Module-3 macromolecules for engineering applications.pptx

Macromolecules for engineering applications is the Module 3 syllabus for applied chemistry for Mechanical stream of 1st year BE students in VTU. It mainly includes regarding polymers, synthesis of various polymers and its properties and applications, composites and lubricants.

1. Module 3: Macromolecules for Engineering applications Dr. MALLIKARJUNA H R Associate Professor Department of Chemistry

2. Introduction: Polymers form a very important class of materials without which the life seems very difficult. They are all around us in everyday use; in rubber, in plastic, in resins, and in adhesives and adhesives tapes. Polymers have existed in natural form since life began and those such as DNA, RNA, proteins and polysaccharides play crucial roles in plant and animal life.

3. The word polymer is derived from greek words, meaning poly “many” and mers “parts” Polymers: are macromolecules, which are obtained by covalently linking large number of small molecules, called monomers. Polymerization: The reaction by which the monomers combine to form polymer is known as polymerization

4. Methods of polymerization: Addition polymerization This type of polymerization involves step wise addition of monomer unites initiated by initiators The formation of polyethylene, polypropylene and polystyrene is an example of addition polymerization Condensation polymerization Condensation polymerization, a form of step-growth polymerization, is a process by which two molecules join together, resulting loss of small molecules such as water, ammonia, HCl etc

5. Molecular weight of polymers : Number Average Molecular Weight ( The number average molecular weight is the statistical average molecular weight of all the polymer chains in the sample and is given by   where, M 1 , M 2 , M 3 ............ M i is molecular weight of polymer chains and n 1 , n 2 , n 3 ................ n i is number of chains of that molecular weight.  

6. Weight average molecular weight ( The weight average molecular weight is given by     where, w and M represent the weight and molecular mass of each species.Since , w = nM , the above equation can be written as ,  

7. C-polyvinyl chloride or Chlorinated polyvinyl chloride (C-PVC): Synthesis : The monomer vinyl chloride is treated with peracid under pressure to obtain polyvinyl chloride (PVC). PVC is then subjected to a chlorination reaction initiated by UV light in a water slurry or fluidized bed chlorination process to get C-PVC. In PVC , a chlorine atom occupies 25% of the bonding sites on the carbon backbone where as 40% of the bonding sites on the backbone are filled with chlorine atoms in C-PVC.

8. Properties: CPVC is a linear polymer and thermoplastic in nature. CPVC is inherently inert to acids, bases, and is corrosion resistant. CPVC has excellent mechanical properties, it is rigid and can with stand high pressure and stress. CPVC has high tensile strength even under high temperatures. CPVC has increased temperature resistance compared to PVC. CPVC has higher glass transition temperature ( Tg ) compared to PVC. CPVC has excellent dielectric properties

9. Applications CPVC are used for hot-water supply pipes up to 90°C, and it has high tensile strength even under high temperatures. CPVC has corrosion resistance properties hence its used in industrial liquid handling. CPVC are used in handling agricultural fertilizers and irrigation, as well as drain, waste, and venting pipes. CPVC is commonly used as insulation on electric wires. CPVC is used in commercial plumbing, chemical processing, mineral mining, electrical power production, and water, wastewater treatment.

10. Fibres Fibres are elongated and thread-like structures where in the molecules are woven resulting in the linear string like assembly that are thin, long, and flexible. They are widely used in various industries, including textiles, construction, composites, and medical materials. The fibres can be broadly classified in two types, 1. Natural fibres : obtained from plants and animals 2. Synthetic fibres : man made

11. Kevlar fibers: Synthesis properties and applications Kevlar fibers: is the registered trademark for are a class of heat-resistant and strong synthetic fibers of aromatic polyamide (para-aramid). Synthesis : Kevlar is synthesized by condensation polymerization by reacting 1,4-phenylene-diamine ( p - phenylenediamine ) and 1,4-benzenedicarbonyl chloride ( terephthaloyl chloride) in the presence of N-methyl- pyrrolidone (NMP) solvent by the elimination of hydrochloric acid as a byproduct at <20 °C

12. Properties Kevlar fibre is strong and light weight High tensile strength and High impact strength Flame retardant Resistant to air, ozone , oil, and water Resistant to corrosive chemicals but on longer exposure to acids and alkalis Kevlar fibre disintegrates. Thermal insulating property and stable up to 450 °C.

13. Applications: Kevlar is a well-known component of personal armor such as combat helmets, ballistic face masks, and ballistic vests. It is used as an inner lining for some bicycle tires to prevent punctures. In table tennis, plies of Kevlar are added to custom ply blades, or paddles, in order to increase bounce and reduce weight. Used in rope, cable, substitute for Teflon in frying pans.

14. Polyester: Synthesis properties and applications Synthesis : Polyester are usually synthesized by condensation polymerization by reacting dicarboxylic acids and diols at elevated temperature with the elimination of water molecule as a byproduct. It can also be synthesized by reacting benzenedicarbonyl chloride and diols in basic solvents (DMF, NMP) by the elimination of hydrochloric acid as a byproduct at room temperature

15. Properties Strong, resilient, durable, and non-biodegradable Resistant to shrinking, wrinkle and stretching. Resistant to moisture and several chemicals. Its hydrophobic and dries quickly. Polyester does not get affected by bleaching process. Resistant to abrasions, moulds , and fungus. Can be recycled.

16. Applications: Polyesters are also used to make bottles, toys, films, and tarpaulin. Polyesters are used as fabric material (shirts, jackets, etc ). Polyesters are employed in the manufacture of many home furnishing materials such as bed sheets, curtains, blankets, and pillowcases. They are used in liquid crystal displays, holograms, and filters They are used as dielectric film for capacitors. They are used as film insulation for wire and insulating tapes. Because of its water-resistant properties, it is used to make sportswear

17. Poly(methyl methacrylate) (PMMA) : PMMA is synthesized by via a free radical polymerisation of methyl methacrylate in emulsion form at 60-70  C in presence of hydrogen peroxide as initiator .

18. Properties : PMMA is a strong and lightweight material. PMMA melts at 160  C Transparency and glass finish. It also has good impact strength, higher than glass. Hardness and resistance to scratching. Excellent resistance to sun rays (ultraviolet radiation) and weathering aging.

19. Applications : PMMA has good shatter-resistant properties and is a good substitute for glass. PMMA in the form of sheets are used for building windows, skylights, bullet proof security barriers, sanitary ware (bathtubs), Used as lenses and UV Filters Automotive headlamps. Used as LCD screens. PMMA was used in Laser Disc optical media. ( CDs and DVDs ) Used extensively in medical and dental applications because of its biocompatibility. Its extensively used in orthopedic surgery as bone substitutes, Used in fabrication of artificial teeth, bone cement is used to affix implants

20. Teflon (Polytetrafluoroethylene) PTFE is synthesized by free-radical polymerization of by passing tetrafluoroethylene (TFE) into water containing a radical initiator , ammonium persulfate, [(NH 4 ) 2 S 2 O 8 ], at 65-75 °C and a pressure of 10-20 atm.

21. Properties : Teflon is a thermoplastic polymer , which is a white solid at room temperature, Teflon has a melting point of 327 °C Highly flexible, chemical resistant, thermal resistant, non-stick and electrically resistant material. It has low coefficient of friction. It maintains high strength, toughness and self-lubrication at low temperatures down to −268.15 °C, and good flexibility at temperatures above −79 °C Highly insoluble in water, and most of the organic solvents

22. Applications : PTFE is used as a non-stick coating for pans and other cookware . It is very non-reactive, partly because of the strength of carbon–fluorine bonds and so it is often used in containers and pipework for reactive and corrosive chemicals. When used as a lubricant , PTFE reduces friction, wear and energy consumption of machinery. It is also commonly used as a graft material in surgical interventions.

23. Composites Composites are materials made from two or more different constituent materials, typically a matrix material and a reinforcement material , that are combined to create a new material with enhanced properties . The constituent materials can be either natural or synthetic and can have different physical, chemical, and mechanical properties.

24. Carbon-based reinforced composites Carbon-based reinforced composites are a type of composite material where the reinforcement material is made of carbon-based structures, such as graphene and carbon nanotubes (CNTs), which are embedded within a matrix material, such as a polymer, metal, or ceramic.

25. Metal matrix polymer composites MMPCs are composite materials made up of a metallic matrix and a polymer reinforcement. MMPCs combine the advantages of metals, such as high strength, ductility, and thermal conductivity, with the benefits of polymers, such as low density, toughness, and ease of processing. In MMPCs, a metallic matrix, such as aluminum, magnesium, or copper, is reinforced with a polymer, such as nylon, polypropylene, or polyester. The polymer reinforcement is typically in the form of fibers or particles, and it is embedded within the metallic matrix.

26. Lubricants Lubricants are substances that are used to reduce friction and wear between two surfaces that are in relative motion. They are used to facilitate smooth movement and improve the efficiency and durability of machinery and equipment. Lubricants can be in the form of liquids, such as oils, or solids, such as graphite or molybdenum disulfide. They can also be in the form of semi-solids, such as greases, which consist of a thickened oil.

27. Classification 1. Mineral oils: These are petroleum-based oils that are the most commonly used lubricants. They are produced by refining crude oil and can be further refined and processed to improve their properties. 2. Synthetic oils: These are man-made lubricants that are designed to provide superior performance in specific applications. They are made by synthesizing chemical compounds and can have properties that are not found in mineral oils. 3. Vegetable oils: These are derived from plant sources, such as soybeans, canola, and sunflower. They are used as lubricants in some applications, such as in environmentally sensitive areas, due to their biodegradability.

28. 4. Greases: These are lubricants that are a combination of a base oil and a thickener, which gives them a semi-solid consistency. They are used in applications where it is not feasible to use liquid lubricants, such as in high-pressure or high-temperature environments. 5. Solid lubricants: These are lubricants that are in the form of solids, such as graphite, molybdenum disulfide, and PTFE (polytetrafluoroethylene). They are used in applications where liquid or semi-solid lubricants are not effective, such as in high-temperature or vacuum environments.

29. Properties: Lubricants have several properties that are important for their function and effectiveness in reducing friction and wear between two surfaces. High viscosity, Better Flash Pour point Excellent oxidation stability Corrosion resistance Excellent film forming ability and strength on surface.

30. Applications : Engine lubrication Gear and transmission lubrication: Lubricants are used in hydraulic systems to reduce friction and wear between moving parts, such as pistons, cylinders and bearing Lubricants are used in compressors to reduce friction and wear and prevent overheating of the compressor. Lubricants are used in metalworking to reduce friction and heat during machining, cutting, and grinding. Lubricants are used in marine applications to reduce friction and wear between engine components and prevent corrosion in saltwater environments. Lubricants are used in food and pharmaceutical manufacturing to prevent contamination and ensure hygiene. Lubricants are used in electrical systems, such as transformers and switchgear, to reduce friction and wear and prevent overheating.