川大高分子复试专业英语.pptVIP

1.2 The Plastics Industry The resin manufacturers convert chemicals (derived from crude oil, natural gas, coal, and other sources) into the basic polymer materials. Hence, these processes are called polymerization processes. These resins, which require further processing to be useful, are generally made in large, highly integrated manufacturing facilities that resemble oil refineries in their size and scope. The enormous investments required to build such facilities have resulted generally in large petrochemical companies becoming resin manufacturers. Some of the most well-known resin manufacturers are DuPont, ExxonMobile, Dow, Bayer, BASF, and Huntsman, among many others. There are approximately 40 major resin types, with each resin type differing from all others according to the fundamental chemical nature of the polymer. Most of the resin types are available from more than one resin manufacturer. Some of the most common of these resin types are polyethylene, polypropylene, polystyrene, polyvinyl chloride, nylon, polycarbonate, polyurethane, and polyester. Most of the processes used to make resins are flow processes that require careful control over temperature, pressure, flow rate, catalyst, and other associated parameters in order to obtain the desired properties and to minimize the production of unwanted side products. This text skips over most of these details and considers only the most basic concepts in polymerization (in the chapter on polymeric materials). This approach allows the reader to appreciate the general way polymers are made and understand the changes in polymer properties that arise from the polymerization processes. The emphasis of this book is on the molding of the resins after they have been polymerized.00 The resins usually exit from the polymerization reactor in one of three physical forms: liquids, granules, or flakes. The liquids are roughly the consistency of honey. The granules resemble laundry, soap powders in texture, size,