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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 (0.12 in) thickness), [18] and gives a reflection of about 4% from each of its surfaces due to its refractive index (1.4905 at 589.3 nm). [3]
For many applications it has since been replaced by other methods for making PMMA such as extrusion, which gives uniform surface features. However, for applications where strength is critical cell casting techniques are still employed in conjunction with stretching, which produces a stronger overall material.
For the first fifty years, glass was the only material used. The lenses were thin, yet reports of injury were rare. In 1938 perspex (polymethylmethacrylate, or PMMA) began to replace glass in contact lens manufacture. PMMA lenses were easier to produce so the production of glass lenses soon ended. Lenses made of PMMA are called hard lenses. [5]
MMA was discovered by Bernhard Tollens and his student W. A. Caspary in 1873, [5] who noticed and described its tendency to change into a clear, hard, transparent substance especially in sunlight. [6]
PMMA is also known by trade names such as Lucite, Perspex and Plexiglas. It serves as a sturdy substitute for glass for items such as aquariums, buttons, motorcycle helmet visors, aircraft windows, viewing ports of submersibles, and lenses of exterior lights of automobiles.
Poly(methyl acrylate) (PMA) is a family of organic polymers with the formula (CH 2 CHCO 2 CH 3) n.It is a synthetic acrylate polymer derived from methyl acrylate monomer. The polymers are colorless.
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PMAA has a pKa of ~4.8, meaning that at neutral pH the MAA groups in the network are almost entirely deprotonated making it an anionic polymer. PMAA can act as a polyelectrolyte and has the ability to absorb and retain water.