Plastics

Monomers Basic building block of polymer

Polymers Large molecules with repeating monomers Monomers are joined together Possess different properties than the monomers that make them up Types: Natural Synthetic

Polymer Production Addition Polymerization Condensation Polymerization

1) Addition Polymerization Monomers simply added together Polymer has ALL atoms from monomer a) initiation b) propagation c) termination

a) Initiation A compound starts the reaction, free radical Reaction product is free radical Product reacts with another compound and so on

b) Propagation Radical joins a molecule A bigger radical is formed and reacts with another molecule…….forms bigger radical, etc.

c) Termination Polymerization ends Molecule is produced that has ALL paired electrons No unpaired electrons are available to react

2) Condensation Polymerization Small part of monomer is NOT part of the final molecule Monomers have 2 or more functional groups Polymers formed by functional groups linking together Production of commercial polymers

Polymer Properties General term for “plastics”---synthetic polymer Based on molecular structure 2 types— Thermoplastic polymers True plastic Pressure applied to form shape and heat softens material 2) Thermosetting polymers Permanently hard with high temperatures and pressure Not possible to mold or soften

1) Density Dependent on structure High density Low density Linear molecules with no branching, just chains Easily pack together Strong intermolecular forces Low density Molecules with branched chains, prevents crystal structure Molecules cannot pack together Less intermolecular forces

2. Hardness/Rigidity Hard plastic Thermosetting polymer Ex. Bakelite, steering wheels

3) Flexibility/Elasticity Material’s capability to withstand forces without breaking Amount of cross-linking determines how flexible material is Elasticity— Material’s capability to go back to its original shape after removal of a force Ex. Rubber

Synthetic Polymers Modern manufactured polymers Synthetic rubber Various types Possible to have “copolymerization” Copolymer formed from 2 types of monomers Fibers/fabrics Fiber—natural/synthetic material in thread structure Fiber quality depends on tensile strength Ex. Cotton, wool, silk

Biomedical Polymers Plastics used in the medical field Joint replacements Heart valves Artery replacement Wound covers