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polyolefins (1).ppt

  2. 2. CORPORATE TRAINING AND PLANNING Polypropylene Introduction Preparation of Polypropylene Structure Property Relationship Tacticity Properties of isotactic PP General properties Additives for isotactic PP Processing Considerations Processing techniques Grading of PP Applications Modification of Polyolefins
  3. 3. CORPORATE TRAINING AND PLANNING Polypropylene Introduction Polypropylene (PP) is a linear polymer, composed of repeating units of isopropane.  The main attractive features of PP are - Exceptional flex life, - Good surface hardness, - High chemical resistance, - Good stability in boiling water, - Excellent electrical property - Long-life integral hinge application. Polymerization CH2=CH H3C CH2-CH CH3 n n
  4. 4. CORPORATE TRAINING AND PLANNING Preparation of Polypropylene  PP is prepared by using Ziegler type catalyst – titanium tri chloride with aluminium tri ethyl, aluminium tri butyl, or aluminium di ethyl chloride in naphtha under nitrogen atmosphere to form slurry consisting of 10% catalyst and 90% naphtha.  The molecular weight can be controlled by using hydrogen as a chain transfer agent.  In suspension process, propylene is charged into the polymerization vessel under pressure while the catalyst and the reaction diluent are metered in separately.
  5. 5. CORPORATE TRAINING AND PLANNING Ziegler Natta Polymerization  Polymerization reactions especially of olefins and dienes catalysed by organometallic compounds is known as coordination polymerization.  The first step in polymerization is the formation of a monomer – catalyst complex between the organometallic compound and the monomer.  Here Mt indicates metals like Ti, Mo, Cr, Ni.  In the formation of monomer – catalyst complex, a coordination bond is involved in between a carbon atom of the monomer and the metal of the catalyst. Hence the polymerization effected by such catalyst systems is called coordination polymerization. H2C Mt R Organo metallic catalyst + CH CH H2C H2C Diene monomer H2C-R Mt H2C CH CH CH2 Monomer catalyst complex
  6. 6. CORPORATE TRAINING AND PLANNING  Ziegler Natta catalysts are such type of catalyst as existed in coordination polymerization.  It comprises of two components as against single component organo metallic component and other consisting of halides of IV-VIII group elements having transition valences.  The co-catalysts are organo-metallic compound such as alkyls, aryls and hydrides of I-IV metals.  The commonly used catalysts and co-catalysts are Titanium chlorides (both tri and tetrachlorides) and triethyl aluminium i.e. Al(C2H5)3, diethyl aluminium chloride Al (C2H5)2Cl.
  7. 7. CORPORATE TRAINING AND PLANNING  Aluminium alkyls acts as the electron acceptor and the titanium halide acts as electron donor. Therefore these two forms a coordination complex which is necessary for coordination polymerization.  The formed complex is insoluble in the solvent .  Many structures are proposed for these complexes Al Ti Cl Cl Cl R R R Cl Cl Ti Al R R Cl R Ti Cl R Cl Cl Cl
  8. 8. CORPORATE TRAINING AND PLANNING  From the active centre, the chain reaction propogates and form a solid surface of catalyst complex phase and the monomer is complexed with metal ion of the active centre before it inserts into growing chain.  When catalyst and co-catalyst components are mixed , there occurs a chemisorption of the aluminium alkyl (electro positive in nature) on the Titanium Chloride solid surface, resulting in the formation of an electron deficient bridge complex as Al (C2H5)3 + TiCl3 Co-catalyst catalyst R R Al R Ti Cl Cl Cl An active centre
  9. 9. CORPORATE TRAINING AND PLANNING  The monomer is attracted towards Ti-C bond (C from alkyl group R)in the active centre. When it forms a π -complex with Titanium ion. The rate of reaction is influenced by the electrons present in the active centre. R R Al R Ti Cl Cl Cl + CH2=CHCH3 R R Al R Ti Cl Cl Cl CH2=CHCH3 ACTIVE CENTRE PROPENE
  10. 10. CORPORATE TRAINING AND PLANNING The bond between R and Ti opens up producing an electron deficient Ti and a carbanion at R. The Titanium ion attracts the π electron pair of monomer and forms a sigma bond. While the counter ion attracts electron-deficient centre of the monomer. The monomer is then inserted into a transition state ring structure. R R Al R Cl Ti Cl Cl CH2=CHCH3 R Ti Cl Al CH2 CH CH3
  11. 11. CORPORATE TRAINING AND PLANNING This transition state now gives rise to the chain growth at the metal carbon bond regenerating the active centre. Repeating the whole sequence with addition of a second monomer the structure of resultant chain growth as The monomer insertion is repeated in this manner and orientation of the substituent group of monomer is always taken from the metal ion end resulting a stereo regular polymer. Al H2C Cl CH R CH3 Ti CH2=CHCH3 Al H2C CH-CH2 H3C H3C CH R Ti Cl +
  12. 12. CORPORATE TRAINING AND PLANNING Flow Diagram Catalyst Propylene Solvent solvent hexane Atactic polymer Solvent,atactic and alcohol recovery waste-water removal alcohol water catalyst preparation polymerization degasssing catalyst removal centrifugation Alcohol PP water
  13. 13. CORPORATE TRAINING AND PLANNING Metallocene Polymerization  Metallocene polymerization is catalyzed by metallocenes.  It allows to make polymers of very high molecular weights in comparision to Ziegler Natta catalyst.  Metallocene polymerization is also good for making polymers of very specific tacticities.  A metallocene is a positively charged metal ion sandwiched between two negatively charged cyclopentadienyl anions.  Cyclopentadienyl anoin is made from cyclopentadiene.
  14. 14. CORPORATE TRAINING AND PLANNING  In Cyclopentadienyl most of the carbon atoms has one hydrogen atom but one carbon atom has two hydrogen atoms. One of those two hydrogen atoms are acidic which separates very easily.  So, the carbon atom is left with only one hydrogen atom with an extra pair of electrons. C C C C C H H H H H H H C C C C C H H H H H Cyclopentadiene Cyclopentadienide anion
  15. 15. CORPORATE TRAINING AND PLANNING  The ring in anionic form is very stable.  These cyclopentadienyl ions have a charge of –1.When a cation like Fe with a +2 charge comes along , two of the anions forms an iron sandwich called as ferrocene.  When a metal with a bigger charge is involved, like zirconium with a +4 charge, the Zirconium will bond to two chloride ions to balance the charge, -1 charge on each to give a neutral compound. Cl Zr Cl bis- Chlorozirconocene
  16. 16. CORPORATE TRAINING AND PLANNING  In Zirconocences extra chlorine ligands can not be adjusted in between the cyclopentadienyl rings.  To make room for the chlorines, the rings tilts with respect to each other.  This tilting happens whenever a metallocene has more ligands than just the two cp rings.
  17. 17. CORPORATE TRAINING AND PLANNING  In bis- Chlorozirconocene each cp ring has aromatic ring fused to it. The two-ring system fused to a phenyl ring is called an indenyl ligand.  There is an ethylene bridge that links the top and bottom cp rings.  These two features make this compound a great catalyst for making isotactic polymers.  The bulky ligands pointed in opposite directions guide the incoming monomers so that they can only react when pointed in the right direction to give isotactic polymers.  The ethylene bridge holds the two indenyl rings in place.
  18. 18. CORPORATE TRAINING AND PLANNING  To make Zirconocene complex catalyze a polymerization, a co- initiator methyl allumoxane (MAO) is added to it.  The chlorines of zirconocenes are labile that means they like to fall off of the zirconocene.MAO replace them with some of its methyl groups. The methyl groups can fall off too. When one of them falls off a complex is formed. Zr H3C H3C CH2 CH2 The positively charged zirconium is stabilized because the electrons from the carbon-hydrogen bond are shared with the zirconium to form a α-agostic association Zr C H H H + alpha - agostic association
  19. 19. CORPORATE TRAINING AND PLANNING  Zirconium still lacking in electrons. The bonding is satisfied by the olefin monomer. In Propylene, carbon- carbon double bond is having electrons to share, so it shares a pair with the zirconium to satisfy the bonding. Zr C H H H + H3C C H C H H Zr C H H H + H3C C H C H H
  20. 20. CORPORATE TRAINING AND PLANNING The precise nature of the complex between the zirconium and the propylene is complicated. This compexation stabilizes the zirconium but not for long. When this complex forms, it rearrange itself into a new form. The electrons in the zirconium-methyl carbon bond shift to form a bond between the methyl carbon and one of the propylene carbons.  The electron pair that had been forming the alkene- metal complex shifts to form an outright bond between the zirconium and one of the propylene carbons.
  21. 21. CORPORATE TRAINING AND PLANNING Zr C H H H + H3C C H C H H Zr C H H H + H C CH3 C H H + Zr C H H H + H C CH3 C H H Zr C H H H + H C CH3 C H H  As can be seen in the picture, this happens through a four membered transition state. Also zirconium ends up just like it started, lacking a ligand, but with an agostic association with a C-H bond from the propylene monomer.
  22. 22. CORPORATE TRAINING AND PLANNING  Another propylene monomer react just like the first one. Zr C H H H + H C CH3 C H H C C H H H H3C Zr C H H H + H C CH3 C H H C C H H H H3C  The propylene coordinates with the zirconium , then the electrons shuffle.
  23. 23. CORPORATE TRAINING AND PLANNING Zr C H H H + H C CH3 C H H C C H H H H3C Zr C H H H + H C CH3 C H H C C H H H H3C  When second propylene monomer has added to the chain, the methyl groups are always on the same side of polymer chain which leads to an isotactic polymer.
  24. 24. CORPORATE TRAINING AND PLANNING  The propylene monomer always approaches the catalyst with its methyl group pointed away from the indenyl ligand. Zr H3C CH2 CH2 H2C=C H CH3 +  If the methyl group were pointed towards the indenyl ligand, the two would bump into each other keeping the propylene from getting close enough to the zirconium to form a complex. So, only when the methyl group is pointed away from the indenyl ligand, the complex of ziroconium with propylene is formed
  25. 25. CORPORATE TRAINING AND PLANNING  When the second monomer is added it approaches from the other side and its methyl group away from indenyl ring . Zr CH3 CH2 CH2 CH3-CH2-CH- + H3C C=CH2 H  The methyl group is pointed up rather than down.  This is so because the second propylene is adding from the opposite side as the first,it must be pointed in the opposite direction if the methyl groups are to end up on the same side of the polymer chain.
  26. 26. CORPORATE TRAINING AND PLANNING Structure Property Relationship  PP is a linear polymer with little or no branching.  Methyl group in the chain leads to increase in melting point and chain stiffening.  The tertiary carbon atom provides a site for oxidation so that the polymer is less stable than PE in the presence of oxygen.  Methyl group leads to products of different tacticity.  Commercial polymers are usually about 90-95% isotactic. CH2-CH CH3 n
  27. 27. CORPORATE TRAINING AND PLANNING Tacticity Isotactic C H H C C C C C C H CH3 H H H H H H H H CH3 CH3 Syndiotactic Atactic C H H C C C C C C H CH3 H H H H H H H H CH3 CH3 C C C C C C CH3 H H CH3 CH3 CH3 C C H H H H H H H H H H
  28. 28. CORPORATE TRAINING AND PLANNING Properties of isotactic PP Compare to Polyethylene  It has lower density (0.90 gm / cc).  It has a higher softening point and hence a higher maximum service temperature.  Articles can withstand boiling water and can be subjected to steam sterilizing operations.  It has a higher brittle point.  It is more susceptible to oxidation. Atactic PP  Atactic PP is an amorphous some what rubbery in nature.  Commercial polymer is usually 90-95% isotactic and rest is blocks of atactic and syndiotactic structures.
  29. 29. CORPORATE TRAINING AND PLANNING Properties of Polypropylene Name Value Unit Specific gravity 0.90 -- Tensile Strength 35.5 MPa Tensile modulus 1380 MPa Flexural modulus 1690 MPa Elongation at break 35-350 % Impact Strength (Izod ) 37 J/m Hardness R100 --- HDT (under 1.82 MPa load.) 55 °C Glass transition temperature 5 °C Melting point 164 °C Dielectric Strength 24-28 KV/mm
  30. 30. CORPORATE TRAINING AND PLANNING General Properties Chemical properties  No solvent affects PP at room temperature. Polypropylene will dissolve in Decaline at 130°C.  Aromatic and chlorinated solvents often swell polymer at elevated temperature.  Strong oxidizing acids slowly attacks the resin (fuming HNO3).
  31. 31. CORPORATE TRAINING AND PLANNING Electrical properties  PP is an excellent insulator due to its non-polarity.  It is used in many molded products, as well as in winding coils and transformers. Flammability  PP burns slowly and can be identified by an odour of crude oil.  Flame–retardant grades are available for specific electrical applications.
  32. 32. CORPORATE TRAINING AND PLANNING Mechanical properties  Commercial grades of PP is tough and having good impact resistance.  PP becomes more brittle than many other thermoplastics at zero temperature. Weathering properties  Standard grades have shorter life when exposed to the outdoor.  Discoloration, colour fade and crazing occur in products not stabilized with anti oxidants or carbon black.
  33. 33. CORPORATE TRAINING AND PLANNING Additives for Isotactic PP Fillers  About 3% of PP compounds are filled with talc.  Talc filler improves stiffness and heat deformation resistance.  Talc filled PP compounds are used in heater housings, car mounting components and several domestic appliances.  Talc filled PP sheet is used as an alternative to carton board.
  34. 34. CORPORATE TRAINING AND PLANNING  In comparison to the talc filled grades the CaCo3 filled grades claimed to have Higher impact strength. Brighter colour. Higher thermal stability. Improved fatigue strength. Lower stiffness and tensile strength.
  35. 35. CORPORATE TRAINING AND PLANNING Rubbers  Particularly butyl rubber is used to reduce the brittleness of PP.  Rubbers are used because of their Reasonable price. Good weathering properties. Negligible toxicity easy processability and re- processability. Pigments  The selection of pigments for PP follows the same considerations as for PE because of the higher processing temperature and lesser resistance to oxidation, selection does require more care.
  36. 36. CORPORATE TRAINING AND PLANNING Carbon black  To improve the resistance to UV light, carbon black is used as a light screener.  Hindered amine UV stabilizers (HALS) are used to improve the UV resistance of PP material. Antioxidants  Antioxidants are necessary for prevention from adversity of oxidation.  For optimum processing stability a single antioxidant of the phenol alkane type, for e.g., 1,1,3 –tris (4 hydroxy - 2 methyl, 5 – t – butyl phenyl) butane, tends to give the best results.
  37. 37. CORPORATE TRAINING AND PLANNING Processing Considerations  Processing of Polypropylene is similar to Polyethylene, particularly high-density polyethylene.  Flow properties depend on molecular weight and additives present.  Unfilled grades generally considered as easy flow.  Flow Path: wall thickness ratios of 175:1 are possible on 1mm wall thickness sections.  Thermal stability is quite good in the absence of oxygen so that there is no need to purge with another material when shutting down.
  38. 38. CORPORATE TRAINING AND PLANNING Processing techniques Injection Molding  Recommended processing temperatures are in the range of 210 to 275°C.  Injection pressures are of 150 to 180 MPa depending on the grade of the material.  Because of crystallanity there is high molding shrinkage and is reasonably uniform in all directions.
  39. 39. CORPORATE TRAINING AND PLANNING Pipe Extrusion  PP-R has less heat conductivity compare to PE, therefore needs longer time to melt.  This requires longer L/D ratio 30:1.  The melt temperature is recommended to be 220- 230°C.
  40. 40. CORPORATE TRAINING AND PLANNING Manufacturing Process of BOPP Film - BOPP film is manufactured with the blown method. Molten resin is extruded from a circular die to form a thick tube. The tube is stretched with air pressure at controlled temperature to achieve transverse orientation and simultaneously pulled by take off nips to achieve machine direction orientation.
  41. 41. CORPORATE TRAINING AND PLANNING Grading of Polypropylene MFI (gm/10 min) Grade 3-5 Blown film grade 9-11 Cast film grade 16 Extrusion coating grade 11 General purpose injection grade 1.9 Bottle grade
  42. 42. CORPORATE TRAINING AND PLANNING Trade Names Haldia Petrochemicals Ltd, India - Halene PP IPCL, India - Koylene Reliance, India - Repol Exxon Mobil, US - Escorene Mitsui petrochemical, Japan - Sunlet PP Mobil Chemical, US - Bicor PP Sumitomo, Japan - Esprene Mitsubishi , Japan, - Noblen
  43. 43. CORPORATE TRAINING AND PLANNING Applications Automotive  PP is used in bumpers, steering wheel covers, profiles, consoles, door pockets, radiator grills, spoilers, rubbing strips, fenders, wheel arches, truck linings, mud flaps, seat covers, plumbing, integral hinges, accelerator pedals, glove boxes and air- intake noise suppressors. Packaging  PP is used in packaging for goods wrapping, sleeping bags, films for packing tobacco products, candy, cosmetics, contact lens cases, first aid cases, drums and jerry cans, tool boxes, cheese wrap, electrical capacitors, synthetic turf, clothing inner liners, wiping clothes, films for textile goods and medicines.
  44. 44. CORPORATE TRAINING AND PLANNING Electrical / Electronics  PP is used in cable connectors and fittings, cable and wire coatings, industrial lights, transformer housings, insulators for electrical fencing, aerial parts, switch gears, radio and TV housings, capacitors, coil forms, control knobs etc. Appliances  PP is used in dish racks, pump housings, door handles, air cleaners and washing machine parts, bleach and detergent dispensing units, agitators, tub liners, housing for appliances, valve and control assemblies, drain tubes, PP silverware baskets.
  45. 45. CORPORATE TRAINING AND PLANNING Household  PP is used in buckets, thermo flask cases, strainers and chairs, baby feeding bottle warmers, microwave oven trays, labels for soft drink bottles, canvass for luggage, air conditioner parts, floor and ceiling pans, dehumidifiers, room humidifiers, knife sharpeners, can openers, hair dryers, coffee makers.
  46. 46. CORPORATE TRAINING AND PLANNING Applications Multilayer PP coating for Offshore applications Car Dashboard and Bumper Coffee Maker and Toaster PP furniture
  47. 47. CORPORATE TRAINING AND PLANNING Modification of Polyolefins  Ethylene-vinyl acetate (EVA) copolymer.  Ethylene-ethyl acrylate (EEA) copolymer.  Ethylene-methyl acrylate (EMA) copolymer.  Ethylene-acrylic/methacrylic acid copolymer.  Ethylene-propylene copolymer.
  48. 48. CORPORATE TRAINING AND PLANNING Ethylene–Vinyl acetate (EVA) copolymer.  Both filled and unfilled EVA copolymers have good low temperature flexibility and toughness.  EVA with 15-20 mol % Vinyl acetate content are rubbery copolymers.  About 28% Vinyl acetate content are used in hot–melt adhesives.  EVA films are used for liquid packaging, frozen foods, meat wrap, ice bags, drum liner.  Molded and extruded EVA resins are use in flexible toys, bumper pads, hose , gasketing.
  49. 49. CORPORATE TRAINING AND PLANNING Ethylene–acrylate copolymers  Ethylene–ethyl acrylate (EEA) and ethylene–methyl acrylate (EMA) copolymers with up to 20% weight EA, MA content respectively are commercially available.  EEA resins have higher thermal stability and can withstand higher processing temperatures than EVA.  EMA resins yield blow film with rubber like limpness and extremely high dart-drop impact strength. They find useful applications in extrusion coating, co-extrusion and laminating applications.
  50. 50. CORPORATE TRAINING AND PLANNING Ethylene–acrylic/methacrylic acid copolymers (EAA/EMa)  Copolymers up to 6.5% acrylic acid and 15% by weight of methacrylic acid are used for melt processing applications.  The acid group promotes excellent adhesion to various substrates and increases abrasion resistance and stress cracking resistance  These resins are extrusion coating onto aluminium foil for pouches, for composite toothpaste tubes, wire and cable applications, blown or extruded films for packaging of food and other products and various lamination applications.
  51. 51. CORPORATE TRAINING AND PLANNING Ethylene–Propylene Copolymers  Two main types of ethylene (E) propylene (P) resins are EPM and a terpolymer (EPDM).  Rubbers which are rich in either ethylene or propylene have higher tensile strength and elongation at break (%) in the unvulcanized state than those rubbers which contain equal amounts of E and P.  EPM rubbers can be vulcanized only by peroxides or high energy radiation.  In EPDM the third monomer has two double bonds; one enters the polymerization process and the other C=C bond remains as a side chain available for vulcanization with sulphur/accelerator systems.