Colouring virgin polymer is a solved problem. You start from a known, consistent, near-colourless base and add pigment.
Recycled material breaks that assumption in every direction at once. The base colour moves between loads, the material is already partly degraded, it carries contamination and odour, and its melt behaviour is not the same twice. Every one of those needs a different answer.
The core problem: you are matching onto a moving target
Post-consumer recyclate is not a colour. It is a range.
A PCR polyolefin stream might arrive grey-beige one week and yellow-grey the next, depending on what went into the collection, how it was washed, how many heat histories it has carried, and what the sorting yield looked like that month.
If you match a shade against Monday’s material and run Thursday’s, the shade shifts – and no amount of pigment quality prevents that, because the problem is underneath the pigment.
Three practical responses, in order of cost:
1. Measure the incoming base. Take a colour reading of every incoming lot as a plaque or a film. It takes minutes and it converts a surprise into a known variable. This is the single highest-return change most recyclers and converters can make.
2. Match to a tolerance band, not a point. Agree a ΔE tolerance with your customer that reflects the reality of recycled feedstock. A ΔE that is achievable in virgin material may not be achievable in PCR at any sensible cost, and it is far better to negotiate that at the specification stage than at the rejection stage.
3. Correct in the masterbatch, per lot. For high-value work, a supplier can adjust the correction in the concentrate against your measured base colour. This is real work and it is priced accordingly, but it is what makes tight-tolerance recycled colour possible.
Dark colours are your friend
The physics is unavoidable: you can shift a colour darker, never lighter.
A grey-beige recyclate can become black, dark grey, navy, dark green or brown without difficulty, because the pigment dominates whatever was underneath. The same recyclate cannot become white, pastel or bright yellow – the base colour shows through and the result is dirty and inconsistent.
This drives real design decisions:
- Products intended for high recycled content should be designed in dark colours wherever the brand allows it. Getting this into the design brief is worth more than any amount of clever formulating downstream.
- Black is where recycled content is easiest, which is why so much PCR ends up in black. It is also where the carbon black quality question matters most, because you are covering a variable base.
- For light colours, high TiO₂ loading is the only route, and it is expensive. Titanium dioxide has to hide the base entirely before you can build a shade on top. Expect meaningfully higher masterbatch dosages than the equivalent virgin product.
- Optical brighteners help a great deal here. Recyclate’s yellow-grey cast is exactly what a brightener corrects, and it is far cheaper than adding more TiO₂. See optical brighteners in plastics.
Restabilisation: the part that is not about colour
Recyclate arrives with its antioxidant package partly consumed. It has been extruded at least once, often several times, and each pass uses up stabiliser and does a little more damage to the molecular weight.
Which means that if you simply add colour and reprocess, you are putting already-tired material through another heat history with nothing left to protect it. The output is more degraded, more yellow and mechanically weaker than it needed to be.
A restabilisation package – antioxidant, and process stabiliser – is standard practice in serious recycling and it is frequently supplied as part of the masterbatch. It is the cheapest quality improvement available in a recycled stream, and it is routinely skipped.
For outdoor products add UV stabilisation on top, sized for the exposure. And where yellowing is a concern, use a non-discolouring antioxidant system rather than relying on hindered phenol alone – see why white plastic yellows.
Contamination and filtration
Recycled feedstock carries what the collection carried: paper fibre, label adhesive, aluminium fragments, wood, other polymers, sand.
Most of it is removed by melt filtration, but two consequences remain for your colour supply.
Your screen packs are already working harder than they would on virgin. A masterbatch with a poor filter pressure value adds its own load to a filtration system that is close to its limit. FPV matters more in recycled processing than anywhere except thin film – ask for the number. See black specks in plastic parts.
Cross-polymer contamination changes what the carrier must do. A PE stream with a few percent PP in it is a different material from clean PE, and a carrier chosen for clean PE may behave differently. For badly mixed streams, a compatibiliser does more for part quality than any pigment choice.
Odour – the problem nobody puts in the specification
Post-consumer material smells. It carries residues of whatever it contained, plus degradation products from its heat histories, plus whatever it absorbed in collection and storage.
For an industrial product this is often tolerable. For anything a consumer holds – a household article, a personal care pack, a toy, a cosmetic closure – it is a rejection.
Odour is managed with odour-absorber or odour-neutraliser masterbatch, which is a genuinely different thing from a fragrance. An absorber captures the volatile compounds; a fragrance covers them. For consumer products the absorber is usually the right answer, sometimes with a light fragrance on top.
If you are quoting recycled content into a consumer-facing product, raise odour before the sample stage. It is the most common reason a technically successful PCR trial fails commercially.
The regulatory push
India’s Plastic Waste Management Rules and the EPR framework have introduced mandatory recycled content obligations for specified plastic packaging categories, phased in over time and stepping up.
Two practical implications:
Recycled content is becoming a compliance requirement, not a marketing choice. Manufacturers who have treated PCR as optional are finding they need working PCR formulations on a deadline.
Confirm the current obligation for your category directly against the latest notification. The targets and categories have been amended more than once, and secondary sources go stale quickly. Do not plan a formulation programme against a figure from a blog – including this one.
What to tell your masterbatch supplier
- The recyclate stream: polymer, source, PCR or PIR, and how many heat histories
- A colour reading of your actual base material, ideally across several lots so they can see the spread
- Recycled content percentage, and whether it will change
- Target shade with a physical reference and an agreed ΔE tolerance
- Process and wall thickness
- Whether the product is consumer-facing, for odour
- Outdoor exposure, if any
- Existing filtration setup and mesh
- Any food contact or regulatory requirement
FAQs
Why is recycled plastic harder to colour than virgin? Because the base colour varies between lots, the material is already partly degraded, and it carries contamination. You are matching a shade onto a substrate that moves, so the colour moves with it.
Can recycled plastic be made white or pastel? Only with high titanium dioxide loading, and at meaningfully higher cost, because the base colour must be hidden completely before a shade can be built. Dark colours are far easier and more consistent in recycled material.
Does recycled plastic need extra stabiliser? Yes. Recyclate arrives with its antioxidant package partly consumed from previous heat histories. Restabilisation is the cheapest quality improvement available in a recycled stream and it is frequently supplied through the masterbatch.
How do I deal with the smell of recycled plastic? With an odour-absorber masterbatch, which captures the volatile compounds, rather than a fragrance, which covers them. For consumer-facing products, raise odour before the sample stage.
What is a realistic colour tolerance for recycled material? Wider than for virgin, and it should be negotiated at the specification stage. Measuring the incoming base colour of every lot is the single most effective step toward holding a tolerance at all.
Why does filter pressure value matter more with recycled material? Because your melt filtration is already loaded with contamination from the recyclate. A masterbatch with poor FPV adds to a system that is close to its limit, causing more frequent screen changes and pressure spikes.
Is recycled content mandatory in India? Mandatory recycled content obligations apply to specified plastic packaging categories under the EPR framework, phased over time. Confirm the current requirement for your category against the latest notification rather than a secondary source.