This article discusses postconsumer plastics recyclate quantities, the classification of plastics recycling into primary, secondary, tertiary, and quaternary categories, and how the life cycle of plastics is affected by recycling. The recycling processes of polyethylene terephthalate (PET), which accounts for the largest percentage of plastic recycling, high-density polyethylene (HDPE) plastics, the other large-volume plastic recyclate, as well as vinyl resins and polycarbonate resins are described. The life cycle of plastics has four phases: poly formation, part fabrication, product service, and disposal. Landfilling is still the primary method of final disposal, and incineration is another option, but recycling has become a viable alternative. The article presents a comparison between secondary and tertiary recycling.

Ingot casting is the vital conduit between molten metal provided by primary production and recycling and the manufacture of aluminum and aluminum alloy products. A number of ingot casting processes have been developed to ensure the soundness, integrity, and homogeneity required by downstream manufacturing processes. This article starts with a review of the different forms of ingot and the molten-metal processing techniques involved in ingot casting. It then describes the open-mold casting and direct chill (DC) ingot casting processes. The process variations and solidification in the DC process are summarized. The article explains continuous processes, namely, twin-roll strip casting, slab casting, and wheel-belt processes. It concludes with information on postsolidification processes, including stress relief and scalping, and a discussion of safety practices for ingot casting.

Ingot casting is the vital conduit between molten metal provided by primary production and recycling, and the manufacture of aluminum and aluminum alloy products. This article discusses various ingot forms, such as remelt ingot, billets, ingots for rolling, fabricating ingot, and particle ingot and powder. It describes the molten metal processing and ingot casting process in terms of open-mold casting and direct chill process. The article examines the continuous processes that provide commercial alternatives to conventional ingot casting. It reviews the postsolidification processes in terms of stress relief, homogenization, and scalping. The article concludes with a discussion on safety limited to ingot casting.

This article focuses on the recycling of metals including iron and steel, stainless steel, superalloys, nickel, aluminum, copper, precious metals, lead, magnesium, tin, titanium, and zinc. It provides information on the identification and sorting of scrap metals and discusses the equipment and procedures used for small-scale and large-scale scrapping operations.

Many nonferrous metals, including aluminum, nickel, copper, and others, are among the few materials that do not degrade or lose their chemical or physical properties in the recycling process. As a result, these metals can be recycled an infinite number of times. This article focuses on the recycling of nonferrous alloys, namely, aluminum, copper, magnesium, tin, lead, zinc, and titanium, providing details on the sources, consumption and classification of scrap, and the technological trends and developments in recycling.

Product design greatly influences the recycling and reuse of manufacturing materials. This article presents a design for recycling strategy based on ease of disassembly, minimizing process scrap, using readily recyclable materials, and labelling or otherwise identifying parts. It also discusses the concept of life-cycle analysis (LCA), a quantitative accounting of the environmental and economic costs of using a given material and the energy required to make, distribute, operate, and eventually dispose of the host product and its constituent materials. An important but often overlooked step in the LCA process is to identify potential improvement pathways.

Aluminum possesses many characteristics that make it highly compatible with recycling. Production of aluminum from scrap has a number of advantages. This article discusses the technology for the recovery, sorting, and remelting of aluminum. It describes the collection and acquisition of aluminum scrap in transportation, packaging, electrical and electronic, and building and construction sectors. The article reviews the technologies used to accomplish comminution for aluminum: shearing, knife shredding, and swing-hammer shredding. It provides a description of the devices used in scrap sorting, such as hand sorting, air classification, magnetic separation, eddy-current separation, heavy-media separation, and sensor-based sorting. The article also describes thermal processing, refining and casting, and dross processing of aluminum. It provides information on reverberatory and electric furnaces used for melting aluminum.

Life-cycle engineering is a part-, system-, or process-related tool for the investigation of environmental parameters based on technical and economic measures. This article focuses on life-cycle engineering as a method for evaluating impacts. It describes the four steps of life-cycle analysis, namely, goal definition and scoping, inventory analysis, impact assessment and interpretation, and improvement analysis. The article discusses the applications of life-cycle analysis results and presents a case history of life-cycle analysis of an automobile fender.

A significant amount of the worldwide demand for metals is met with recycled materials acquired by metal producers in the form of purchased scrap. This article focuses primarily on the methods and technology used to process and repurpose the vast amounts of purchased scrap that recirculate in the industrial supply chain. It describes the U.S. market for iron and steel scrap, providing information on scrap use by industry, factors influencing demand, and the purchased scrap supply. Iron and steel recycling is discussed separately from stainless steel and superalloy recycling in this article, as the scrap industry treats them differently. The scrap processing of iron involves collection, separation and sorting, size reduction and compaction, detinning, blending, and incineration. The recycling of stainless steels and superalloys follows the same process, but requires several additional steps, including secondary nickel refining, degreasing, and separation of metallurgical wastes.

This article discusses Allenby's two streams for environmental aspects of design: generic and specific concerns. Generic concerns include guidelines that provide the structure in which specific techniques can be developed and used. Specific methods are environmentally responsible for design and specific information that engineers can use. These methods include life cycle assessment, environmental impact assessment, quality function deployment, design for “X”, failure modes and effects analysis, and design for disassembly.

This article discusses the advantages of polymer matrix composite for automotive application in terms of design drivers, noise, vibration, harshness efficiency, process materials property constraints, safety and reliability, design optimization, structural and appearance requirements, recyclability, and processability. It describes the properties of high-volume composites used in automotive industries. The article provides a discussion on state-of-the-art and developing technologies in automotive field.

Ceramic and glass manufacturers take environmental regulations into consideration during all stages of the product cycle, from research and development to purchasing, processing, end use, and disposal. Ceramic and glass products are finding application in the construction industry and as raw materials for other processes. This article describes the recycling of in-process scrap and industrial wastes (fly ash, red mud, metallurgical waste, and other waste products), and applications of these recycled products. It focuses on environmental regulations such as Resource Conservation and Recovery Act and Clean Air Act. The Clean Air Act requires all states to meet minimum emissions standards for nitrogen-oxygen compounds, volatile organic compounds, and carbon monoxide.

Alloy 362.0, low-iron premium die-casting alloy, is made from recycled secondary metal scrap and was developed to have equivalent or better mechanical properties than Silafont-36 and/or Aural-2. This datasheet provides information on key alloy metallurgy, processing effects on physical and mechanical properties, and applications of this alloy.

This article illustrates various rheocasting processes. These include new rheocasting, semisolid rheocasting, subliquidus casting, rheo-diecasting, swirled enthalpy equilibration device process, slurry-on-demand process, and continuous rheoconversion processes.

Semisolid metal (SSM) processing, also known as semisolid metal casting, semisolid forming, or semisolid metal forging, is a special die casting process. This article discusses the origin and advantages of the SSM processing. It describes three major semisolid processing routes: thixocasting, rheocasting, and thixomolding.

Thixomolding is a method of molding thixotropic semisolid magnesium alloy pellets in a machine that resembles an injection molding machine in physical appearance and operation. This article describes the process of thixomolding. The use of hot sprues and hot runners in the thixomolding is discussed. The article provides information on thixoblending and summarizes results from two independent studies of the mechanical properties of recycled AZ91D. It also describes the factors on which the mechanical properties depend and illustrates microstructures of semisolid thixomolded AZ91D.

The primary fossil fuels are generally defined as coal, oil, natural gas, tar sands, and shale oil. This article discusses the characteristics and the types of fuels used in fossil and fuel industries. It describes the energy conversion in fuels and outlines the efficiency of a heat engine with the help of the Carnot equation.

Dross, which is the oxide-rich surface that forms on melts due to exposure to air, is a term that is usually applied to nonferrous melts, specifically the lighter alloys such as aluminum or magnesium. This article describes dross formation and ways to reduce it, the economic implications of dross, and in-plant enhancement or recovery of dross. It discusses the influence of the melter type on dross generation and the influence of charge materials and operating practices on melt loss. Fluxing is a word applied in a broad sense to a number of melt-treating methods. The article also discusses the in-furnace treatment with chemical fluxes.

This article presents a background of green chemistry and green coatings, and a summary of the key concerns of the green coating procurement process. It includes a discussion on green marketing and the seven sins of greenwashing, an overview of the environmental certification standards and regulatory environments, and the importance of performance during the duty cycle.

Engineering design should result in a product that performs its function efficiently and economically within the prevailing legal, social, safety, and reliability requirements. This introductory article discusses some key considerations in design, material selection, and manufacturing that a materials engineer should take into account to satisfy such requirements. It includes a brief section on concurrent engineering, which companies use to ensure that all needed input is obtained and addressed concurrently throughout the product lifecycle, including material selection and processing, product design, cost analysis, manufacturing, recyclability, and performance.