Industry Perspective and Introduction

Lead is a metal of wide historical significance. It is now a very mature commodity and as such exhibits declining intensity of use, with broad replacement in many of its traditional uses. Much of the replacement results from acute awareness of the effects of lead on human health and the environment. 

Lead was widely used in ancient times, dating back over 7000 years. It was often mined and produced as a co-product of silver, which was highly prized for ornamentation and jewellery and later for coinage. Lead served as a collector for silver and gold and often smelting was conducted primarily for this purpose. Lead was separated from the precious metals by oxidation in the cupellation process . 

It was used for the construction of large windows from smaller fragments of glass at a time before large-sheet glass production was possible. Stained glass windows still remain as a prominent example of this art. 

Lead s oxides as red and white lead were used as paint pigments dating from ancient Egyptian times until the mid 20th century. They provide good pigment coverage and relatively stable colour, but have been phased out of use in recent times for health and environmental reasons. 

As a pure metal, lead is soft and malleable with low mechanical strength. This is an advantage in some apphcations such as weatherproofing, but one consequence is that under stress the metal will easily deform to reheve that stress, or creep , and this can take place over long periods of time. Indeed, lead can aeep under its own weight, and to avoid this effect the safe tensile stress is 1.7 MN/m and in compression, 2.75 MN/m. Lead can be alloyed to improve its strength properties, and antimony was commonly used as a hardener. Pure lead is in fact rarely used. 

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This introduction was written to aid scientists and technicians in the pharmaceutical and allied industries in the selection of procedures and approaches that may be employed to achieve a successful outcome with respect to product performance and process validation. The authors of the following chapters explore the same topics from their own perspectives and experience. It is hoped that the reader will gain much from the diversity and richness of these varied approaches. 

More promising from an industrial perspective, however, is the separation of the oxidation zone from the aqueous one effected by the catalytic material itself, through the selective adsorption of the reagents. The introduction of Titanium Silicalite-1 (TS-1), in which the hydrophobic properties of the pores protect the active sites from the inhibition of the external aqueous medium, was a demonstration of the concept. The catalyst, the substrate and the aqueous soluhon of hydrogen peroxide can, in this case, be mixed together, with a great simplification of the process and also a reduction of the hazards. Three commercial processes. 

Gubbins KE, Quirke N (1996) Introduction to molecular simulation and industrial applications methods, examples and prospects. In Gubbins KE, Quirke N (eds) Molecular simulations and industrial applications. Gordon and Breach Science Publishers, Amsterdam Maginn EJ, Elliot JR (2010) Historical perspective and ctnrent outlook for molecular dynamics as a chanical engineering tool. Ind Eng Chem Res 49 3059-3078 Friesner RA (2005) Ab initio quantiun chemistry methodology and applications. Proc Natl Acad Sci USA 102 6648-6653... 

Bell R(2010) Introduction and revision of lEC 61508. SIAS 2010, Tampere, Finland Bishop P, Bloomfield R (1998) A methodology for safety case development. In Redmill F, Anderson T (eds) Industrial perspectives of safety-critical systems. Springer Docker TWO (1979) Some aspects of computer simulation modelling. In Computer performance evaluation - a professional development seminar. New Zealand Computer Society, Hamilton... 

It could be envisioned that one of the future trends in development of TPEEs will continue to be modification of chemical structure of these copolyesters. Continuation of the development of advanced materials with various molecular structures is important from a fundamental and industrial perspective. It can be expected that one of the future trends could be the introduction of hyperbranched and dendritic segments into these block copolymers. Also, some progress has been achieved in incorporation of liquid crystalline sequences into the backbone or as side chains. 

The need for weU-trained technical service professionals is expected to continue as an essential aspect of the chemical industry, despite the phenomenal growth ia electronic methods of information storage, retrieval, and transmission. Advanced troubleshooting of complex customer processes and accelerated accurate product development and market introductions should continue to be principal elements of technical service personnel duties. Increased levels of integration, perhaps blurring the lines between suppHer and customer, may come to pass. There are already instances of personnel swapping between customers and suppHers for extended periods to allow cross-fertilization of ideas and provide more accurate perspectives for the companies involved in these efforts. Technical service and research personnel have been those persons most directly involved in such efforts. 

This entry on free-radical polymerization discusses relevant aspects from a chemical processing perspective. It briefly discusses the chemistry and mechanism, the types of reactors and processes typically used in the industry, and other relevant reaction engineering and processing aspects. This should provide an introduction to the process with more detailed information included in the references herein. 

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