POLYMER-: A polymer is a large molecule of high molecular weight obtained by the chemical interaction of many small molecule of low molecular weight of one or more type. The process of manufacture of polymer is called polymerization.
POLYMERIZATION-: It is a process of conversion of low molecular weight substance into high molecular weight substance with or without the elimination of by product such as HCl, H2O, NH3 etc.
CLASSIFICATION OF POLYMERS
- BASED ON THEIR SOURCES
- Natural polymers-: The polymers which are obtained from natural sources such as plant and animals are called natural polymer.
Eg. Cotton, jute, wool, silk etc
- Synthetic polymer-: The polymer which are synthesized from simple molecule are called synthetic polymer.
Eg. Nylon66, pVC, Teflon , Ployester etc.
- BASED ON THEIR THERMAL BEHAVIOUR
- Thermoplastic polymer – eg. PVC , polyethelene etc.
- Thermosetting polymer- eg. Bakelite, urea-formaldehyde etc.
III.BASED ON THEIR MECHANISM OF POLYMERIZATION
- Addition polymer- eg. PVC , polyethylene etc.
- Condensation polymer- eg. Polyester , Nylon66 etc.
IV.BASED ON THEIR PROPERTIES
- Elastomer- eg. Natural rubber
- FIbres – eg. Jute, wood , silk etc
- Resins- eg. Urea-formaldehyde, Epoxy resins etc
- Plastics- eg. PVC, Teflon etc
TYPES OF POLYMERIZATION
- ADDITION(CHAIN) POLYMERIZATION-: A polymerization in which monomers containing one or more doubles bond are linked to each other without the elimination of any by product usually in the presence of initiator is called addition polymerization.
Eg. i. Formulation of polythene
n CH2= CH2 [- CH2 – CH2 -]n
- CONDENSATION(STEP) POLYMERIZATION-: A polymerization reaction in which bi or poly functional monomers undergoes intermolecular condensation with continuous elimination of by products such as HCl, H2O, NH3 etc. is called condensation or step polymerization.
Egs: 1. Formation of Nylon66
n NH2-(CH2)6-NH2 + n HOOC- (CH2)4– COOH
Hexamethylene diamine Adipic acid[-NH-(CH2)6-NH-CO-(CH2)4-CO-] n + 2n H2O
QUESTION & ANSWER
I.What are the main features of addition polymerization??
1. Only olefinic compounds can undergo addition polymerization.
2. No elimination of by products.
3. Double bond provides required bonding sites.
4. The addition of monomers takes place rapidly.
5. Linear polymers are produced.
6. The addition polymerization is brought about by free radical, ionic or co-ordination mechanism.
7. The molecular weight of the polymer is an integral multiple of the monomer.
8. The elemental composition of the polymer is same as that of monomer
II. What are the main features of condensation polymerization??
1. The monomers having two or more reactive functional groups can undergo condensation polymerization.
2. There is elimination of by products.
3. Polymerization proceeds through intermolecular condensation.
4. The polymer chain build up is slow and stepwise.
5. Polymerization is catalysed by acids or alkali.
6. Linear or cross-linked polymers are produced.
7. The elemental composition of the polymer is different from that of the monomer
III. why do the different polymer have different properties??
They have different chemical composition(different monomer unit) different structures, different ways of being fabricated etc.
IV. How does the molecular-level structure of these polymers influence their physical properties?
The structure (e.g., extent of branching) determines how the individual polymer molecules can orient (or “pack”) in the solid state. This, in turn, influences physical properties such as density, crystallinity, melting point, and strength.