This thesis investigates injection molding from an environmental standpoint, yielding a system-level environmental analysis of the process. There are three main objectives: analyze the energy consumption trends in injection molding machinery, explore the environmental performance of different technological alternatives, and provide a transparent life cycle inventory (LCI) identifying the mayor players in terms of environmental impact.The choice of injection molding machine type (hydraulic, hybrid or all-electric) has a substantial impact on the specific energy consumption (SEC), energy used per kg of processed polymer. The SEC values for hydraulic, hybrid and all-electric machines analyzed are 19.0, 13.2 and 12.6 MJ/kg respectively (including auxiliaries, compounding and the inefficiency of the electric grid). For hydraulic and hybrid machines SEC seems to exhibit a decreasing behavior with increasing throughput. This derives from spreading fixed energy costs over more kilograms of polymer as throughput increases. For allelectric machines SEC is constant with throughput. As viscosity and specific heat capacity increase so does SEC. Finally, SEC varies greatly with part shape. The thinner and the greater the projected area of the part the greater the SEC.When the polymer production stage is included in the analysis, the energy consumption values increase up to 100 MJ/kg. After polymer production, injection molding and extrusion have the greatest environmental impact in the whole LCI. The overall injection molding energy consumption (excluding polymer production) in the U.S. on a yearly basis amounts to 2.06 x 108 GJ. This value is of similar magnitude to the overall U.S. energy consumption for sand casting, and to the entire electricity production of some developed countries

In this study we use a thermodynamic framework to characterize the material and energy resources used in manufacturing processes. The analysis and data span a wide range of processes from "conventional" processes such as machining, casting, and injection molding, to the so-called "advanced machining" processes such as electrical discharge machining and abrasive waterjet machining, and to the vapor-phase processes used in semiconductor and nanomaterials fabrication. In all, 20 processes are analyzed. The results show that the intensity of materials and energy used per unit of mass of material processed (measured either as specific energy or exergy) has increased by at least 6 orders of magnitude over the past several decades. The increase of material/energy intensity use has been primarily a consequence of the introduction of new manufacturing processes, rather than changes in traditional technologies. This phenomenon has been driven by the desire for precise small-scale devices and product features and enabled by stable and declining material and energy prices over this period. We illustrate the relevance of thermodynamics (including exergy analysis) for all processes in spite of the fact that long-lasting focus in manufacturing has been on product quality--not necessarily energy/material conversion efficiency. We promote the use of thermodynamics tools for analysis of manufacturing processes within the context of rapidly increasing relevance of sustainable human enterprises. We confirm that exergy analysis can be used to identify where resources are lost in these processes, which is the first step in proposing and/or redesigning new more efficient processes.

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