Polymerization

    Cards (59)

    • Polymerization method

      Process of creating a polymer
    • Types of polymers

      • Thermoplastic
      • Thermoset
    • Thermoplastic
      • Solid at room temperature that can be melted and softened by heating, placed into a mold or other shaping device, and then cooled to give the desired shape
      • Can be reshaped at any time by reheating the part
    • Example of thermoplastic
      • Chocolate bar
    • Monomer
      The smaller units from which larger polymer molecules are made
    • Example of thermoplastic polymer

      • H-C=C-X-H, where X can be H, CH3, Cl, etc.
    • Thermoset
      • Can be either liquid or solid at room temperature
      • When placed into a mold and then heated, they initially drop in viscosity (liquify) but then cure (harden) upon further heating, thus giving the desired shape and solid properties
      • After curing, if thermosets are reheated, they will soften somewhat but do not melt and therefore cannot be reshaped
    • Example of thermoset
      • Baking a cake
    • Types of polymers

      • Elastomer
      • Thermoplastic elastomer
    • Elastomer
      • Known as rubber
      • Elastic deformation > 200%
      • Thermoset or lightly crosslinked thermosets
      • Polymer chain consist of coil-like molecules that can reversibly stretch by applying a force
    • Thermoplastic elastomer

      • Special group of polymers
      • Processing is easy like thermoplastics
      • Behavior is elastic like elastomers
    • Comparison of the three polymer categories

      • Thermoplastic: Flexible linear chains (straight/branched)
      • Thermosetting: Rigid three-dimensional network (chains maybe linear/branched)
      • Elastomer: Thermoplastics or lightly cross-linked thermosets, consist of spring-like molecules
    • Examples of polymers
      • Thermoplastic: Polyethylene (LDPE, HDPE, LLDPE), Polypropylene, Polyvinyl chloride (PVC), Polystyrene (PS)
      • Thermoset: Phenolics (PF), Amino Plastics (urea formaldehyde, melamine formaldehyde), Epoxies, Polyurethanes, Imides/polyimides
      • Elastomer: Natural Rubber, Isoprene Rubber (synthetic rubber), Butadiene rubber (BR), Styrene Butadiene Rubber (SBR), Ethylene-Propylene Elastomer (EPM and EPDM), Silicones
    • Polymerization
      The process of creating a polymer
    • Addition polymerization

      Chain-growth polymerization involving the linking together of molecules incorporating double or triple chemical bonds
    • Addition polymerization

      • Unsaturated monomers (with extra internal bonds) break and link up with other monomers to form the repeating chain
      • Involves a chain mechanism with three fundamental steps: initiation, propagation and termination
    • Examples of addition polymers

      • Polyethylene, Polypropylene, Poly(vinyl chloride) (PVC)
    • Initiation (in addition polymerization)

      The first step where an initiator decomposes into free radicals in the presence of monomers
    • Propagation (in addition polymerization)

      The stage where monomer reacts with the free radical of the initiator, adding thousands of monomers to the chain
    • Termination (in addition polymerization)

      The step that halts the growth of the polymer chain, typically by combination or disproportionation of free radicals
    • Condensation polymerization
      Polymers formed when a small molecule condenses out during the polymerization reaction
    • Condensation polymerization

      • Stepwise reaction between functional groups of monomers
      • Involves the elimination of a small molecule, usually water or ammonia
      • Monomers are not the same as in addition polymerization
    • Examples of condensation polymers
      • Polyester, Polyimide
    • Condensation polymers

      Formed from a series of reactions, in which two species (monomer) can react at any time leading to a larger molecule
    • Condensation polymerization

      1. Stepwise reaction occurs between the chemically reactive groups or functional groups on the reacting molecules
      2. A small molecule, usually water / ammonia is eliminated
    • Condensation polymers

      • Polyester
      • Polyimide
    • Monomers for condensation polymerization
      • Have functional groups (like alcohol, amine, or carboxylic acid groups)
      • Each monomer has at least two reactive sites, which usually means two functional groups
    • Glycol
      A molecule has more than one alcohol (-OH) group
    • Amine

      A molecule has an amino (-NH2) group
    • Diamine (or diamino)
      A molecule contains two amino groups
    • Acid
      A molecule contains a carboxylic acid group (-COOH)
    • Amide linkage formation

      When a carboxylic acid and an amine react, a water molecule is removed, and an amide molecule is formed
    • Ester linkage formation

      When a carboxylic acid and an alcohol react, a water molecule is removed, and an ester molecule is formed
    • Monomers involved in condensation polymerization have functional groups
    • These functional groups combine to form amide and ester linkages
    • When this occurs, a water molecule is removed. Since water is removed, we call these reactions condensation reactions (water condenses out)
    • When involved condensation process in the polymerization = condensation polymerization
    • A water molecule is removed as the ester linkage is formed
    • The polymer chain is a polyester because the monomers are all joined by ester linkages
    • Condensation/Step growth polymerization

      • All molecular species are present throughout
      • Usually (but not always) polymer repeat unit has fewer atoms than had the monomer
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