40207_40 - REUSE A ND DISPOSAL Harry E . PebZy 40 40.1...

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REUSE AND DISPOSAL 40 Harry E. PebZy 40.1 INTRODUCTION As the United States and the world become more conscious of the shortage of landfill space and the need for conservation, they will be driven to find ways to solve or alleviate the problem by developing methods for reuse or other disposal of materials. Composite materi- als offer a particular challenge because of the nature of the reinforcements and fillers. In the case of thermoset composites, the matrix or resin cannot be remelted or reprocessed as can be done with thermoplastic matrices. Many of the non-composite thermoplastics are rou- tinely collected and recycled in towns and cities throughout the world. This chapter will primarily deal with thermoset composites because of the challenge of finding methods to put these materials back into use, and in a viable economic scenario. Most of the recy- cling effort involves reuse of sheet molding compound (SMC) because of its considerable potential in the automotive market and its emerging economic viability. Technology involving SMC is usually applicable to bulk molding compound (BMC) also. Thermoplastic composites will also be discussed. Hybrid composites, presumably because of their rela- tively small usage and more complex makeup, have had no reported recycling attention, but some of the reuse technologies described herein should be useful. Several practical tech- nologies for recycling and reuse have been Handbook of Composites. Edited by S.T. Peters. Published in 1998 by Chapman & Hall, London. ISBN 0 412 54020 7 developed but the problem of markets for the reprocessed composites remains largely unsolved. Plastics recycling is generally classified into four categories by final product or by-product, as follows: 1. Primary: Recycling a plastic product into an identical or similar new product; 2. Secondary: Recycling a plastic product into a new product that has less demanding physical or chemical properties; 3. Tertiary: Converting plastic wastes into basic chemicals or fuels through a process such as pyrolysis; 4. Quaternary: Burning the plastics and recov- ering their heat energy. Composites are recycled in all of these cate- gories, with the fourth, burning for energy recovery, of the least value. 40.2 HISTORICAL PERSPECTIVE Recycling of certain commodity thermoplas- tics, particularly polyethylene (PE) and polyethylene terephthalate (PET), has become a routine matter in thousands of cities and towns in the past few years. There have been upturns and downturns in recent years in balancing availability of PE and PET with demand for products and markets. One example is the demand for plastic soda bot- tles for conversion to polyester for garments (Disenhouse, 1994). The situation illustrates an important point, common to all industries: it is not only a question of developing tech-
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884 Reuse and disposal nologies for reuse but making it economically Carbon fiber viable to do so.
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This note was uploaded on 03/16/2010 for the course MECHANICAL ME765401 taught by Professor Prof.sulis during the Spring '10 term at Institut Teknologi Bandung.

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40207_40 - REUSE A ND DISPOSAL Harry E . PebZy 40 40.1...

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