Introduction to Polymers and Plastics
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Questions and Answers

What is the main difference between thermoplastics and elastomers?

  • Thermoplastics cannot be reformed by reheating, while elastomers can be reheated and reformed.
  • Thermoplastics can be reheated and reformed, while elastomers cannot be reformed by reheating. (correct)
  • Both thermoplastics and elastomers cannot be reformed by reheating.
  • Both thermoplastics and elastomers can be reheated and reformed.

    • What are the advantages of plastics mentioned in the text?

  • Maximum finishing and maximum lubrication.
  • Minimum finishing and noise reduction.
  • Wide range of properties and good insulation. (correct)
  • Minimum lubrication and heavy weight.

    • In polymerization, what is the functionality of a monomer?

  • The weight of the monomer.
  • The number of active bonds in a monomer. (correct)
  • The size of the monomer.
  • The reactivity of the monomer.

    • What is the process involved in chain growth polymerization?

    <p>Formation of long chains by covalent bonds from small molecules (monomers).</p> Signup and view all the answers

    What is the range of degree of polymerization (DP) mentioned in the text?

    <p>3500-25000</p> Signup and view all the answers

    What is the defining characteristic of thermosetting plastics?

    <p>They cannot be reformed by reheating; they are set by a chemical reaction.</p> Signup and view all the answers

    What is the process of extending a polymer chain by the addition of monomers called?

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

    Which type of polymerization involves the chemical reaction taking place in more than two reaction sites, forming a 3D network?

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

    What is the average molecular weight determined by in materials science and engineering?

    <p>Special physical and chemical techniques</p> Signup and view all the answers

    In the sample problem example, what is the degree of polymerization if a particular type of polyethylene has a molecular mass of 150,000 g/mol?

    <p>$5357 (mers/mol)$</p> Signup and view all the answers

    What is needed for initiation in chain polymerization?

    <p>A radical</p> Signup and view all the answers

    What occurs during termination in chain polymerization?

    <p>Combining of two chains</p> Signup and view all the answers

    What happens in stepwise polymerization?

    <p>Formation of linear polymers and small byproducts</p> Signup and view all the answers

    What does the degree of polymerization represent?

    <p>$\frac{molecular ext{ mass ext{ }(g/mol)}}{mass ext{ of a mer }(g/mer)}$</p> Signup and view all the answers

    What is the role of a termination free radical in chain polymerization?

    <p>To combine two chains</p> Signup and view all the answers

    How is the energy of the system affected during chain polymerization?

    <p>Energy decreases due to polymerization</p> Signup and view all the answers

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