Polymethyl methacrylate

Polymethylmethacrylate (POL-ee-meth-uhl-meth-AK-rill-ate) is a clear thermoplastic resin used to make windshields, visors, coatings for baths, advertising signs, and contact lenses. It is also widely used in dentistry and medicine. A thermoplastic resin is one that becomes soft when heated and hard when cooled. It can be converted back and forth any number of times between the solid and liquid states by further heating and cooling.

1. Polymethyl
Methacrylate
(PMMA)

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

3. INTRODUCTION
Acrylicplasticreferstoafamilyofsynthetic,orman-made,
plasticmaterialscontainingoneormorederivativesofacrylic
acid.Themostcommonacrylicplasticispolymethyl
methacrylate(PMMA),whichissoldunderthebrandnames
of
Plexiglas,Lucite,Perspex,andCrystallite.
PMMAisatough,highlytransparentmaterialwithexcellent
resistancetoultravioletradiationandweathering.Itcanbe
colored,molded,cut,drilled,andformed.Theseproperties
makeitidealformanyapplicationsincludingairplane
windshields,skylights,automobiletaillights,andoutdoor
signs.OnenotableapplicationistheceilingoftheHouston
Astrodomewhichiscomposedofhundredsofdouble-
insulatingpanels of PMMA acrylicplastic.

5. Manufacture of polymer
Free Radical Polymerization

7. Raffinate-1andRaffinate-2canberegardedasstagesintheprocessingofCrude
C4sstreams.Thefirststageoftheprocessistoremove,bysolventextraction,the
valuablebutadienewhichmaybe40-45%ofthestream.WhatisleftisRaffinate-1.
ItconsistsofIsobutylene,thetwonormalisomers,butene-1andbutene-2and
smallquantitiesofbutanesandothercompounds.Removaloftheisobutylene,
usuallybyreactionwithMethanoltoproduceMTBE,leavesRaffinate-2.
Raffinate-1 is a chemical building block used in the manufacture of methyl tertiary
butyl ether (MTBE) and isobutylene (IB).

8. Acrylicplasticpolymersareformedbyreactingamonomer,suchasmethyl
methacrylate,withacatalyst.
Atypicalcatalystwouldbeanorganicperoxide.
Acrylicplasticsareavailableinthreeforms:
flatsheets,
elongatedshapes(rodsandtubes),
moldingpowder.
Moldingpowdersaresometimesmadebyaprocessknownassuspension
polymerizationinwhichthereactiontakesplacebetweentinydropletsofthe
monomersuspendedinasolutionofwaterandcatalyst.Thisresultsingrains
ofpolymerwithtightlycontrolledmolecularweightsuitableformoldingor
extrusion.

9. Acrylicplasticsheetsareformedbyaprocessknownasbulkpolymerization.
Inthisprocess,themonomerandcatalystarepouredintoamoldwherethe
reactiontakesplace.
Twomethodsofbulkpolymerizationmaybeused:
batchcell
continuous.
Batchcellisthemostcommonbecauseitissimpleandiseasilyadaptedfor
makingacrylicsheetsinthicknessesfrom0.06to6.0inches(0.16-15cm)and
widthsfrom3feet(0.9m)uptoseveralhundredfeet.
Thebatchcellmethodmayalsobeusedtoformrodsandtubes.
Thecontinuousmethodisquickerandinvolveslesslabor.Itisusedtomake
sheetsofthinnerthicknessesandsmallerwidthsthanthoseproducedbythe
batchcellmethod.

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. Young's modulus 1800 -3100 MPa
Tensile strength 48 -76 MPa
Elongation 2 -10 %
Compressive strength 83 -124 MPa
Impact strength 0.16 -0.27 J/cm
Quantity Value Unit
Glass temperature 105 -105 °C
Service temperature -40 -90 °C
Density 1170 -1200 kg/m
3
Friction coefficient 0.54 -0.54
Refraction index 1.492 -1.492
Shrinkage 0.3 -0.8 %
Water absorption 0.3 -0.4 %

13. Current uses for PMMA
Includemanyusessimilartothosefor
whichitwasfirstdevelopedbutinclude
manythingsneverimaginedbythe
inventors!Apartiallistoftheusesfor
PMMAincludes:

14. SafetyglasssuchasPlexiglassandLucite–uses
rangefromwindowsforaquariumsandunder-
waterrestaurantstosafetyshieldsathockey
rinkstoskylightsinyourhometosimple
paperweights

15. Medical Uses
Usedasbonecementforusein
arthroplasticproceduresofthehip,knee,
andotherjointsforthefixationofpolymer
ormetallicprostheticimplantstoliving
bone.
Used in Pacemakers

16. Dentures!

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

18. Acrylic Paints
Acrylic “latex paints” often contain PMMA
suspended in water

19. Blacklight Tattoo Ink
Madeof97.5%PMMA and2.5%
microspheresoffluorescentdyesuspended
inUVsterilized,distilledwaterwithno
preservativesorotheradditives.

21. Breakdown of PMMA
Autoignitesat445°C(833°F)
BurnscleanlytoproduceH
2OandCO
2
Virtuallysmokelesscombustion
Hassuperiorrecyclability
Canberegroundandreused
Canbedepolymerizedbacktomonomer,
purgedofimpurities,andreploymerizedback
toPMMA

22. 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)