Synthetic Polymers
World D — Polymers & Biomolecules
40.A — ADDITION POLYMERS
R40.01 Polythene (LDPE vs HDPE)
- LDPE: Highly branched, cannot pack well. Flexible, used for plastic bags and squeeze bottles.
- HDPE: Linear chains pack closely. High density and rigid. Used for buckets and tough pipes.
R40.02 Polyvinyl Chloride (PVC)
- Monomer: Vinyl chloride ($CH_2=CHCl$).
- Tough, rigid, and resistant to chemicals/fire (due to Chlorine).
- Used for plumbing pipes, electrical insulation, and vinyl flooring.
R40.03 Teflon (PTFE)
- Polytetrafluoroethylene. Monomer: $CF_2=CF_2$.
- Extremely unreactive. C-F bonds are incredibly strong.
- Used as non-stick coating for cookware and industrial seals.
R40.04 Polystyrene (PS)
- Monomer: Styrene (Vinyl benzene).
- Contains bulky benzene rings preventing close packing.
- When blown with gas, forms foam (Styrofoam) for insulation and packaging.
40.B — CONDENSATION FIBERS
R40.05 Polyamides (Nylon 6,6)
- Formed from a diamine and a dicarboxylic acid.
- Amide linkages (-CONH-) hold the chain.
- Strong intermolecular hydrogen bonds make it a tough fiber (Ropes, textiles, bristles).
♳
R40.06 Polyesters (Terylene/PET)
- Formed from a diol and a dicarboxylic acid.
- Ester linkages (-COO-) hold the chain.
- Crease-resistant fabric (Dacron/Terylene) and plastic water bottles (PET).
40.C — THERMOSETTING RESINS
🔌
R40.07 Bakelite
- Phenol-Formaldehyde resin.
- Heavily cross-linked 3D network formed via condensation.
- Heat/electricity insulator. Used in electrical switches and handles of utensils.
🍴
R40.08 Melamine Resin
- Melamine-Formaldehyde polymer.
- Highly cross-linked and extremely hard.
- Used for unbreakable crockery and laminate countertops.
40.D — SYNTHETIC RUBBERS
🌳
VS
R40.09 Natural vs Synthetic Rubber
- Natural rubber (polyisoprene) is soft and gets sticky when hot.
- Synthetic rubbers are engineered for high durability, oil resistance, and mechanical strength.
S
S
R40.10 Vulcanization
- Heating raw rubber with Sulfur.
- Creates sulfur cross-links (-S-S-) between polymer chains.
- Improves elasticity, prevents melting when hot or becoming brittle when cold.
BUNA-S
R40.11 Buna-S & Buna-N
- Buna-S (SBR): Copolymer of Butadiene and Styrene. Used for car tires.
- Buna-N: Copolymer of Butadiene and Acrylonitrile. Resistant to oil/petrol, used for tank linings.
🌱
R40.12 Biodegradable Polymers
- Most synthetic polymers pollute for centuries (non-biodegradable).
- New engineered polymers (like PHBV or PLA) contain ester bonds that bacteria can break down over time.