Matt surfaces

When a molten plastic is forced through a die it is found that under certain conditions there will be defects in the extrudate. In the worst case this will take the form of gross distortion of the extrudate but it can be as slight as a dullness of the surface. In most cases flow defects are to be avoided since they affect the quality of the output and the efficiency of the processing operation. However, in some cases if the flow anomaly can be controlled and reproduced, it can be used to advantage - for example, in the production of sheets with matt surface finish. Flow defects result from a combination of melt flow properties, die design and processing conditions but the exact causes and mechanisms are not completely understood. The two most common defects are... 

The emissivity of the surfaces. Dull matte surfaces are good emitters/receivers bright reflective surfaces are poor ones. 

High strength Temperature stability Specific splicing tendency Matt surface 1 5 PETP... 

The most important methods used in in-situ studies of electrode surfaces are various modifications of reflection spectroscopy in the ultraviolet through infrared regions. For electrochemical applications, the specular reflection (at smooth electrode surfaces) is much more important than the diffuse reflection from matt surfaces. The reflectivity, R, of the electrode/ electrolyte interface is defined by ... 

J. Chen, T.L. Hoeks, K. Inoue, and D. Shen, Polycarbonate compositions and articles formed therefrom, with matte surfaces and high light transmissions, US Patent 7 514 523, assigned to SABIC Innovative Plastics IP B.V. (Bergen op Zoom, NL), April 7, 2009. 

Methods of Determination. Lightness. The white pigment powder is compressed in a suitable powder press to give an even, matt surface. The CIE tristimulus value Y is measured with color measuring equipment. For standards, see Table 1 ( Lightness ). Apparatus spectrophotometer or tristimulus colorimeter, powder press, white standard. 

The irradiance E falling onto the receptor when viewing a matte surface can be considered to be the product between the reflectance of the object R (the percentage of incident light that is reflected by the object) and the irradiance L falling onto the object. 

Figure 3.1 A matte surface is shown in (a) and a perfect mirror in (b). The matte surface absorbs part of the incoming light. The remaining light is reflected equally in all directions. The perfect mirror reflects all of the incoming light.

Please note that you cannot take a matte surface paper and make it glossy by applying steam. That being said, the change in gloss level on some air-dried glossy emulsions can be dramatic. Each type of paper, and indeed each individual emulsion batch, can behave differently. 

In the simplest form a cylinder with a polished or a matt surface is brought into contact with the film—in order to improve the quality of the surface for printing, or to make matt film from a calender with polished rolls. In this process, while the upper surface of the film is modified to requirements, the reverse usually is marked by the rubber backing roller. 

Fillers. Inert inorganic substances such as calcium carbonate, clay, silicates, and asbestos are often utilized in vinyl compositions where clarity is not a requirement. While the carbonates and clay are used ostensibly to reduce cost, beneficial results are forthcoming. The carbonates produce a dry, matte surface and are claimed, because of their alkaline nature, to benefit heat and light stability. Clay improves electrical insulation. Silicates enhance surface dryness. Asbestos fibers provide the reinforcement necessary for dimensional stability in floor tile. Antimony oxide, per se or as a surface coating on an inert carrier, provides flame retard-ance. Their only major adverse effects are to reduce tensile strength and elongation and require an increase in plasticizer level to compensate... 

Two types of filters are available polycarbonate and cellulose nitrate. Polycarbonate filters are used for endothelial chemotaxis assays. These filters are sided, with a matt and a shiny surface. The cells are allowed to adhere to the shiny surface prior to migration, and then stimulated to migrate to the matt surface. 

Cannel coal is a dull, compact, bituminous coal, that is to say it is rich in volatile hydrocarbons and bums very easily. It consists of varied plant debris, and under magnification it can be seen that it is made up of spores. It is brittle with a slightly paler sheen than that of jet and does not take such a high polish. It has a conchoidal fracture but produces a black powder when worked. It was more commonly used for large pieces than for jewellery. It leaves a black streak when mbbed against a matt surface such as unglazed porcelain. 

A greyish, slightly rough, matt surface that is carved suggests bog oak (Fig. 2.5). 

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