Q.List the materials which do not decay even after a long time.

PHBV and Nylon-2-Nylon-6 are biodegradable copolymers; ordinary Nylon-6,6 is a non-biodegradable synthetic polyamide.

• PHBV (poly-beta-hydroxybutyrate-co-beta-hydroxyvalerate) is a copolymer of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid, produced/degraded by micro-organisms — it is biodegradable and used in packaging and medical implants.

• Nylon-2-Nylon-6 is an alternating polyamide copolymer of glycine (H2N-CH2-COOH) and 6-aminohexanoic acid — the amide linkages here are readily hydrolysed/degraded biologically, making it biodegradable.

• Nylon-6,6, made from hexamethylenediamine and adipic acid, is a tough, chemically resistant fibre-forming polyamide that resists microbial degradation — it is NOT biodegradable.

Nylon-2-nylon-6 is the standard example of a biodegradable polyamide copolymer.

Nylon-2-nylon-6 is formed by the alternating condensation copolymerisation of glycine ($H_2N$–$CH_2$–$COOH$, an amino acid) and 6-aminohexanoic acid (ε-aminocaproic acid, $H_2N$–$(CH_2)_5$–$COOH$), giving repeating amide (peptide-like) linkages. Because it contains ester-like/peptide amide linkages similar to natural proteins, it is biodegradable, unlike ordinary nylons.

Biodegradable polymers are broken down by microorganisms in the environment into simple, non-toxic products; PHBV is a well-known example used to make packaging films and orthopaedic devices.

Biodegradable polymers are polymers that can be decomposed by the action of biological agents (bacteria, enzymes) in the environment, breaking down into harmless, simple by-products (like CO2, H2O and biomass), unlike conventional plastics which persist for a very long time.

Example: PHBV (poly-beta-hydroxybutyrate-co-beta-hydroxyvalerate) is a biodegradable copolymer of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid, formed by polyesterification. It is used in specialty packaging, orthopaedic devices, and controlled drug release, and is degraded by soil bacteria.

Other accepted examples: Nylon 2-nylon 6 (a biodegradable polyamide copolymer), and PLA (polylactic acid).

A biodegradable polymer is one whose chain can be enzymatically broken down by microorganisms into simple, environmentally-safe products (CO₂, H₂O, biomass) rather than persisting in the environment for centuries like conventional plastics.

Most synthetic polymers (like polyethylene or PVC) have carbon–carbon backbones that microorganisms cannot easily attack, so they persist in landfills/oceans for very long periods, causing plastic pollution. Biodegradable polymers are specifically designed with hydrolysable linkages (usually ester or amide bonds, similar to those found in natural biomolecules) built into their backbone, so that soil/water bacteria can secrete enzymes that break these bonds, decomposing the polymer into small, harmless, naturally recyclable molecules.

Example: PHBV (poly-β-hydroxybutyrate-co-β-hydroxy valerate) is a copolymer of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid; it is widely used for packaging and controlled drug release precisely because it degrades naturally in the environment. Another example is Nylon-2-nylon-6, an alternating polyamide copolymer of glycine and amino-caproic acid, which also degrades biologically due to its amide linkages (chemically analogous to the peptide bonds of proteins).