Processing—Key Factors

Processors cover a wide range— from tiny, garage shops to billion-dol-lar multinational companies, from custom parts producers to original-equipment manufacturers captive operations. They include specialists in different types of processing, in particular, classes of materials, specific types of parts or industries, etc. Some just pass plastic through a machine, some also make molds, others also decorate parts and assemble them. Some have become complete contract manufacturers, with an emphasis on plastics. However, there are key factors that apply to each of these diversified entities. 

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The properties of fillers which induence a given end use are many. The overall value of a filler is a complex function of intrinsic material characteristics, eg, tme density, melting point, crystal habit, and chemical composition and of process-dependent factors, eg, particle-si2e distribution, surface chemistry, purity, and bulk density. Fillers impart performance or economic value to the compositions of which they are part. These values, often called functional properties, vary according to the nature of the appHcation. A quantification of the functional properties per unit cost in many cases provides a vaUd criterion for filler comparison and selection. The following are summaries of key filler properties and values. 

Additional complications can occur if the mode of deformation of the material in the process differs from that of the measurement method. Most fluid rheology measurements are made under shear. If the material is extended, broken into droplets, or drawn into filaments, the extensional viscosity may be a more appropriate quantity for correlation with performance. This is the case in the parting nip of a roUer in which filamenting paint can cause roUer spatter if the extensional viscosity exceeds certain limits (109). In a number of cases shear stress is the key factor rather than shear rate, and controlled stress measurements are necessary. 

The commodity nature of the product and the easy access to the Hcensed processes enable new producers, particularly in developing countries, to enter the global styrene merchant market with Htde experience in styrene technology. Access to ethylene, which caimot be easily transported by means other than pipelines, is a key factor in considering new styrene faciHties. Timing, or luck, is even more important because the supply and demand of styrene are seldom in balance and the price fluctuates broadly and rapidly as a result. Most of the time, the producers either suffer losses (1981—1985, 1991—1993) or enjoy handsome profits (1987—1990, 1994—mid-1995). Investments in styrene plants are known to have been recovered in less than a year, but prosperity encourages over-investment and lean years may foUow. 

The importance of the capabilities and qualifications of technical and operations staff at the toller site was emphasized in Chapter 2, The Toller Selection Process. It may have been a key factor in the selection of a toller. The expertise of the client personnel is equally important during this phase of the tolling effort. 

The reasons for the long-term, commercial robustness of phenolic technology include low cost, versatility, heat and flame resistance, durability, strength and stiffness, low toxicity, and ease of processing. Some key factors are discussed in detail below. 

The assessment of the amount of primary product or useful product is a key factor in process or unit-operation efficiency. If the product is sent off-site for sale, then the amount produced is likely to be documented in company re-cords. However, if the product is intermediate, meant for input to another process or unit operation, then the output may not be so easy to quantify. 

Some limitations are associated with UV radiation for disinfection. These include (1) The process performance is highly dependent on the efficacy of upstream devices that remove suspended solids (2) Another key factor is that the UV lamps must be kept clean in order to maintain their peak radiation output (3) A further drawback is associated with the fact that a thin layer of water (< 0.5 cm) must pass within 5 cm of the lamps. 

Table 4.1 is a representative list of the types of hazards and hazardous events that research chemists are attempting to address in searching for the best chemistry. Some key factors to consider relative to process hazards include ... 

The most important feature of o/w suspension polymerization is the formation of an oil droplet suspension of the monomer in the water and the maintenance of the individual droplets throughout the polymerization process. Droplet formation in an oil-in-water mixture is accomplished and controlled by two major factors mechanical stirring and the volume ratio of the monomer phase to water. The stirring speed is a key factor in controlling the size of oil droplets and the final size of the polymers. The stirring speed usually needs to be over... 

One of the key factors controlling the reaction rate in multiphasic processes (for reactions talcing place in the bulk catalyst phase) is the reactant solubility in the catalyst phase. Thanks to their tunable solubility characteristics, the use of ionic liquids as catalyst solvents can be a solution to the extension of aqueous two-phase catalysis to organic substrates presenting a lack of solubility in water, and also to moisture-sensitive reactants and catalysts. With the different examples presented below, we show how ionic liquids can have advantageous effects on reaction rate and on the selectivity of homogeneous catalyzed reactions. 

In this book we have decided to concentrate on purely synthetic applications of ionic liquids, just to keep the amount of material to a manageable level. FFowever, we think that synthetic and non-synthetic applications (and the people doing research in these areas) should not be treated separately for a number of reasons. Each area can profit from developments made in the other field, especially concerning the availability of physicochemical data and practical experience of development of technical processes using ionic liquids. In fact, in all production-scale chemical reactions some typically non-synthetic aspects (such as the heat capacity of the ionic liquid or product extraction from the ionic catalyst layer) have to be considered anyway. The most important reason for close collaboration by synthetic and non-synthetic scientists in the field of ionic liquid research is, however, the fact that in both areas an increase in the understanding of the ionic liquid material is the key factor for successful future development. 

Now that we have dealt with most exist factors, lets see whether the process is profitable or not. A key factor in industry is profitability regardless of technical achievement Objective procedures to aid such assessment are based on the return on investment (ROI) as the criterion. 

Spent Zirflex Process Decladdent. The basic perceived need is to devise an3 develop a simple process for selective and efficient removal of plutonium (and 21 1Am) from spent Zirflex process decladdent solution. To satisfy this need, it may be necessary--or prove beneficial—to determine, by appropriate physiochemical methods, the nature of the plutonium (and americium) species in the decladding solution. Availability of a satisfactory transuranium removal scheme may be one of the key factors in devising an alternative to storage in expensive double-shell tanks for spent Zirflex process solution at the Hanford site. 

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