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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 .
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What are polymers composed of?
A chain of carbon atoms, which are held together by strong covalent bonds
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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.
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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
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What process did Charles Goodyear discover, and what is it referred to?
Chain Cross-linking by adding sulfur to rubber, known as vulcanization
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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
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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.
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Define: Paraffin
"Not Very Reactive" - i.e. Wax and Kerosene
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Define: Hydrocarbons
Carbon Atom in which all four surrounding atoms are hydrogens. Resulting compound is called methane
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Define: Ethane
Similar compound to methane, has two central carbon atoms with six hydrogen atoms.
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Define: Propane
Three Carbon atoms, where the middle one forms a covalent bond with the other two. Eight Hydrogen atoms
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Define: Butane
Four Carbon atoms, ten hydrogen atoms
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