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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]
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 .
A multiple-wythe masonry wall may be composed of a single type of masonry unit layered to increase its thickness and structural strength, or different masonry units chosen by function, such as an economical concrete block serving a structural purpose and a more expensive brick chosen for its appearance.
For many applications it has since been replaced by other methods for making PMMA such as extrusion, which gives uniform surface features.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.
Diagram shows slab and rib width with rules of thumb formula. Slab depth is typically 75 mm (3 in) to 130 mm (5 in) thick. [5] [3] As a rule of thumb, the depth should be 1 ⁄ 24 of the span. [5] The width of the ribs is typically 130 mm (5 in) to 150 mm (6 in), and ribs usually have steel rod reinforcements. [5]
201 concrete steps rise about 100 feet to the intersection of Upper Mesa Road and Amalfi Drive. There is no railing except for the topmost 18 steps, so descending requires caution. (The stairs are sometimes incorrectly called the "La Mesa stairs"--La Mesa Drive is elsewhere in Santa Monica, and there is a La Mesa Stairway in the city of La Mesa ...
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.