Properties of Commercial polymers:
A) Nylon-6,6 :
It is a polymide, manufactured by condensation of adipic acid and heaxamethylenediamine. It is called nylon-6,6 because, both monomers adpic acid, HOOC-(CH2) -NH2 contain six carbon atoms in their molecules.
An aqueous solution of heaxamethylenediamine is treated with an aqueous solution of adipic acid and then the mixture is warmed at 75°C at high pressure in the absence of air, when nylon salt is formed. Water is then evaporated from the salt solution and the salt is heated to about 280°C in an inert atmosphere of nitrogen to prevent oxidation. Heating is continued for about 3 hours when molecules of salt polymerise to give colinear polymer, called nylon-6,6.
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| Nylon-6,6 |
Nylon-6,6 is a colourless solid. To get fibres it is melted and the melt is forced through fine orifices of spinnerets in a chamber in which cold air is circulated. To increase the strength and elasticity, the fibres are stretched several times of their original length.
Properties of Nylon-6,6:
1) It has high tensile strength and elasticity.
2) It has low melting point 263°C and low affinity for water.
3) Microorganisms and moth do not affect nylon which is also resistant to chemical attack from a variety of substances, including sea-water and dry cleaning liquids.
4) It is insoluble in almost all inorganic solvent but readily dissolves in phenol and formic acid.
Uses of Nylon-6,6:
1) It is used in making sails, fishing nets and lines, laundry bags and oil filters.
2) It is used for driving belts, conveyor belting, reinforcing for rubber tyres, artificial fur coats, lifting gears and sieve.
3) Due to high tenacity and elasticity it is used for the manufacture of ropes, parachutes, safety belts, gliders tow ropes, sheer stocking and under wears.
4) Blends of nylon staple with wool are also commonly used for socks, cardigans and suitings.
B) Terylene (Dacron) :
Terylene is the British name for Dacron. It is a polyester, manufactured by condensation Polymerisation of dimethyl terephthalate and ethylene glycol and hence the name terylene.
Dimethyl terephthalate (DMT) is first condensed with 2 moles of ethylene glycol at about 230°C, when trans esterification takes place and dihydroxy diethyl terephthalate is formed as a monomer. This monomer is then heated in vacuum to 260°-300°C to form terylene polymer by Polymerisation reaction.
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| Terylene |
The polyester chips are dried and then fed into a hopper. Then they are passed into the melting vessel and forced through the spinneret. The solidified filaments are brought together and passed to the drawtist machine so that the yarns are streched five times it's original length.
Properties of Terylene:
1) It is insoluble un almost all inorganic and organic solvents.
2) It is resistant to many chemical, micro organisms, and friction.
3) It is strong and has good elasticity.
4) It absorbs very little water due to which clothes made of terylene dry quickly.
5) It has crease resistance property and requires very little ironing.
Uses of terylene:
1) Most important use of terylene is in textile industry. Clothes are made up of pure terylene and can mixed with wool (terywool) and with cotton (terycot).
2) Terylene can be made into films and are used in making of magnetic recording tapes-recorders.
3) High tensile strength of these fibres, has been used in making conveyor belts, safety belts, fishing nets, ropes, sails, dry bags, covers for houses and paper making belts.
C) Polyvinyl Chloride (PVC) :
The monomer, vinyl chloride, which is a gas at ordinary temperature, can be prepared by adding HCl to acetylene Or cracking ethylene dichloride.
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Polyvinyl chloride |
Properties of PVC:
1) It is syndiotactic partially and has no completely regular structure and therefore has low crystallinity.
2) Polymer chains are mainly linear with little branching.
3) It is highly insoluble material and resists the action of acids and alkalies.
4) It is good electrical insulator.
Uses of PVC:
1) It is used as insulator for cables.
2) Manufacture of artificial leather.
3) House holding articles such as -table cloths, curtains, gramophone records, floor converings (mats).
4) Pipes and other liminated materials.
D) Acrylics:
Acrylic resin are manufactured by addition Polymerisation from acrylic or methacrylic acids and their ester, nitrile and amide derivatives.
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| Acrylics |
Properties of Acrylic:
1) They are hard, brittle, transparent and hygroscopic solids.
2) They are soluble in water and polar organic solvents.
3) They are insoluble in non-polar solvents.
Uses of Acrylic:
1) They are used as thickness, binders, adhesives and suspending and flocculating agents.
2) Polyacrylamide is used for water purification, especially in paper making and mining operations.
3) They are used to improve the flow properties of water, to adjust the dry strength of paper, and in secondary and tertiary oil recovery.
E) Teflon:
The polymer produced in Britain known as Fluon and in U.S.A as Teflon. The monomer used is tetrafluoroethylene (F2C=CF2) which is a gas at room temperature with b.p. -76°C.
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| Teflon |
Properties of Teflon:
1) Teflon molecule has a highly regular structure with a configuration leading to 136 helix.
2) It is highly crystalline and has high melting point (335°C).
3) High mechanical strength over a long range of temperature (-100° to 350°C).
4) It is non-flammable, a first class electrical insulator, self-lubricator.
5) It is highly viscous and does not flow readily.
Uses of Teflon:
1) Teflon is used in making articles such as pump valves and pipes, gaskets, seats and protective linings in chemical plants.
2) Used for coating of raincoat.
3) It is used as electrical insulations.
4) It is used as non-stick surface to prevent adhesion of glues, doughs, confectionary mixture.
5) Thin Fluron sleeves are used to prevent the locking of stoppers and joints in chemical apparatus.
F) Polyethylene:
Polyethylene is the simplest synthetic polymer made by addition Polymerisation of ethylene at high temperature and pressure.
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Polyethylene |
The monomer ethylene can be prepared either by hydrogenation of acetylene or by dehydration of ethanol. It can be produced by the process of cracking of petroleum products. Ethylene is a gas at room temperature, having boiling point -104°C.
There are two different types of polyethylene:
a) Low density polyethylene (LDPE) :
It is produced by the high pressure Polymerisation of ethylene using oxygen as the initiator. High pressure about 1500 atmosphere and temperature range of 180°-125°C are used.
Low density polyethylene consists of molecules that are branched. The branching occurs during Polymerisation by intermolecular or intramolecular chain transfer.
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Low density polyethylene |
Properties of LDPE:
1. Its density is low (around 0.91 to 0.92 g/c.c.) and is less Crystalline.
2. Its solubility is low at lower temperatures but with increasing temperature its solubility in organic solvents (toluene, xylene, decalin, carbon tetrachloride) increases.
3. It consists of polymer chains which are branched.
4. It is bad conductor of electricity.
Uses of LDPE:
1. It is used in making films, which are used to make bags, packing materials, wrapping material.
2. It is chemically inert and highly flexible. This property is used in making 'squeeze bottles' and many attractive containers.
3. It can be moulded into pipes used for water supply.
4. It is bad conductor of electricity and hence used in making insulations in electric cables.
b) High density polyethylene (HDPE) :
It is prepared by two methods:
1) By coordination Polymerisation of ethylene using Ziegler-Natta catalyst- (Triethyl aluminum frame and titanium tetra chloride).
2. By Polymerisation with the help of metal oxide catalyst, such as chromium oxide or molybdenum oxide supported over alumina -silica bases.
Properties of HDPE:
1. It consists of unbranded linear and hence high crystallinity and high density (0.965 g/c.c.)
2. It has a higher tensile strength and hardness.
3. It has higher melting point (144-150°C).
Uses of HDPE:
1. It is used in for making house hold articles, toys, bottles which cannot be squeezed.
G) Acryonitrile:
It has principally been made from acetylene and hydrogen cyanide. They are reacted with a liquid catalyst containing Cuprous chloride, hydrohen chloride and alkali chlorides at atmosphere pressure, thus,
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Acryonitrile |
A new process for manufacturing acryonitrile from propylene ammonia and air has led to successful commercial operations. The catalyst used is Mo or Bi.
Properties and uses:
1. As the content of acryonitrile increases in the polymer chain, properties change predictably. The glass transition temperature increases approximately 1.5°C for each percent increase acryonitrile.
2. Properties such as hysteresis loss, resilience and low temperature will correspondingly change.
H) Buna-N:
It is a copolymer of 75% butadiene and 25% acryonitrile. It is prepared by emulsion Polymerisation. Dispersion medium is water. The emulsifying agents used in this process are soaps, fatty acids (olive mysteric and palmitic acid or anionic soaps and cationic soaps such as dodecyl amine hydrochloride etc.Cumene hydroperoxide is used as Polymerisation initiators and Fe²+ salts as Polymerisation promoters in small amounts and Na2P4O7 as complexing agent. To stop the reaction as desired point, chain sweepers such as hydroquinone are used. They are called as Polymerisation terminators.
Properties of Buna-N:
1. It shows excellent resistance to heat, sunlight, acids oils and salts. It is less resistant to alkalies than natural rubber. It is attributed to the presence of cyano groups (-CN). On account of the presence of acryonitrile (25%) in the copolymer, the product obtained is solvent resistant rubber. If the concentration of acryonitrile is increased, the resistance to acids, oils, solvents etc. also increases.
2. The copolymer is low in tensile strength as it possesses irregular structure structure like SBR rubber. The tensile strength is increased by adding reinforcing pigment.
3. Abrasion resistance is upto the mark.
4. It is less resilient (elastic,rubbery) than natural rubber.
5. Heat resistance is upto the standard.
6. The freezing point also increases with addition in nitrile content.
7. The vulcanized-nitrile rubber is more resistant to heat and ageing than natural rubber and may be exposed to high temperature.
8. When properly vulcanized with carbon black, it is used in petrol pipes and tanks.
Uses of Buna-N:
1. It is used in making fuel tanks, gasoline hoses (tubing, pipes), conveyer belts, higher altitude air craft compounds etc.
2. It is also used in tank linings, gaskets, priting rollers, adhesives, oil resistant foams and automobile parts.
3. In the form of latex, it is used for impregnating paper, textiles and leather.
So, this are the properties. of commercial polymers.