Engineering morphology

The development of materials with an engineered morphological structure, such as selective membranes and nanostructures, employs principles of aggregation in these interesting technical solutions. Here, we consider some basic principles of aggregation, methods of studies, and outcomes. The discipline is relatively new therefore for the most part, only exploratory findings are available now. The theoretical understanding is still to be developed and this development is essential for the control of industrial processes and development of new materials. 

Very recently, the concept of apparent or engineering morphology has been presented (van Suijdam, 1986, van Suijdam and Dusseljee 1987), with account taken of the macroscopic nature of microbial suspensions. The aim is to have a parameter that... 

Fig. 27. Recognition at crystal interfaces and its role in the engineering of crystal morphology and configurational assignment of molecules (176,177).

The use of PC—ABS blends has grown significantly in the early 1990s. These blends exhibit excellent properties, particularly low temperature ductihty, reduced notch sensitivity, and ease of melt fabrication. The blend morphology (229), ABS composition, thermal history (215), PC content and molecular weight (300), processing conditions, etc, all affect the mechanical behavior of PC—ABS blends. These blends have been most frequently used in automotive and other engineering appHcations. 

As regards the general behaviour of polymers, it is widely recognised that crystalline plastics offer better environmental resistance than amorphous plastics. This is as a direct result of the different structural morphology of these two classes of material (see Appendix A). Therefore engineering plastics which are also crystalline e.g. Nylon 66 are at an immediate advantage because they can offer an attractive combination of load-bearing capability and an inherent chemical resistance. In this respect the arrival of crystalline plastics such as PEEK and polyphenylene sulfide (PPS) has set new standards in environmental resistance, albeit at a price. At room temperature there is no known solvent for PPS, and PEEK is only attacked by 98% sulphuric acid. 

Lahav, M. and Leiserowitz, L., 2001. The effect of solvent on crystal growth and morphology. Chemical Engineering Science, 56(7), 2245-2254. 

Commercial thermoplastics are the engineering materials containing two or more compatibilized polymers that are chemically bounded in a way that creates a controlled and stable morphology with a unified thermodynamic profile. In view of multiplicity and contradictory requirements of various properties for most of the applications, almost all the commercial PBAs are made of two or more thermoplastics, elastomeric modifiers along with a series of compatibilizers with modifiers compounded together. A considerable number of blends have been appearing in the market regularly, some of which are listed in Table 9. 

Finally, analytical equipment was used for characterisation, such as XRD, SEM, TEM, LM and light scattering. These were available either in the School of Chemical Engineering or other departments and research centres in the Universiti Sains Malaysia. However, owing to limited access to the high-end analytical equipment to analyse the membrane, the surface morphology of the membrane and the porous ceramic support was only characterised with SEM and LM. 

There are two major frontiers in membrane research, one technological and the other scientific. At the technological frontier, chemical engineers can make important contribntions to the development of new materials, the engineering of stractnre or morphology into membranes, and the identification of new ways of using permselective membranes. 

Huang, J., Xia, C., Cao, L. and Zeng, X. (2008) Facile microwave hydrothermal synthesis of zinc oxide one-dimensional nanostructure with three-dimensional morphology. Materials Science and Engineering B, 150, 187-193. 

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