PTFE 2200 Homework 6 Laura Hughey 1. PE Molecule a. Length: .741 nm x 5000 = 3705 nm b. Width: .494 nm x 5000 = 2470 nm 2. In a crystal, atoms are arranged on a periodic lattice. A crystal has both short and long range order. Bond angles and atomic separations are maintained. Only the lattice and the repeat unit are required to generate a crystal of infinite size. Polymer crystals are more complex than most ionic or metallic crystals. They have the same general properties, however the chains in polymer crystals are arranged linearly or helically and contain secondary (intermolecular) bonding. 3. Most synthetic fibers are not crystalline, but instead semicrystalline. The driving force for the formation of crystalline regions in a fiber is hydrogen bonding. The fiber tries to maximize bonding to achieve the lowest energy state where it then becomes a crystal. The reason polymers do not crystallize 100 percent and are instead semicrystalline is that the long chains are entangled in the melt and, upon
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Crystal, Polymer Crystals, long range order, intermolecular) bonding., covalent cysteine crosslinks