Poly(methyl methacrylate)
- PMMA
- Poly ( methyl-2- methylpropenoat )
- Plexiglas (registered trademark)
- Acrylic ( colloquial)
- O- Glass ( colloquial)
Thermoplastic
Fixed
Approximately 1.19 g · cm -3
About 105 ° C.
Only a few solvents, e.g. acetone
Polymethylmethacrylate ( PMMA abbreviation, colloquially acrylic glass or plexiglass) is a synthetic, glass-like thermoplastic.
History
Acrylic glass was developed in 1928 around the same time in Germany, the UK and Spain and in 1933 brought to the market. It is now produced in large quantities and find use in a wide range of applications. The first contact lenses made of plastic were produced about 1939 of PMMA. One of the first everyday products made of PMMA were cover of Radio - phonograph combinations ( Braun SK 4 of 1956, the so-called " Snow White's Coffin "). In addition, the material is used as a medicine in the so-called bone cement for stabilization of implants in bone.
Production
PMMA is routinely produced by free-radical emulsion, solution and bulk polymerization (including living polymerization methods ). In this way produced PMMA is atactic and completely amorphous. An anionic polymerisation of PMMA is also possible. Produce 1 kg of PMMA, are needed in about 2 kg of petroleum.
Synthesizing by radical polymerization
The following mechanism takes place (here with dibenzoyl peroxide as a reaction partner of methyl methacrylate ).
1 radical formation
Because organic peroxides decompose homolytically at low heat, they are well suited as radical images. First, dibenzoyl peroxide is cleaved before separating from the resulting radicals CO ₂.
2 chain initiation
Now the resulting radical reacts with methyl methacrylate (MMA ) to a new, larger free radical.
3 chain growth
When the radical chain growth resulting in second again reacts with the methyl methacrylate. This reaction happens all the time, so that more and more radicals are formed.
4 chain termination
Chain growth can be terminated in two ways: First, two radicals can meet, secondly, the MMA be depleted. Using the first option is shown.
Structure and properties
Pressure, temperature and duration of the course of the polymerization process thereby have influence on the average length of the polymer chains and the cross-linking and entanglement of the polymer chains with each other. This in turn has a direct impact on some physical and chemical properties, which can differ slightly from the values listed below depending on the production.
PMMA burns crackling, with yellowish flame, sweet odor, without dripping and without residue. When tapping with a fingernail PMMA sounds compared to transparent polystyrene not tinny due to lower hardness.
PMMA is beyond 100 ° C for plastic deformation, and this deformation is thermally reversible. It allows a good machining, can be cut very well with CO2 lasers or engrave and is more scratch resistant than other thermoplastics. By gluing or welding connections are possible. It transmits light better than mineral glass, is easy to color, weather-and aging-resistant, resistant to acids, alkalis medium concentration, oil and petrol. However, ethanol, acetone and benzene attack PMMA. Therefore acrylic glass surfaces shall not be cleaned with alcohol or solvents also, otherwise stress crack corrosion. It absorbs UV light ( apart from special UV-transparent variants for use in X-ray lithography or tanning beds).
The good weathering stability of the methacrylate polymers is due to the purely aliphatic structure and the steric hindrance of the polymer chain. Are used in the polymerization of other monomers ( alkyl or aryl methacrylates ) are used, it is possible to adapt the properties of the copolymer product requirements. Thus, by appropriate choice of the alcohol residue of the ester monomer, for example, the polymer softening be influenced: Long-chain esters, such as lauryl and stearyl methacrylate are already showing waxy polymer properties; Esters with highly branched alcohol radical yield polymers with reduced solution viscosity.
Copolymer combinations of anionic and cationic PMMA result Interpolyelektrolytkomplexe (IPEC ). They are mainly used to wrap drugs and release them in good predetermined manner.
The design possibilities are very diverse. So it can be used not only as replacing glass in windows, but also for household items such as bowls.
Technical properties of PMMA:
- Thermal conductivity: 0.19 W / ( m · K)
- Specific heat capacity: 1.47 kJ / (kg · K)
- Refractive index: 1.492 (compared to 1.45 to 1.9 for mineral glass)
- Elastic, due to impact-resistant ( however, there are special impact- enhanced versions )
- Modulus of elasticity ( train ): 2700-3200 N / mm ²
- Dielectric strength: 35-40 kV / mm
- Tensile strength: 70 N / mm ²
- Permittivity at 50 Hz: 3.7
Areas of application
Of polymethyl methacrylate, a plurality of transparent and non- transparent objects, goods, components, semi-products or semi-finished products will be produced for use in various fields. PMMA is for example essential in dentistry, where it is used for prostheses. For this, the resin is colored with metal salts, such that the typical pink color is obtained. In clear form, it is used for dressing rails. The plastic is freely mixed and cured under heat and pressure. It can also activators are added.
Overview of important applications:
- Industry and crafts Automobile industry: turn signals and tail lights lenses, reflectors, light guide, Tür-/Säulenverkleidungen in the exterior region ( covering of A-/B-/C- columns)
- Construction: Polymer concrete, industrial flooring, glazing (eg double -skin sheets ), for sealing and coating of balconies and terraces, detail waterproofing flat roofs, Industrietorverglasungen ( Plustherm system glazing), plumbing and interior components eg for bathtubs, furniture, room dividers, door panels, lampshades etc.
- Semiconductor industry: use as a resist ( photoresist ) or part of it in the photo - and electron-beam lithography for the production of circuits and printed circuit boards
- Light and optics: floodlit signs and " acrylic light design ", light covers, illuminated advertising, sight glass, lenses, Fresnel lenses, optical fibers
- Aircraft industry: windows, hoods, headlights covers
- Machinery protection: Safety hoods and doors
- Model and prototype: as a mineral glass replacement for single pieces and small series
- Pyrotechnics: Part of the delay sets
- Shipbuilding: submarine pressure hull, see also → Deep Rover DR1002
- Textile Industry: Part of copolymer fibers ( acrylic ), see also → polyacrylonitrile
- Watch industry: watch glass
- Medicine Optic: Hard intraocular lenses, spectacle lenses
- Surgery: enriched with gentamicin PMMA spheres raised as chains for continuous antibiotic treatment
- Hearing aid technology: earplugs ( Otoplasty)
- Orthopedics: As in the case of infections, as well as surgical bone cement, for example for anchoring hip as well as the augmentation of, for example, for the treatment of fractures kyphoplasties
- And other areas or products Visual arts: The material and image support
- Horticulture: For example, for roofing and side parts of greenhouses
- Household Goods: bowls, housings, containers, salad spoons, salt and pepper mills
- Adhesives: Methylmethacrylatklebstoff for compounds of metals and plastics
- Music Instruments: Drum, key coverings of pianos
- Smoking Goods: For the manufacture of water pipes, bongs so-called
- Jewelry: So-called plugs and other jewelry for eg dilated piercings.
Trademarks and trade names
PMMA has been known under the trade name Plexiglas, filed in 1933 by Otto Röhm. In Europe, this is a registered trademark of Evonik Röhm GmbH, in the USA the altuglass International ( Arkema group). However, Evonik markets under the name Deglas be Plexiglas in the USA.
In Europe, the altuglass International Group PMMA marketed under the name altuglass; Arkema Group PMMA under the name Oroglas.
In the GDR, the brand name O- glass was used ( for " organic glass "). The only manufacturers were the nitrogen Piesteritz. Retrieved from " Piesteritz " is derived from the trade name Piacryl.
There are a number of other proprietary trade names, including Biacryl, Conacryl, Deglas, deacon, Friacryl, Hesaglas, Limacryl, PerClax and Vitroflex.
Acrylic glass is a generalized, non-proprietary name for PMMA.
Recycling
The recycling code for polymethyl methacrylate is 07