Polymers - 18

A very large molecule built from many small units or molecules called monomers. Monomers are joined together by covalent bonds. The chemical process of joining the large number of monomers to form a polymer is called polymerisation

They must be unsaturated, contain C=C or $C\equiv C$

Results in the formation of only one product, the polymer. Monomers join together without any loss of atoms or molecules

high temp & pressure, catalyst. Reason: High temp & pressure provides the activation energy required to break the strong C=C bond Catalyst increases rate of reaction

Mass of polymer formed using a given number of monomers equals the total mass of monomers used

As clingfilm to wrap food, plastic ziploc bags and plastic grocery bags, to make plastic toys, plastic pails

Plastic waste cannot be decomposed hence take up space in landfills and accumulates

Plastics thrown into the sea endanger marine animals e.g. turtles mistaking plastic bags for food and choking on them. Plastics also clog up rivers and drains potentially becoming breeding grounds for mosquitoes

Plastics are flammable and when incenerated, poisonous gases are formed. E.g. PVC producing acidic and corrosive hydrogen chloride gas; polyethene producing carbon dioxide

Mechanical recycling where chemical composition of recycled plastic remains unchanged. Small pieces of plastics are melted, cooled, and pulled into strands then cut into pellets used to make new products

Uses chemical reactions e.g. cracking to convert plastic waste into different useful raw materials. Plastic waste e.g. polyethene waste are cracked to form short-chain alkanes and alkenes. Conditions for cracking include high temps and presence of catalyst

Steps in recycling may produce wastewater containing harmful substances which needs to be treated before release to prevent water pollution

May be more expensive than disposal in landfills or incineration due to energy, machinery and manpower costs in transportation, sorting, and cleaning, thus not being economically viable if those costs exceed market value of recycled plastics

Time and effort to educate people to form new lifestyle habits of correct recycling, inappropriate disposal of recyclable plastics together with food waste, throwing non-recyclable items into recycling bins