Lesson 33 of 34
A hydrolysable link helps degradation, but conditions still determine the rate
Chemical structure, processing and collection systems all affect a material's useful life and environmental cost.
A-Level 9476 (2026-2027)
I can explain difficulty biodegrading poly(alkenes).Syllabus
Syllabus 9476, 11.10(e). Explain difficulty biodegrading poly(alkenes).
I can relate polyester/polyamide degradation to hydrolysis.Syllabus
Syllabus 9476, 11.10(f). Relate polyester/polyamide degradation to hydrolysis.
I can evaluate plastic recycling and finite resources.Syllabus
Syllabus 9476, 11.10(g). Evaluate plastic recycling and finite resources.
A hydrolysable link helps degradation, but conditions still determine the rate
Chemical structure, processing and collection systems all affect a material's useful life and environmental cost.
Poly(alkenes) have strong C-C and C-H bonds and no groups in the chain that water can easily split. Because they are so unreactive, living things find them hard to break down. Cutting plastic into smaller pieces does not turn it into small harmless molecules. Breaking into fragments and biodegrading are different processes.
Polyesters and polyamides contain ester or amide links that can be hydrolysed. So they usually biodegrade more easily than a poly(alkene) chain. How fast they actually break down still depends on temperature, water, how crystalline the polymer is, the chain structure and suitable microorganisms. Having ester or amide links does not guarantee fast decay everywhere.
| Dimension | Questions that matter |
|---|---|
| Economic | What are collection, sorting, cleaning, transport and processing costs? Does recycled material retain enough quality and market demand? |
| Environmental | How much virgin feedstock and energy are saved? What are the emissions, contamination and losses across the full process? |
| Social | Are collection systems accessible? Can users sort the material reliably? How are workers and communities affected? |
The materials and the raw materials used to make them are limited. Reusing and recycling can reduce the need for new material. But mixed polymers, additives and dirt can make recovery hard. A material made from plants is not automatically biodegradable. A biodegradable material is not suitable for every recycling stream. State the trade-off that the data support, and do not judge a material by one label alone.
Check your understanding
Which polymer is most likely to be broken down by hydrolysis in the environment?
Show the answer
Poly(lactic acid), a polyester
Poly(lactic acid) has ester links in its main chain. Water, helped by microbial enzymes, can hydrolyse these links and cut the chain.
Check your understanding
A town is deciding whether to recycle used plastic bottles. Which pair is one economic and one environmental factor?
Show the answer
The cost of collecting and sorting bottles; the crude oil saved and the energy used in reprocessing
Economic factors are about money: collection, sorting and cleaning costs against the price of recycled plastic. Environmental factors include saving finite crude oil, less landfill, and the energy and CO2 of transport and reprocessing.