introductionnnnnnnn to polymerrrrrrr1.pptx

introductionnnnnnnn to polymerrrrrrr1.pptx

1. Key points to remember: Polymer:  A molecule made up of many repeating subunits (monomers) linked together.  Macromolecule:  A very large molecule, which can be made up of repeating units (like in a polymer) or different types of subunits that don't repeat.  Example: Polymer:  A strand of DNA, where the repeating subunit is a nucleotide.  Macromolecule not a polymer:  A lipid molecule, which can be made up of different fatty acid chains and glycerol, not repeating units.  A polymer is a large molecule or a macromolecule, which essentially is a combination of many subunits. Polymers  are long chain; giant organic molecules are assembled from many smaller molecules called  monomers . A chemical reaction forming polymers from monomers is called  polymerization

2. semi synthetic polymers

3. Man made Cross-linked polymers are insoluble in all solvents because the polymer chains are tied together by strong covalent bonds .

4. The process by which these small units (simple molecules or monomers) transform into a polymer is called the process of polymerization or simply polymerization. Let’s look at a polymerization example of ethylene: n CH2 = CH2 → (CH2 - CH2-)n Ethylene         Polyethylene polymerization

5. Plasticizers : Certain plastics do not soften much on heating. These can be easily softened by the addition of some organic compounds which are called plasticizers. For example, polyvinyl chloride (PVC) is very stiff and hard but is made soft by adding di-n- butylphthalate (a plasticizer). Some other common plasticizers are dialkyl phthalates and cresyl phthalate. Bakelite, melamine, formaldehyde resin Examples are polystyrene,, PVC, SBR, Teflon, PMMA, terylene .

6. Broadly polymerization can be classified into two categories , Step-Growth or  Condensation Polymerization Chain-Growth or Addition Polymerization Addition Polymerization As the name suggests addition polymers form when an addition reaction occurs. The repeating monomers form a linear or branch structure depending on the type of monomer. During addition polymerization, the monomers rearrange themselves to form a new structure. But there is no loss of an atom or a molecule. Again there are four types of addition polymerizations which are Free Radical Polymerization: Here the addition polymer forms by addition of atoms with a free electron in its valence shells. These are known as free radicals. They join in a successive chain during free radical polymerization. Cationic polymerization: A polymerization where a cation is formed causing a chain reaction. It results in forming a long chain of repeating monomers Anionic Vinyl Polymerization: Involves the polymerization of particularly vinyl polymers with a strong electronegative group to form a chain reaction’ Ex-Styrene Coordination Polymerization: This method was invented by two scientists Ziegler and Natta who won a Nobel Prize for their work. They developed a catalyst which let us control the free radical polymerization. It produces a polymer which has more density and strength.

7. Tacticity is a chemical concept that describes the relative stoichiometry of adjacent  chiral centres  in a macromolecule. A macromolecule is a large molecule such as a  polymer . Tacticity is important in determining the properties of a polymer. It is because the structure of a polymer regulates other properties like rigidity, crystallinity, etc. An atactic polymer is a polymer material where the substituents in a carbon chain are arranged in a random manner. Usually, polymers that form via  free radical polymerization  has this structure; for example, polyvinyl chloride. Atactic polymers have an  amorphous  structure due to the random arrangement of substituent groups. An isotactic polymer is a polymer which has the substituents on the same side of the carbon chain. That means; all the substituents of the polymer material are located on the same side of the backbone of the polymer. For example, industrially prepared polypropylene is isotactic. Syndiotactic polymers are polymer materials which have the substituents in an alternating pattern. Therefore, substituent groups have alternate positions along the backbone of the polymer.

8. Types of Polymers There are many types of polymers including synthetic and natural polymers. Natural biopolymers Polypeptides in  proteins  - silk, collagen, keratin. Polysaccharides ( Carbohydrate chains ) -  cellulose ,  starch ,  glycogen Nucleic acids  -  DNA  and RNA Synthetic polymers Plastics Elastomers - solids with rubber-like qualities Rubber  (carbon backbone often from hydrocarbon monomers) silicones  (backbone of alternating silicon and oxygen atoms). Fibers Solid materials of intermediate characteristics Gels or viscous liquids

9. Polymerization manufacturing process

10. Polymerization manufacturing process

11. Polymerization manufacturing process

12. LDPE Process conditions Pressure 1000-2500 atms Temperature 100-300 o C peroxide catalyst

13. High Density Polyethylene (HDPE) HDPE  is a type of polyethylene, the most common plastic, which accounts with more than 34% of the global plastic market. It is a polymer composed of a large number of repeating units (known as monomers), and its chemical formula is (C2H4)n. When compared to other polyethylene categories, high-density polyethylene has comparatively little branching.  HDPE is known for its high strength-to-density ratio and is widely used in plastic bottles, pipes, geo membranes, and plastic lumber applications. Its strong molecular structure makes it resistant to chemicals and moisture, making it suitable for various containment and packaging applications. Low Density Polyethylene (LDPE) LDPE stands for low-density polyethylene. LDPE is less dense than other linear polyethylenes like HDPE. It is known for its light, flexible, and soft plastic yet tough nature. However, LDPE low-density polyethylene is not suitable for applications where high temperature and stiffness are a top priority. LDPE is used for manufacturing various containers, dispensing and squeezing bottles, tubing, plastic parts of computer components, molded laboratory equipment, and many caps and closures. It is robust enough to be almost unbreakable.  HDPE Properties Highly resistant to various chemicals Outstanding impact strength Weather resistance Moisture resistance Highly recyclable LDPE Properties Good flexibility Translucent High tensile strength Tear and corrosion resistance Low water absorption HDPE Uses HDPE pipes and fittings Chemical containers Picnic ware Pond liners Milk pack Shampoo bottles LDPE Uses Plastic bags Stretch and shrink films Plastic wraps Squeeze bottle LDPE plastic wire

14. Additives used in Polymer

15. Bakelite is a polymer made up of the monomer's phenol and formaldehyde. This phenol-formaldehyde resin is a thermosetting polymer. When the phenol is taken in excess and the reaction medium is made acidic , the product of the  condensation  reaction obtained is acidic. Whereas, when the quantity of formaldehyde taken is more than that of phenol in the reacting mixture, and the reaction occurs in a basic medium , the condensation product is known as Resol . Bakelite is obtained when Novolac is allowed to undergo cross-linking in the presence of a cross-linking agent. In general, phenol taken in excess acts as the cross-linking agent. .

16. Some important properties of bakelite are listed below. It can be quickly molded. Very smooth molding can be obtained from this polymer. Bakelite moldings are heat-resistant and scratch-resistant. They are also resistant to several destructive solvents. Owing to its low electrical conductivity, bakelite is resistant to electric current.

17. Coarse Particle any natural or synthetic organic compound consisting of a noncrystalline or viscous liquid substance called resin. Raw material: Formaldehyde 1.5 to 2 mol Phenol 1 mole alkaline : Ammonia Resin kettle

18. Polyurethane is a versatile synthetic thermoset polymer. Commonly abbreviated as PUR and PU, it is known for its wide application in various industries and offers excellent properties such as strength, durability, flexibility, and thermal stability. Polyurethane Production Process of Polyurethane The production process of polyurethane involves a chemical reaction between a polyol (alcohol with multiple reactive hydroxyl groups per molecule) and an isocyanate compound. A small amount of a catalyst is often added to stimulate the reaction. This reaction forms a pre-polymer, which is then exposed to additional heat or chemicals to generate the final polyurethane product. The characteristics of the final product can be varied by altering the types and ratios of the initial polyol and isocyanate compounds.

19. Polyurethane (PU) is a polymer having organic units joined by  urethane  (also known as carbamate). Urethane is a compound that has an O-R group and an NH-R group bonded to the same carbonyl carbon. Polyurethanes are prepared by the polymerization of  toluene-2,6-di-isocyanate  and  ethylene glycol.  If the reaction is carried out in the presence of a blowing agent, the product is polyurethane foam.

20. Properties of Polyurethanes 1. Polyurethane has high load capacity in both tension and compression that may change shape under heavy load but will return to its original shape once the load is removed with little compression. 2. Polyurethanes possess  high tear resistance  along with high tensile properties. 3. Polyurethane material will remain stable with minimal swelling in water, oil, and grease. 4. Polyurethanes exhibit good electrical insulating properties.

21. Applications of Polyurethane Polyurethane finds use in many everyday items due to its incredible versatility. This is attributable to the many forms it can take, such as rigid foam, flexible foam, elastomers, and coatings , each suited to specific applications. Foams:  Foams are the most common form of polyurethane, seen in items like furniture, bedding, and automotive seating. Rigid polyurethane foam is an excellent insulation material for refrigerators and homes . Elastomers:  As an elastomer, polyurethane is resistant to wear and tear, making it suitable for industrial parts and consumer products like shoes and sports equipment. Adhesives and Binders:  Polyurethane adhesives offer high strength, flexibility, and resistance to impact, heat, and chemicals. They’re used in many applications such as construction, woodworking, and automotive industries. In the form of binders, they are employed in the creation of foundry cores. Coatings and Sealants:  Polyurethane coatings provide a resilient, protective layer against environmental factors. These are often used to enhance the lifespan of infrastructure and machinery, while sealants offer excellent resistance to water, UV, and abrasion, providing a durable finish to a variety of materials.

22. Rubber