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) Date: April 14, 2000 Slide:3 Use of Selected Commodities

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:4 Material in a Typical U.S. Automobile Unit:kg

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:5 Flow of Plastics in an Automobile Unit:kg

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:6 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

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:7 Fundamentals of Plastics (cont.) Major molecular structure which determines the properties of the polymer linear branched cross-linked network. Additives fillers plasticizers colorants

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:8 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

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:9 Thermoplastics: Applications Source: Kalpakjian, S., “Manufacturing processes for engineering materials”

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:10 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

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:11 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

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:12 Processing of Plastics Source: Kalpakjian, S., “Manufacturing processes for engineering materials”

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:13 Toxic Chemical Released by Industries

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:14 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

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:15 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

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:16 Recycling Technology The 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

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:17 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

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:18 Materials Compatibility Chart

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:19 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 ASTM D SPI Voluntary National Container Material Code System

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:20 Plastics Identification System (ISO )

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:21 Categories of Plastics (The Society of Plastics Industry)

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:22 Use of Plastics in Packaging

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:23 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.

Environmentally Conscious Design & Manufacturing (ME592) Date: April 14, 2000 Slide:24 Degradable Plastics Biodegradable plastics Degradation results from the action of naturally occurring microorganisms such as bacteria, fungi, and algae. E.g. synthetic biodegradable materials Photodegradable plastics