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Polymethyl Methacrylate

Polymethyl Methacrylate. (PMMA). Monomer. Methyl Methacrylate (MMA) Formula : H 2 C = CHCOOCH 3 Structure :. Formation. Free Radical Polymerization. Step 1 : Free radical (R*) plus methyl methacrylate. →.

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Polymethyl Methacrylate

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  1. Polymethyl Methacrylate (PMMA)

  2. Monomer • Methyl Methacrylate (MMA) Formula : H2C = CHCOOCH3 Structure :

  3. Formation • Free Radical Polymerization

  4. Step 1 : Free radical (R*) plus methyl methacrylate →

  5. Step 2 : Polymerization - MMA radical plus MMA :repeated many, many times Step 3 : Termination – occurs when two radicals join

  6. Catalysts • Multiple catalysts can be used in production of PMMA. Some of these are: • Butyl Lithium • Highly active catalysts based on group 4 metallocenes • An aluminum system supported by salen ligands

  7. Why Use Different Catalysts? • Different catalysts result in different versions of the polymer • Variation is due to the placement of the ester (R-O-R) and methyl (CH3) groups along the polymer backbone

  8. Isotactic – similar groups on same side of chain • Syndiotactic – two groups alternate • Atatactic – displays no regular pattern • Every other carbon in the chain is a steriocenter

  9. History of PMMA • Developed by three companies at approximately the same time in 1928 • Röhm and Haas • Du Pont • ICI (Imperial Chemical Industries) • First came on market 1933

  10. Historical uses of PMMA • Du Pont first used PMMA primarily for cast products (rods, tubes, and blocks) • ICI and Röhm and Haas focused on producing sheets of PMMA to be used as safety glass • Röhm and Haas introduced Plexiglass to market in 1936 and ICI followed with Perspex later that same year

  11. Properties of PMMA • Lighter than glass (density is about half that of glass) • Shatter proof • Softer and easier to scratch than glass (scratch resistant coatings may be applied) • Transmits more light than glass (92% of visible light) • Does not filter UV light (may be coated with UV film) • More transparent than glass, so windows can be made thicker

  12. Current uses for PMMA • Include many uses similar to those for which it was first developed but include many things never imagined by the inventors! A partial list of the uses for PMMA includes:

  13. Safety glass such as Plexiglass and Lucite – uses range from windows for aquariums and under-water restaurants to safety shields at hockey rinks to skylights in your home to simple paperweights

  14. Medical Uses • Used as bone cement for use in arthroplastic procedures of the hip, knee, and other joints for the fixation of polymer or metallic prosthetic implants to living bone • Used in Pacemakers

  15. Dentures!

  16. Artificial eye lenses used for cataract surgery • Suspended in collagen and implanted to reduce wrinkles in cosmetic procedures

  17. Acrylic Paints • Acrylic “latex paints” often contain PMMA suspended in water

  18. Blacklight Tattoo Ink • Made of 97.5% PMMA and 2.5% microspheres of fluorescent dye suspended in UV sterilized, distilled water with no preservatives or other additives • The ink received USFDA approval in 1995 for use in animals, plants and fish for the purpose of tracking migration, growth patterns; breeding habits etc.

  19. Breakdown of PMMA • Autoignites at 445° C (833° F) • Burns cleanly to produce H2O and CO2 • Virtually smokeless combustion • Has superior recyclability • Can be reground and reused • Can be depolymerized back to monomer, purged of impurities, and reploymerized back to PMMA

  20. Potential Toxicity • PMMA is an essentially non-toxic material • No workplace exposure limits • MMA • Respiratory effects may result from chronic low level exposure or from short term acute exposure • Exposure primarily occupational (production of monomer and its polymers, doctors, nurses, dentists, and dental technicians)

  21. Ingestion of PMMA/MMA • Oral LD50 (in rats) PMMA = 11,700 mg/kg • Oral LD50 (in rats) MMA – 7,872 mg/kg

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