Search results
Results From The WOW.Com Content Network
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]
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.
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.
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]
Time-resolved simulation of a pulse reflecting from a Bragg mirror. A distributed Bragg reflector (DBR) is a reflector used in waveguides, such as optical fibers.It is a structure formed from multiple layers of alternating materials with different refractive index, or by periodic variation of some characteristic (such as height) of a dielectric waveguide, resulting in periodic variation in the ...
converts from incident air kerma to MGD, with a glandularity of 50%, based on breast thickness and HVL. c {\displaystyle c} corrects for glandularity other than 50%, depending on the breast thickness and HVL, with two versions for ages 50–64 and 40–49.
In addition, the rate constant of propagation (kp) during free radical polymerization of methacrylic acid is dependent on the monomer concentration. Using pulsed layer polymerization size-exclusion chromatography techniques, it was determined that there is a minor decrease in kp for partially ionized MAA as monomer concentration increases while ...