( effect of side group)

STRUCTURE-PROPERTY RELATIONSHIP

Presentation on

Presented by : MUHAMMAD UMAIR BUKHARI MME-

09E-08

FOR MORE HELP CONTACT ME

Muhammad Umair Bukhari

Engr.umair.bukhari@gmail.com

www.bzuiam.webs.com

03136050151

WHAT IS A POLYMER?

• A long molecule made up from lots of small molecules called • monomers.

For the Thermoplastics (polyethylene) • Tensile strength• Creep resistance• Impact toughness• Wear resistance• Melting temperature

All increases with increase in average molecular weight or degree of polymerization. As the average molecular weight increases, the melting temperature increases that’s makes the processing more difficult.

So, for the ease of polymer processing, we can use of bimodal molecular weight distribution.

Relationship With Degree Of Polarization

POLYSTYRENE COFFEE CUP

• In certain applications such as for the polystyrene coffee cup ,

• It is important to insure that the residual monomer concentration is extremely small because of the toxic concerns. polystyrene coffee cup

• In polyethylene, the linear chains easily rotate and slide when stress is applied, and no stronger polar bonds are formed between the chains

• Thus, polyethylene has low strength.

EFFECT OF SIDE GROUPS

Vinyl Compound• One of the hydrogen atom is replaced with a

different atom or atom group.• When R is chlorine in the side group, product is

Polyvinyl Chloride • When the side group is CH3, product is

Polypropylene

EFFECT OF SIDE GROUPS

Polypropylenerope

• Addition of the benzene ring as a side group gives

Polystyrene

• CN group produces Polyacrylonitrile

Po l y a c r y l o n i t r i l e fi b e r

Vinylidene compound• When two of the hydrogen atoms are replaced,

the monomer is a vinylidene compound• Examples: Polyvinylidene Chloride

Polymethyl Methacrylate

EFFECT OF SIDE GROUPS

P M M A L e n sPo l y m e t h y l m e t h a c r y l a t e

Larger atoms such as chlorine or groups of atoms such as methyl and benzene make it more difficult for the chains to

Rotate Uncoil Disentangle Deform by viscous flow

under the high temperature and applied stress.

This condition leads to• Higher strength• Higher stiffness• Higher melting temperature

EFFECT OF SIDE GROUPS

• The chlorine atoms are strongly attracted by hydrogen bonding to hydrogen atom on adjacent chain.

This is the reason why PVC is more rigid than many other polymers.• When low molecular weight compounds such

as plasticizer are added to PVC , the glass temperature is lowered.

• This make PVC more ductile and workable and known as vinyl.

EFFECT OF SIDE GROUPS

Polytetrafluoroethylene• In Polytetrafluoroethylene all four hydrogen atom in

the polyethylene structure are replaced by fluorine.• Strength is not much greater than that of

polyethylene.• C-F bond permits PTFE to have high melting point.• Low friction non-stick characteristic that make the

polymer useful for bearings and cookware.

• Branching reduce the density stiffness and strength of the polymer.

EFFECT OF SIDE GROUPS

Any Question

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