Poly(methyl methacrylate)

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Poly(methyl methacrylate)
PMMA repeating unit.svg
Identifiers
CAS number9011-14-7 YesY
KEGGC19504 N
Jmol-3D imagesImage 1
Properties
Molecular formula(C5O2H8)n
Molar massvaries
Density1.18 g/cm3[1]
Melting point160 °C (320 °F)[2]
Refractive index (nD)1.4905 at 589.3 nm.[3]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references
 
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This article is about the transparent plastic sometimes called acrylic glass. For the glass/plastic laminate often called "safety glass", see laminated glass. For the neurotoxic designer drug PMMA, commonly sold as MDMA, see Para-Methoxy-N-methylamphetamine. For other uses, see Acrylic (disambiguation).
Poly(methyl methacrylate)
PMMA repeating unit.svg
Identifiers
CAS number9011-14-7 YesY
KEGGC19504 N
Jmol-3D imagesImage 1
Properties
Molecular formula(C5O2H8)n
Molar massvaries
Density1.18 g/cm3[1]
Melting point160 °C (320 °F)[2]
Refractive index (nD)1.4905 at 589.3 nm.[3]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references
B-17G Plexiglas bombardier nose compartment, an early large-scale use of Plexiglas in 1943. Note the pilot cockpit above and behind.
World War II era Lucite sweetheart pin.

Poly(methyl methacrylate) (PMMA) is a transparent thermoplastic often used as a lightweight or shatter-resistant alternative to glass.

Although it is not technically a type of glass, the substance has sometimes historically been called acrylic glass. Chemically, it is the synthetic polymer of methyl methacrylate. The material was developed in 1928 in several different laboratories by many chemists such as William Chalmers, Otto Röhm and Walter Bauer and was first brought to market in 1933 by the Rohm and Haas Company, under the trademark Plexiglas.[4] It has since been sold under many different names, including Acrylite, Lucite, and Perspex.

PMMA is an economical alternative to polycarbonate (PC) when extreme strength is not necessary. Additionally, PMMA does not contain the potentially harmful bisphenol-A subunits found in polycarbonate. It is often preferred because of its moderate properties, easy handling and processing, and low cost. Non-modified PMMA behaves in a brittle manner when loaded, especially under an impact force, and is more prone to scratching than conventional inorganic glass, but modified PMMA can achieve high scratch and impact resistance.

The full correct name is poly(methyl 2-methylpropenoate). (It is a common mistake to use "an" instead of "en".)

History[edit]

The first acrylic acid was created in 1843. Methacrylic acid, derived from acrylic acid, was formulated in 1865. The reaction between methacrylic acid and methanol results in the ester methyl methacrylate. In 1877 the German chemist Wilhelm Rudolph Fittig discovered the polymerization process that turns methyl methacrylate into polymethyl methacrylate. In 1933 the brand name "Plexiglas" was patented and registered by another German chemist, Otto Röhm. In 1936 ICI Acrylics (now Lucite International) began the first commercially viable production of acrylic safety glass. During World War II both Allied and Axis forces used acrylic glass for submarine periscopes and aircraft windshields, canopies, and gun turrets. Incidentally, airplane pilots whose eyes were damaged by flying shards of PMMA fared much better than those injured by standard glass, demonstrating the much increased compatibility between human tissue and PMMA as compared to glass.[5]

Names[edit]

PMMA has been sold under a variety of brand names and generic names. It is often generically called acrylic glass,[6] although it is chemically unrelated to glass. It is sometimes called simply acrylic, although acrylic can also refer to other polymers or copolymers containing polyacrylonitrile. Other notable trade names include:

Synthesis[edit]

PMMA is routinely produced by emulsion polymerization, solution polymerization, and bulk polymerization. Generally, radical initiation is used (including living polymerization methods), but anionic polymerization of PMMA can also be performed. To produce 1 kg (2.2 lb) of PMMA, about 2 kg (4.4 lb) of petroleum is needed. PMMA produced by radical polymerization (all commercial PMMA) is atactic and completely amorphous.

Processing[edit]

The glass transition temperature (Tg) of atactic PMMA is 105 °C (221 °F). The Tg values of commercial grades of PMMA range from 85 to 165 °C (185 to 329 °F); the range is so wide because of the vast number of commercial compositions which are copolymers with co-monomers other than methyl methacrylate. PMMA is thus an organic glass at room temperature; i.e., it is below its Tg. The forming temperature starts at the glass transition temperature and goes up from there.[14] All common molding processes may be used, including injection molding, compression molding, and extrusion. The highest quality PMMA sheets are produced by cell casting, but in this case, the polymerization and molding steps occur concurrently. The strength of the material is higher than molding grades owing to its extremely high molecular mass. Rubber toughening has been used to increase the toughness of PMMA owing to its brittle behavior in response to applied loads.

Handling, cutting, and joining[edit]

PMMA can be joined using cyanoacrylate cement (commonly known as superglue), with heat (welding), or by using solvents such as di- or trichloromethane[15] to dissolve the plastic at the joint, which then fuses and sets, forming an almost invisible weld. Scratches may easily be removed by polishing or by heating the surface of the material.

Laser cutting may be used to form intricate designs from PMMA sheets. PMMA vaporizes to gaseous compounds (including its monomers) upon laser cutting, so a very clean cut is made, and cutting is performed very easily. However, the pulsed lasercutting introduces high internal stresses along the cut edge, which on exposure to solvents produce undesirable "stress-crazing" at the cut edge and several millimetres deep. Even ammonium-based glass-cleaner and almost everything short of soap-and-water produces similar undesirable crazing, sometimes over the entire surface of the cut parts, at great distances from the stressed edge. Annealing the PMMA sheet/parts is therefore an obligatory post-processing step when intending to chemically bond lasercut parts together. This involves heating the parts in an air circulating oven from room temperature up to 90 °C (at a rate of no more than 18 degrees per hour) down to room temperature (at a rate of no more than 12 degrees per hour). Temperature should be maintained as follows: one hour for 3 mm thickness, two hours for up to 6 mm thickness, four hours for up to 12 mm thickness, and six hours for up to 20 mm thickness. A rapid annealing cycle is reliable for thin sheets and involves placing them in a pre-heated oven to 80 °C for one hour, then removing parts from the oven and allowing to cool to room temperature. This added time component should be factored into the whole fabrication process, and the alternative Zero-rake sawcutting technique may provide better cost-effectiveness, unless complex non-straight line edges are required. In this respect PMMA has an advantage over competing polymers such as polystyrene and polycarbonate, which require higher laser powers and give more messy and charred laser cuts.

In the majority of applications, it will not shatter. Rather, it breaks into large dull pieces. Since PMMA is softer and more easily scratched than glass, scratch-resistant coatings are often added to PMMA sheets to protect it (as well as possible other functions).

Acrylate resin casting[edit]

Illustrative and secure bromine chemical sample used for teaching. The sample vial of corrosive and poisonous liquid has been cast into an acrylic plastic cube

Methyl methacrylate "synthetic resin" for casting (simply the bulk liquid chemical) may be used in conjunction with a polymerization catalyst such as MEKP, to produce hardened transparent PMMA in any shape, from a mold. Objects like insects or coins, or even dangerous chemicals in breakable quartz ampules, may be embedded in such "cast" blocks, for display and safe handling.

Properties[edit]

Skeletal structure of methyl methacrylate, the constituent monomer of PMMA

PMMA is a strong and lightweight material. It has a density of 1.17–1.20 g/cm3,[1][16] which is less than half that of glass.[1] It also has good impact strength, higher than both glass and polystyrene; however, PMMA's impact strength is still significantly lower than polycarbonate and some engineered polymers. PMMA ignites at 460 °C (860 °F) and burns, forming carbon dioxide, water, carbon monoxide and low-molecular-weight compounds, including formaldehyde.[17]

PMMA transmits up to 92% of visible light (3 mm thickness), and gives a reflection of about 4% from each of its surfaces on account of its refractive index (1.4905 at 589.3 nm).[3] It filters ultraviolet (UV) light at wavelengths below about 300 nm (similar to ordinary window glass). Some manufacturers[18] add coatings or additives to PMMA to improve absorption in the 300–400 nm range. PMMA passes infrared light of up to 2,800 nm and blocks IR of longer wavelengths up to 25,000 nm. Colored PMMA varieties allow specific IR wavelengths to pass while blocking visible light (for remote control or heat sensor applications, for example).

PMMA swells and dissolves in many organic solvents; it also has poor resistance to many other chemicals on account of its easily hydrolyzed ester groups. Nevertheless, its environmental stability is superior to most other plastics such as polystyrene and polyethylene, and PMMA is therefore often the material of choice for outdoor applications.[19]

PMMA has a maximum water absorption ratio of 0.3–0.4% by weight.[16] Tensile strength decreases with increased water absorption.[20] Its coefficient of thermal expansion is relatively high at (5–10)×10−5 K−1.[21]

Modification of properties[edit]

Pure poly(methyl methacrylate) homopolymer is rarely sold as an end product, since it is not optimized for most applications. Rather, modified formulations with varying amounts of other comonomers, additives, and fillers are created for uses where specific properties are required. For example,

Poly(methyl acrylate)[edit]

Main article: Poly(methyl acrylate)

The polymer of methyl acrylate, PMA or poly(methyl acrylate), is similar to poly(methyl methacrylate), except for the lack of methyl groups on the backbone carbon chain.[22] PMA is a soft white rubbery material that is softer than PMMA because its long polymer chains are thinner and smoother and can more easily slide past each other.

Uses[edit]

Being transparent and durable, PMMA is a versatile material and has been used in a wide range of fields and applications such as: rear-lights and instrument clusters for vehicles, appliances and lenses for glasses. PMMA in the form of sheets affords shatter resistant panels for building windows, skylights, bullet proof security barriers, signs & displays, sanitary ware (bathtubs), LCD screens, furniture and many other applications. It is also used for coating polymers based on MMA provides outstanding stability against environmental conditions with reduced emission of VOC. Methacrylate polymers are used extensively in medical and dental applications where purity and stability are critical to performance.[citation needed]

Transparent glass substitute[edit]

Close-up of pressure sphere of Bathyscaphe Trieste, with single conical window of PMMA (Plexiglas) set into sphere hull. The very small black circle (smaller than the man's head) is the inner side of the plastic "window," and is only a few inches in diameter. The larger circular clear black area represents the larger outer-side of the thick one-piece plastic cone "window."
10 meter deep Monterey Bay Aquarium tank has acrylic windows up to 33 cm thick to withstand the water pressure

Daylight redirection[edit]

Medical technologies and implants[edit]

Artistic and aesthetic uses[edit]

Lexus Perspex car sculpture.
Plexiglas art by Manfred Kielnhofer
Kawai acrylic grand piano.

Other uses[edit]

Biodegradation[edit]

The Futuro house was made of fibreglass-reinforced polyester plastic; polyester-polyurethane, and poly(methylmethacrylate) one of them was found to be degrading by Cyanobacteria and Archaea.[43][44]

See also[edit]

References[edit]

  1. ^ a b c Compare Materials: Acrylic and Soda-Lime Glass. Makeitfrom.com. Retrieved on 2012-05-09.
  2. ^ Smith & Hashemi 2006, p. 509.
  3. ^ a b Refractive index and related constants – Poly(methyl methacrylate) (PMMA, Acrylic glass). Refractiveindex.info. Retrieved on 2014-10-27.
  4. ^ Rohm and Haas Innovation – Plexiglas Triumphs. Rohmhaas.com. Retrieved on 2010-08-29.
  5. ^ Joe Schwarcz (6 November 2012), The Right Chemistry: 108 Enlightening, Nutritious, Health-Conscious and Occasionally Bizarre Inquiries into the Science of Daily Life, Doubleday Canada, p. 226, ISBN 978-0-385-67160-6 
  6. ^ PMMA (Altuglas International) and Methacrylics. Arkema.com (2010-05-20). Retrieved on 2010-08-29.
  7. ^ "The ACRYLITE® brand - ACRYLITE® - Colors, patterns and functions". Acrylite.net. Retrieved 2013-10-05. 
  8. ^ Lucite, Merriam Webster dictionary.
  9. ^ "Trademark Electronic Search System". TESS. US Patent and Trademark Office. p. Search for Registration Number 0350093. Retrieved 29 June 2014. 
  10. ^ "Plexiglas". Altuglas International. 
  11. ^ "FAQ". Plaskolite. Retrieved 2011-01-23. Manufacturer of Optix 
  12. ^ "Perspex". Oxford Dictionaries. Retrieved 2014-03-14. 
  13. ^ "Altuglas International". more than a 
  14. ^ Ashby 2005, p. 519.
  15. ^ http://www.science-projects.com/Plastics/PlexiglasWork.htm
  16. ^ a b DATA TABLE FOR: Polymers: Commodity Polymers: PMMA. Matbase.com. Retrieved on 2012-05-09.
  17. ^ Zeng, W. R.; Li, S. F.; Chow, W. K. (2002). "Preliminary Studies on Burning Behavior of Polymethylmethacrylate (PMMA)". Journal of Fire Sciences 20 (4): 297–317. doi:10.1177/073490402762574749. INIST:14365060. 
  18. ^ Altuglas International Plexiglas UF-3 UF-4 and UF-5 sheets. Plexiglas.com. Retrieved on 2012-05-09.
  19. ^ Myer Ezrin Plastics Failure Guide: Cause and Prevention, Hanser Verlag, 1996 ISBN 1-56990-184-8, p. 168
  20. ^ Ishiyama, Chiemi; Yamamoto, Yoshito; Higo, Yakichi (2005). Buchheit, T.; Minor, A.; Spolenak, R. et al., eds. "Effects of Humidity History on the Tensile Deformation Behaviour of Poly(methyl –methacrylate) (PMMA) Films". MRS Proceedings 875: O12.7. doi:10.1557/PROC-875-O12.7 (inactive December 22, 2013). 
  21. ^ "Tangram Technology Ltd. – Polymer Data File – PMMA". 
  22. ^ Polymethyl acrylate and polyethyl acrylate, Encyclopædia Britannica. Britannica.com. Retrieved on 2012-05-09.
  23. ^ Kutz, Myer (2002). Handbook of Materials Selection. John Wiley & Sons. p. 341. ISBN 0-471-35924-6. 
  24. ^ Terry Pepper, Seeing the Light, Illumination. Terrypepper.com. Retrieved on 2012-05-09.
  25. ^ Ken Yeang:Light Pipes: An Innovative Design Device for Bringing Natural Daylight and Illumination into Buildings with Deep Floor Plan, Nomination for the Far East Economic Review Asian Innovation Awards 2003
  26. ^ Lighting up your workplace – Queensland student pipes light to your office cubicle, May 9, 2005
  27. ^ Kenneth Yeang, World Cities Summit 2008, June 23–25, 2008, Singapore
  28. ^ Gerchikov, Victor; Mossman, Michele; Whitehead, Lorne (2005). "Modeling Attenuation versus Length in Practical Light Guides". LEUKOS 1 (4): 47–59. doi:10.1582/LEUKOS.01.04.003 (inactive December 23, 2013). 
  29. ^ How Serraglaze works. Bendinglight.co.uk. Retrieved on 2012-05-09.
  30. ^ Glaze of light, Building Design Online, June 8, 2007
  31. ^ Robert A. Meyers, "Molecular biology and biotechnology: a comprehensive desk reference", Wiley-VCH, 1995, p. 722 ISBN 1-56081-925-1
  32. ^ Apple, David J (2006). Sir Harold Ridely and His Fight for Sight: He Changed the World So That We May Better See It. Thorofare NJ USA: Slack. ISBN 1-55642-786-7. 
  33. ^ Kaufmann, Timothy J.; Jensen, Mary E.; Ford, Gabriele; Gill, Lena L.; Marx, William F.; Kallmes, David F. (2002-04-01). "Cardiovascular Effects of Polymethylmethacrylate Use in Percutaneous Vertebroplasty". American Journal of Neuroradiology 23 (4): 601–4. PMID 11950651. 
  34. ^ "MIT Material Property Database". Professors Carol Livermore and Joel Voldman. 20 February 2004. Retrieved 19 March 2013. 
  35. ^ Rho, Jae Young; Ashman, Richard B.; Turner, Charles H. (1993). "Young's modulus of trabecular and cortical bone material: Ultrasonic and microtensile measurements". Journal of Biomechanics 26 (2): 111–9. doi:10.1016/0021-9290(93)90042-D. PMID 8429054. 
  36. ^ Miller (1996). Review of Orthopedics (4 ed.). Philadelphia: W. B. Saunders. p. 129. ISBN 0-7216-5901-2. 
  37. ^ professionalplastics.com
  38. ^ F. J. Duarte (Ed.), Tunable Laser Applications (CRC, New York, 2009) Chapters 3 and 4.
  39. ^ a b Lapshin, R. V.; Alekhin, A. P.; Kirilenko, A. G.; Odintsov, S. L.; Krotkov, V. A. (2010). "Vacuum ultraviolet smoothing of nanometer-scale asperities of Poly(methyl methacrylate) surface". Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques 4 (1): 1–11. doi:10.1134/S1027451010010015. 
  40. ^ – Blacklight Tattoo Ink – Blacklight Tattoo Ink FAQ. Crazychameleonbodyartsupply.com. Retrieved on 2012-05-09.
  41. ^ Uhl, Alexander R.; Romanyuk, Yaroslav E.; Tiwari, Ayodhya N. (2011). "Thin film Cu(In,Ga)Se2 solar cells processed from solution pastes with polymethyl methacrylate binder". Thin Solid Films 519 (21): 7259–63. Bibcode:2011TSF...519.7259U. doi:10.1016/j.tsf.2011.01.136. 
  42. ^ JS2K-PLT. Ibanezregister.com. Retrieved on 2012-05-09.
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Bibliography[edit]

External links[edit]