environmentally conscious design & manufacturing (me592) date: april 14, 2000 slide:1...
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Environmentally Conscious Design & Manufacturing (ME592)
Date: April 14, 2000 Slide:1
Environmentally Conscious Design & Manufacturing
Class 17: Plastics
Prof. S. M. Pandit
Environmentally Conscious Design & Manufacturing (ME592)
Date: April 14, 2000 Slide:2
Agenda
• Use of Plastics
• Fundamentals of plastics
• Design guidelines
• Recycling and degradation of plastics
Environmentally Conscious Design & Manufacturing (ME592)
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Use of Selected Commodities
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Material in a Typical U.S. Automobile
Unit:kg
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Flow of Plastics in an Automobile
Unit:kg
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Fundamentals of Plastics
• Composition: polymer molecules and various additives
• General characteristics: lower density, strength, elastic modulus and thermal and electrical conductivity, and higher coefficient of thermal expansion
• Two major classes of polymers:• Thermoplastics• Thermosets
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Fundamentals of Plastics (cont.)
• Major molecular structure which determines the properties of the polymer
• linear• branched• cross-linked• network.
• Additives • fillers• plasticizers• colorants
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Thermoplastics • Definition: Type of polymer which softens and
melts when heated but resolidified upon cooling
• Typical examples:- Acrylics- Nylons - Polyethylene- Polypropylene- Polystyrene
• Recyclability- Easy to recycle
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Thermoplastics: Applications
Source: Kalpakjian, S., “Manufacturing processes for engineering materials”
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Thermosets • Definition: Type of polymer which does not soften
appreciably when heated.
• Typical examples:- Epoxy- Polyester - Polyimides
• Recyclability- Difficult or impossible to recycle- Burned to recover a portion of their chemical
bond energy
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Thermosets: Applications Alkyds: Good electrical insulating properties, impact resistance, dimensional stability
applications: electrical and electronic components
Epoxies: excellent mechanical and electrical properties, dimensional stability, strong adhesive properties, good resistance to heat and chemicals applications:tools and dies, adhesives, pressure vessels, tanks
Polyesters: good mechanical, chemical, and electrical properties applications: boat, luggage, chairs, automobile bodies
Polyimides: good mechanical, chemical, and electrical properties applications: pump components, electrical connectors for
high-temperature use
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Processing of Plastics
Source: Kalpakjian, S., “Manufacturing processes for engineering materials”
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Toxic Chemical Released by Industries
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Design Guideline
The American Plastics Council provided design guideline for designers:
• Using fewer materials to make the new product
is better
• Using plastics can be compatible for recycling
• Using material that can be recycled
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Recycling of Plastics: Facts
• In the plastics industry, only a small portion is recycled(that is, PET bottles, styrofoam cups, plates and trays).
• 58 billion pounds of plastic resin sold in the United States and less than 1 % was recycled.
• One of the most pressing environmental issues is the mounting problem of solid waste disposal. Plastic materials of all kinds present about 7 percent of the municipal waste stream
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Recycling TechnologyThe following recycling technologies for plastics are needed:
• Complete plastic identification• Ways to remove paints, metallic coatings, well adhered
labels, or foam insulation from recyclable plastic• Separation of rubber and other elastomers from plastics
with similar densities• Separation of metal foils from recyclable plastic• Identification and removal of potentially hazardous
materials (small batteries, mercury relays, beryllium copper and lead-based solder)
Source: Zhang et al.: J.of Manufacturing systems 16(5), 1997
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Materials Compatibility
• The mingling of different polymers in the recycled stream makes recycling of plastics difficult.
• There is a need for separating plastic components into appropriate categories based on composition.
Design consideration:• Use as few different types of materials as possible• Ensure all materials can be easily separated from the
primary plastics• More than one type of plastics used should be compatible
with one another
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Materials Compatibility Chart
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Materials Identification
When many types of plastics are used in a product and plastic formulations are incompatible, identification system will make recycling easy.
Three major plastics identification systems:
• ISO 1043-1• ASTM D1972-91• SPI Voluntary National Container Material Code System
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Plastics Identification System
(ISO 1043-1)
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Categories of Plastics(The Society of Plastics Industry)
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Use of Plastics in Packaging
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Plastics Degradation
• It takes at least 50 year for plastics to break down in
the environment. • Degradation accelerates the breakdown of plastics.• Degradation can be implemented by chemical,
biological activity, or exposure to sunlight.
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Degradable Plastics
• Biodegradable plasticsDegradation results from the action of naturally occurring microorganisms such as bacteria, fungi, and algae.E.g. synthetic biodegradable materials
• Photodegradable plastics