Plastic Regrind and How Buyers Judge Its Value

Plastic regrind is plastic that has been ground back down into flake or chip, either from factory scrap or from washed post-consumer waste, and is sold in that form rather than melted into pellets. It is a real traded commodity with its own price ladder, and the rung a given batch sits on is decided almost entirely by consistency.

Regrind is unusual among recycled materials because the same load looks completely different from the two ends of the transaction. To the plant producing it, it is output to be graded and moved. To the moulder buying it, it is an input risk to be tested before it goes anywhere near a screw. This page is written twice for that reason — once from the selling side, once from the buying side — because the questions genuinely do not overlap.

What Regrind Actually Is

Dictionaries define regrind as material that has been ground again, which is true and tells you nothing useful. The trade definition is narrower: regrind is size-reduced plastic that has not been through an extruder. Everything else follows from that one fact.

It comes from two quite different places, and the distinction sets the price before anything else is measured. Post-industrial regrind is factory scrap — sprues, runners, rejected mouldings, trim, purgings — ground on site. The polymer is known, the colour is known, the heat history is one cycle, and it is usually clean enough to go straight back into the process that made it. Post-consumer regrind has been used, collected, sorted and washed before grinding. It carries an unknown history and a contamination question that never fully closes, and it trades well below post-industrial material of the same polymer — although it is the only one of the two that counts towards a recycled content requirement.

Physically, regrind is what leaves a crusher after the screen: flake in the region of 12–20 mm for bottle material, coarser for thick-wall scrap. Bulky input such as drums, crates and purgings passes through a shredder first, because a crusher cannot take it whole. The screen size sets the flake size, and it also decides how much of the batch comes out as fines — dust and fragments far smaller than the target. Fines matter more than their weight suggests. They absorb moisture faster than flake, they melt ahead of it and can degrade while the rest is still solid, and they cause the bridging and inconsistent dosing that moulders complain about. A batch described as “20 mm regrind” that is ten percent dust is not the material the description implies.

Flake size is set by the crusher screen and differs by stream: 8–16 mm for rigid drums, crates and pipe, 12–20 mm for PET bottle material, and 60–100 mm for film and woven sacks, which are cut rather than ground. A crusher screen runs 8–100 mm across its range, so the size in your specification is a screen choice made once, not something adjusted later. The machine behind that choice is costed on its own terms: what the size-reduction stage costs to run is broken out crusher by crusher, with the parameter ranges that move each figure.

Regrind is also not the same thing as recycled pellets. Pellets have been melted, filtered and cut, which removes solid contamination and produces a uniform, free-flowing shape. That extra step is why pellets carry a premium and why regrind carries a discount.

If You Are Selling Regrind

The seller’s problem is that the value of a load is set by its worst characteristic, not its average one.

What actually decides what you get paid

Polymer certainty comes first. A load described as PP that contains a few percent PE is not slightly worse PP — for many applications it is unusable, because the two do not blend into a predictable melt. Polymer purity is decided upstream at sorting and, for mixed-density streams, in a sink-float separation tank; it cannot be improved after grinding.

Colour comes second and it is one-directional. Natural and light material can go anywhere. Mixed colour goes to applications where appearance does not matter, at a lower price, and no amount of washing brings it back. Sorting by colour before grinding is the only lever, and it is a labour cost you either pay or accept as a discount.

Moisture comes third and it is the one most often mishandled, because material can leave the line dry and arrive wet. A centrifugal dryer at around 1500 rpm brings washed flake to 0.5–2% and a hot-air stage takes it below 1%, but hygroscopic material left in an open bag in a humid warehouse climbs back up. Bag it properly, keep it inside, and ship it reasonably soon after it is made.

Then flake size consistency, and finally fines content, which most sellers do not measure and most serious buyers do. Fines are worth a paragraph of their own because they are the one property a seller can still fix cheaply. Dust comes from the crusher screen being finer than it needs to be, from blunt knives tearing rather than cutting, and from material recirculating in the chamber longer than intended. All three are adjustable. A vibrating screen deck after the crusher removes what is already there, and it costs a fraction of what the same problem costs as a permanent discount on every load.

What the buyer is going to test

Two numbers do most of the work, and it is worth knowing them before a load leaves rather than after.

Melt flow index tells the buyer how the material will behave in their machine. It also reveals history: heavily degraded material shows a shifted MFI, and a batch whose MFI does not match the grade being claimed will be questioned. Moisture is checked because it causes splay, bubbles and, in polyesters, chain scission during processing.

Beyond those two, expect a visual check for colour consistency and black specks, a screen test for fines and oversize, and on any serious quantity a trial run. The trial is the one that decides repeat business, because it exposes what a sample cannot: whether bag forty behaves like bag one.

Where the grade is actually won

Almost everything that lifts a batch happens before the crusher, not after. Sorting harder, separating colours, running the material through a proper plastic recycling washing line rather than a rinse, adding a friction washer where the dirt is adhering rather than loose, and keeping metal out of the feed all raise the ceiling. After grinding, your options narrow to screening out fines and drying properly. Which of those stages your material actually justifies is the subject of the machines a plastic recycling line actually needs.

There is one larger step available, which is to stop selling regrind and start selling pellets. Putting the flake through a pelletizing line adds melt filtration, which removes solid contamination that no mechanical stage caught, and produces a uniform pellet that doses accurately. It costs capital, power and a heat cycle. Whether it pays depends on the buyers available to you, which is the subject of where to sell recycled plastic granules.

One thing that costs nothing and returns more than most equipment: describe the material honestly. A buyer who receives what the specification said will come back at the same price. A buyer who receives a surprise will discount every future load whether or not the next one is good.

If You Are Buying Regrind

The buyer’s problem is the mirror image. You are not buying a specification, you are buying a batch, and the two are only as related as the seller’s process control makes them.

Judging a load before you pay for it

Start with the question of what the material was. Post-industrial scrap from a named process is a different risk from post-consumer material of unknown origin, even at identical stated polymer and MFI. Ask what it was before it was ground; a seller who cannot answer is telling you something.

Then insist that the sample comes from more than one bag. This is the single most useful precaution in the whole transaction. Regrind is produced in batches and bagged in batches, and the variation that ruins a production run is variation between bags, not within one. A perfect sample drawn from one bag out of forty proves that one bag was good.

Check for fines by pouring some through a screen, look at the bottom of the bag where dust settles, and put a magnet through a handful. Then run a small quantity on the actual machine before committing to the volume. Nothing on paper substitutes for that.

How much you can blend

There is no universal percentage, and any supplier who offers one without asking about your part is guessing. What sets the limit is the application: a structural component with a defined impact requirement tolerates far less than a thick-walled non-visible part, and a thin-wall part with a Class A surface tolerates less again because contamination shows.

The workable method is to establish it empirically. Start low, hold everything else constant, and step the ratio up until something moves — surface finish, cycle time, reject rate, a mechanical property you test. Then step back one increment and write that number down as your limit for that material from that supplier. It is specific to all three of those variables, and it changes if any of them changes.

The blocked screen — where cheap regrind gets expensive

The failure that costs real money is not a bad part. It is a blocked screen pack.

Regrind has never been through a melt filter, so any solid contamination that survived sorting and washing is still in it: metal fragments, paper fibre, sand, unmelted foreign polymer. In an extruder that arrives at the screen pack, pressure climbs, output falls, and eventually the line stops for a changeover. Each event is minutes of downtime, a screen, and a quantity of purged material. Do it three times in a shift and the saving on the material is gone.

This is the honest comparison between regrind and recycled pellets. Pellets have already been through a filter — typically 40–120 mesh — and part of the premium you pay for them is the screen changes you do not make. If your process runs fine mesh or your tolerance for unplanned stops is low, cheap regrind is frequently the more expensive option.

Food contact

The short answer is no, unless a specific process has been assessed for it. Food-contact use depends on the recycling process being evaluated by a regulator — in Europe by EFSA under the food contact materials framework — and generic regrind of unknown origin has not been. Post-industrial regrind of a food-grade resin, generated and reused inside the same controlled process, is a different and much narrower case, and it is a question for your own compliance function rather than for your material supplier.

Virgin, Regrind and Recycled Pellets Side by Side

Put the three next to each other and the price ladder explains itself.

Regrind is not simply cheaper recycled material. It is material whose remaining processing cost has been transferred from the seller’s plant to the buyer’s, in the form of screen changes, dosing variability and testing. Sometimes that transfer is a bargain and sometimes it is not, and which one it is depends on the buyer’s process rather than on the material.

There is a third force on the market now that has nothing to do with either party’s process. Regulated recycled-content requirements are pulling demand towards documented, traceable material, and documentation is easier to attach to a pelletized product with a controlled input stream than to a mixed load of flake — the position set out in PCR resin and recycled content requirements.

Frequently Asked Questions