See through clarity

As mentioned previously, the see-through clarity of the coextruded films deteriorates with the presence and extent of the wavelike interfacial instability. Quantitative... 

The transmission of light across a clear and colorless test specimen within a very narrow angle is the subject of test standard ASTM D1746. This defines a specular transmittance, a term used only with the most transparent of polymeric materials. The specular transmittance is directly associated with the image-forming characteristics of the test specimens. Expressions such as transparency, clarity, see-through clarity, and image resolution are used in this context. 

ASTM D-1746 correlates see-through clarity with regular transmittance. However the correlation is not very strong for highly diffusing materials. There is no method widely accepted for this property. The work of Webber is often cited as a popular approach (32). 

See-through Clarity and Light Transmission of BOPP films... 

The see-through clarity of biaxially oriented D-PP films was dependent on the cooling rate during sheet preparation. Qualitatively, objects viewed through quenched films were clearer than slowly-cooled films, which were much clearer than overnight-cooled films... 

There are two important multilayer flow instability phenomena. The first is an interface that changes, migrating spatially and progressively downstream in both the x and y directions, as shown in Fig. 12.31. It has been established that this instability becomes more pronounced with increasing viscosity ratios (64). The second manifests itself with the onset of wavelike irregularities at the interface, which, because of the prevailing periodicity of below 1 pm, result in loss of see-through optical clarity (65). 

D 1003-61, BS 2782 (515A). Again expressed as a percentage See-through D1746-62T (Transparency of plastic sheeting). Clarity BS 4618 Section 5.3. 

This may involve the collation of packages of similar or variable shapes. The most popular form uses either a direct shrink wrap (e.g. multi-packs) or a shallow tray which is usually made from corrugated board or solid board. Thermoformed plastic trays with a formed base (and/or a lid/cover) are also widely employed (e.g. bottles and aerosols). These systems offer restriction to pilferage and due to the see-through nature of the film may avoid the need for external labels. (Internal labels may be necessary if stock is controlled via a bar code.) Although LDPE has the major use, PVC may occasionally be used for its higher clarity. Gauges of 25 to 100 m are usually employed. 

Homopolymers are made in a single reactor with propylene and catalyst. It is the stiffest of the three propylene types and has the highest tensile strength at yield. In the natural state (no colorant added) it is translucent and has excellent see through or contact clarity with liquids. In comparison to the other two types it has less impact resistance, especially below O C. 

Natural and S5mthetic silica, and talc, influence haze, clarity, transparency, see-through, and gloss (results of various methods of determination of optical properties) as was documented in various parts of this book. There are many improved additives among diatomaceous earth, synthetic silicas and modified talcs which minimize ehanges in optieal properties. 

Some optical properties of films were also measured. These include standard methods of yellowness index and haze determination, as well as the see-through method developed for experimental studies of the effect of antiblocks on optical properties of films.The see-through test assigns a measurable value (distance in inches) to observable clarity differences seen by the human eye. A single layer of film is mounted to an 8-inch diameter embroidery hoop or solid frame. The distance between the eye chart and the observer eye is 48 inches. The film is moved toward the letter chart until all letters are clearly visible. The distance between the film and chart is recorded. The greater the distance, the better the film clarity. ... 

The polymeric products can be made to vary widely in physical properties through controlled variation in the ratios of monomers employed in thek preparation, cross-linking, and control of molecular weight. They share common quaHties of high resistance to chemical and environmental attack, excellent clarity, and attractive strength properties (see Acrylic ester polymers). In addition to acryHc acid itself, methyl, ethyl, butyl, isobutyl, and 2-ethylhexyl acrylates are manufactured on a large scale and are available in better than 98—99% purity (4). They usually contain 10—200 ppm of hydroquinone monomethyl ether as polymerization inhibitor. 

Figure 15 A portion of the structure of koilates formed through self-inclusion by the centrosymmetric self-complementary koilands 14 (a) and 11 (b) and the interconnection of consecutive koilates by hexadiyne molecules 33 (c) (see text for more details). For the sake of clarity, hydrogen atoms are not represented.

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