Addition polymerization, its examples and uses

Definition, examples, Process, uses, Advantages and Disadvantages

1. ADDITION POLYMERIZATION 1

2. List Of Contents Introduction History Physical properties Mechanism Examples & Uses Advantages & Disadvantages References 2

3. INTRODUCTION 3

4. POLYMERIZATION-ADDITION POLYMERS POLYMERS A polymers are long chain giant organic molecules Formed of many smaller molecules covalently bonded in a repeating pattern Primary components of all sorts of plastics and related compound Consist of many repeating monomer units in long chain MONOMERS Small molecules containing double bond which make up the polymer are called monomers. 4

5. POLYMERIZATION-ADDITION POLYMERS ADDITION POLYMERS A polymer formed by chain addition reaction between monomer units that are repeatedly added to form long chain without the elimination of any by product molecules. Monomers are usually the derivatives of alkenes General reaction is : n is number of monomers have value in hundred or even thousands (1000-30000) 5

6. HISTORY 6

7. HISTORY The first useful addition polymer was made accidentally ICI chemists Reginald Gibson and Eric Fawcett In 1933 At high temperatures and high pressures They set up an experiment to react ethene with benzaldehyde in the hope of producing a ketone. They left the reaction vessel overnight, and the next morning they found a small amount of a white waxy solid. It was shown later that this solid was polyethylene. 7

8. IUPAC definition Chain polymerization: Chain reaction in which the growth of a polymer chain proceeds exclusively by reaction(s) between monomer(s) and active site(s) on the polymer chain with regeneration of the active site(s) at the end of each growth step. The term "addition polymerization" is deprecated by IUPAC (International Union of Pure and Applied Chemistry ). 8

9. PHYSICAL PROPERTIES 9

10. Physical Properties OF Addition Polymers The principal characteristics associated with polymers are a consequence of the nature and covalent arrangement of the monomers units. Covalent bonds do not account for most of polymers. Weaker intermolecular forces between chains must be considered. Hydrogen bonding, electrostatic interactions and van der Waals are believed important than “weaker” interactions. Bonding and nonbonding interactions are important lead to variety of physical characteristics. PVC are sufficiently hard &strong, used in “building materials”. Bakelite is hard but is also brittle. Polymers such as rubber are known as elastomers . 10

11. MECHANISM 11

12. Mechanism of Addition Polymerization The formation of a polymer by addition polymerization is an example of a chain reaction. Once a chain reaction gets started, it is able to keep itself going. The three steps of this reaction to focus on are: how the reaction gets started (INITIATION) how the reaction keeps going (PROPAGATION) how the reaction stops (TERMINATION) A commonly used mechanism involving a free radical Consider an example of polymerization ethylene to form polythene TYPES OF PEROXIDES USED Hydrogen Peroxides H 2 O 2 Benzoic Peroxides (BPO)                      12

13. 1-INITIATION Initiation take place in two parts First Part: A peroxide molecule breaks up into two reactive free radicals. Light or heat can provide the energy needed for this process. We can write an equation for this process: 13

14. INITIATION Second Part: The second part of initiation occurs when the free radical initiator attacks and attaches to a monomer molecule. This forms a new free radical, which is called the activated monomer. We can write an equation for this process, too: 14

15. 2-PROPAGATION In the propagation phase, the newly-formed activated monomer attacks and attaches to the double bond of another monomer molecule. This addition occurs again and again to make the long polymer chain. we can write an equation for this reaction: 15

16. 3-TERMINATION This chain reaction cannot go on forever. The reaction must terminate. A growing polymer chain joins with another free radical. We watched a peroxide break up to form two radicals. It makes sense that two free radicals could join to make a stable bond. The equation representing this step of the chain reaction can be written simply as: 16

17. OVERALL MECHANISM 17

18. EXAMPLES & USES 18

19. 1-POLYETHENE (Polythene) Polyethylene is one of most common polymers, obtained by polymerizing ethylene 19

20. Two Varieties of Polyethylene Low Density Polyethylene Abbreviated as LDPE Produced at a high pressure (about 2000 atm) at evaluated temperatures (near 200 C) Using oxygen, peroxide and free radical as the initiator Used for thin plastic films and other packaging materials High Density Polyethylene Abbreviated as HDPE Produced at a low pressure (about 7 atm) at 60-70 C Ziegler-Natta type catalyst is used Used in the manufacture of toys and other house hold articles 20

21. Ziegler-Natta Catalyst 21

22. USES OF POLYETHYLENE Used to made plastic bottles, plastic bags, toys, house hold articles and harder plastic objects such as milk crates. 22

23. 2-POLYVINYL CHORIDE Polyvinyl chloride also known as PVC is formed by addition polymerization of vinyl chloride (H 2 C= CHCl ) 23

24. USES OF PVC PVC is a hard resin, and is used to make plastic pipes, rods and compact disc PVC is extensively used for plumbing pipes Softer PVC is used for imitation leather, plastic coats, floor covering & plastic squeeze bottles 24

25. 3-POLYISOPRENE Polyisoprene is a polymer of isoprene and is better known as rubber. It is produced naturally by rubber trees, but several variants have been developed which demonstrate improvements on the properties of natural rubber. 25

26. 4-POLYPROPYLENE Prepared by polymerization of propylene using the Ziegler-Natta type catalyst Prepared in isotactic, syndiotactic or atactic form USES: In package films, pipes, storage tanks, seat covers and ropes 26

27. 5-POLYSTYRENE Polystyrene is also known as polyvinyl benzene, industrially produced by free radical polymerization of styrene, using the suspension or bulk technique. The product is an amorphous, brittle material. USES: In insulation & in molded items Used in molded container, lids, jars and bottles 27

28. ADVANTAGES & DISADVANTAGES Addition polymerizations are usually carried out in bulk and solution polymerization 28

29. Advantages and disadvantages of Bulk polymerization ADVANTAGES The system is simple and requires thermal insulation The polymer is obtained pure Large castings may be prepared directly Molecular weight distribution can be easily changed with the use of a chain transfer agent DISADVANTAGES Heat transfer and mixing become difficult as the viscosity of reaction mass increases The problem of heat transfer is compounded by the highly exothermic nature of free radical addition polymerization The polymerization is obtained with a broad molecular weight distribution due to the high viscosity and lack of good heat transfer. Very low molecular weights are obtained. . 29

30. Advantages and Disadvantages of solution polymerization ADVANTAGES Manipulation of polymerization conditions is relatively simple Additives can easily be used and there is a broad range of design possibilities. (Various properties can be achieved.) Thin film coating is possible DISADVANTAGES Uses organic solvents Requires the use of solvent recovery equipment Difficult to use at high concentrations 30

31. References https://www.answers.com/Q/What_are_the_advantages_and_disadvantages_of_addition_polymerisation https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Polymers/Addition_Polymers https://www.materialsworldmodules.org/resources/polimarization/3-addition.html https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Book%3A_Introductory_Chemistry_(CK-12)/25%3A_Organic_Chemistry/25.19%3A_Polymerization_-_Addition_Polymers 31