Polymers

Question 1

Polymers

Answer 1

Covalent molecular substances composed of many small molecules joined together, Naming: Poly[monomer]

Question 2

Monomers

Answer 2

Small molecules, joined together by a polymerisation reaction

Question 3

Types of polymers

Answer 3

Many found in nature (biodegradable), E.g- carbohydrates, proteins, cotton, spider silk, latex, Synthetic, E.g- polyesters, nylon, Teflon, polythene, PET

Question 4

Structural properties of polymers

Answer 4

Determined primarily by the type of monomer used, factors: length, branching, cross-linking

Question 5

How chain length affects polymers

Answer 5

As chain length increases, strength of dispersion forces increases, increasing melting and boiling point, Increased dispersion forces makes the polymer harder and more rigid

Question 6

How branching affects polymers

Answer 6

Occurs when some monomers react with sites on the side of the polymer chain instead of the polymer chain, Causes polymers chains to be further apart, decreasing the strength of the intermolecular forces which decreases melting and boiling point as well as density but increases flexibility, High density polyethene has up to 95% crystalline regions, Low density polyethene has as low as 65% crystalline regions

Question 7

How cross-linking affects polymers

Answer 7

When polymer branches are covalently bonded to neighbouring polymer chains meaning it can’t be reshaped due to the strong covalent bonds

Question 8

Thermoplastic

Answer 8

When there are no cross-links, can be heated and reshaped/recycled

Question 9

Thermoset plastic

Answer 9

Can’t be turned into a liquid and moulded, decompose or burn when heated, can’t be recycled

Question 10

Elastomers

Answer 10

when only occasional cross-links are present, chains can move past each other when stretched but cross-links return once force is released, E.g rubber bands, stockings, car tyres

Question 11

Addition polymerisation

Answer 11

Monomer is unsaturated (contains a double or triple bond), Requires a catalyst to initiate the reaction, Double or triple bond is broken (opens molecule) and single bonds are formed between the monomers

Question 12

Condensation polymerisation

Answer 12

Two monomers which have functional groups on each end of the monomer, Water is eliminated, Repeating unit- comes from both reactants, E.g- polyesters, polyamides, silicones

Question 13

Polyesters

Answer 13

Typically formed by combining a dicarboxylic acid monomer with a diol monomer in a condensation polymerisation reaction, Produces water molecules

Question 14

Polyethylene terephthalate (PET)

Answer 14

Monomers- ethane-1,2 diol and benzene-1,4-dicarboxylic acid, Used in: Fabrics, Recyclable drink bottles, Food packaging

Question 15

Polyamides

Answer 15

Typically formed by combining a dicarboxylic acid monomer with a diamine monomer in a condensation polymerisation reaction, Produces water molecules

Question 16

Nylon

Answer 16

Easily drawn into fibres with high tensile strength, Used to make strong, lightweight materials for clothes, parachutes, ropes, fishing line and guitar strings, Can also make hard, rigid plastics that can be used pipe

Question 17

Silicones

Answer 17

Have an alternative backbone of silicon and oxygen with organic groups attached to each silicon atom, Considered inorganic polymers as there is no carbon in the backbone, Made by condensation polymerisation, Can be oils, greases or rubbery solids, Repels water and water-based products so is used in lubricants, waterproofing, furniture and car polishes, Also used in medical implants

Question 18

Advantages of polymers

Answer 18

Can be designed for improved physical and chemical properties, Developing biodegradable and recyclable polymers

Question 19

Copolymers

Answer 19

Polymer made from at least two different monomers, Both addition and condensation polymers

Question 20

Crystallinity

Answer 20

Materials made from polymers consisting of many long chains that twist around each other, with intermolecular forces from one chain to another, Many polymeric materials contain both crystalline regions and amorphous regions, Percentage of the polymer that is crystalline affects the properties (not percentage of amorphous)

Question 21

Crystalline regions

Answer 21

closely packed and have stronger intermolecular forces which prevents transmission of light and appears cloudy

Question 22

Amorphous regions

Answer 22

randomly tangled and unable to pack close together meaning they are less rigid, weaker and often more transparent

Question 23

Additives

Answer 23

Used to improve or extend the properties of the polymers, Include pigments and UV stabilisers, flame retardants and plasticisers

Question 24

Plasticisers

Answer 24

Small molecules added to polymers during manufacture, Forces polymers slightly further apart, weaking intermolecular forces making the material softer and more flexible

Question 25

Foamed polymers

Answer 25

Formed by blowing gas through melted polymer material, Eg. Polystyrene foam- produced by introducing pentane into melted polystyrene beads which causes them to swell up to produce the lightweight, insulating, shock-absorbing foam used for packing material

Question 26

Environmental impact of polymers

Answer 26

Many polymers are derived from petroleum which is non-renewable and thus increases the environmental impact associated with their production, Plastics are durable, chemically resistant and lightweight however this means they biodegrade very slowly, Waste plastics persist for a long time and low density means they take up a lot of room in land fill and burning releases toxic products

Question 27

Two ways of recycling

Answer 27

Reprocessing- involves shredding, melting and reshaping used plastic into clean products (can only be used by thermoplastics)
Depolymerisation- involves breaking the polymer back into monomers usually by heating, requires a large amount of energy and has a low yield making it less economically viable than reprocessing