Sheet production

Realization of the USCT method for restoring of SD of PMF of material in thick-sheet products with plane parallel surfaces under the unilateral access required special designs of US blocks, in which taken into account particularities of the NDTO, of the method and of the... 

Tables 2—5 Hst some typical properties or ranges of properties for the more common film and sheet products. Although these values are good for comparative purposes, actual performance tests are best to determine suitabiHty for use. Properties of multiple-layer films or sheets in laminar stmctures cannot always be predicted from values for the individual polymer layers. Use conditions of stress, temperature, humidity, and light exposure all strongly influence performance. Film and sheet manufacturers can recommend product combinations or variations that may provide significant performance advantages to the user.

Polyester sheet products may be produced from amorphous poly(ethylene terephalate) (PET) or partiaHy crystallized PET. Acid-modified (PETA) and glycol modified (PETG) resins are used to make ultraclear sheet for packaging. Poly(butylene terephthalate) (PBT) has also been used in sheet form. Liquid-crystal polyester resins are recent entries into the market for specialty sheet. They exhibit great strength, dimensional stabHity, and inertness at temperatures above 250°C (see Polyesters,thermoplastic). 

The basic methods for forming film or sheeting materials may be classified as follows melt extmsion, calendering, solution casting, and chemical regeneration. Of special note is the use of biaxial orientation as part of the critical manufacturing steps for many film and sheet products. 

Coextrusion. An increasingly popular technique to produce tailored film or sheet products is to coextmde one or more polymer types in two or more layers of melt (6). In this fashion the benefits of specific polymer types or formulations may be combined. Thus high cost barrier resins may be combined with a low cost thicker layer of standard resin to achieve an optimum barrier film at lower cost. Thin sUp-control layers may be used on the surface of a bulk layer of opticaUy clear resin to obtain an aesthetic film with good handleabUity. Lower melting outer layers may be used to provide heat sealing for polymers that seal with difficulty by themselves. 

Table 6 shows the sales estimates for principal film and sheet products for the year 1990 (14). Low density polyethylene films dominate the market in volume, followed by polystyrene and the vinyls. High density polyethylene, poly(ethylene terephthalate), and polypropylene are close in market share and complete the primary products. A number of specialty resins are used to produce 25,000—100,000 t of film or sheet, and then there are a large number of high priced, high performance materials that serve niche markets. The original clear film product, ceUophane, has faUen to about 25,000 t in the United States, with only one domestic producer. Table 7 Hsts some of the principal film and sheet material manufacturers in the United States.

Aluminum and aluminum alloys are employed in many appHcations because of the abiHty to resist corrosion. Corrosion resistance is attributable to the tightly adherent, protective oxide film present on the surface of the products. This film is 5 —10 nm thick when formed in air if dismpted it begins to form immediately in most environments. The weathering characteristics of several common aluminum alloy sheet products used for architectural appHcations are shown in Eigure 30. The loss in strength as a result of atmospheric weathering and corrosion is small, and the rate decreases with time. The amount of... 

Cast analysis of carbon is not appropriate for Type I. Sheet products analysis is appropriate for checking proper type of material. Extremely low carbon levels can be checked accurately usiag carbon-combustion chromatographic-type analy2ers. 

Pressure sensitive adhesives can be coated on a substrate such as a polyester or paper backing to make a tape or label, or on a release liner to make a transfer adhesive, or a special substrate to make a graphic film or retro-reflective sheeting product. In some cases, where precision placement of the PSA is required, one may also coat directly on the substrate using techniques such as screen-printing. 

Besides the typical tape and label products discussed earlier, larger sheeting products are often applied using pressure sensitive adhesives. Examples of these sheeting products include ... 

Retroreflective sheeting products used on traffic control signs and retro-reflective license plates for vehicles. 

TABLE 15.1 Calcutation of Total Elementary Flows from the Steel-Sheet Product System of Fig. 15.3... 

Sheet forming processes, such as vacuum forming, do have effects on the product. The designer should be aware that these will affect the performance of one s product and one should learn how to modify the design to minimize any deleterious effects. Probably the most serious problem encountered in formed film or sheet products results from the fact that the materials are made from film or sheet at temperatures well below the melt softening point of the plastic, usually near the heat distortion temperature for the material. Forming under these condition when the draw down ratio is exceeded for a specific plastic can result in over stretched orientation of the material, the production of frozen-in stresses, poor product reproducibil-... 

The specimen is mounted in a punch-type shear fixture, and the punch (1 in. diameter) is pushed down at a rate of 0.05 in./min until the moving portion of the sample clears the stationary portion. Shear strength is calculated as the force per area sheared. Shear strength is particularly important in film and sheet products where failures from this type of load may occur (Fig. 2-21). This property can be used for comparison with other materials and for determination of the forces needed for punching openings (holes, etc.). 

Analysis by thin layer chromatography (TLC) indicates product formation and a small amount of starting material. TLC was performed on Merck Silica gel 60 F-254 coated on aluminum sheets. Product 3 has Rf = 0.44 (elution with 70 30 petroleum ether-ethyl acetate visualization with iodine vapor). 

Ten mil Lexarf PC film containing no UV-stabil izers was obtained from Sheet Products Section, Mt. Vernon, Indiana. Reference films containing various additives were prepared by dissolving the additive and Lexan PC resin in dichloromethane and casting films from solutions containing about 5% solids. 

Bill of Material Routing Sheets Production Orders Scheduled Orders... 

Sheet production, of methacrylic ester polymers, 16 282 Sheet silicon, 23 40—41 Shell a-olefin manufacture, 17 713—714. See also Shell higher olefins process (SHOP)... 

The food producer has full responsibility for the choice of suitable antioxidant and should obtain all information about the antioxidant from the data sheet (product information) that declares its safety. In most countries the antioxidants used in the product must be labelled on the package. Customers prefer foods with a minimum of additives as indicated by E number, and so the trend is directed towards mixtures of spices that contain antioxidants that do not need to be declared. 

Assumes a <20 pm thick Nb cladding layer over a 130 pm steel core. Cost information is based on discussions with ATI Wah Chang, a leading worldwide producer of Nb sheet product. 

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