition polymers are formed by a condensation reaction.

<p>False (B)</p> Signup and view all the answers

What is the monomer unit of Polyethene?

<p>Ethene</p> Signup and view all the answers

HDPE is prepared at a low temperature of __________°C.

<p>60-70</p> Signup and view all the answers

Which property is true for Low Density Polyethene (LDPE)?

<p>It is chemically inert. (A)</p> Signup and view all the answers

What initiator is used in the preparation of LDPE?

<p>Benzoyl peroxide</p> Signup and view all the answers

HDPE exhibits extensive branch formation.

<p>False (B)</p> Signup and view all the answers

What is the primary reason for the conductivity in inherently conducting polymers?

<p>Intrinsic structure of the polymer (C)</p> Signup and view all the answers

The conductivity of polymer composites is due to the matrix polymer.

<p>False (B)</p> Signup and view all the answers

Name one application of conducting polymers.

<p>Electrode materials in rechargeable batteries.</p> Signup and view all the answers

Liquid crystal polymer is often formed by linking various __________ molecules.

<p>mesogen</p> Signup and view all the answers

Match the following types of polymers with their applications:

<p>Conducting Polymers = Humidity sensors Liquid Crystal Polymer = Lower processing temperatures Polyaniline = Printed circuit boards Emeraldine Base = Lethography resistors</p> Signup and view all the answers

Which of the following is considered an intrinsically conducting polymer?

<p>Polyaniline (C)</p> Signup and view all the answers

Doping with oxidizing or reducing agents increases the conductivity of inherently conducting polymers.

<p>True (A)</p> Signup and view all the answers

Which monomer is commonly used in the synthesis of liquid crystal polymers?

<p>p-hydroxybenzoic acid</p> Signup and view all the answers

Which type of co-polymer consists of alternating A and B units throughout the chain?

<p>Alternate Co-polymers (A)</p> Signup and view all the answers

Elastomers are characterized by strong intermolecular forces.

<p>False (B)</p> Signup and view all the answers

What type of co-polymer includes a main chain of one type of monomer with branches of another type?

<p>Graft Co-polymers</p> Signup and view all the answers

Thermo-plastics are known for being __________, allowing them to be reshaped multiple times.

<p>recyclable</p> Signup and view all the answers

What happens to thermo-sets when exposed to heat?

<p>They become hard but alter their shape (B)</p> Signup and view all the answers

Match the following polymer classifications to their definitions:

<p>Elastomers = Weak intermolecular forces Fibres = Strong intermolecular forces Thermo-plastics = Reprocessable upon heating Thermo-sets = Irreversible change upon heating</p> Signup and view all the answers

Random co-polymers have a regular order of arrangement of their monomer units.

<p>False (B)</p> Signup and view all the answers

Name one example of a thermo-set polymer.

<p>Bakelite</p> Signup and view all the answers

What is the primary chemical bond characteristic of polyamides?

<p>Amide linkages (A)</p> Signup and view all the answers

Bakelite is classified as a thermoplastic polymer.

<p>False (B)</p> Signup and view all the answers

What is the melting temperature range of the polymer discussed?

<p>130-138°C</p> Signup and view all the answers

Polyesters are formed by the condensation of a bifunctional acid and a bifunctional _____ where the linkage is ester.

<p>alcohol</p> Signup and view all the answers

Match the following polymers with their respective types:

<p>Nylon-6,6 = Polyamide PET = Polyester Bakelite = Thermosetting Polymer LDPE = Thermoplastic</p> Signup and view all the answers

Which of the following is an application of the opaque polymer mentioned?

<p>Manufacture of fuel tanks (A)</p> Signup and view all the answers

Condensation polymerization involves the elimination of small molecules, such as water.

<p>True (A)</p> Signup and view all the answers

What is the glass transition temperature (Tg) value of the polymer?

<p>-20°C</p> Signup and view all the answers

Flashcards

Polymer

A large molecule made up of many repeating units called monomers.

Monomer

A small molecule that can join with other similar molecules to form a polymer.

Polymerization

The process of converting monomers into polymers.

Natural Polymer

A polymer that occurs naturally in plants and animals.

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Synthetic Polymer

A polymer created by humans, often from petroleum.

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Linear Polymer

A polymer with a straight chain structure.

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Branched Polymer

A polymer with branches extending from its main chain.

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Cross-linked Polymer

A polymer with covalent bonds connecting different chains, making it rigid.

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Alternate Co-polymer

A polymer where monomers A and B alternate regularly in the chain, creating a predictable pattern. Think: ABABABAB...

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Block Co-polymer

A polymer made up of blocks of monomers A and B, with each block repeating in the chain. Think: AAAAAABBBBBB...

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Graft Co-polymer

A polymer where one type of monomer forms the main chain, and another type forms branches off of it. Think: AAAAAAAAAAA with B branches.

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Random Co-polymer

A polymer with no predictable order of monomers A and B in the chain. Think: ABBAAABBB...

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Elastomer

A polymer with weak intermolecular forces, making it flexible and rubbery. Think: Rubber bands.

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Fibre

A polymer with strong intermolecular forces, making it strong and resistant to stretching. Think: Nylon, Terrylene.

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Thermo-plastic

A polymer that can be repeatedly softened by heating and hardened by cooling, retaining its original shape. Think: Polyethylene, PVC, Polystyrene.

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Thermo-set

A polymer that can be softened by heating but cannot be reshaped upon cooling, due to irreversible chemical changes. Think: Bakelite, Epoxy.

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Addition Polymer

A polymer formed by adding monomers together without the loss of any atoms. The monomers are typically unsaturated (containing double or triple bonds).

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Chain Initiation

The first step of addition polymerization where a free radical or other reactive species starts the chain growth.

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Chain Propagation

The step where the growing polymer chain adds more monomers to its structure.

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Chain Termination

The final step where the growing chain reaction stops, resulting in a stable polymer.

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Low Density Polyethylene (LDPE)

Polyethylene with a branched structure, resulting in lower density. Produced under high pressure and temperature with free radical initiation.

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High Density Polyethylene (HDPE)

Polyethylene with a linear, less branched structure, resulting in higher density. Produced at lower pressure and temperature with ionic or Ziegler-Natta catalysts.

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Ziegler-Natta Catalyst

A catalyst used in the production of HDPE. They help create a linear polymer structure.

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Why is LDPE used for packaging?

LDPE has good impact strength, flexibility, and chemical resistance, making it suitable for packaging applications.

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LDPE vs. HDPE

HDPE (High-Density Polyethylene) is denser than LDPE (Low-Density Polyethylene), making it stronger and more opaque. HDPE also has better chemical resistance and barrier properties.

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HDPE Applications

Due to its durability and resistance, HDPE is often used for items like dustbins, cans, buckets, fuel tanks, and corrugated pipes.

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Condensation Polymerization

Condensation polymerization involves monomers joining together with the release of a small molecule, like water. This creates a polymer chain.

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Nylon-6,6

Nylon-6,6 is a condensation polymer formed by reacting a diamine (hexamethylenediamine) with a dicarboxylic acid (adipic acid).

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Polyamides vs. Polyesters

Polyamides are polymers with amide bonds, formed from dicarboxylic acids and diamines. Polyesters have ester bonds, formed from acids and alcohols.

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Thermosetting Polymers

Thermosetting polymers are plastics that irreversibly harden or set when heated, becoming rigid and unable to be reshaped or melted.

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Bakelite

Bakelite is a thermosetting polymer formed by combining phenol and formaldehyde.

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LCPs: Common Types

Three main types of liquid crystal polymers (LCPs) are semi-aromatic copolyesters, copolyamides, and polyester-co-amides.

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LCPs: Advantages

LCPs offer benefits like low melt viscosity, low water absorption, self-reinforcing nature, flame retardancy, high heat resistance, good chemical resistance, and excellent insulation.

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LCPs: Applications

LCPs are used in various applications like electrical connectors to prevent noise interference, vascular catheter reinforcement, surgical instruments for sterilization, and cookware coatings for high-temperature resistance.

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LCPs: Disadvantage: High Cost

LCPs are expensive due to their complex manufacturing process and high performance.

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LCPs: Disadvantage: Anisotropy

LCPs exhibit anisotropic properties, meaning their properties vary depending on the direction of applied load.

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Conducting Polymer

A polymer that can conduct electricity. It's created by adding conductive fillers to an insulating polymer.

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Minimum Filler Concentration

The smallest amount of conductive filler needed to make a polymer start conducting electricity.

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Intrinsically Conducting Polymer

A polymer that conducts electricity by itself, due to the way its molecules are structured.

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Conjugated Electrons

Electrons that can move freely within a molecule, making it possible for the molecule to conduct electricity.

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Doping

Adding specific chemicals to a polymer to make it more conductive.

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Liquid Crystal Polymer (LCP)

A polymer that has properties of both liquids and solids, making it strong and stiff, yet flexible.

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Mesogens

Molecules in liquid crystal polymers that give them their unique properties.

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Study Notes

Polymers

  • Polymers are macromolecules composed of many repeating units.
  • The repeating unit is a monomer.
  • Polymerization is the process of converting monomers into polymers.

Classification of Polymers

  • Based on Origin/Source:

    • Natural Polymers: Found in plants and animals (e.g., proteins, nucleic acids, starch, cellulose, natural rubber).
    • Synthetic Polymers: Man-made polymers (e.g., nylons, polyethylene, PVC, synthetic rubbers).

  • Based on Structure:

    • Linear Polymers: Long, straight chains (e.g., high-density polyethylene (HDPE)).
    • Branched-Chain Polymers: Linear chains with branches (e.g., low-density polyethylene (LDPE)).
    • Cross-Linked Polymers: Chains connected by covalent bonds (cross-links) (e.g., bakelite, melamine).

  • Based on Monomer Type:

    • Homo-polymers: Composed of only one type of monomer (e.g., polyethylene).
    • Co-polymers: Composed of more than one type of monomer.
      • Alternate Co-polymers: Alternating A and B units.
      • Block Co-polymers: Regular alternating blocks of A and B units.
      • Graft Co-polymers: Main chain of one type of monomer with branches of another type of monomer.
      • Random Co-polymers: No regular order of monomer units.

  • Based on Inter-molecular Forces (Ultimate Form):

    • Elastomers: Very weak intermolecular forces (e.g., rubber).
    • Fibers: Strong intermolecular forces (e.g., nylons, terylene).

  • Based on Temperature:

    • Thermoplastics: Soften on heating, harden on cooling, and can be recycled (e.g., polyethylene, PVC, polystyrene).
    • Thermosets: Harden on heating and cannot be softened or recycled (e.g., bakelite, epoxy resins).

Polymer Synthesis

  • Addition Polymerization: Monomer units add to each other without losing any atoms.
  • Condensation Polymerization: Monomer units join together with the elimination of small molecules (e.g., water).

Commercially Available Fibers

  • Polyamides (amide linkages)
  • Polyesters (ester linkages)

Elastomers

  • Can stretch and recover their shape.
  • Examples: Natural rubber, synthetic rubber.
  • Vulcanization improves natural rubber properties by adding sulfur.

Conducting Polymers

  • Organic polymers capable of conducting electricity.
  • Two types: Extrinsically conductive and Intrinsically conductive.

Biodegradable Polymers

  • Polymers that degrade naturally by microorganisms.
  • Key factors for biodegradability: presence of microorganisms, suitable environment, and proper substrate with suitable functional groups.

Specialty Polymers

  • PEEK (Polyether ether ketone): High-performance polymer with excellent mechanical properties, chemical resistance, and high-temperature stability, useful in medical implants, and other high-performance applications.

Polyethyleneimine (PEI)

  • A semi-crystalline polymer used in various applications, including papermaking, flocculation, and cell culture.
  • PEI has different forms in different molecular weights, some linear and other branched.

Liquid Crystal Polymers (LCPs)

  • Have liquid crystal properties.
  • Useful in electrical components, surgical instruments, and other applications requiring high heat resistance and chemical resistance.

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Description

This quiz covers the fundamental concepts of polymers, including their composition and classification. It explores both natural and synthetic polymers, different structural forms, and the types of monomers involved in polymer formation. Test your knowledge on this essential topic in chemistry!

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