Isu semasa dalam industri kimia (plastik).pptx

Slide isu semasa dalam kimia

1. PLASTICS

2. Basic Concepts in polymer Monomer : a simple compound whose molecules can bond together to form polymers. Greek: ‘poly’ means ‘many’ and ‘ mer ’ means ‘same components’ Polymers : substances whose molecules have high molar masses and are composed of a large number of repeating units (structural units). Polymer is a large molecule (macromolecule) build up by the repetition of small chemical units CH 2 CH 2 n CH 2 = CH 2 repeating unit of polymer monomer

3. Polymer Nomenclature Homopolymers named by writing the prefix ‘ poly ’, followed by the monomer name name of monomers having substituents or comprising at least two words are bracketed/parenthesis Examples: polystyrene, poly(vinyl chloride) 1. Souce -based nomenclature based on monomer name Can be used when the monomer can be identified the most common method for naming addition polymers.

4. Examples: ( ethene ) CH 2 = CH 2 polyethylene (PE) CH 2 – CH 2 n (acrylonitrile) CH 2 = CH CN polyacrylonitrile CH 2 – CH CN n polystyrene (PS) (styrene) CH 2 = CH CH 2 – CH n

5. Methyl methacrylate Poly(methyl methacrylate) (PMMA)

6. Copolymers Copolymers are named by writing the prefix ‘poly’, followed by the name of the monomers An infix , called a connective is placed between them that indicates the type of sequential arrangement of the constitutional units within the chains Examples: poly[styrene– alt –(maleic anhydride)] or alt- copoly (styrene/maleic anhydride)

7. 2. Traditional (common/trade) names Nylon : polyamide Lycra®, Spandex® or elastane : polyester- polyurathene copolymer Kevlar® : polyamide thread

8. Monomers funtional group Inter-unit linkage Polymer type –OH + –COOH Polyester –NH 2 + –COOH Polyamide (nylon) 3. Structure-based nomenclature based on polymer structure Can be used when the polymer structure is proven the most common method for condensation polymers , since the polymer typically contains different repeating units than the monomers

9. IUPAC name: Poly[ imino (1-oxohexamethylene)] Common/ trade name: polyamide 6 @ nylon 6 EXAMPLES:

10. Poly(hexamethylene adipamide) @ Poly(iminohexamethyleneiminoadipoyl) Common/ trade name: polyamide 6,6 @ nylon 6,6

11. poly(ethylene terephthalate) – PET

12. Exercise Write the repeating units for the following polymers: Nylon 12 Nylon 6,12

13. Classification of Polymer Natural vs. Synthetic Thermal behavior: thermoplastic vs thermoset Polymer Structure: linear, branched, network

14. 1) Natural vs. Synthetic silk wool DNA collagen protein animal origin Starch Cellulose Natural rubber pectin Plant origin Natural polymers Occur in nature and can be extracted Examples:

15. Synthetic polymer Human-made polymers Examples: nylons, polyester, epoxy, Teflon, synthetic rubber, PE, PP, PS, PVC, PET Mostly non-degradable and often synthesized from petroleum

16. Based on thermal (thermo-mechanical) response Classified as thermoplastics and thermosets 2) Thermal behavior

17. Thermoplastic A material that softens when heated and harden (rigid) again when cooled . The heating and cooling cycles can be applied several times without affecting the properties. Can be heated and shaped over and over again. Can be recycled Examples: PE, PP, PS, PET, PVC, nylon

18. Thermosets Melt only the first time they are heated. During the initial heating the polymer is ‘cured’, hence, it does not melt on reheating . The curing process transforms the resin into a plastic or rubber by a cross-linking process Cannot be melted and re-shaped after it is cured Can only be heated and shaped once Examples: epoxy, melamine, vulcanized rubber

19. 3) Polymer Structure Polymers are made from long, repeating chains of monomers. The structure of polymers depends on the functionality of the monomer molecules Polymer structures: linear, branched, crosslinked /network Polymers which are branched but not crosslinked are generally thermoplastic functionality of a molecule is its interlinking capacity or the number of sites available for bonding with other molecules under the specific polymerization conditions. linear branched crosslinked

20. Linear polymers Linear polymer is simply a chain in which all of the monomers exist in a single line. Example: Teflon (PTFE), HDPE Polytetrafluoroethylene (PTFE)

21. Linear polymers Linear polymer is simply a chain in which all of the monomers exist in a single line. Example: Teflon (PTFE), HDPE Polytetrafluoroethylene (PTFE)

22. Linear polymers Example: HDPE Linear chain Polyethylene (PE)  high density PE (HDPE)

23. Branched polymers Branched polymers occur when groups of units branch off from the long polymer chain. These branches are known as side chains and can also be very long groups of repeating structures Example: Low density PE (LDPE) and LLDPE – branched polyethylene

24. Crosslinked polymers In crosslinked polymers, adjacent chains are joined at various positions along their length. Generally, crosslinking is accomplished by additive atoms or molecules that are covalently bonded to the chains. Polymers that have covalent crosslinks can either be soft (like a rubber band) or hard (like cured epoxy) Example: epoxy, vulcanised rubber,

25. Polymer Additives Additives are added during polymer processing to improve mechanical properties, processability , etc. Fillers To improve tensile strength, abrasion resistance, toughness Decrease cost Eg : carbon black, talc, CaCO 3 , silica, wood flour, etc Plasticizers To reduce the brittleness and stiffness of materials Lower melt viscosity and reduce T g

26. Colourants Dyes or pigments are added to give colour or to alter the colour of polymer materials Stabilizers Antioxidants and UV protections To reduce the risk of mechanical and chemical deterioration, help shield materials from UV light

27. Lubricants To aid processing (make processing easier) Flame retardants Added to inhibit, suppress or delay the production of flames to prevent the spread of fire Eg : alumina trihydrate (ATH), hydromagnesite , borates, organochlorines , organophosphates

28. Biodegradable Plastics

29. What is biodegradable plastic? Decomposed by microorganisms (bacteria, fungi, protozoa, etc ) Break down into water, CO 2 , and biomass, and methane (anaerobic digestion) Example: Bioplastic: Poly(lactic acid) (PLA), thermoplastic starch, poly(butylene succinate) (PBS), polyhydroxybutyrate (PHB) Petroleum-based: poly(butylene adipate terephthalate) (PBAT), polycaprolactone (PCL), PVA Is biodegradable plastic good for the environment?

30. Is biodegradable plastic good for the environment?

31. What is bioplastic? Made from renewable biomass sources Disadvantage: low biostability i.e. sensitive to degradation by biological agents. Advantage?

32. Are bioplastic biodegradable?

33. What is compostable plastics? How does it differ than biodegradable plastics? Biodegradable: decompose naturally Compostable: degrade under specific conditions. E.g. high T, pressure, specific chemical ratio, humidity level, etc. Advantage: rich in nutrients, can be used as fertilizer, soil conditioner, natural pesticide for soil.

34. Forming techniques for plastics

35. The method used in the forming of polymeric materials depends on several factors: Whether the materials is thermoplastic or thermosetting If thermoplastic, the temperature at which it softens The atmospheric stability of the material being formed The geometry and size of the finished product Fabrication normally occurs at elevated temperature, T and often by the application of pressure, P. Moulding is the most common method for forming plastic polymers. E.g.: compression, transfer, blow, injection and extrusion moulding . Granulized or palletized plastic is forced, at elevated T and by P, to flow into, fill and assume the shape of the mould cavity. Forming techniques for plastics

36. Amorphous thermoplastic  formed above the T g . Semicrystalline thermoplastic  formed above the T m . An applied pressure must be maintained as the piece is cooled so that the formed article will retain its shape. Economic benefit: can be recycled. Scrap thermoplastic pieces may be remelted and reformed into new shapes. Fabrication of thermoplastics

37. Fabrication of thermosetting polymers is ordinarily accomplished in two stages: Preparation of a linear polymer ( prepolymer ) in a liquid form. This material is converted into the final hard and stiff product during the second stage, which is normally carried out in a mould having the desired shape. Curing. May occur during heating and/or by the addition of catalysts, and often under pressure. During curing, chemical and structural changes occur on a molecular level: a crosslinked or a network structure forms. After curing, thermoset polymers may be removed from a mould while still hot, since they are now dimensionally stable. Thermosets are difficult to recycle, do not melt, are usable at higher temperatures than thermoplastics and are often more chemically inert. Fabrication of thermosetting