Glasses, light transmission

Plasma processing technologies ate used for surface treatments and coatings for plastics, elastomers, glasses, metals, ceramics, etc. Such treatments provide better wear characteristics, thermal stability, color, controlled electrical properties, lubricity, abrasion resistance, barrier properties, adhesion promotion, wettability, blood compatibility, and controlled light transmissivity. 

Where transparency is required, a range of polymers is available. Polystyrene is the least expensive but polymethylmethacrylate has an outstanding high light transmission combined with excellent weathering properties. Also to be considered are the polycarbonates, glass-clear polyamides, SAN, butadiene-styrene block copolymers, MBS polymers, plasticised PVC, ionomers and cellulose esters such as cellulose acetate. 

U.S. Pharmacopoeia XVIII, Light transmission Chemical resistance-glass... 

Figure 17. Chronology of improvement in light transmission of glasses over periods of history leading to introduction of photonics technology in the information age. Polymer protection of glass surfaces is an essential present feature.

Selenium and cobati arc used in Him glass to add ted and blue hues m amounts only sufficient to balance the green hue resulting from iron oxide present as impurity in most naturally occurring taw materials. The intended result is an even light transmission over the whole visible spectrum. 

The light transmission technique is most frequently used for the determination of average bubble size in gas-liquid dispersion. It has the advantages of quick measurement and on-line operation. The probes are usually made of mirror-treated glass rods (Vermeulen et al., 1955), internally blackened tubes with mirrors (Calderbank, 1958), or fiber optic light guide (Hong and Lee, 1983). 

The vast majority of photochemical syntheses have been conducted in the liquid phase, hence the apparatus assembly for a photochemical reaction must take into account the light transmission characteristics of the material from which the reaction vessels are made. Pyrex glass transmits most of the incident light above about 300 nm and may be used in the construction of apparatus for reactions which require light above this wavelength. Quartz vessels, transparent down to 200 nm, must be used for reactions which require light below 300 nm. Certain types of quartz allow transmission below 200 nm. 

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