(Bio-polymer)-CHM-748-classification of polymers.ppt
- 1. 1 C C C C C C H H H H H H H H H H H H Polyethylene (PE) Cl Cl Cl C C C C C C H H H H H H H H H Polyvinyl chloride (PVC) H H H H H H Polypropylene (PP) C C C C C C CH3 H H CH3 CH3 H repeat unit repeat unit repeat unit
- 3. Classification scheme for the characteristics of polymer molecules Molecular configurations isomerism – different molecular configurations for molecules (polymers) of the same composition Stereoisomerism Geometrical Isomerism
- 4. • Random copolymer: A-B-B-A-A-B-A-B-A-B-B-B-A-A-B • Alternating copolymer: A-B-A-B-A-B-A-B-A-B-A-B-A-B • Block copolymer: A-A-A-A-A-A-A-A-B-B-B-B-B-B-B-B Homopolymer When a polymer is made by linking only one type of small molecule, or monomer, together, it is called a homopolymer. Copolymers When two different types of monomers are joined in the same polymer chain, the polymer is called a copolymer. Structures of Polymers
- 5. • Copolymers • polymer that contains more than one repeating unit • If polymer A has interesting properties, and polymer B has (different) interesting properties, making a “mixture” of polymer should lead to a superior polymer “Random” copolymer – exactly what it sounds like “Alternating” copolymer – ABABABA… “Block” copolymers. “Graft” copolymers. One polymer forms backbone, another polymer is attached to backbone and is a sidechain (it is “grafted” to the other polymer)
- 6. 6 Copolymers two or more monomers polymerized together • random – A and B randomly positioned along chain • alternating – A and B alternate in polymer chain • block – large blocks of A units alternate with large blocks of B units • graft – chains of B units grafted onto A backbone A – B – random block graft alternating
- 8. Polymer Structure linear polymer branched polymer star polymer crosslinked polymer dendrimer • Polymers can exist with various skeletal structures skeletal structures - such as linear, branched or cross-linked or network polymers. Network Net-work polymer Direction of increasing strength
- 9. Head-to-head configuration Bonded to adjacent carbon atoms 9 DR. FATHIA GOMAA Molecular configurations Head-to-tail configuration Bonded to alternate carbons on the same side
- 10. 1. Isotactic configuration Stereoisomerism R groups are situated on the same side of the chain Molecular configurations 10 Stereochemistry of Polymerization
- 11. 2. Syndiotactic On alternate sides Molecular configurations 11 3. Atactic At random position
- 12. Polymer Structure STEREOCHEMISTRY (Tacticity) All phenyl groups on the same side Phenyl groups on alternating sides Phenyl groups distributed randomly
- 13. Geometric isomerism Cis-Isoprene eg., Natural rubber Attacked by acids/alkalis TRANS-Isoprene eg., Gutta Percha Highly resistant to acid/alkalis Molecular configurations 13
- 15. Types of Polymers • Polymer Classifications • Thermoset: cross-linked polymer that cannot be melted (tires) • Thermoplastic: Melt able plastic Elastomer • Elastomers: Polymers that stretch and then return to their original form: often thermoset polymers
- 16. These polymers have the useful property of being Thermosetting—they are made from liquid mixtures that polymerize on heating to form a solid polymer and can therefore be molded easily.
- 17. Thermoset plastics • Contain polymers that cross-link together, to form an irreversible chemical bond • Features & Benefits •Strong mechanical properties •chemical resistance, •heat resistance. • used for sealed products due to their resistance to deformation. 17
- 18. Advantages •More resistant to high temperatures than thermoplastics •Highly flexible design •High levels stability •Cost-effective Disadvantages • Most of them cannot be recycled • Cannot be remolded or reshaped Thermoset plastics
- 19. Thermoplastics • Soften when heated and become more fluid as additional heat is applied. Features & Benefits • No chemical bonding occurs (i.e. reversible). • remolded and recycled . • high strength, shrink-resistance • Easy to bend such as plastic bags. • Highly recyclable • Chemical resistant • Hard crystalline or rubbery surface options • Eco-friendly manufacturing Disadvantages Generally more expensive than thermoset Can melt if heated
- 21. Elastomer • An elastic substance occurring naturally, As natural rubber, • Or Produced synthetically = Natural Rubber monomer
- 22. Natural Rubber Ziegler- Natta catalyst : Titanium or Vanadium (catalyst) + Aluminum alkyl (co catalyst) Produced synthetically
- 23. Synthetic Rubber chloroprene Poly chloroprene - Butyl rubber or neoprene Free Radical Synthesis
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