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New Materials for Next-Generation Commercial Transports 5 Environmentally Compliant Materials and Processes Concern for the environment and the health and safety of workers has become a critical criterion for the selection and application of materials and processes in most manufacturing industries. In the aircraft industry, the concerns center around the organic solvents used in many manufacturing processes and materials systems as well as heavy metals such as chromium and cadmium used in corrosion-resistant coatings. Environmental factors are having a profound effect on the design of new aircraft, the production of current models, and the operation and maintenance of the existing fleet. ENVIRONMENTAL REGULATIONS Federal health and environmental laws have a direct effect on aircraft materials and processes. 1 Some federal laws, including the Resource Conservation and Recovery Act (RCRA), the Clean Air Act (CAA), and the Clean Water Act (CWA), attempt to decrease waste by restricting releases of certain chemicals or compounds and by raising the cost to industry of releasing wastes into the land, air, and water. The Toxic Substance Control Act (TSCA) directly controls the use of hazardous chemicals. Resource Conservation and Recovery Act RCRA involves solid waste management and requires an inventory of releases of certain materials. The most critical materials affected by RCRA are corrosion-inhibiting materials containing heavy metals such as chromium and cadmium. RCRA also places emphasis on reducing waste through recycling or reuse, affecting both in-process waste and end-of-life disposal. The Comprehensive Environmental Response, Compensation and Liability Act, or ''Superfund," provides for penalties and assignment of liability for wastes improperly disposed of under RCRA. Clean Air Act The CAA involves the control of ozone-depleting chemicals in industrial processes. It requires the development of state implementation plans to achieve national, ambient air quality standards. This legislation has a profound influence on aircraft design and operation, because it affects all materials and processes involving volatile organics, including paints and finishes, cleaning and surface preparation, and adhesive bonding. The Clean Air Act's National Emission Standards for Hazardous Air Pollutants (NESHAP) extends the Montreal Protocol's solvent elimination restrictions to require the use of lower-vapor-pressure solvents. Also, NESHAP addresses the reduction and replacement of inorganic hazardous air pollutants such as chromium and cadmium. Clean Water Act The CWA involves control and inventory of pollutants discharged to navigable waters through the National Pollution Discharge Elimination Program. While there is an effect on manufacturing processes such as cleaning and surface preparation, the greatest effect will be on aircraft operations such as paint removal, cleaning, and de-icing. Toxic Substance Control Act TSCA requires manufacturers to obtain approval from the Environmental Protection Agency (EPA) to produce or use new chemicals that may represent an environmental or health risk. TSCA requires the development of materials safety data sheets to document compliance. The EPA may grant limited exemptions for laboratories or facilities involved in the development and testing of new materials that have not yet been fully characterized. WORKPLACE HEALTH AND SAFETY New materials and processes must be developed so that they do not create new health or environmental safety problems. The transporting and processing of the materials are 1 An analysis of the effect of environmental policy on product design is presented in Green Products by Design (OTA, 1992).
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New Materials for Next-Generation Commercial Transports coming under more-strict regulation to protect the health of workers involved in production and distribution. The health and environmental effects of new materials are regulated under the TSCA. The act requires reporting of production levels, use categories, and exposure data from manufacturers and processors of these chemicals. A complete evaluation of toxicity can take as long as five years and is quite costly. Concern about a substance's health effects may arise if there are indications of carcinogenic effects, acutely toxic effects, serious chronic effects, or adverse environmental effects, or if concern exists about the health or environmental effects of one or more impurities or byproducts of the substance. All of the health and safety issues have to be considered in relation to the potential exposure of individuals. For example, a new material could be toxic and still be acceptable if exposure can be minimized by taking the appropriate actions during its manufacture and use. Emphasis has been increasingly placed on approaches to consider health and safety concerns in the original materials selection processes to yield a final product that is safer both to the environment and to the individuals who will be exposed. The effective implementation of such an approach requires methods for assessing toxic potential and to predict the effects on workers. EFFECT ON AIRCRAFT MATERIALS The effect of new materials or processing technologies on worker health and safety and on the environment have become critical factors in their development and introduction. It is important to consider environmental factors throughout the materials life cycle, including raw material extraction and manufacture, transport and handling, fabrication, utilization, and disposal. For materials suppliers, fabricators, aircraft manufacturers, and the airlines, these concerns represent a significant risk and expense in the development of new materials or processes. Environmental regulatory requirements have caused the aircraft manufacturers, suppliers, and end-item users to undertake significant research and development of environmentally compliant materials and processes for implementation purposes. Significant efforts and resources have been directed toward compliance with a myriad of federal, state, and local environmental regulations. In addition, because of the global nature of the aircraft and airline industries, international environmental regulations can have a profound effect on the manufacture and operation of the aircraft fleet. Because of the continued concern for the environment, federal (Occupational Safety and Health Administration and EPA), as well as state and local regulations, are becoming increasingly restrictive and may constrain technology advancements until industry learns to further reduce waste, monitor and control pollution, establish tolerable standards, and dispose of or collect hazardous substances. The cost of responding to changing regulations may in some cases be intolerable for some technologies, especially in the initial stages of technology development. Compliance activities by the aircraft industry include extensive facility modifications; new equipment research and procurement; chemical evaluation and reformulation for solvents, paints, paint strippers, and structural adhesive primers; maintenance procedure revisions; maintenance and repair training; and safety modifications. Federal Aviation Regulations require the airlines to maintain and repair aircraft using materials and processes that are identical or equivalent to those used in the original aircraft manufacture. However, whether the aircraft is new or old, compliance with environmental regulations is mandatory. Airlines, although assisted by manufacturers' research for process modifications, including surface preparation for aluminum prior to bonding, anodizing (boric-sulfuric-replacing chromic acid), and corrosion prevention coatings, must develop many customized maintenance materials to replace processes that are no longer compliant with environmental regulations. Some of the developments linked to compliance with environmental regulations include: chromium reduction and elimination—chromic-acid anodize replacement with boric-sulfuric-acid anodize; Zn-Ni alloy plating or ion-vapor-deposited aluminum coatings as alternative to cadmium plating; modification of vapor degreasers for aqueous cleaning systems; methyl siloxanes as replacements for chlorofluorocarbons and methyl chloroform in precision cleaning; replacement of 1,1,1 trichloroethane in handwipe cleaning operations; computerized inventory data management of hazardous materials, material tracking, and management; and new coating-removal developments, methylene chloride-free paint strippers, low-volatile organic compound coatings, replacement of primers containing ozone depleting substances. As restrictions on disposal become more stringent worldwide, materials suppliers and aircraft manufacturers must consider the issues of recycling and disposal of advanced materials. These considerations must include means to recycle, remanufacture, or reuse in-process scrap as well as components that have reached the end of their service life. The environmental impact of new products can be reduced by considering "green" design issues, such as waste prevention (e.g., through improved materials utilization and component durability) and better materials management (e.g., recovery, disassembly, and separation considerations), throughout the materials development and component design processes (OTA, 1992).
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New Materials for Next-Generation Commercial Transports SUMMARY Concerns related to environmental compatibility and the health and safety of workers have a significant influence on the development and application of all new materials and processes. It is important to consider environmental factors throughout the entire materials life cycle, including new materials extraction and manufacture, transport and handling, fabrication, utilization, and disposal. For next-generation commercial transports, the effects are particularly significant in materials that contain heavy metals or volatile organic compounds or in processes that use solvents. In response to regulatory pressures, the drive to new materials and processes will have the greatest impact on the operation and maintenance of the aircraft fleet in the areas of corrosion protection, surface preparation processes, finish materials, and finish application processes. The FAA should assess the effect of these material changes on the aging of the new aircraft fleet.
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