Materials, reworked

Change in feed composition. This may happen due to change in suppliers or due to introduction of reworked material. Unwanted effect on reaction products, by-products. Varying inhibitor concentrations in monomers from different vendors. Potential for runaway reaction. 

Are standard production batches with added rework material sampled for quality assurance approval after rework is added ... 

Here, the harder partner penetrates the surface of the softer partner resulting in a microcutting process. This problem is particularly pronounced when processing plastics because the fillers and reinforcements that cause wear are added in their pure form, i. e., not coated in melt. The problem applies both for the plastification zone (not in the case of rework materials) as well as for solid fillers. The amount of abrasive wear is primarily determined by ... 

APPROXIMATE COMPOSITION OF TYPICAL TRU CAMPAIGN FEED TEN HFIR TARGETS PLUS REWORK MATERIAL... 

Dirty" rework materials are obtained from the product purification steps, target fabrication, and equipment flushing. 

Since numerous temporary piping connections are made to accommodate multipurpose use of several tanks during a campaign, leaks and/or small spills can occur. Thus, the cell cubicle floors and external portions of the equipment are flushed thoroughly after each campaign. All of the rework materials obtained between campaigns are accumulated, processed by means of one or two cycles of the Cleanex batch extraction process to remove miscellaneous impurities, and recycled to the next campaign. 

Regrind consists of reworked material, i.e. either natural plastic or plastic plus other constituents as per material being moulded. Regrind is usually used to specific levels, e.g. 10%, 15%, 20%, 25% maximum. However, continuous use of regrind may lead to some degradation of either the basic polymer or the other constituents. If regrind is not permitted a specific instruction has to be included in the specification. Some countries do not permit the use of regrind for certain types of product (e.g. for IV, injectibles.)... 

Stability data on a product made in accordance with a new formulation, a significantly modified process, any change in packaging materials, or made from reworked material which might influence stability should be collected at an early stage. 

Specific identification of each batch, including weights, measures, and batch numbers of raw materials, intermediates, or any reprocessed/reworked materials used during manufacturing ... 

Figure 10 Rework (left) and Scrap (right) for Flow Diagrams. Rework and scrap often are more difficult to handle than good product. Even though rework is often concealed, most items have rework. Material-removal scrap occurs in machining and press operations scrap units occur everywhere. (From Work Design Industrial Ergonomics, 5th Ed., by S. Konz and S. Johnson. Copyright 2000 by Holcomb Hathaway, Pub., Scottsdale, AZ. Reprinted with permission)...

Reworked material n. A thermoplastic from a processor s own production that has been reground, pelletized, or solvated, after having been previously processed by molding, extrusion, etc. Note—In many specifications... 

It is most optimum to avoid the use of unstable raw materials or intermediates if at all possible. Where unavoidable, unstable raw material feeds have to be carefully controlled so that concentrations are kept low and the material is consumed as rapidly as it is added. The process should not allow unstable intermediates to accumulate or be isolated. Special attention has to be given to the handling of rework material (see Table 5.3). 

Reworked Material n A thermoplastic from a processor s own production that has been reground, pelletized, or solvated, after having been previously processed by molding, extrusion, etc. NOTE — In many specifications the use of reworked material is limited to clean plastic that meets the requirements specified for the virgin material, and yields a product essentially equal in quality to one made from only virgin material (ASTM D 883). See also Regrind. 

Rough running Rework material combination, improve lubrication... 

Another aspect of flexibility is with respect to process changes (e.g., reaction times can be changed in response to scale-up problems), often resulting from short lead times from lab to manufacture, ability to rework material, and so on. The disadvantages of batch reactors in processing should also be noted. 

In many cases, rework material is also fed to the compounding extruder. 

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