Process/material characteristics

High demands are placed on the substrate material of disk-shaped optical data storage devices regarding the optical, physical, chemical, mechanical, and thermal properties. In addition to these physical parameters, they have to meet special requirements regarding optical purity of the material, processing characteristics, and especially in mass production, economic characteristics (costs, processing). The question of recyclabiUty must also be tackled. 

Some of these isocyanates are commercially available in derivatized form, such as biurets and carbodiimides, to provide materials having improved handling or processing characteristics. 

The piopeities of a ceramic material that make it suitable for a given electronic appHcation are intimately related to such physical properties as crystal stmcture, crystallographic defects, grain boundaries, domain stmcture, microstmcture, and macrostmcture. The development of ceramics that possess desirable electronic properties requires an understanding of the relationship between material stmctural characteristics and electronic properties and how processing conditions maybe manipulated to control stmctural features. 

Design nd Operation. The destruction efficiency of a catalytic oxidation system is determined by the system design. It is impossible to predict a priori the temperature and residence time needed to obtain a given level of conversion of a mixture in a catalytic oxidation system. Control efficiency is determined by process characteristics such as concentration of VOCs emitted, flow rate, process fluctuations that may occur in flow rate, temperature, concentrations of other materials in the process stream, and the governing permit regulation, such as the mass-emission limit. Design and operational characteristics that can affect the destmction efficiency include inlet temperature to the catalyst bed, volume of catalyst, and quantity and type of noble metal or metal oxide used. 

The above comments refer to comparisons between the two compositions at the same glass-fibre level. If, however, comparison is made between a nylon 66 composition with a glass content of x% and a nylon 6 compound with a glass content of (x + 5)%, then the differences in mechanical properties become very small. At the same time the nylon 6 material will have slightly easier processing characteristics and surface quality. 

Subsequent chapters deal with individual classes of plastics. In each case a review is given of the preparation, structure and properties of the material. In order to prevent the book from becoming too large I have omitted detailed discussion of processing techniques. Instead, with each major class of material an indication is given of the main processing characteristics. The applications of the various materials are considered in the light of the merits and the demerits of the material. 

Both thermoplastics and thermosets can reap the benefit of fibre reinforcement although they have developed in separate market sectors. This situation has arisen due to fundamental differences in the nature of the two classes of materials, both in terms of properties and processing characteristics. 

These materials have characteristics of both rubbers and thermoplastics. At room temperature they behave like cross-linked rubbers, but at elevated temperatures the cross-links effectively disappear (they are said to be heat fugitive) and the material may be processed as a thermoplastic. Unlike truly cross-linked (vulcanised) rubbers, these materials may be capable of disolution in solvents, although not necessarily at room temperature. 

As reviewed throughout this book, designing acceptable products requires knowledge of the behavior of the different plastics and their processing characteristics (Chapter 6, MATERIAL VARIABLE and Chapter 8 EQUIPMENT/PROCESSING VARIABLE). 

Preliminary consideration of candidate materials, processes and tooling factors, configuration, thicknesses in section, ribs, bosses, holes, surface characteristics, color, graphics, decoration, and assembly methods will begin to impose some discipline on the product design as it evolves. In the middle and latter phases of the design cycle, two or three concepts should make their validity apparent to all involved. With luck (logic), one will... 

An in-depth understanding of structure-property relationships is perhaps the most important concern for the urethane formulation chemist. Material design objectives often go far beyond physical property requirements and may also include considerations like processing characteristics (i.e., compatibility, reactivity,... 

Material Processing Main Characteristics Typical Applications... 

It has been a long way from early synthetic polymers created as artificial substitutes (Kunststoffe) for scarcening metal resources, to modem materials tailormade to fill specific functions through particular properties and processing characteristics in many areas of application. Ever since they were first prepared, surprising new or improved properties have been discovered or engineered. 

Membrane Types Key membrane properties include their size rating, selectivity, permeability, mechanical robustness (to allow module fabrication and withstand operating conditions), chemical robustness (to fabrication materials, process fluids, cleaners, and sanitizers), low extractibles, low fouling characteristics, high capacity, low cost, and consistency. 

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