Different States• Different parts of a plastic may be ordered
or random• Ordered is crystalline• Random is a glass structure• Since most polymers have a random
structure – Cold – glass state– Warm – rubber state
• Glass transition temperature, Tg, separates
Tg’s
• Polystyrene - 100°C – plastic utensils
• LDPE - -100°C – soft plastics– Melts at 108°C
• Natural rubber – way below 0°C – tires
• Polyester - 73°C – non-wrinkle fabrics
Natural Rubber
• Monomer is cis - isoprene
• Slowly flows and is sticky
• 1839 – Charles Goodyear discovered vulcanization– X-linking with sulfur– Elastomer
• Synthetic rubber, hard and brittle – trans– True synthetic (cis) not until 1955
Conducting polymers
• Alternating single and double bonds in chain– Example polyacetylene or polyethyne
• Conduction can be directional– Along chains but not across
Recycling
• Solid waste: 4 lbs / person per day– For 250 million people in US – 1 billion lbs/day
• Make up of garbage?
Recycling
• Solid waste: 4 lbs / person per day– For 250 million people in US – 1 billion lbs/day
• Make up of garbage?
• In order to recycle, 4 things needed:– Collection– Sorting– Reclamation– End-use
Problems for plastic
Problems for paper
Amount Recycled
• Aluminum cans – 65%
• Paper – 20%
• Glass – 10%
• Plastic – 3% - Why?– Economics– Sorting
• Plastic container codes