Classification Of Polymers
Presented byDevansh GuptaM.Sc Polymer ScienceSemester 1
ContentsSome Basic DefinitionsClassification Of PolymersBy OriginBy MonomerBy Thermal ResponseBy Mode Of FormationBy StructureBy Application & Physical PropertiesBy TacticityReference
The word polymer comes from the Greek words poly (meaning many) and meros (meaning parts).Example: POLYETHYLENE = (ETHYLENE+ ETHYLENE+......)n Where n = 4,000
Polymers are very large molecules made when hundreds of monomers join together to form long chains.
MonomerThe small individual repeating units/molecules are known as monomers(means single part).Imagine that a monomer can be represented by the letter A. Then a polymer made of that monomer would have the structure: -A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-
PolymerizationThe process by which the monomer molecules are linked to form a big polymer molecule is called polymerization. Polymerization is a process of bonding monomer, or single units together through a variety of reaction mechanisms to form longer chains named PolymerAs important as polymers are, they exist with monomers, which are small, single molecules such as hydrocarbons and amino acids.
Classification Of Polymers By Origin By Monomer By Thermal Response By Mode Of Formation By Structure By Application & Physical Properties By Tacticity
By OriginNatural PolymersPolymers which are isolated from natural materials are called as natural polymers. E.g. Silk, Wool, Natural rubber, Cellulose, Starch, Proteins etc.
Natural RubberHevea Brasiilensis
Semisynthetic PolymersThe polymers obtained by simple chemical treatment of natural polymers to improve their physical properties like lustrous nature, tensile strength are called semisynthetic polymers E.g. Cellulose acetate, Cellulose nitrate
Polymers synthesized in laboratory from low molecular weight compounds, are called as, synthetic polymers. E.g. Nylon, Terylene, Polyethylene, Polystyrene, Synthetic rubber, Nylon, PVC, Bakelite, Teflon etc.
By MonomerHomo PolymersA polymer consist of identical monomers is called homo polymer. E.g. Polyethylene, PVC, Polypropylene, Nylon 6
Co PolymersA polymer consist of monomers of different chemical structure are called copolymers. E.g. Nylon 6,6
By Thermal ResponseThermoplastic PolymersThey are easily moulded in desired shapes by heating and subsequent cooling at room temperature.They are soft in hot and hard on coding.They my be linear or branched chain polymers. E.g. PE, PVC, PS, PP
Thermosetting PolymersThis polymer is hard and infusible on heating.These are not soft on heating under pressure and they are not remolded.These are cross linked polymers and are not reused. E.g. Bakelite
By Mode Of FormationAddition PolymersThe polymers formed by the addition of monomers repeatedly without removal of by products are called addition polymers.These polymers contains all the atoms of monomers hence their molecular weight are integral multiple of monomer unit. E.g. Teflon, Polyethylene, Polypropylene, PVC.
They are formed by the combination of two monomers by removal of small molecules like H2O, Alcohol or NH3. Their molecular mass is not the integral multiple of monomer units.They have ester and amide linkage in their molecules. E.g. Polyamides(Nylons), Polyesters(PET)
By StructureLinear PolymersIn these polymers monomers are linked with each other and form a long straight chain.These chains has no any side chains.Their molecules are closely packed and have high density, tensile strength, and melting point. E.g. HDPE, Nylons
Branched PolymersThey have a straight long chain with different side chains.Their molecules are irregularly packed hence they have low density, Tensile strength and melting point. E.g. LDPE, LLDPE
Cross-linked PolymerIn these monomeric units are linked together to constitute a 3D network.The links involved are called cross links.They are hard, rigid .and brittle due to their network structure.
E.g. Bakelite, Melamine, Formaldehyde resins, Vulcanized rubber
By Applications & Physical PropertiesFibersIf polymer is drawn into long filament like materiel whose length is at least 100 times its diameter, are said to be converted into fiber.They have high tensile strength because of high intermolecular attractive force like Hydrogen bonding.Highly crystalline. E.g. Nylon, Terylene.
PlasticsPolymer is shaped into hard and tough utility articles by application of heat and pressure, is known as plastics. Here the intermolecular force between polymeric chains are intermediate between elastomers and fibers.They are partially crystalline. E.g. Polystyrene, PVC, PMMA
ElastomersThey are solids with rubber like elastic properties.Here the polymeric chains are held together by the weakest intermolecular forces so they are highly amorphous in nature.These weak binding forces permit them to be stretched. E.g. Natural rubber, BUNA-S, BUNA-N, Vulcanised rubber
ResinsLow molecular weight.Polymers which are used as adhesives, sealants etc., in a liquid form are described as liquid resins. E.g. Epoxy adhesives and polysulphides sealants.
By TacticityTacticity simply means deposition of side groups in space.The head to tail configuration in which the functional groups are all deposited on the same side of the chain, is called isotactic polymers.If the deposition of side groups is in alternating fashion, it is called synditactic polymers.If the deposition of side groups are at random around the main, it is called atactic polymers.
Other Parameters Of Classification By CrystallinityCrystalline Monomers arranged in ordered way.Amorphous Monomers arranged in random way.
By Backbone AtomOrganic Polymer Backbone is made-up of carbon atom.Inorganic Polymer Backbone is made-up of other atoms
ReferencesPolymer Science - Gowariker V. R., New age International PublishersTextbook of Polymer Science - Billmeyer F. W, Wiley India PublishersAdvanced Polymer Chemistry Manas Chanda Marcel Dekker INC.