Engineering Chemistry: Polymers Quiz
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Questions and Answers

What is the primary monomer that forms natural rubber?

  • Ethylene
  • Butadiene
  • 2-methyl-1,3-butadiene (correct)
  • Polyisoprene

    • What is a key drawback of raw rubber related to temperature?

  • It can withstand extreme cold without issues.
  • It is brittle at room temperature.
  • It becomes too hard at high temperatures.
  • It becomes so soft at high temperatures. (correct)

    • What process significantly enhances the elasticity of rubber?

  • Polymerization
  • Coagulation
  • Vulcanization (correct)
  • Hydrogenation

    • Who developed the vulcanization process for rubber?

    <p>Charles Goodyear</p> Signup and view all the answers

    Which property makes raw rubber unsuitable for use with certain chemicals?

    <p>High water absorption capacity</p> Signup and view all the answers

    What is the purpose of compounding rubber?

    <p>To impart specific properties for particular applications.</p> Signup and view all the answers

    Which rubber composition may contain the highest percentage of sulphur?

    <p>Battery case rubber</p> Signup and view all the answers

    How much sulphur is typically found in tyre rubber?

    <p>3 to 5%</p> Signup and view all the answers

    Which of the following is NOT a reason for compounding rubber?

    <p>To reduce production costs.</p> Signup and view all the answers

    What type of rubber may need compounding for improved electrical insulation?

    <p>Silicone rubber</p> Signup and view all the answers

    What is a common additive used in the compounding process of rubber?

    <p>Calcium carbonate</p> Signup and view all the answers

    What characteristic can be modified through the compounding of rubber?

    <p>Flexibility and durability</p> Signup and view all the answers

    Which of these compounds is likely to increase the resilience of rubber?

    <p>Carbon black</p> Signup and view all the answers

    In rubber compounding, which of the following is primarily used for enhancing strength?

    <p>Reinforcement agents</p> Signup and view all the answers

    What is one key benefit of compounding rubber with specific additives?

    <p>It can create specialized properties for different applications.</p> Signup and view all the answers

    What is one classification of polymers based on their origin?

    <p>Natural and synthetic</p> Signup and view all the answers

    Which polymerization mechanism involves the formation of free radicals?

    <p>Free radical polymerization</p> Signup and view all the answers

    What does the term 'tacticity' refer to in polymers?

    <p>The arrangement of side groups on the polymer backbone</p> Signup and view all the answers

    Which of the following is NOT a type of co-polymerization?

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

    What is the glass transition temperature (Tg) affected by?

    <p>The molecular structure of the polymer</p> Signup and view all the answers

    What is the primary distinction between low-density polyethylene (LDPE) and high-density polyethylene (HDPE)?

    <p>Molecular branching</p> Signup and view all the answers

    Which polymer is produced through condensation polymerization?

    <p>Nylon 6:6</p> Signup and view all the answers

    What is the primary purpose of vulcanization in natural rubber processing?

    <p>To enhance elasticity and strength</p> Signup and view all the answers

    What is the formula for calculating the dispersity index (PDI)?

    <p>PDI = Mw / Mn</p> Signup and view all the answers

    Which method is NOT used to determine the weight-average molecular mass (Mw)?

    <p>Osmotic pressure measurement</p> Signup and view all the answers

    What is the number average molecular weight (Mn) for a polymer sample with 50 molecules of 10000, 35 of 12000, and 15 of 14000?

    <p>11300</p> Signup and view all the answers

    Which of the following properties is used to determine the number-average molecular mass (Mn)?

    <p>Depression in freezing point</p> Signup and view all the answers

    How is the degree of polymerization (DP) calculated if the molecular weight of the monomer is 1000 and Mn is 13000?

    <p>DP = Mn / Molecular weight of monomer</p> Signup and view all the answers

    Which of the following best describes a property of TEFLON?

    <p>Exceptionally high chemical resistance</p> Signup and view all the answers

    What applications are common for TEFLON?

    <p>Non-lubricating bearings</p> Signup and view all the answers

    Which molecular weight formula is correct for the calculation of Mw?

    <p>Mw = (50x10000) + (35x12000) + (15x14000)</p> Signup and view all the answers

    What is the main catalyst used in the manufacturing of HDPE via coordination polymerization?

    <p>Ziegler-Natta catalyst</p> Signup and view all the answers

    Which statement accurately describes the properties of HDPE compared to LDPE?

    <p>HDPE has a higher specific strength due to stronger intermolecular forces.</p> Signup and view all the answers

    What is the primary type of polymerization involved in the formation of phenol-formaldehyde (PF) resins?

    <p>Condensation polymerization</p> Signup and view all the answers

    Which factor significantly influences the nature of the PF resin produced?

    <p>Molar ratio of phenol to formaldehyde</p> Signup and view all the answers

    What characteristic of novolacs is defined by the phenol to formaldehyde molar ratio?

    <p>Linear structure forms when the ratio is &gt; 1, catalyzed by an acid.</p> Signup and view all the answers

    Which of the following applications is NOT commonly associated with HDPE?

    <p>Thermoplastic elastomers</p> Signup and view all the answers

    Which feature of PF resins leads to their thermosetting nature?

    <p>Extensive branching during molding operations</p> Signup and view all the answers

    What temperature can HDPE withstand continuously without deterioration?

    <p>110 °C</p> Signup and view all the answers

    Study Notes

    Engineering Chemistry Course Details

    • Course Name: Engineering Chemistry
    • Course Code: CHY1001
    • Lecture Series No: 1
    • Credits: 4
    • Mode of Delivery: Hybrid

    Polymers

    • Definition: Long chain molecules composed of repeating structural units called monomers.
    • Classification:
      • Origin: Natural (e.g., rubber, cellulose) and Synthetic (e.g., polyethylene, nylon)
      • Thermal Behaviour: Thermoplastics (soften on heating and solidify on cooling) and Thermosets (become rigid on heating and cannot be remelted)
    • Polymerization Reactions:
      • Addition Polymerization: Monomers add to form a polymer without the loss of any atoms.
      • Condensation Polymerization: Monomers combine with the loss of a small molecule, such as water.
      • Co-polymerization: Two or more different monomers combine to form a polymer. Types:
        • Alternating
        • Random
        • Block
        • Graft
    • Tacticity: Arrangement of substituent groups on polymer chains (Isotactic, Syndiotactic, Atactic)
    • Functionality: Number of reactive sites on a monomer.
    • Degree of Polymerization (DP): Average number of monomer units in a polymer chain.
    • Molecular Weight:
      • Number Average Molecular Weight (Mn): Calculated based on the number of molecules of each molecular weight.
      • Weight Average Molecular Weight (Mw): Calculated based on the weight of molecules of each molecular weight
      • Dispersity Index (PDI): Mw / Mn
      • Determination of Mn: Colligative properties (lowering of vapor pressure, osmotic pressure, depression of freezing point, elevation of boiling point)
      • Determination of Mw: Light scattering, ultra-centrifugal techniques
    • Glass Transition Temperature (Tg): The temperature at which a polymer transitions from a rigid, glassy state to a rubbery, flexible state. Factors affecting Tg:
      • Chain flexibility
      • Intermolecular forces
      • Molecular weight
    • Polythene (LDPE & HDPE)
      • Properties of LDPE: Lower density, flexible, easily processed, used in films, bags, packaging.
      • Properties of HDPE: Higher density, stronger, more rigid, resistant to chemicals, used in bottles, pipes, containers.
    • Nylon (6:6, 6, 6:10, 11):
      • Properties: Strong, resistant to abrasion, good thermal stability, used in fibers, ropes, gears.
    • PF Resins:
      • Formation: Condensation polymerization, thermosetting polymers.
      • Types: Novolacs and Resoles
      • Properties: Linear, low molecular weight, soluble, fusible, prepolymers.
      • Moulding Process: Branching and cross-linking forming highly cross-linked, insoluble, hard, rigid, infusible products.
    • Natural Rubber:
      • Monomer: Isoprene (2-methyl-1,3-butadiene)
      • Properties: High tensile strength, good elasticity, impermeable to gases.
      • Drawbacks: Soft at high temperatures, brittle at low temperatures, susceptible to oxidation and degradation.
      • Vulcanization: Heating rubber with sulfur (or other vulcanizing agents) to increase elasticity and reduce plasticity.

    Teflon (Polytetrafluoroethylene - PTFE)

    • Properties: Extremely tough, high softening point, high chemical resistance, high density, waxy touch. It can be punched, machined, and drilled.
    • Uses:
      • Insulating materials (motors, transformers, cables, wires, fittings)
      • Gaskets, packing, pump parts, tanks, chemical-carrying pipelines, tubing
      • Coatings
      • Non-lubricating bearings and non-sticking stop-cocks

    Compounding of Rubber

    • Definition: Mixing of raw rubber with other substances to impart specific properties.
    • Purpose: Improve specific properties of rubber, such as strength, flexibility, and resistance to degradation.

    HDPE (High Density Polyethylene)

    • Properties: High strength-to-density ratio, high density, little branching, strong intermolecular forces, high tensile strength, hard, opaque, heat resistant.
    • Applications:
      • 3D printer filament
      • Banners
      • Bottle caps
      • Chemical resistant piping systems
      • Food storage containers
      • Fuel tanks for vehicles
      • Electrical and plumbing boxes
      • Folding chairs and tables

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    Description

    Test your understanding of polymers in Engineering Chemistry. This quiz covers definitions, classifications, polymerization reactions, and characteristics of various types of polymers. Perfect for students of the CHY1001 course!

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