Material Science

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Material Science
2010-05-26 00:54:09

Material Science Final
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  1. What are the three main types of polymers called, and what does each one do?
    • 1. Elastomer: Can be stretched by large amounts and returns to original length when the stress is removed.
    • 2. Thermoplastic: Becomes soft when heated so it can be shaped, and becomes rigid again when cooled.
    • 3. Thermosets: Become more rigid when heated because the chains become cross-linked with covalent bonds .
  2. What are polymers composed of?
    A chain of carbon atoms, which are held together by strong covalent bonds
  3. Why are polymers so strong, yet so flexible?
    • 1. In most polymers, the atoms are not bonded in a three dimensional network, but in a lineal chain.
    • 2. There are only secondary bonds between chains which are too weak to prevent bond rotation and chains from sliding over one another.
  4. What are the three common approaches to strengthening polymers/stop their chain movement from going over one another?
    • 1. Chain Crosslinking: Inserting some permament links between adjacent chains to restrict their relative movement.
    • 2. Chain Stiffening: Replacing some of the small hydrogen atoms on the chain with large groups of atoms - gets in each others way to restrict movement.
    • 3. Chain Crystallization: Packing the chains in a parallel closely packed arrangement
  5. What process did Charles Goodyear discover, and what is it referred to?
    Chain Cross-linking by adding sulfur to rubber, known as vulcanization
  6. This process happens to rubber if too much sulfur is added?
    Ebonite, which is a rigid black solid, used for bowling balls and clarinets for years
  7. Define: Steric Hindrance
    When carbon atoms attempt to rotate their atoms around a cone, but cannot because the large groups of atoms gets in each others' way. There is a sort of atom group repulsion which occurs.
  8. Define: Paraffin
    "Not Very Reactive" - i.e. Wax and Kerosene
  9. Define: Hydrocarbons
    Carbon Atom in which all four surrounding atoms are hydrogens. Resulting compound is called methane
  10. Define: Ethane
    Similar compound to methane, has two central carbon atoms with six hydrogen atoms.
  11. Define: Propane
    Three Carbon atoms, where the middle one forms a covalent bond with the other two. Eight Hydrogen atoms
  12. Define: Butane
    Four Carbon atoms, ten hydrogen atoms