MECH 210 081114 - Polymer Structures

MECH 210 081114 - Polymer Structures - MECH 210 081114...

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MECH 210 081114 Polymer Structures Review: Covalent bond: A chemical bond formed by the sharing of one or more pairs of electron between two adjacent atoms. These covalently bonded atoms each contributes one electron to the bond, and the shared electrons may be considered to belong to both atoms. The atoms do not have charges since the electrons are not lost or gained by the atoms. A “ - ” denotes a single covalent bond , “ = ” denotes double covalent bond , and “ denotes triple covalent bond . Unsaturated molecule: Molecule with atoms that are not bonded to the maximum number of neighboring atoms allowed making it possible to attach additional atoms or molecules. Typically, molecules that have double or triple covalent bonds are unsaturated . Functionality: The number of sites at which new molecules can be attached to an existing molecule having unsaturated bonds. van der Waals bond: A secondary interatomic bond between adjacent molecular dipoles, which may be permanent or induced. Dipole is a pair of equal yet opposite electrical charges that are separate by a small distance. Hydrocarbons: Materials having their molecules composed of hydrogen and carbon atoms. Paraffin compounds: Compound molecules with chemical formula C n H 2n+2 Polymer: Very large molecules made up of many (poly-) identical mers (-mer) are called polymers . Isomerism: A phenomenon where compounds of the same chemical composition have different molecular structures. Phenyl group: molecule denoted by a simplified structure Classification of Polymers Based on the general characteristics (1) Thermoplastic polymers : Polymers that can be reheated and remelted numerous times – can be easily recycled. They are composed of long-chain molecules by joining together smaller monomers. They typically behave in a plastic, ductile manner. These polymers soften and are formed by viscous flow at elevated temperatures. Thermoplastics are also separated into those which are either crystalline or noncrystalline. (2)
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MECH 210 081114 - Polymer Structures - MECH 210 081114...

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