Transparency/opacity

Finally, the nature of the crystalline microstmcture, ie, crystal size and morphology and the textural relationship among the crystals and glass, is the key to many mechanical and optical properties, including transparency/opacity, strength and fracture toughness, and machinabiUty. These microstmctures can be quite complex and often are distinct from conventional ceramic microstmctures (6). 

Transparency/Opacity. Some plastics can approach or equal the transparency of glass. 

How do transparency, opacity, and gloss correlate with polymer morphology Explain. 

Appearance 9- pir-9n(t)s (14c) n. Manifestations of the nature of objects and materials through visual attributes such as size, shape, color, texture, glossiness, transparency, opacity, etc. 

Actually one has to be very careful to use the transparency/opacity argument only. This argumentation is true for rigid fractals, ue. if the bonds are rigid rods. A better way of arguing is the calculation of the fractal dimension of a given cluster by the presence of other clusters, which could have a different fractal dimension. This calculation can be done with the usual Flory theory described earlier in the chapter. 

Optical Properties. Owing to the high crystallinity of HDPE, most thick-waHed articles made from HDPE resins are opaque. Significant surface roughness can also add to the opacity. Thin HDPE film, in contrast, is translucent, but its transparency is significantly lower than that of LDPE or LLDPE film. The ultraviolet transmission limit of HDPE is around 230 nm. 

Gels. Amorphous hydrated silicas of a purity and stmcture typical of those used ia type 1 dentifrices and the liquid portion (humectant system) of type 1 dentifrices both have approximately the same refractive iadex, ie, about 1.47. As a result, the type 1 dentifrices represented ia Table 1 are inherently transparent or translucent. In the marketplace it has become popular to refer to such dentifrices as gels. For marketing reasons some companies have chosen to opacify these products, with titanium dioxide, for example. The opacified products are identical ia functionality, stmcture, and all other ways, except opacity, to their translucent or transparent counterparts. 

The commercial success of ABS polymers has led to the investigation of many other polyblend materials. In some cases properties are exhibited which are superior to those of ABS and some of the materials are commercially available. For example, the opacity of ABS has led to the development of blends in which the glassy phase is modified to give transparent polymers whilst the limited light aging has been countered by the use of rubbers other than polybutadiene. 

Opacity or transparency is important when the amount of light to be transmitted is a consideration. These properties are usually measured as haze and luminous transmittance. As reviewed haze is defined as the percentage of transmitted light through a test specimen that is scattered more than 2.5° from the incident beam. Luminous transmittance is the ratio of transmitted light to incident light. Table 5-7 provides the optical and various other properties of different transparent plastics. 

Jellies made with sunflower pectin show small air bubbles that could be responsible for the slight opacity observed with amidated pectin jellies are very transparent as it is also referred by several authors. 

Prior to the addition of the silica precursor (TEOS), the acidic copolymer solution appears transparent and the SANS data shows that the copolymer forms spherical micelles of size 7.1 nm (figure 1-a). After the addition of TEOS, the solution becomes immediately turbid. Most probably, it is because TEOS is hydrophobic and forms an emulsion droplets under stirring when added to the solution [3], Then, the opacity increases with time (figure 1-b), until a thick white precipitate forms after about 23 minutes (figure 1-c). 

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