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Polymethyl methacrylate
*** Shopping-Tip: Polymethyl methacrylate
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Image:PMMA-repeat.png 100px|{{PAGENAME}}
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IUPAC nomenclature Chemical name
| poly(methyl 2-methylpropenoate)
|-
|
Chemical formula
| (
Carbon C5Oxygen O2Hydrogen H8)
''n''
|-
| Synonyms
| polymethylmethacrylate
PMMA
poly(methyl methacrylate)
methyl methacrylate resin
|-
|
Molecular mass
| xx.xx g/mol
|-
|
CAS registry number CAS number
| 9011-14-7
|-
|
Density
| 1.19 g/cm
3
|-
|
Melting point
| 130-140°C (265-285°F)
|-
|
Boiling point
| xx.x °C
|-
|
Refractive index
| 1.492 (λ=589.3 nm)
|-
|
V-number
| 55.3
|-
|
Simplified molecular input line entry specification SMILES
| C[C](C)C(=O)OC
|-
| {{chembox header}} |
wikipedia:Chemical infobox Disclaimer and references
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image:Methyl-methacrylate-skeletal.png right|100px|thumb|Structure of [[methyl methacrylate, the monomer that makes up PMMA]]
'''Polymethyl methacrylate''' ('''PMMA''') or poly(methyl 2-methylpropenoate) is the
synthetic polymer of
methyl methacrylate. This
thermoplastic and
transparency (optics) transparent plastic is sold by the tradenames '''Plexiglas''', '''Perspex''', '''Acrylite''', '''Acrylplast''', and '''Lucite''' and is commonly called '''acrylic glass''' or simply '''acrylic'''.
The material was developed in
1928 in various laboratories and was brought to market in
1933 by the German Company
Rohm and Haas (GmbH & Co. KG).
Properties
The material is often used as an alternative to
glass. Differences in the properties of the two materials include:
*PMMA is lighter: its
density (1190 kg/m
3) is about half that of glass.
*PMMA does not shatter.
*PMMA is softer and more easily scratched than glass. This can be overcome with scratch-resistant coatings.
*PMMA can be easily formed, by heating it to 100 degrees
Celsius.
*PMMA transmits more light (92% of visible light) than glass.
*Unlike glass, PMMA does not filter UV (
ultraviolet) light. PMMA transmits UV light, at best intensity, down to 300
nanometre nm. Some manufacturers coat their PMMA with UV films to add this property.
*PMMA allows
infrared light of up to 2800
nanometre nm wavelength to pass. IR of longer wavelengths, up to 25,000 nm, are essentially blocked. Special formulations of colored PMMA exist to allow specific IR wavelengths to pass while blocking visible light (for remote control or heat sensor applications, for example).
PMMA can be joined using
cyanoacrylate cement (so-called "Superglue"), or by using liquid
dichloromethane di- or
chloroform trichloromethane to dissolve the plastic at the joint which then fuses and sets, forming an almost invisible weld. PMMA can also be easily polished to restore cut edges to full transparency.
To produce 1 kg of PMMA, about 2 kg of
petroleum is needed. In the presence of air, PMMA ignites at 460°
Celsius C and burns completely to form only
carbon dioxide and
water.
If in the structure of PMMA the
methyl groups (CH
3) attached to the C atoms are replaced by single hydrogen atoms, we obtain
polymethyl acrylate poly(methyl acrylate), a white soft rubbery material. It is softer than PMMA because its long polymer chains are thinner and smoother and can more easily slide past each other.
Uses
Image:Ithaa1.jpg thumb|right|Underwater restaurant ''[[Ithaa'', five meters below sealevel, is encased in PMMA]]
PMMA is used for instance in the lenses of automobile running-lights. The spectator protection in
ice hockey stadiums is made of PMMA, as are the largest windows and
aquarium aquariums in the world. The material is used to produce
laserdiscs, and sometimes also for
DVDs, but the more expensive
polycarbonate (also used for
CDs) has better properties when exposed to moisture.
Acrylic paint essentially consists of PMMA suspended in
water; however since PMMA is
hydrophobic, a substance with both hydrophobic and hydrophilic groups needs to be added to facilitate the suspension.
PMMA has a good degree of compatibilty with human tissue, and can be used for replacement
intraocular lenses in the
eye when the original lens has been removed in the treatment of
cataracts. Hard
contact lenses are frequently made of this material; soft contact lenses are often made of a related polymer, in which acrylate monomers are used that contain one or more
hydroxyl groups to make them
hydrophilic.
In
orthopedics, PMMA bone cement is used to affix implants and to remodel lost bone. It is supplied as a powder with liquid
Methyl methacrylate methyl methacrylate (MMA); when mixed together these yield a dough-like cement that gradually hardens in the body. Surgeons can judge the curing of the PMMA bone cement by the smell of MMA in the patient's breath. Athough PMMA is biologically compatible, MMA is considered to be an irritant and a possible carcinogen.
Dentures are often made of PMMA. In
cosmetic surgery, tiny PMMA microspheres suspended in some biological fluid are injected under the skin to reduce wrinkles or scars permanently.
Recently, a
blacklight-reactive
tattoo ink using PMMA
microcapsules has surfaced. The technical name is BIOMETRIX System-1000, and it is marketed under the name "Chameleon Tattoo Ink". This ink is reportedly quite safe for use, and claims to be
FDA approved for use on wildlife that may enter the food supply.
See also
* Other transparent plastics:
polystyrene,
polycarbonate
Category:Plastics
Category:Organic polymers
Category:Optical materials
Category:dielectrics
de:Polymethylmethacrylat
es:Plexiglás
fr:Polyméthacrylate de méthyle
it:Polimetilmetacrilato
nl:Polymethylmetacrylaat
ja:アクリル樹脂
pl:Szkło akrylowe
fi:Akryyli
zh:�甲基丙烯酸甲酯
*** Shopping-Tip: Polymethyl methacrylate
