HIDROCARBON GROUPS

Polymer = many mers POLYMER MICROSTRUCTURE

POLYMER MATERIALS

Covalent chain configurations and strength: Direction of increasing strength MOLECULAR STRUCTURE Homopolymers

MOLECULAR STRUCTURE Copolymers

MOLECULAR STRUCTURE Copolymers

Molecular weight, M w : Mass of a mole of chains. Tensile strength (TS): --often increases with M w. --Why? Longer chains are entangled (anchored) better. % Crystallinity: % of material that is crystalline. --TS and E often increase with % crystallinity. --Annealing causes crystalline regions to grow. % crystallinity increases. MOLECULAR WEIGHT & CRYSTALLINITY

CRYSTALLINITY

POLYMER CRYSTALS

6 Compare to responses of other polymers: --brittle response (aligned, cross linked & networked case) --plastic response (semi-crystalline case) TENSILE RESPONSE: ELASTOMER CASE

Decreasing T... --increases E --increases TS --decreases %EL T AND STRAIN RATE: THERMOPLASTICS

Stress relaxation test: --strain to   and hold. --observe decrease in stress with time. Relaxation modulus: Data: Large drop in E r for T > T g. (amorphous polystyrene) TIME DEPENDENT DEFORMATION

VULCANIZATION

TENSILE RESPONSE: BRITTLE & PLASTIC

CRYSTALLIZATION, MELTING AND GLASS TRANSITION PHENOMENA IN POLYMERS Dependence of polymer properties as well as melting and glass transition temperatures on molecular weight

POLYMER TYPES

FORMING TECHNIQUES FOR PLASTICS