After-processing

Figure 14.9 The composite curves after process modifications shows a much reduced energy target. (From Smith and Linnhoff, Trans. IChemE, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers )...

Sample taken into the lab for analysis after processing the gross sample. 

Theie aie only a few fat replacement products based on protein. LITA is a com protein—polysaccharide compound the role of the polysaccharide is to stabilize the protein (zein). The final product is 87% protein and 5% polysaccharide. The mixture, spray dried after processing, claims to look like cream on rehydration. It is low in viscosity, flavor, and lubricity, and is stable to mild heating. The protein particle size is 0.3—3 p.m (55). 

Ingredients used in pet foods are usually high in nutritional quaHty but generally not desirable as human foods primarily because they do not conform to human taste or processing expectations. By-products such as rendered proteins and fat converted into pet foods may have a derivation unappealing to humans, yet after processing may actually be more free of microorganisms and toxins than foods consumed by humans. 

Properties. The crystallinity of FEP polymer is significantly lower than that of PTFE (70 vs 98%). The stmcture resembles that of PTFE, except for a random replacement of a fluorine atom by a perfluoromethyl group (CF ). The crystallinity after processing depends on the rate of cooling the molten polymer. The presence of HFP ia the polymer chain teads to distort the highly crystallized stmcture of the PTFE chaia and results ia a higher amorphous fractioa. 

Specific Interactions. Ideas oa the subject of specific iateractions between PVC and a plasticizer molecule, as a basis of plasticization, can be considered a more detailed form of some of the ideas already discussed. Clearly some mechanism of attraction and interaction between PVC and plasticizer must exist for the plasticizer to be retained in the polymer after processing. 

Cured sihcone LIM mbber can be fabricated with physical properties equivalent to heat-cured mbber (385). Shore A hardness can range from 30 to 70, depending on formulations. Typical physical properties include tensile strengths as high as 9.7 MPa (1400 psi), 500—775% elongation at break, and tear strength of >30 N/mm (180 Ib/in.). Compression sets of less than 10% can be achieved if the material is baked after processing. 

Use of some oilseed proteins in foods is limited by flavor, color, and flatus effects. Raw soybeans, for example, taste grassy, beany, and bitter. Even after processing, residues of these flavors may limit the amounts of soybean proteins that can be added to a given food (87). The use of cottonseed and sunflower seed flours is restricted by the color imparted by gossypol and phenoHc acids, respectively. Flatus production by defatted soy flours has been attributed to raffinose and stachyose, which are removed by processing the flours into concentrates and isolates (88). 

Directed Oxidation of a Molten Metal. Directed oxidation of a molten metal or the Lanxide process (45,68,91) involves the reaction of a molten metal with a gaseous oxidant, eg, A1 with O2 in air, to form a porous three-dimensional oxide that grows outward from the metal/ceramic surface. The process proceeds via capillary action as the molten metal wicks into open pore channels in the oxide scale growth. Reinforced ceramic matrix composites can be formed by positioning inert filler materials, eg, fibers, whiskers, and/or particulates, in the path of the oxide scale growth. The resultant composite is comprised of both interconnected metal and ceramic. Typically 5—30 vol % metal remains after processing. The composite product maintains many of the desirable properties of a ceramic however, the presence of the metal serves to increase the fracture toughness of the composite. 

A good sensitizing dye does not interfere with other system properties. Sensitizing dyes can sometimes influence the intrinsic response of a chemically sensitized emulsion, leading to desensitization or additional sensitization. The dye can also interfere with development rate, increase or decrease unwanted fog density, and remain as unwanted stain in the film after processing. The dye should have adequate solubihty for addition to the emulsion, but should not wander between layers in the final coating. 

To provide for suitable timing of the pH reduction over the wide range of temperatures that may be encountered, the instant films may use polymeric timing layers in which permeabiUty to alkaU varies inversely with temperature. In the integral films, where all components are retained within the film unit after processing and the moisture content remains high for several days, care must be taken to avoid materials that could migrate or initiate unwanted reactions even at reduced pH. 

Fig. 22. Micrographs of Polachrome film, (a) is a cross section of the unprocessed film (lOOOX) (b) is portion of a red image area after processing, with dense positive silver overlying the blue and green lines (250X) (c) and (d) are portions of a hiU color image, showing the image stmcture at 30X and 500X.

The distinction between thermoplastic and thermoset is particularly cloudy in the case of PBIs because they are formed and processed as thermoplastics but after processing exhibit properties that are more closely related to thermosetting materials. Hence they, too, are usually considered pseudothermoplastics. 

Noscapine [128-62-1] (45) is the second most abundant alkaloid found in opium. Unlike most opium alkaloids, however, it has an isoquinoline rather than a phenanthrene ting system. Noscapine was first isolated in 1817 but its antitussive activity was not demonstrated pharmacologically until 1952 (63). Clinical studies have confirmed its effectiveness. It is not a narcotic and has a wide margin of safety when given orally. Death could be produced in rats only with doses > 800 mg/kg (64). Noscapine is isolated from the water-insoluble residue remaining after processing opium for the manufacture of morphine. 

Once the PSSR team is satisfied with their review, a form such as Example 4-1, Pre-startup Safety Review Completion Form can be used to capture their approval for startup. For simple changes, this one-page form may be all that is required. In the case of extensive modifications, a detailed checklist of items examined by the team may accompany this form. It could include unsatisfactory findings as well as respective recommendations. If recommendations were made, these must be prioritized. Some may need to be resolved before startup others may be appropriately addressed after processing has begun. Some items reviewed by one company for extensive modifications and logged in addition to the one-page form are ... 

It is sometimes necessary to remove flux residues after processing due to their corrosive nature. This can be an added source of variability. 

These and other considerations have led to attempts to produce materials which effectively cross-link on cooling to room temperature after processing but which on reheating appear to lose their cross-links. Several approaches to such fugitive cross-linking have been made in recent years of which the following have come to, or at least near to, commercial fruition ... 

Polycarbonate melts adhere strongly to metals and if allowed to cool in an injection cylinder or extrusion barrel may, on shrinkage, pull pieces of metal away from the wall. It is therefore necessary to purge all equipment free of the resin, with a polymer such as polyethylene, after processing. 

Determine how materials will be held awaiting processing and after processing. 

The fact that these kinds of chemical reactions occur during the processing were further demonstrated by the testing of the insoluble material in the blends. The data showed that after dimethylformamide (DMF) treatment and after processing, the solubles significantly increased, It also showed that the insoluble content is also related to the TPU content in the blending system. It peaks at the TPU content of 15%-20%, after which the amount drops dramatically. Accordingly, the mechanical properties of the material also showed the same trend. 

Table 6-9 General properties of TPs during and after processing...

Additive, slip An additive modifier that acts as an internal lubricant which exudes to the surface of the plastic during and immediately after processing providing the necessary lubricity to reduce or eliminate coefficient of friction in molded parts, film, etc. products. 

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