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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 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]
para-Methoxymethamphetamine (PMMA), also known as 4-methoxy-N-methylamphetamine (4-MMA), is a serotonergic drug of the amphetamine family related to para-methoxyamphetamine (PMA). It is the 4- methoxy analogue of methamphetamine .
Methacrylic acid, abbreviated MAA, is an organic compound with the formula CH 2 =C(CH 3)CO 2 H. This colorless, viscous liquid is a carboxylic acid with an acrid unpleasant odor.
Ultrasonic welding can be used to join ASA to PVC, ABS, SAN, PMMA, and some others. [4] ASA can be solvent-welded, using e.g. cyclohexane, 1,2-dichloroethane, methylene chloride, or 2-butanone. Such solvents can also join ASA with ABS and SAN. Solutions of ASA in these solvents can also be used as adhesives. [4]
Polymers are composed of long molecular chains which form irregular, entangled coils in the melt. Some polymers retain such a disordered structure upon freezing and readily convert into amorphous solids. In other polymers, the chains rearrange upon freezing and form partly ordered regions with a typical size of the order 1 micrometer. [3]
The first polymeric form of methacrylic acid was described in 1880 by Engelhorn and Fittig. The use of high purity monomers is required for proper polymerization conditions and therefore it is necessary to remove any inhibitors by extraction (phenolic inhibitors) or via distillation. [ 2 ]
It has a low glass-transition temperature about 10 °C (12.5 °C in case of PMA 38). [4] It is soluble in dimethyl sulfoxide (DMSO). [4] PMA is water-sensitive and unlike PMMA, is not stable against alkalies. [2] High-energy radiation leads to cross linking in PMA. However in polymethyl methacrylate (PMMA), a compound similar to PMA ...