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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For many applications it has since been replaced by other methods for making PMMA such as extrusion, which gives uniform surface features.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.
The most accurate and expensive masks are those created by electron-beam lithography, which provides resolutions as fine as 0.1 μm in resist 4 μm thick and 3 μm features in resist 20 μm thick. An intermediate method is the plated photomask, which provides 3-μm resolution and can be outsourced at a cost on the order of $1000 per mask.
The principal application, consuming approximately 75% of the MMA, is the manufacture of polymethyl methacrylate acrylic plastics . Methyl methacrylate is also used for the production of the co-polymer methyl methacrylate-butadiene-styrene (MBS), used as a modifier for PVC .
Gypsum concrete is lightweight and fire-resistant. A 1.5-inch slab of gypsum concrete weighs 13 pounds per square foot versus 18 pounds per square foot for regular concrete. [10] Even though gypsum concrete weighs less, it still has the same compressive strength as regular concrete, based on its application as underlayment or top coat flooring ...
It consists solely of concrete flights interconnected by right- and left-hand turns. There are 189 steps producing an overall vertical change of about 115 feet. [1] On the Pacific Palisades side of Santa Monica Canyon is the so-called "secret Mesa stairway", which is much less used although it has more steps than either of the above.
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Traditionally, PMMA (acrylic) comprises the core (96% of the cross section in a fiber 1mm in diameter), and fluorinated polymers are the cladding material. Since the late 1990s much higher performance graded-index (GI-POF) fiber based on amorphous fluoropolymer (poly(perfluoro-butenylvinyl ether), CYTOP [1]) has begun to appear in the marketplace.