Properties effect 133-4 translucency

Optical Properties and Radiation Effects. Within the range of wavelengths measured (uv, visible, and near-ir radiation), Teflon PFA fluorocarbon film transmits slightly less energy than FEP film (29) (Table 6). In thin sections, the resin is colorless and transparent in thicker sections, it becomes translucent. It is highly transparent to it radiation uv absorption is low in thin sections. Weather-O-Meter tests indicate unlimited outdoor life. 

Colloidal dispersions may appear either translucent or cloudy, depending on the type of colloid and the degree of particle concentration and dispersion. The colloidal particles cannot be easily distinguished from water. They possess properties that are very different from other solid settable suspensions and from solutions. When the colloidal particles are < 5 pm, they have erratic aleatory movements known as Brownian movements, caused by collisions with molecules from the dispersion medium. When a light beam passes through a colloidal dispersion, this reflects and scatters light (Tyndall effect). 

Although an exact explanation of the almost linear displacement in the sensitivity between these two systems is not yet available, the observations show that this difference is affected by the properties of the matrix. For example, among clear materials polycarbonate based membranes are not very effective for the broad band and UV exposures, probably because of the light absorption in the matrix. Tinted microcolumn membranes and translucent materials with interconnected pores produce even lower sensitivities. 

In this chapter we examine four key properties of ceramic materials all of which we can classify as optical. (1) Ceramics can be transparent, translucent, or opaque for one particular composition. (2) The color of many ceramics can be changed by small additions additives, dopants, or point defects. (3) Ceramics can emit light in response to an electric field or illumination by light of another wavelength. (4) Ceramics can reflect and/or refract light. We will discuss why these effects are special for ceramics and how we make use of them. 

The same trends can stiU be observed in fibre reinforced plastics, although the reinforcement will moderate the changes in mechanical properties. However, there are other possibilities, such as glass fibre-resin debonding, caused by water absorption from aqueous liquids. This can mean a reduction in translucency. Load transfer between fibres is also less effective. Carbon fibres, in contrast, are unaffected by water below 1000°C. 

Already many lightweight membrane structures are in existence, and an increasing number of them are planned for the future, e.g. football stadium roofs. For such structures the combination of materials produces widely differing properties. Some projects are very cost-effective, while others are used for more expensive building constructions. Some constructions are of a temporary nature, some are erected at a fixed location some are required to be portable, while others may remain in place for decades. Textile roofs or walls may be open or closed according to the time of day or the position of the sun others stay fixed in one position. Some materials are required to have high translucency others may be designed for maximum insulation. 

Silicone coated glass fabric has good flame-retardant properties, releases little smoke, leaves no toxic combustion products and is more weather resistant than PVC. However, its self-cleaning effect is inferior to that of PTFE. Silicone is more flexible and protects the glass fabric better than PTFE and has very good translucency, because the refraction indices of fibreglass and silicone are similar. 

Zhang H, Kim B-N, Morita K, Hiraga HYK, Sakka Y (2011) Effect of sintering tempraature on optical properties and microstiucture of translucent zirconia prepared by high-pressure spark plasma sintering. Sci Technol Adv Mater 12 055003... 

Depending on the distribution of micro/nanofiller in the polymer matrix, the composites may be classified as microcomposites or nanocomposites. These two types of composites differ significantly with respect to their properties. The nanocomposites show improved properties compared to pure polymer or that of microcomposites. It started only back in 1990, when Toyota research group showed that the use of montmorillonite can improve the mechanical, thermal, and flame retardant properties of polymeric materials without hampering the optical translucency behaviour of the matrix. Since then, the majority of research has been focused in improving the physicochemical properties, e.g. mechanical, thermal, electrical, barrier etc. properties of polymer nanocomposites using cost effective and environmental friendly nanofillers with the aim of extending the applications of these materials in automotive, aerospace, construction, electronic, etc. as well as their day to day life use. The improvements in the majority of their properties have invariably been attributed... 

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