POLYMERA giant molecule consisting of a large number of small units (building blocks) joined together in a chain arrangement. The term polymer is used to describe both a RUBBER and a PLASTIC

MONOMERSingle units which when joined together form a polymer.

POLYMERISATION The process of producing polymers from monomers. (the joining together of monomer units to form a polymer chain)

DEGREE OF POLYMERISATION The number of monomer units contained in a polymer chain. Usually represented by the symbol n n

Most polymer consist of carbon and hydrogen (along with some other elements) bonded together. These materials are called HYDROCARBON polymers MonomerCH 2 CH 2 Ethene Polymer CH 2 CH 2 CH 2 CH 2 CH 2 or CH 2 Polyethene

ELASTICITYThe ability of a material to return to its original shape when a deforming force is removed.

PLASTICITYThe ability of a material to retain its shape after the removal of the deforming force which produced the shape.

ELASTOMERan elastic material requiring relatively small forces to produce large deformations. These are generally RUBBER materials

PLASTICa polymeric material that exhibits plasticity. They usually require the application of heat in order that low forces will produce a change in shape.

THERMOPLASTICS The polymer is softened by heating, shaped and then cooled to retain shape. This process is repeatable as no chemical change occurs in the polymer. REPROCESS HEATSHAPEPOLYMERCOOL

Examples of Common Thermoplastics Polymer NameAbbreviation PolythenePE PolypropylenePP PolystyrenePS Polymethylmethacrylate (Perspex)PMMA Polyamide (Nylon)PA Acrylonitrile Butadiene StyreneABS

THERMOSETS The polymer is softened by heating, shaped and then further heated to produce a chemical change (cross linking) which gives permanence of shape. This process is irreversible therefore the material cannot be reprocessed. HEATSHAPEPOLYMERHEAT

Examples of Common Thermosets Polymer NameAbbreviation Phenol FormaldehydePF Urea FormaldehydeUF Melamine FormaldehydeMF

ELASTOMERS (RUBBER) The polymer is softened by heating, shaped and then further heating produces a chemical change (cross linking) which gives permanence of shape. This process is irreversible therefore the material cannot be reprocessed. HEATSHAPEPOLYMERHEAT

Examples of Common Elastomers Polymer NameAbbreviation Natural RubberNR Styrene Butadiene RubberSBR Chloroprene RubberCR Acrylonitrile Butadiene RubberNBR Isobutylene Isoprene Rubber (Butyl)IIR Ethylene Propylene RubberEPR or EPDM

Strength : the force required to rupture or break a sample. ( to cause failure ) Failure Mode : based on the direction of the applied force i.e. tensile compression torsion impact flexural shear tear

Tensile Strength