13.5 Polymerisation In Alkenes Flashcards
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
