The short answer
Post-consumer recycled (PCR) resin molds like its virgin family but varies more. Expect wider melt flow from lot to lot, more gels and specks, odor and volatiles that need venting, limited colors, and lower impact and stress-crack resistance. Dry hygroscopic PCR (especially rPET) harder than virgin, check melt flow and contamination on every lot, start around 10–25% blended with virgin, and step up while the part still passes. Food contact needs an FDA no-objection letter for the recycling process.
This page covers processing. For which content counts and how to document it, see adding recycled content (PCR or PIR). For the grades we source, see recycled resin (PCR / PIR).
PCR, PIR and regrind
- PCR: plastic recovered after its end use, from households or commercial and institutional users. Many state packaging laws and brand targets count only PCR.
- PIR (post-industrial or pre-consumer): scrap diverted from a manufacturing waste stream. More consistent, but often not counted toward PCR targets.
- Regrind fed back into the process that made it counts as neither. See regrind limits by resin.
What changes vs. virgin
Melt flow varies. A PCR stream is a mix of many original grades. Polypropylene from mixed packaging can range from low-flow blow-molding grades to high-flow injection grades, so one lot fills a mold and the next flashes or shorts. Ask for melt flow on every lot and a spec range, not a single typical value. See melt flow index explained.
Contamination and gels. Labels, paper, adhesives, other polymers and metal fines survive washing in small amounts. Recyclers remove most of it with melt filtration (screen changers or continuous filters). Ask what filter fineness the recycler uses; thin film and thin-wall parts need finer filtration than crates and pallets. In molding, contamination shows as black specks and weak weld lines; in film it shows as gels.
Odor and volatiles. Residues from the first life (food, detergents, fragrances) come off in the barrel. Vent the mold well, clean vents more often, and watch for mold deposit. Odor matters for consumer goods and automotive interiors; ask for an odor rating or smell a sample before a trial.
Moisture. Washed flake and some pellets arrive wetter than virgin. Hygroscopic PCR (PET, nylon, PC/ABS) needs full drying. rPET is the hardest case: it hydrolyzes in the melt, losing intrinsic viscosity (IV), and has already lost some in its first life. Bottle and preform work dries to about 0.005% (50 ppm) at 149–177°C / 300–350°F; amorphous flake must be crystallized first or it clumps. See the resin drying guide.
Color. Mixed-color PCR is gray to black, so many PCR parts are dark. Natural HDPE from milk jugs and clear rPET allow lighter colors but cost more. Agree on a color range and speck standard with your customer before the trial. See color inconsistency.
Properties. Expect lower impact strength and elongation, and lower stress-crack resistance in HDPE containers. Small amounts of another polymer (PE in PP, or PP in PE) act as weak points. Place weld lines away from loaded areas.
PCR by resin: issues, incoming checks and starting blends
| Resin | Typical issues | Check on incoming lots | Starting blend with virgin |
|---|---|---|---|
| PP | Wide melt flow (blow and injection packaging mixed), PE contamination, odor, gray color | Melt flow per lot, PE content (DSC), ash, odor, color chip | 10–25% |
| HDPE | Natural jug stream is a low-flow blow grade; mixed color; lower stress-crack resistance; PP contamination | Melt flow and density per lot; ESCR for containers; gels and color | 25–50% in bottles; 10–30% in injection parts |
| LDPE / LLDPE | Gels, ink and label residue, moisture from washing, odor | Gel count or film trial, melt flow, moisture, ash | 10–30% in non-food film |
| PET / rPET | IV loss, moisture, acetaldehyde, PVC or glue specks, slight yellow or gray tint | IV, moisture, color (L*, b*), black speck count, PVC content | 25–50% to start; up to 100% with suitable food-grade rPET |
| ABS | Mixed with HIPS or PC from electronics scrap, legacy flame retardants, dark colors only | Melt flow, impact, FTIR identity, bromine screen (XRF) | 10–30% |
| PC/ABS | Blend ratio varies by source, hydrolysis, splay | Melt flow, impact, moisture, FTIR | 10–25% |
| PS / HIPS | Impact varies with rubber content, odor from foam streams, color | Melt flow, impact, odor | 10–30% |
| PA6 / PA66 (carpet, nets, airbags) | Viscosity spread, moisture, PA6 and PA66 mixed, PP from carpet backing | Relative viscosity or melt flow, moisture, DSC melt peaks, ash | 10–30% mechanical; depolymerized PA6 can run like virgin |
Starting points for a molding trial, not limits. Streams and grades vary widely; your part testing and your customer's requirements set the final ratio.
How to run a PCR trial
- Get lot data on two or three lots: melt flow, density, ash, moisture, and IV for PET. Compare the spread, not just the average.
- Start low. Blend 10–25% PCR with your current virgin grade, dried and mixed by weight.
- Test the parts for the properties that matter: impact or drop, stress cracking, color, odor, dimensions.
- Step up about 5–10% at a time and stop where the part still passes with margin.
- Lock the process. Set incoming limits for each lot and record the blend ratio for every run.
Food contact and UL parts
In the U.S., FDA reviews recycling processes case by case under a voluntary program (its guidance on recycled plastics in food packaging was last updated in 2021) and issues a no-objection letter covering a resin type and conditions of use. Customers expect the recycler to hold one and to show that your use falls within it. FDA does not approve or list recycled resin itself, and the finished article remains the manufacturer's responsibility. In the EU, recycled plastic for food contact falls under Regulation (EU) 2022/1616. See FDA food-contact compliance.
For UL-recognized parts, a recycled grade needs its own recognition. UL evaluates mechanically recycled plastics under UL 746S, with multi-batch consistency testing.
Verifying content claims
Ask for a third-party recycled-content verification (for example, to UL 2809 or the Global Recycled Standard) that states the PCR or PIR percentage, plus a COA for each lot. Chain-of-custody records trace the material from collection to pellet. Some chemically recycled content is allocated by mass balance across a producer's output; some customers and laws accept it and some do not, so ask first. Recycled grades also differ from off-grade virgin; see prime vs. off-grade.
What to send us
- The base resin and grade you run now
- Target PCR or PIR percentage, and how it must be documented
- Color, food-contact or UL needs, and the properties the part must hold
- Quantity and ship-to city
A polymer chemist reviews whether a recycled stream can hold your spec or whether a PCR and virgin blend is the better path. Every lot ships with a COA, and orders start at one gaylord. We aim to send your quote within one to three business days.
Common questions
What is the difference between PCR and PIR resin?
PCR (post-consumer recycled) comes from products that have finished their use, such as bottles, film and appliance housings. PIR (post-industrial or pre-consumer) comes from manufacturing scrap diverted from a waste stream. A molder's own regrind fed back into the same process counts as neither.
Does PCR resin process differently from virgin?
Yes, mostly in consistency. Melt flow varies more from lot to lot, contamination and gels are more common, it often smells and gives off more volatiles, color is limited to gray or dark for many streams, and impact and stress-crack resistance are usually lower.
How much PCR can I blend with virgin resin?
A common approach is to start around 10–25% PCR, test the parts, and raise it in steps of about 5–10% while the part still passes. Some non-critical parts and bottles run 100% recycled content, but each part has its own limit.
Can PCR resin be used for food contact?
Only if the recycling process is suitable for that use. In the U.S., FDA reviews recycling processes case by case under a voluntary program and issues a no-objection letter that covers a resin type and conditions of use. Customers expect the recycler to hold one; FDA does not approve the resin itself.
Why does rPET need so much drying?
PET hydrolyzes at melt temperature, so any moisture cuts its molecular weight, measured as intrinsic viscosity (IV). Recycled PET has already lost some IV, so it must be dried thoroughly, typically to about 0.005% (50 ppm) for bottle and preform work, and crystallized first if it is amorphous flake.
How do I verify a recycled-content claim?
Ask the recycler for a third-party recycled-content verification that states the PCR or PIR percentage and the standard it was audited to, along with a lot COA. Keep your own blend records, since they back the percentage you report.
Does PCR resin work in UL-rated parts?
Only if the recycled grade has its own UL recognition. UL now evaluates mechanically recycled plastics under UL 746S, which requires testing several batches for consistency; the virgin grade's yellow card does not carry over.
Tell us the resin and recycled content you need
A polymer chemist reviews every request, then matches your grade or finds a qualified equivalent and prices it.
What to send for an accurate quote
- The grade name, from any supplier, or a data sheet
- Color (natural, black or a custom match)
- Fill type and percentage, if any
- Melt flow, if you know it
- Quantity for this order and what you use in a year
- Ship-to city and state or province