13.5 Polymerisation In Alkenes
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What is addition polymerisation?
Formation of a very long molecular chain, by repeated addition reactions of many unsaturated alkene molecules (monomers)
What is a monomer?
A small molecule that combines with many other monomers to form a polymer
How is addition polymerisation carried out in industry?
High temperatures High pressure Presence of catalysts
What is a repeat unit?
Specific arrangement of atoms in the polymer molecule that repeats over and over again
How is the repeat unit written?
Always written in square brackets
Uses of poly(ethene)
Supermarket bags Shampoo bottles Children’s toys
Poly(chloroethene) uses
Pipes Sheets/films Insulation cables Flooring
Poly(propene) uses
Children’s toys Guttering uPVC windows
Poly(styrene) uses
Packaging material Food trays/cups
Poly(tetrafluoroethene) uses
Coating for non stick pans Cable insulation
Why are polymers suitable for storing food?
Lack of reactivity
Why are polymers hard to dispose of?
They are unreactive Non biodegradable
Recycling polymers
Conserve fossil fuels by decreasing waste going to landfill Once sorted, polymers are chopped into flakes, washed, dried and melted Recycled polymer is cut into pellets and used by manufacturers to make new products
Why is PVC difficult to recycle?
High chlorine content Dumping in landfill is not sustainable When burnt, releases Hydrogen Chloride - corrosive gas
How is PVC recycled now?
Using solvents to dissolve the polymer High grade PVC is recovered by precipitation from the solvent and used again
How are waste polymers used as fuel?
They have a high stored energy value Can be incinerated to produce heat, generate steam to drive a turbine - produces electricity
What is feedstock recycling?
Chemical and thermal processes that reclaim monomers, gases, or oil from waste polymers Products from feedstock recycling resemble those produced from crude oil in refineries These materials can be used as raw materials to produce new polymers
Advantage of feedstock recycling
Can handle unsorted and unwashed polymers
What are bioplastics made of?
Plant starch Cellulose Plant oils Proteins
What are biodegradable polymers broken down into?
Water, Carbon Dioxide and biological compounds
How are biodegradable polymers made?
Made of starch or cellulose Contain additives that change the structure of traditional polymers so microorganisms can break them down
How do photodegradable polymers work?
Contain bonds that are weakened by absorbing light to start degradation Or light absorbing additives are used