Manufacturing processes nucleation

Variations of Silica Sol Manufacturing Process. As shown in Figure 4, the four methods, A-l, A-2, B-l, and B-2, use different technical combinations of nucleation, particle growth, and concentration. In any of these methods the raw material aqueous water-glass solution is diluted, and sodium is removed with a cation-exchange resin to obtain an active silicic acid. The characteristics of these four processes are shown in Table I. 

K. Kobayashi, N. Mutsukura, and Y. Machi, Catalyst effect for diamond nucleation in the low pressure process, Mater, and Manufacturing Processes, 7(3) 395-403... 

Concentrates (also known as masterbatches) of bicyclic dicaiboxylate salt (e.g., disodium bicyclo[2.2.1]heptane-2,3-dicarboxylate, commercial product known as HPN-68) are nucleating additives used to facilitate typical thermoplastic manufacturing processes. " They impart high peak crystallization temperatures. They are suitable for use in small and large appliances. ... 

It is crucial to the whole of the manufacturing process that the melt remains sufficiently free of crystals so that it stays in a glassy state during machining and subsequent annealing. Later conversion into its partially crystalline condition is possible because of the difference between the temperature for maximum nucleation rate and the temperature for maximum crystal growth rate. 

The optimisation of manufacturing processes of cellular polymers involves the control of fluidodynamic behaviour of macromolecular viscoelastic materials containing a dissolved gas at high concentration and at thermodynamic conditions able to promote the formation of gas bubbles in the melt. Nucleation and growth rates, which determine the final morphology of the foam are related to the physical and the rheological properties of the polymeric melt surface tension, elongational viscosity of the polymer/gas system, solubility and diffusivity of the gas into the melt. 

In a quiescent melt, the minimum temperature for sporadic creation of precursors (or equivalently, since = 0, sporadic nucleation) can be estimated based on thermodynamic arguments. For example, for iPP, Janeschitz-Kriegl [148] found that this minimum temperature is close to the nominal melting point (typically between 160°C and 165°C). Since crystallization is very slow in this regime, experiments and manufacturing processes are usually conducted at lower temperatures, where Equation (14.19) is accurate. 

Polyethylene. This is essentially a closed-ceU insulation manufactured at 448 2 K by an extmsion process. A blowing agent and nucleating agent are employed to control the ceU size, and primary use is in insulating pipelines for hot and chilled water lines, air conditioning, and processing systems. 

Fig. 4. Diagram of the two-step process to manufacture nucleation track membranes, (a) Polycarbonate film is exposed to charged particles in a nuclear reactor, (b) Tracks left by particles are preferentially etched into uniform cylindrical pores (8).

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