Mod 7 - Polymers

Question 1

What are addition polymers?

Answer 1

Polymers made from monomers with C=C bonds that open to form long, saturated chains (e.g., PE, PVC, PS, PTFE).

Question 2

How does addition polymerisation occur?

Answer 2

1) Initiation: free radical (e.g., from H2O2) reacts with C=C.

2) Elongation: radical adds more monomers.

3) Termination: two radicals form a covalent bond.

Question 3

Structure and properties of HDPE

Answer 3

Linear, unbranched chains → high density, strong dispersion forces, high melting point, crystalline, hard.
Uses: bottles, toys, utensils.

Question 4

Structure and properties of LDPE

Answer 4

Branched chains → lower density, weaker dispersion forces, lower melting point, amorphous, flexible.
Uses: bags, films, packaging.

Question 5

Structure and properties of PVC

Answer 5

From chloroethene; Cl causes permanent dipoles → stronger forces, higher melting point. Can be rigid or flexible. Durable, acid-resistant, good insulator.
Uses: rigid – pipes, frames; flexible – cling wrap, cable insulation.

Question 6

Structure and properties of PS

Answer 6

From styrene (ethene + benzene ring); bulky rings → brittle, transparent, low density, thermally/electrically insulating.
Uses: Styrofoam, cassette cases, tool handles.

Question 7

Structure and properties of PTFE

Answer 7

From tetrafluoroethene (all H replaced by F); strong dispersion/dipole forces → high melting point, chemically inert, flame/acid resistant, low friction.
Uses: non-stick pans, gaskets, engineering components.

Question 8

What are condensation polymers?

Answer 8

Polymers formed via condensation reactions, producing a small molecule (e.g., H2O). Usually involve two monomer types and are thermoplastics.

Question 9

Types of condensation reactions

Answer 9

Esterification: alcohol + carboxylic acid → ester + H2O
Amidation: amine + carboxylic acid → amide + H2O

Question 10

Polyesters: structure and monomers

Answer 10

Formed by esterification between dicarboxylic acids & dialcohols, or monomers containing both –OH & –COOH.
Example: PET for textiles.

Question 11

Polyesters: properties and uses

Answer 11

High tensile strength, abrasion & heat resistant, thermoplastic, hydrophobic.
Uses: clothing, carpets, bottles, fruit containers, appliances.

Question 12

Polyamides (nylon): structure and monomers

Answer 12

Formed via amidation between amine & carboxylic acid groups.
Monomers: amino acids (Nylon 6) or diamine + dicarboxylic acid (Nylon 66). Can use diacyl chloride to avoid side reactions.

Question 13

Polyamides: properties and uses

Answer 13

Hydrogen bonding → high tensile strength, abrasion-resistant, elastic, thermoplastic, absorbs moisture.
Uses: clothing, carpets, ropes, nets, tents, seat belts.

Question 14

Polyesters vs polyamides

Answer 14

Similarities: condensation polymers, high tensile strength, abrasion-resistant, thermoplastic, used in textiles.
Differences: polyesters – heat-resistant, hydrophobic; polyamides – stronger, absorb moisture, used in ropes/nets.