Degradable polymers — common mistakes

Be precise with your terminology. 'Biodegradable' implies breakdown by microorganisms, which usually involves hydrolysis of ester or amide links. 'Photodegradable' implies breakdown by light, which involves absorption of UV by C=O groups leading to C-C bond fission. They are not the same process!

Not exactly. All compostable plastics are biodegradable, but not all biodegradable plastics are compostable. 'Compostable' has a stricter definition: the material must break down in a composting environment within a specific timeframe (e.g., 90 days) into non-toxic components. Some biodegradable plastics may break down too slowly or leave behind residues not suitable for compost.

Alkaline hydrolysis is saponification. Instead of producing a carboxylic acid, you will form the sodium salt of the carboxylic acid (a carboxylate salt) and the alcohol. For example, hydrolysing PLA with NaOH would produce sodium lactate and water.

It is generally not advisable. The additives that promote photodegradation can destabilise the recycled polymer blend, making the final recycled product weak and unreliable. This is a key challenge in managing plastic waste streams.

Biodegradable polymers like poly(glycolic acid) (PGA) and poly(lactic acid) (PLA) are used for dissolvable stitches. They are strong enough to hold tissue while it heals, but then they safely hydrolyse in the body into harmless products (like glycolic acid and lactic acid) which are then metabolised and excreted. This avoids the need for a second procedure to remove the stitches.