Processes windows

Because of its high stability, the processing window (range of processing conditions) is wider than for many other thermoplastics. The main points to bear in mind are ... 

The surface formed by the treatment must be reproducible. Reproducibility requires that the prepared surface be independent of surface contamination, mill-scale, and other variations of nominally identical alloy surfaces. Reproducibility is facilitated if the treatment has wide processing windows so that... 

Procedures should specify the process "windows" for safe operation. 

The Optimization Xpert Automated design of experiments that builds on the foundation established in Setup Xpert and allows users to further optimize the combination of processing parameters to determine a robust good parts processing window. 

Reece, J., Daniel, D. and Bloom R., Identifying a plasma etch process window. In Understanding Industrial Designed Experiments (Schmidt S. and Launsby R., eds.), 2nd ed. AIR Academy Press, Colorado Springs, CO, 1989. 

FIG. 54. Optimum values for pressure and frequency for uniform (thickness variation <57i) film deposition. The shaded area signifies the process window. Also shown are similar data by Chatham and Bhat [146]. 

Thus, there is a small process window where high-p,T processing is effective and process control may have an important role here to maintain processing at optimal conditions. 

Figure 2.2. DSC thermograms of n = 6 monomer illustrating melting point processing window at three stages of purification (top, crude monomer product middle, insufficiently purified monomer bottom, sufficiently purified monomer).

Low-level incorporation of IPA (5-10 mol %) widens the processing window by lowering the melting point of the polyester while also retaining the crystallinity, Tg and toughness of the PCT homopolymer. At higher IPA incorporation levels, chain crystallization is severely restricted so that at 35 mol % of IPA and higher, the amorphous copolyesters do not crystallize without the addition of an added nucleator [55-59],... 

In combinatorial-type materials studies - as in all research problems - suitable constraints must be identified to yield a tractable experimental space for investigation. These constraints can include a processing window and limitations of the elements investigated. For example, some metals might be too expensive for a particular end use. By reducing the number of experiments to a suitably small number, then exhaustive understanding of a particular system becomes feasible. In any proposed combinatorial study it is therefore critical to first establish a clear vision of the goal of the study, so that parameters of the study can be defined and constrained. 

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