POLYMERS & COMPOSITES

Transcription

1 POLYMERS & COMPOSITES Polymers - definition polymerization types addition and condensation polymerization free radical polymerization mechanism Plastics, classification preparation, properties and used of PVC, Teflon, polycarbonate, polyurethane, nylon-6,6, PET Rubber vulcanization of rubber, synthetic rubbers butyl 1 rubber, SBR, Composites definition, types of polymers matrix composites FRP only. 1

2 POLYMERS AND COMPOSITES Introduction: In this modern world, polymers are an integral part of every one s life style. They have different structures and applications ranging from domestic articles to sophisticated scientific and medical instruments. These materials are used as fibres, rubbers, plastics, adhesives, paints, etc. Infact, the existence of life is virtually the formation, transformation and decomposition of bio-polymers viz. Carbohydrates, Proteins and Nucleic acids. Therefore, in view of their importance, a proper understanding of polymeric materials is very essential. The word Polymer is derived from two Greek words, Poly - Many and Meros - Units. A polymer is a macro-molecule (giant molecule) which is formed by the repeated linkage of a large number of small molecules (monomers). Example: Polythene is a polymer formed by repeated linkages of a large number of Ethylene molecules. (Monomer) (Polymer) Where n degree of polymerization, it can be 10 4 or more. TERMINOLOGY: POLYMER: A polymer can be defined as, a macromolecule of high molecular weight which is formed by the combination of large number of small molecules of low molecular weight. MONOMER: A large number of small molecules repeatedly combine to give a macro molecule (polymer) of high molecular weight are called monomers. DEGREE OF POLYMERISATION: The number of monomeric units contained in a polymer is called degree of polymerization. 2

3 POLYMERIZATION: The chemical process which leads to the formation of polymer is called polymerization. TYPES OF POLYMERSIATION: Based on the synthesis in which elimination of by products formed, polymerizations are broadly classified into two types. POLYMERISATION ADDITION POLYMERISATION CONDENSATION POLYMERIATION ADDITION POLYMERISATION: It is also called chain polymerization. The process in which large number of identical monomers repeatedly combines to give a polymer without the elimination of any byproducts is called addition polymerization. Example: Example for addition polymers: Polythene (PE), Polyvinyl chloride (PVC), Polystyrene (PS), Polypropylene (PP), etc. CONDENSATION POLYMERISATION: It is also called step polymerization. The process in which large number of two or more different types of monomers combines to give a polymer with the elimination of by-products like H 2 O, HCl, methanol, etc is called condensation polymerization. Example: 3

4 Example for condensation polymers: Nylon, Bakelite, Polyethylene terephthalate (PET), etc DIFFERENCES BETWEEN ADDITION POLYMERISATION & CONDENSATION POLYMERISATION: Sl. No ADDITION POLYMERISATION 1 It requires the presence of double bond in the monomer. CONDENSATION POLYMERISATION It requires two reactive functional groups to be present at both ends of the monomer. There should be atleast two different bi- or poly functional monomers having functional groups with affinity for each other. 2 No by-product is formed. Generally a by-product is formed. 3 Homo-chain polymer is formed. Hetero-chain polymer is formed. 4 Thermoplastics are obtained. Thermosetting plastics are obtained. 5 The growth of chain is at one active centre. The growth of chain occurs at minimum of two active centres. 6 The molecular weight of the polymer is a multiple of the molecular weight of the monomer. The molecular weight of the polymer is not a multiple of the molecular weight of the monomer. 7 Example: Polymerization of ethylene to form polyethylene. Example: Condensation polymerization of Terephthalic acid and ethylene glycol to form polyethylene terephthalate. PLASTICS: Plastics are high molecular weight organic materials which can be moulded into any desired form by the application of heat and pressure in the presence of a catalyst. In recent years, plastics have attained great importance in day to day s life, due to their certain unique properties. Advantages of plastics: They are light in weight. They have low melting point. They are highly resistant to corrosion. They can be cast/mould into any desired shapes easily. They are not affected by insects, moth, fungi, vermin, etc. It requires low fabrication cost to make any desired shapes. 4

5 They have high resistance to abrasion. They have high refractive index. They have good shock absorption capacity. They have tensile strength upto 5,500 kg/sq.cm. They do not absorb water. They have good dimensional stability. They do not react with light, oils, acids and dampness, etc The shades/colours do not fade easily. Plastic surfaces possess shining and glossy surfaces, which appeal eyes. Disadvantages: High cost, Combustibility, Poor ductility, Softness, Deformation under load, Embrittlement at low temperatures, Low heat-resistance. Uses of plastics: For making electrical goods. For making furniture. In aeronautical engineering. For making handles for tools and covers of machines. For making special type of paints. For making bearings for propeller shafts, used in paper industry and rolling mills. For heat and sound insulation in cold storage, refrigeration, air-conditioning building, theaters, auditoriums and for packing works. For making overhead water tanks and pipes to convey water, oils, gases, chemicals, etc. For making household articles like combs, toys, trays, toilet goods, lenses, films, tooth brush bristles, syringes, etc. For making synthetic fibres like terylene, nylon, etc. House hold items made of various kinds of plastics. 5

6 CLASSIFICATION OF PLASTICS: Plastics are classified into two types. They are (i) Thermoplastics (ii) Thermosetting plastics Thermo plastics: They have either linear or branched structures. Their polymeric chains are held together by weak Vander Waals forces / dipole dipole forces (London forces) / Hydrogen bonds. There is no cross-links. On heating, they soften readily and become hard and rigid on cooling. That s why they can be remoulded, reshaped and reused. They are soft, weak and less brittle; they are soluble in organic solvents. Example: Poly Ethylene (PE), Poly Vinyl Chloride (PVC), Poly Propylene (PP), Poly Styrene (PS), Poly Methyl Methacrylate (PMMA), etc Thermosetting plastics: They have three dimensional, cross-linked, networked structures. Their polymeric chains are held together by strong covalent bonds. There are many cross-links. Heating does not soften them, since softening would require breaking of covalent bonds. That s why they can t be remoulded, reshaped and reused. They are hard, strong and more brittle. They are insoluble in organic solvents. Example: Bakelite, Polyester. DIFFERENCES BETWEEN THERMO PLASTICS AND THERMOSETTING PLASTICS: Sl.N o THERMO PLASTICS THERMOSETTING PLATICS 1 They are formed by addition They are formed by condensation polymerization. polymerization. 2 They have either linear or branched They have three dimensional, cross - structures. linked network structure. 3 Adjacent polymer chains are held together by either Vander Waal s forces or dipole Adjacent polymer chains are held together by strong covalent bonds. dipole forces or by Hydrogen bonds. 4 They soften on heating and stiffen on They do not soften on heating. cooling. 5 They can be re-moulded, re-shaped and reused. They can t be re-moulded and hence can t be re-used. 6 They can be recycled. They can t be recycled. 7 They are soluble in organic solvents. Due to strong bonds and cross-linking, they are insoluble in organic solvents. 8 They are very soft, weak and less brittle. They are hard, strong and more brittle. 9 There is no change in their chemical There is a change in their chemical composition during the moulding process. 10 Examples: PE, PP, PVC, PMMA, PS, PTFE, etc, 6 composition during the moulding process. Examples: Epoxy resin, vulcanized rubber, Bakelite, Poly Urethane foam, etc.

7 FREE RADICAL POLYMERISATION MECHANISM: It involves the following steps. STEPS CHAIN INITIATION CHAIN PROPAGATION CHAIN TERMINATION CHAIN INITIATION PRODUCTION OF FREE RADICALS BY THE HOMOLYTIC CLEAVAGE OF AN INITIATOR ADDITION OF FIRST MONOMER TO RADICAL TO PRODUCE THE CHAIN INITIATING SPECIES A. Chain initiation step B. Chain propagation step C. Chain termination step A. Chain initiation step: It involves two reactions. (i) The production of free radicals by the homolytic cleavage of an initiator to give a pair of radicals, R o. (ii) The addition of first monomer (M) to the radical to produce the chain initiating species, M 1 o. Thus, the polymerization of monomer, CH 2 =CHY, takes in the form 7

8 B. Chain propagation step: The growth of M 1 o occurs by the addition of large number of monomers. C. Chain termination step: It involves two methods. (i) By coupling / combination. (ii) By disproportionation. The hydrogen atom of one radical centre is transferred to another radical centre. This results two polymers, one is saturated and another is unsaturated. POLY VINYL CHLORIDE (PVC): Prepartion: PVC is obtained by heating water-emulsion of vinyl chloride in presence of a small amount of benzyl peroxide or hydrogen peroxide in an autoclave under pressure. The vinyl chloride is prepared by treating acetylene at 1 to 1.5 atm pressure with HCl at o C in presence of metal chloride as catalyst. C 2 H 2 + HCl Acetylene o C 8 CH 2 =CH Cl Vinyl chloride

9 Properties: It is colourless, odourless, non-inflammable and chemically inert powder. It has excellent resistance to light, atmospheric oxygen, inorganic acids, alkalis & oils, but soluble in hot ethyl chloride and Tetra hydro furan (THF). It has outstanding strength, rigidity and stiffness. It is partially syndiotactic. It has high softening point (148 o C). Uses: It is used for making sheets, which are employed for tank-linings, light-fittings, safety helmets, refrigerator components, tyres, cycle & motor cycle mudguards, etc. It is used for the production of pipes, cable insulations, rain coats, etc. It is used for making injection moulding articles like toys, tool-handles, toiledgoods, radio components, chemical containers, conveyor belts, etc. Articles made of PVC Lap tap stand Pipes Earth model Hand bag Traffic cones Stethoscope 9

10 PTFE (POLY TETRA FLUORO ETHYLENE): It is commercially called Teflon and Fluon. Preparation: Teflon is obtained by polymerization of water-emulsion of Tetrafluoro ethylene, in presence of small amount of benzoyl peroxide under high pressure. Properties: It has an excellent resistance to heat and electricity. It has an excellent thermal stability. It has high chemical resistance towards all chemicals (except hot alkali,hot F 2 ) It has high density, g/cc. It has low co-efficient of friction. It can be machined, punched and drilled. It has high softening point (350 o C) due to the presence of Fluorine atoms. Uses: It is used as an insulation material for motors, transformers, cables, wires, fittings, etc. It is used for making gaskets, pump parts, tank linings, chemical carrying pipes, tubings and tank, etc. It is used for coating and impregnating glass fibres, asbestos fibres and cloths, etc. It is used in the making of non-lubricated bearings and non-sticking stopcocks for burette, etc. Articles made of PTFE Non-stick cook ware Computer mouse Insulation tape Hose Racquets Travelling Bags 10

11 POLY CARBONATES (PC): Preparation: It is commercially called Lexan and Merlon. It is prepared by interaction of diphenyl carbonate with bisphenol-a [2,2-bis(4-oxyphenyl)propane]. Properties: It has high impact and tensile strength over a wide range of temperature. It is soluble in organic solvents and alkalis. It has good dimensional stability, stiffness and transparency, etc. It has an excellent electrical insulation property. Uses: It is used for making moulded domestic ware, plugs, switches, etc. Since it is an electrical insulator, it is widely used in electrical and electronics industries. Articles made of PC Compact Disc Key board Camera Spectacles Calculator Mixie jars 11

12 POLY URETHANE: Preparation: It is also called Perlon U. It is obtained by treating 1, 6 hexane diisocyanate with 1, 4 butane diol. Properties: It is less stable than polyamides. It has an excellent resistance to abrasion and solvents. Uses: It is used as coatings, films, foams, adhesives and elastomers, etc. Resilient polyurethane fibres are used for formulating garments and swim suits, etc. It is used to cast to produce gaskets, seal and printing rolls, etc. Articles made of Poly urethane Shoe Cushion seat Pocket diapers Winter dress materials Rolling chair Motor cycle hand grip 12

13 NYLON 6, 6: Preparation: It is obtained by the condensation polymerization of Hexamethylene diamine and Adipic acid in 1:1 molar ratio. It is also prepared from 1, 3 butadiene. Properties: It is translucent, whitish and horny, etc. It has high melting point, ( o C). It has an excellent resistance to high temperature and abrasion. It is insoluble in common organic solvents like benzene, acetone, etc, but soluble in phenol and formic acid. It has good moulding and extrusion properties. Properties of nylon fibres: They are light, horny and high melting, etc. They are insoluble in common solvents. They have good strength. 13

14 They absorb little moisture. They are very flexible and retain to original shape after use. They are resistant to abrasion. On blending with wool, the strength and abrasion resistance of latter increases. Uses: Nylon 6, 6 is primarily used for fibres in making socks, carpets and dresses, etc. It is used for making filaments for ropes, bristles for tooth - brushes and films, tyre cords, etc. Articles made of Nylon 6,6 Bolt and nut Shoe Bag Judo and Karate gloves Bouncy castle Rope 14

15 POLY ETHYLENE TEREPHTHALATE (PET): It is commercially called Terylene and Dacron. Preparation: It is prepared by condensation polymerization of terephthalic acid and ethylene glycol in basic medium. Properties: It is a good fibre-forming material due to the presence of polar group and symmetrical structure. It s fibre has high stretch resistance, high-crease and wrinkle resistance, etc. It has high resistance to mineral and organic acids, but is less resistance to alkalis. It has good mechanical properties like high modulus, tensile strength, tear strength and impact strength, etc which are retained up to o C. Blends of PET fibre with cotton and other cellulosic fibres have better feel and moisture permeation. Uses: It is mostly used for making synthetic fibres like Terylene, Dacron, etc It is used for blending with wool to provide better crease and wrinkle resistance. As glass reinforcing material in safety helmets, aircrafts battery boxes, etc. To make magnetic recording tape. Glass filled PET mouldings are used for the houses of toasters, coffee makers, car heater and water meter, etc. Fibre applications like wearing apparel, curtain, thread, tire cord and fabrics for industrial filtration. PET Jars & Containers PET Bottles Key board Tooth Brush - Bristles Chemistry models Sails made of Dacron (Pentakis Dodecahedron) 15

16 RUBBERS (ELASTOMERS): Rubbers are high polymers, which have elastic properties in excess of 300 percent. An elastomer molecule is not straight chained as in the case of Poly Ethylene, but in the form of a coil and consequently it can be stretched like a spring. The unstretched rubber is amorphous. As stretching is done, the macro molecules get partially aligned with respect to another, thereby causing crystallization and consequently, stiffening of material occurs. On releasing the deforming stress, the chains get reverted back to their original coiled state and the material again becomes amorphous. Schematic representation of coiled elastomer chain of natural rubber. Natural rubber consists of basic material latex, which is a dispersion of isoprene. During the treatment, these isoprene molecules polymerize to form, long-coiled chains of cis-poly isoprene. The molecular weight of raw rubber is about 1,00,000 1,50,000 gram. Natural rubber is made from the plants like havea brasillians and guayule, and the rubber latex is obtained by making incisions in the bark of the rubber trees. The latex is transferred to a factory for treatment. 16

17 Structure of natural rubber. Drawbacks of rubber: It becomes soft at high temperature and is too brittle at low temperature. So it can be used in the temperature range of o C only. It is weak, because of its low tensile strength, 200 Kg per Sq.cm. It has large water absorption capacity. It is non-resistant to non-polar solvents like benzene and CCl 4, etc. In organic solvents, it undergoes swelling and gradual disintegration. Due to it s oxidation in air, it is not durable. It is attacked by oxidizing agents like HNO 3, H 2 SO 4, Chromic acid, Sodium hypochlorite, Chlorine dioxide, etc. It possesses marked tackiness, which means that under pressure two fresh raw rubber surfaces coalesce together to form a single piece. When stretched to a great extent, some molecular chains undergo, sliding or slippage over each other, hence it suffers from permanent deformation. VULCANIZATION: Vulcanization of raw rubber with Sulphur as vulcanizing agent. 17

18 To improve the properties of rubber, it is compounded with various chemicals like Sulphur, H 2 S, benzoyl chloride, etc. The process of heating the raw rubber at o C with sulphur is called vulcanization. The added sulphur combines chemically at the double bonds of different rubber molecules and provides crosslinking between the chains. This cross-linking during vulcanization brings about a stiffening of the rubber by anchoring and consequently preventing intermolecular movement of rubber springs. The amount of Sulphur added determines the extent of stiffness of vulcanized rubber. For example, a tyre rubber contains 3 5% Sulphur, but a battery case rubber may contain as much as 30% Sulphur. Advantages of vulcanization or advantages of vulcanized rubber: Vulcanized rubber, has good tensile strength and extensibility. has an excellent resilience. Has high resistance to moisture, oxidation and abrasion, etc. Possess low water-absorption tendency. has low elasticity. has better resistance to organic solvents like CCl 4, benzene, petrol, etc. has only slight tackiness. has useful temperature range, 40 to 100 o C. SYNTHETIC RUBBERS (ELASTOMERS): A synthetic rubber is a vulcanisable man-made rubber like polymer, which can be stretched to at least twice it s length, but it returns to its original shape and dimensions as soon as stretching force is released. Example: Styrene-butadiene rubber (SBR), Nitrile rubber, Neoprene, Butyl rubber, Thiokol, Hypalon and Polyurethane rubber, etc. BUTYL RUBBER (GR-I): Preparation: It is prepared by the co-polymerization of isobutene with small amounts of isoprene. Properties: It has very low permeability to air and other gases. It has an excellent resistance to heat, abrasion, ageing, chemicals like HNO 3, H 2 SO 4, HCl and HF, polar solvents like alcohol and acetone, etc. It is soluble in hydrocarbon solvents like benzene, toluene, etc. 18

19 It has high resistance to Ozone. It has good electrical insulating properties. Uses: It is used to make cycle and automobile tubes, hoses, conveyor belts, etc. It is used to make tank-linings, insulation for high voltage wires and cables, etc. STYRENE BUTADIENE RUBBER (SBR / GR S or Buna S): Preparation: It is obtained by co-polymerization of 1,3 butadiene and styrene by weight in the ratio 3:1. Properties: It resembles the processing characteristics of natural rubber. It possesses high abrasion resistance, high load bearing capacity and resilience. It oxidizes in presence of Ozone. It swells in oils and solvents. It can be vulcanized like natural rubber using Sulphur or Sulphur monochloride (S 2 Cl 2 ). Uses: It is used for the manufacture of motor cycle tyres. It is also used for floor tiles, shoe soles, gaskets, foot-wear components, wire and cable insulations, carpet backing, adhesives, tank-lining, etc. ************************** 19

20 COMPOSITES Introduction: Each class of basic engineering materials (metals, high polymers and ceramics) has its own outstanding and unique properties along with certain limitations. Any of these cannot be properly used where very stringent and specific requirements are needed. For example, structural materials required for Gas turbines, high temperature treators, super sonic aircrafts, missiles, space crafts, etc must have high specific strength, stiffness and excellent resistance to corrosion, abrasion, impact and heat. In order to meet the above requirements, technologists and scientists have developed a new class of materials called composites. A composite material may be defined as any multiphase material which consists of two or more physically and/or chemically distinct phases with an interface separating them. Composite materials possess combination of properties. Generally they are dense and also increase in strength and stiffness without the disadvantage of brittleness. Example: 1.Wood a composite of cellulose fibres and lignin cementing materials. 2.Bone a composite of a soft, but strong protein callogen, and brittle and hard material apaptite. 3.Insulation tape, Rein forced concrete, packing paper impregnated with wax/bitumen, etc. Advantages of composite materials or Advantages of composite materials over the conventional materials: Higher specific strength. Lower specific gravity. Higher specific stiffness. Maintain structure, even up to high temperature. Better toughness, impact and shock-resistance. Easy to fabrication. Low electrical conductivity. Low thermal expansion. Better corrosion and oxidation resistance. Applications of composites: In automobile industries, transportation industries, turbine engines, wire drawing dies, valves, pump parts, spray nozzles, storage tanks, etc. In fabrication of roof and floors, furniture, sports goods, high speed machinery, etc 20

21 Marine applications like propellers, shafts, hulls, spars (for racing boats) and other ship parts, etc. Aeronautical applications like components of rockets, aircrafts, missiles, and helicopters, etc. Communication antennae, electronic circuit boards (eg. PCB), etc Safety equipments like ballistic protection. FIBRE REINFORCED COMPOSITES: Fibre-reinforced-composites involve three components. Filament Polymer matrix (excapsulating agent for the filaments) Bonding agent (which ties fibre filaments to polymer) Properties of FRC: High specific strength High specific modulus High fracture strength Excellent shock resistance High stiffiness High wear resistance Maintain strength at high temperature FIBRE REINFORCED POLYMER COMPOSITES Glass FRPC Carbon FRPC Armid FRPC Alumina &/or Carbon FR Metal Composites 1. Glass fibre-reinforced polymer composites: Properties: Lower density Higher tensile strength and impact resistance Excellent resistance to corrosion and chemicals Applications: To make automobile parts, storage tanks, transportation industries and plastic pipes, etc. 21

22 2.Carbon fibre-reinforced polymer composites: Properties: Excellent reistance to corrosion Lighter density & Maintain the strength even at high temperature Applications: To make structural components of aircraft & helicopters. To make sports goods, fishing rods, etc 3. Armid fibre-reinforced polymer composites: Type: 1. Short fibre-reinforced composites: Properties: High aspect ratio, High surface area & Inherent toughness High strength, Heat stability & wear resistance. Applications: To make automobile brakes and clutches. Type: 2. Long fibre-reinforced composites: Properties: Capable to absorb energy High ductility Good compressibility Applications: To make commercial aircrafts, helicopter parts (blades, motor housing),and protective apparel (thermal and ballistics), etc. 4. Alumina &/or carbon fibre-reinforced metal composites: properties: High specific strength, stiffness & abrasion resistance High creep resistance & dimensional stability. Low density, wear resistance, resistant to thermal distortion Applications: Matrix-Al alloy used to make components of engine in automobile industry. Matrix-Ni and Co based alloy used to make components of turbine engines. ***************** 22

23 References: Engineering chemistry 15 th Edition By Jain and Jain, Dhanpat Rai Publishing Company, New Delhi. Engineering chemistry S.S. Dara, S.Chand & Co., New Delhi. Text Book of Physical chemistry by R.D. Madan, S. Chand & Co. New Delhi. Part A Question Bank: 1. Define polymer with an example. 2. What is meant the degree of polymerization? 3. Write any two examples for homopolymer and heteropolymer. 4. What is meant by polymerization? 5. Distinguish addition and condensation polymerization. 6. Define monomer with any two examples. 7. Define thermoplastics. Give any one example. 8. Define thermosetting plastics. Give any one example. 9. Write down the repeating units of PET and Nylon 6, Write the monomers of Nylon Name any two synthetic polymers which are used for making textile fibres. 12. What is meant the term vulcanization of rubber? Mention its uses. 13. What is the main purpose of vulcanization? 14. What is an elastomer? 15. Why cannot thermosetting plastics be reused and reshaped? 16. Why are plastics indispensable in everyday life? 17. What is addition polymerization? Give one example. 18. What is condensation polymerization? Give one example. 19. Write down the steps involved in the free radical polymerization. 20. What are plastics? Give any two examples. 21. What are the advantages of plastics? 22. Mention any four drawbacks of plastics. 23. Differentiate thermoplastics from thermosetting plastics. 24. Name the monomers of polycarbonate. 25. Why is Teflon used in the electric appliances? 26. Why is Teflon highly chemical resistant? 27. Give the preparation and uses of PVC. 23

24 28. Give the preparation and uses of PTFE. 29. What are the repeating units present in Nylon 66 and PET? 30. Differentiate between homo chain polymer and hetero chain polymers. 31. PVC is soft and flexible whereas bakelite is hard and brittle. Give reason. 32. Give the preparation of polycarbonate. 33. Give the preparation of Nylon How will you synthesize Dacron? 35. Write a note on Polyurethane. 36. State the monomers used in the following: a. Butyl rubber b. Terrylene c. PVC d. Merlon e. SBR 37. Distinguish elastomers from plastics. 38. What is meant by FRP. 39. Write a note on natural rubber. Give two examples. 40. What are composite materials? Give two examples. 41. What are synthetic rubbers? Give two examples. 42. Give the preparation of butyl rubber. 43. Give the preparation of SB rubber. 44. Mention any four advantages of vulcanization. 45. Write any four drawbacks of natural rubber. 46. Mention any four applications of rubber 47. List the characteristics of composite materials. 48. Mention any four applications of composite materials. 49. Write down the types of FRC. Part B 1. Distinguish between thermoplastics and thermosetting plastics. 2. Differentiate addition and condensation polymerizations. 3. Discuss the free radical mechanism of addition polymerization. 4. Explain addition and condensation polymerization with suitable examples. 5. a) What is meant by vulcanization of rubbers. Mention its uses. b) Explain why natural rubber needs vulcanization. How is it carried out? 6. Discuss briefly the process of vulcanization of rubber. 7. What are elastomers? Give preparation and applications of butyl rubber and SB Rubber. 24

25 8. Describe the method of preparation, properties and applications of the following polymers. a) PVC b) PC c) PTFE 9. Describe the method of preparation, properties and applications of the following polymers. a) PU b) Nylon 66 c) PET 10. Discuss the potential applications of polymer reinforced concrets in any three of the following fields: Transportation, aircraft & aeroplane, construction, corrosion, resistance material and electric industries. 11. What are composite materials? Discuss the type of polymer matrix composites. ******************************************** ASSIGNMENT QUESTIONS 1.Discuss the free radical mechanism. 2. Differences between addition and condensation polymerizations. 3. Explain addition and condensation polymerization with suitable examples. 4. Explain the process: Vulcanization of rubber. 5. Differences between thermoplastics and thermosetting plastics. 6. Discuss the preparation, properties and applications of the following polymers. a) PVC b) PC c) PTFE d) PU e) Nylon 66 f) PET 7. Explain about composite materials. 8. Explain the preparation, properties and uses of butyl rubber and SB rubber. ********* OBJECTIVE TYPE QUESTIONS WITH ANSWERS : 1. Define the word mer a)many b) More c) Parts d)cloth 2. Polymers are generally a)micro molecules 25

26 b) Macromolecules c) Nanoparticles d) Atoms 3. Monomers can be defined as a)repeated linkage of molecules b)repeated units c) Repeated atoms d) All the above 4. DP is explained as a) Number of repeating units in a polymer b) No of macromolecules c) No of polymers in polymer d) None of these 5. Thermoplastics are held together by a) Chemical bonds b) Vanderwaal s forces of attraction c) Covalent bonds d) Ionic bonds 6. Bakelite is not dissolved in benzene because a) Bakelite is a thermosetting resin b) Benzene is an inorganic solvent c) Benzene is an organic solvent d) a,c both. 7. Thermosetting resins are formed by a) Addition polymerization b) Condensation-polymerization c) Co-polymerization d) compensation polymerization 8. Thermo plastics are formed by a) Condensation polymerization b) Concentration polymerization c) Addition polymerization d) Co-polymerization 9. Thermoplastics are weak, soft because, a) Strong covalent bonds between the chains b) Weak vanderwaal s forces c) Strong physical forces d) Ionic bonds 10. Thermoplastics forms linear polymers because it follows, a) Condensation polymerization b) Addition polymerization c) Co-polymerization d) Graft-copolymerization 11.Find out the Degree of polymerization for the following polymer POLYETHYLENE (CH2-CH2-CH2-CH2-CH2-CH2) 26

27 a) 4 b) 3 c) 5 d) Molecular weight of high polymers, a) b) c) d) 10,000-2,00, Linear homopolymer can be expressed like the following a) A-A-A-A-A-A b) A-A-A-A-A / A-A-A c) A-A-A-A / A-A-A-A / A-A-A-A d) A-A-A-A-B-B-B-B 14. Addition polymerization reaction can be identified by the following 1. It should contain double or triple bonds 2. Elimination of byproducts 3. No elimination of by products 4. It should not contain double or triple bonds a) 1,3 only b) 1,4 only c) 1,2,3 d) only Condensation polymerization can be identified by the following condition 1) Reaction between simple polar groups 2) Elimination of small by products 3) No elimination of by products 4) All the above. a) 1,2 only b) 1,3 only c) 1,2,3,4 d) only Condensation polymerization can also be called as a) Chain polymerization b) Chain growth polymerization c) Stepwise polymerization d) Step step polymerization 17. The following one is the mechanism of addition polymerization 27

28 a) Ionic mechanism b) Co-operation mechanism c) Co-ordination mechanism d) None of these 18. Which is not a step of a free radical mechanism? a) Initiation b) Initiator c) Propagation d) Termination 19. It is not an advantage of plastics a) Light in weight b) Easily moulded c) Low heat resistance d) High resistance to abrasion 20. Thermoplastics formed by using a) Condensation mechanism b) Addition polymerization c) co-polymerization d) All the above. 21. Percentage of purpose plastics production in the world a) 60 % b) 75% c) 90% d) 85% 22. During dehydrocholorination of ethylene dichloride in vapour phase amount of temperature is needed. a) c b) c c) c d) c 23. This is not commercially available PVC a) Exon b) Neon c) Geon d) Velon 24. It is not a property of PVC a) Good strength b) Lightness c) Soluble in acids d) Chemical resistance 25. PVC is used in the form of sheets like the following a) Pipes b) Rain coats c) Motor cycle mudguards d) Cables 28

29 26. Find out the monomer of Teflon a) CH2=CH2 b) CF2=CF2 c) CF2-CF2 d) CF2=CH2 27. Polymerization of Teflon at elevated pressure in presence of water using initiator such as, a) PdO2 b) PtO c) H2O2 d) NiO2 28. During the preparation of monomer of Teflon the following chemicals are used a) CaF2,Cl2 b) H2SO4 c) HF d) All the above. 29. It is not a property of Teflon a) Affected by water b) No attack of corrosive reagents c) High thermal stability d) Low co-efficient of friction 30. Teflon is also called as, a) Neon b) Fluon c) Geon d) Tygon 31. Teflon is used to prepare a) Mudguards b) Plugs c) Gaskets d) None of these 32. These are the monomers of polycarbonates a) Dibutylcarbonate, Bisphenol A b) Diphenyl carbonate, Biphenyl c) Calcium carbonate, Naphthalene d) Diphenyl carbonate, Bisphenol A 33. Teflon is dissolved in benzene because, a) It is an inorganic solvent b) It is a n organic solvent c) Teflon Is a polymer d) Teflon is a monomer 34. Monomers of polyurethane are, a) 1,4 Butanediol, 1,6- hexanediisocyanate b) 1,4-octanediol, 1,6 hexamediisothiocyanate c) Diphenyl carbonate, Bisphenol A d) Hexamethylene diamine, Adipic acid 29

30 35. Match the following 1) Teflon Lexan 2) Polycarbonate Perlon-U 3) Polyurethane Nylon 6,6 4) Polyamide Fluon a) 2,3,1,4 b) 2,3,4,1 c) 3,2,1,4 d) 4,1,2,3 36. The following polymer which is used to prepare swim suits a) Polycarbonate b) Perlon-U c) Teflon d) PVC 37. The common representation of amide is a) CONH2 b) NCOH c) HCON d) CNOH 38.Nylon is a a) Synthetic aromatic polyamide b) Natural aromatic polyamide c) Synthetic aliphatic polyamide d) Natural aliphatic polyamide 39. Nylon6, Nylon 6,6 and Nylon 6,10. The number represents a) Number of nitrogen atoms b) Number of hydrogen atoms c) No of oxygen atoms d) No of carbon atoms 40. Monomer of Nylon 6,6 is a) Heptamethylene diamine, alitic acid b) Hexamethylene diamine, adipic acid c) Pentamethylene diamine, sabasic acid d) Hexamethylene diamine,sabasic acid 41. Nylon 11 can be prepared from a) D-amino undecanoic acid b) β- amino undecanoic acid c) ω-amino undecanoic acid d) µ-amino undecanoic acid 42. Melting point of nylon is a) c b) c c) c d) c 30

31 43. How PET is prepared a) Reaction of ethylene glycol with terephthalic acid b) Reaction of ethylene glycol with Bisphenol A c) Reaction of ethylene glycol with Epichlorohydrin d) Reaction of glycol with Bisphenol A 44. Plastizers are used for a) Giving elasticity b) Giving thermal stability c) To reduce the cost d) To provide the colour 45. Fillers are used to a) Provide the colour b) To provide the thermal stability c) To reduce the cost d) All the above 46. In compression moulding the following temperature, pressure is used a) c & kg/cm 2 b) c & kg/cm 2 c) c & kg/cm 2 d) c & kg/cm It is not an advantage of an injection moulding a) High mould cost b) Low finishing cost c) Low loss of materials d) High speed production 48. Nylon 11 is prepared by a) Addition polymerization b) Co-polymerization c) Self condensation polymerization d) Condensation reaction without any byproduct. 49. HDPE is prepared under a) High pressure with Ziegler Natta catalyst b) Low pressure with Pt catalyst c) Low pressure with Ziegler Natta catalyst d) Low temperature with catalyst. 50. During disproportionation step in addition polymerization we are getting, a) Two saturated macromolecules b) Two unsaturated macromolecules c) Both saturated and unsaturated macromolecules d) Two unsaturated and one saturated macromolecules 51. Vulcanization is the process of addition of a) Mn b) Fe c) Br d) S 31

32 52. It is an advantage of a vulcanized rubber a) Good tensile strength b) Low elasticity c) Slight tackiness d) All the above 53. It is used to manufacture motor cycle tyres a) Buna S rubber b) GR-I c) Natural rubber d) Vulcanized natural rubber 54. The molecular weight of raw rubber is a) 10,000 15,000 gms b) 1,00,000 1, 50,000 gms c) 1,00,000 5,00,000 gms d) gms 55. PET is prepared by the condensation polymerization of terephthalic acid and ethylene glycol in medium. a) Acidic b) Basic c) Neutral d) All the above ANSWERS : 1. c 2.b 3.b 4.a 5.b 6.a 7.b 8.c 9.b 10.b 11.b 12.d 13.a 14.a 15.a 16.c 17.d 18.b 19.c 20.b 21.d 22.d 23.b 24.c 25.c 26.b 27.c 28.d 29.a 30.b 31.c 32.d 33.b 34.a 35.b 36.b 37.a 38.c 39.d 40.b 41.c 42.b 43.a 44.a 45.c 46.a 47.a 48.c 49.c 50.c 51.d 52.d 53.a 54.b 55.b ****************************** UNIT III SURFACE CHEMISTRY ASSIGNMENT QUESTIONS : 1. Derivation of langluir s adsorption isotherm 2. Explain the factors affecting the adsorption of gases on solids. 3. Application of adsorption. 4. explain the contact theory. 5. Difference between the physisorption and chemisorption 6. Explain the adsorption of solute from solution 32

33 7. How activated carbon used in pollution abatement 8. Explain the Freundlich s adsorption isotherm. 9. Explain the ion exchange adsorption. OBJECTIVE TYPE QUESTIONS : 1. When compared to liquids solids are having large adsorption characteristic because of its a) Large concentration b) Large surface area c) Large surface tension d) Less surface area 2. The solid that takes up a gas or vapour or a solute from a solution is called a) Absorbent b) Adsorption c) Adsorbent d) Absorption 3. The gas or solute which is held to the solid surface is called a) Adsorbate b) Absorbate c) Adsorbent d) Sorption 4. Absorption is a) Substance is randomly distributed b) The substance is uniformly distributed on a particular place c) The substance is uniformly distributed throughout the body of the solid or liquid. d) All the above 5. Ammonia is aadsorbed in water. For the above statement findout the adsorbent and adsorbate. Adsorbent adsorbate a) Water Ammonia b) Ammonia Water c) Ammonia Ammonia d) Water Water 6. Adsorption is a) Bulk phenomenon b) Built phenomenon c) Surface phenomenon d) Both a,c 7. Sorption is a a) Surface phenomenon 33

34 b) Bulk phenomenon c) Built phenomenon d) Both adsorption and absorption 8. The released of absorbed substances into the surrounding medium is called a) Sorption b) Desorption c) Adsorption d) Desorbent 9. The following pair is the correct classification of adsorption a) Chemical adsorption,electrical adsorption b) Mechanical and electrical adsorption c) Physical and mechanical adsorption d) Physical and chemical adsorption 10. When the temperature raises means this adsorption is decreases a) Physical adsorption b) Chemical adsorption c) Sorption multi adsorption 11. Heat of adsorption is very low in the case of a) Chemisorption b) Electrical adsorption c) Physisorption d) Sorption 12. Adsorption is a a) Endothermic process b) Exothermic process c) Random process d) Both a,b 13. Findout the factors not affecting the adsorption a) Temperature b) Pressure c) Concentration d) Nature of the adsorption 14. When compared to HCl, the H2 gas posses less adsorption nature because of a) High vanderwaal s forces b) Low vanderwaal s forces c) Chemical bonds d) Both a,c 15. When the surface area increases what about the adsorption a) Decreases b) Considerable change c) Increases 34

35 d) No change 16. Freundlich adsorption isotherm is represented as a) x/m = kp n b) x/n = kp m c) k/c = mk p d) pn k = m/x 17. This is not a limitation of freundlich s adsorption isotherm a) Equation is purely empherical b) Valid only upto certain pressure c) K,n are pressure dependent d) K,n are temperature dependent. 18. The adsorbed gas behaves ideally in phase. a) Vapour b) Liquid c) Solid d) All 19. The freundlich adsorption isotherms fails when the concentration of adsorbate is a) Low b) Very high c) high d) very low 20. Freundlich adsorption isotherm valid only upto certain and fails at higher a) Temperature b) Concentration c) ph d) pressure 21. The maximum amount of adsorption is called as a) Saturation b) Neutralization c) Filteration d) None of these 22. adsorption of N2 on charcoal at a) c b) c c) c d) c 23. During permuit process ( zeolite) releases ions after softening. a) Mg 2+ b) Na + c) Ca 2+ 35

36 d) K Colloidal ferric hydroxide is used to remove poison from our body. a) Arsenic b) Antimony c) Mercury d) All the above 25. Colloidal silica and alumina gel used for removing the of the room. a) Temperature b) Humidity c) Pressure d) Light 26. The scarcity of water in foreigh countries can be avoided by adding a) Lactic acid b) Stratic acid c) Palmitic acid d) Acetic acid 27. Activated carbon acts as a good adsorbent because it posses, a) Large size b) More active c) More surface area d) Most powerful decolourant. 28. Activated carbon is able to adsorb any organic solvent at about F and release it on heating at F. a) 50 & F b) 60 & F c) 150 & F d) 100 & F+ 29. AC can able to remove the constituents from water a) COD b) Colour c) Phenol d) All the above 30. GAC can be differ from PAC by its a) Diameter b) Concentration c) Temperature d) Pressure 31. In direct process activation is carried out by heating char particles in retorts at a) c 36

37 b) c c) c d) c 32. Activation of char particles cannot be activated by the following a) Direct process b) Indirect process c) Briquetting process d) Chemical process 33. In sugar industries it is used as a decolourizing agent, a) Silica gel b) Alumina gel c) Colloidal ferric hydroxide d) Activated carbon 34. Activated carbon removes colour because of its. a) Large surface area b) Large pore volume c) Small in size d) All the above 35. It is used to remove the taste from water, vegetable, animal fats a) Carbohydrate b) Aromatic hydrocarbon c) Carbon d) Activated carbon 36. In physisorption the rate of adsorption increases with increase of pressure of the a) Adsorbent b) Adsorbate c) Sorption d) Metal surface 37. In chemisorption, adsorption increases with increase of a) Temperature b) Concentration c) Pressure d) Size of the adsorbent 38. This adsorption depends on the surface area of the adsorbent. a) Physisorption b) Chemisorption c) Both a,b d) None of these. 39. The adsorption of gas on a solid adsorbent in a closed vessels is a a) Revert b) Reversible c) Irreversible 37

38 d) All the above 40. The adsorption isotherm is a relationship between the magnitude of adsorption with pressure at constant. a) Temperature b) Pressure c) Concentration d) Volume 41. In chemisorption adsorption increases with of pressure of the adsorbate. a) Increases b) Decreases c) Average change d) None of these. ANSWERS: 1. b 2.c 3.a 4.c 5.b 6.c 7.d 8.b 9.d 10.a 11.c 12.b 13.c 14.a 15.c 16.a 17.c 18.a 19.b 20.d 21.a 22.c 23.b 24.a 25. b 26.b 27.c 28.d 29.d 30.a 31.c 32.b 33.d 34.d 35.d 36.b 37.a 38.c 39.c 40.a 41.a 38