Viscosity optical glasses

Figure 14.5 Hardnesses of optical glasses versus softening temperatures at which their viscosities become approximately 1011 Poise. A few of the points are labeled with their names. Data from Bastick (1950).

From the optical point of view conventional optical materials, like glasses or plastics, are well characterized. By looking at the manufacturer catalogs for optical glass and plastics (www.us.schot.com www.ohara.corp.com/index.html Mills, 1986 Simonds, 1964) it is possible to find the properties of tens of glasses and plastics. Among those properties are the chemical, thermal, mechanical (micro hardness) and optical. Chemical properties include climate, staining, acids and alkali resistance. Thermal properties include viscosity and thermal expansion. Optical properties include refractive index and dispersion, secundary spectrum and internal transmittance, to mention but a few. 

A different system has been introduced by Index Instruments [2]. This modular analysis system (MAS) provides the analysis of up to four different parameters refractive index, density, colour and optical rotation. A wide range of viscosities can be handled. The analysis, wash and drying times can be selected by computer control so that crosscontamination can be reduced to undetectable levels. Samples are only in contact with inert materials such as glass, synthetic sapphire, PTFE and 316 stainless steel. 

Monomeric l.c. s show in the polarizing microscope under crossed polarizers characteristic textures, owing to their optical anisotropy 51). Examining a nematic phase, which is sandwiched between untreated glass plates, typical interferences are observed, because of the variations of the optical axis with respect to the incident of light. The nematic polymers exhibit a similar bevahior. In Fig. 10a a typical picture of the texture of a polymer is shown. While for 1-l.c, s the texture can be observed immediately after preparation because of their low viscosity, in most cases the polymers samples... 

This monograph, I believe, is unique in that it covers the broader topic of pyrometry the latter chapters on infrared and optical temperature measurement, thermal conductivity, and glass viscosity are generally not treated in books on thermal analysis but are commercially and academically important. I have resisted the urge to elaborate on some topics by using ex-... 

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