The Inventor's Notebook
PET Recycling
– And What It Could Look Like Under Today’s R&D Tax Relief Rules
Published: 16th March 2026
Author: Beck on Tech
In the early 1970s, long before “circular economy” became boardroom vocabulary, a fibre chemist named Nathaniel C. Wyeth was wrestling with a problem that had nothing to do with recycling. Working at DuPont, Wyeth wanted to make plastic bottles that were strong enough to hold carbonated drinks without exploding under pressure. Glass was heavy and fragile. The world needed lighter packaging.
Wyeth’s answer was a polymer already known to science: polyethylene terephthalate a.k.a. PET. By carefully controlling its crystallinity and orientation during processing, he created bottles that were tough, transparent and remarkably light. In 1973, he patented the first PET beverage bottle. The age of lightweight plastic packaging had arrived.
But innovation has consequences. PET‘s success was meteoric. By the 1980s, billions of bottles were in circulation. Durable, cheap and ubiquitous, they quickly became a symbol of convenience… and mounting waste.
Then came the second act of the story: the engineers who asked not how to make better bottles, but how to unmake them.
The Birth of Bottle-to-Bottle Recycling
By the late 1980s and early 1990s, researchers realised PET had a hidden superpower: unlike many mixed plastics, it could be melted and reprocessed with relatively little loss in properties if contamination could be controlled.
Mechanical recycling emerged first. Collected bottles were:
- Sorted (often by resin identification and colour)
- Washed and decontaminated
- Shredded into flakes
- Melt-filtered and re-extruded into pellets
These pellets could be spun into polyester fibre or, with sufficiently rigorous decontamination, made back into food-grade bottles.
A parallel, more radical path also developed: chemical recycling.
Instead of melting PET, chemists broke it back into its monomers, terephthalic acid (TPA) or dimethyl terephthalate (DMT), and ethylene glycol, using glycolysis, methanolysis or hydrolysis. These purified building blocks could then be repolymerised into virgin-quality PET.
By the early 2000s, “bottle-to-bottle” closed-loop recycling was not just technically possible; it was commercially viable. Today, recycled PET (rPET) is one of the most widely used recycled plastics globally.
On Global Recycling Day, PET recycling stands as a case study in how science can turn a waste problem into a materials solution.
The Science That Made It Work
The technical challenge wasn’t melting plastic. It was safety and performance.
Food-grade rPET required:
- Removal of contaminants (e.g., food residues, adhesives, other polymers)
- Control of intrinsic viscosity (to maintain mechanical strength)
- Demonstration that unknown contaminants would not migrate into food
European regulators required rigorous challenge testing, deliberately contaminating PET and proving that the recycling process removed hazardous substances to safe levels. This led to advances in:
- Solid-state polycondensation to rebuild molecular weight
- Vacuum decontamination reactors
- Analytical migration testing
The innovation wasn’t a single breakthrough. It was cumulative, uncertain and experimentally driven, exactly the kind of work modern R&D frameworks are designed to recognise.
Would PET Recycling Qualify for R&D Tax Relief Today?
Under current UK R&D tax relief rules, a project qualifies if it seeks to achieve an advance in science or technology by resolving scientific or technological uncertainty. PET recycling could fit within the scope of the current R&D tax relief criteria, provided certain criteria were met:
Seeking an Advance in Science or Technology
To qualify under R&D tax relief, a project must contribute to an advance in science or technology and address a scientific or technological uncertainty, rather than simply apply routine engineering.
Researchers sought advances in:
- Polymer decontamination science
- Rebuilding molecular weight after thermal degradation
- Demonstrating food-contact safety through migration modelling
These were advances in materials science and chemical engineering, not just business improvements.
Was there Technological Uncertainty?
Engineers were likely to have faced genuine uncertainties, including:
- Could contaminants be removed to food-grade standards?
- Would repeated melt cycles irreversibly degrade polymer chains?
- Could solid-state polycondensation restore intrinsic viscosity reliability?
- Would recycled PET perform identically under carbonation pressure?
At the time, these answers were not publicly available or readily deducible. Systematic experimentation was required.
Was There a Process of Investigation/Experimentation?
Recycling pioneers undertook:
- Controlled contamination challenge tests
- Pilot-scale reactor trials
- Iterative extrusion and viscosity measurements
- Migration and analytical chemistry studies
These are likely to qualify as R&D activities, as they involved experimental design, testing, analysis and iteration.
Which Costs Would Likely Qualify Today?
If undertaken today by a UK company, qualifying expenditure could include:
- Staff costs for polymer scientists and process engineers
- Consumables (chemicals, test batches, pilot-scale materials)
- Prototype processing equipment
- Externally provided workers or subcontracted lab testing
- Software used in process modelling
Would Chemical Recycling Also Qualify?
Depolymerising PET back to monomers involved significant chemical uncertainty:
- Optimising catalysts
- Managing side reactions
- Controlling purity at industrial scale
These challenges align with the definition of resolving scientific or technological uncertainty in chemistry and process engineering.
Why This Story Matters on Global Recycling Day
PET recycling is more than a waste-management success. It’s proof that environmental progress often emerges from rigorous, uncertain, experimental work.
The engineers who closed the loop on polyester weren’t “just improving a process”. They were solving polymer degradation kinetics, contaminant diffusion modelling and solid-state reaction engineering.
In today’s language, they were likely to be conducting qualifying R&D.
The climate transition depends on thousands of similar advances:
- Advanced sorting technologies
- Enzymatic depolymerisation
- Multi-layer plastic separation
- Low-energy chemical recycling
Each carries technological uncertainty. Each requires systematic investigation. We believe that each is the kind of innovation that R&D tax relief is designed to support.
Global Recycling Day is often framed as behavioural change: recycle more, waste less.
But its deeper message is technological: recycling at scale only works because scientists pushed materials beyond what was previously possible.
The PET bottle was invented to solve a packaging problem.
Recycling it solved a planetary one.
Bibliography
- Wyeth, N. C. (1973). Biaxially oriented polyethylene terephthalate bottle. US Patent 3,733,309.
- https://patents.google.com/patent/US3733309
- Awaja, F., & Pavel, D. (2005). Recycling of PET. European Polymer Journal, 41(7), 1453–1477.
- https://doi.org/10.1016/j.eurpolymj.2005.02.005
- Welle, F. (2011). Twenty years of PET bottle to bottle recycling—An overview. Resources, Conservation and Recycling, 55(11), 865–875.
- https://doi.org/10.1016/j.resconrec.2011.04.009
- Al-Sabagh, A. M., et al. (2016). Greener routes for recycling of polyethylene terephthalate. Egyptian Journal of Petroleum, 25(1), 53–64.
- https://doi.org/10.1016/j.ejpe.2015.03.001
- European Food Safety Authority (EFSA). (2011). Scientific opinion on the criteria to be used for safety evaluation of mechanical recycling processes for PET.
- https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2011.2184
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