Compatibilizers for Recycled Plastics: 5 Compatibilizer Types, Dosage and Blend-Pair Selection

Compatibilizers for recycled plastics are block, graft or reactive copolymers, compounded into mixed recyclate at roughly 2-10 wt%, that hold immiscible polymers such as polyethylene and polypropylene together instead of letting the blend split at its phase boundaries. Mixed streams are the rule rather than the exception, because as little as 5 % polypropylene in recycled HDPE can cut slow-crack-growth resistance by up to 40 %, so which chemistry repairs which blend pair?

Compatibilizers are one of the few groups of plastic additives that exist mainly because of recycling: sorting separates plastic waste into resin-rich fractions, never into pure ones, and the fraction that remains needs a chemistry that holds the mix together.

This page sets out the mechanism, the 5 compatibilizer classes used in recyclate, a blend-pair dosage table for mixed PE/PP, PO/PET, PP/PA, PE/EVOH, PE/PA and styrenic streams, how much compatibilizer a compound needs, how it is added and tested, the PPWR and food-contact rules that drive and limit the practice, and who supplies the grades.

Key figures

• 2-10 wt% is the typical compatibilizer dose in recyclate
• 5 compatibilizer types cover the recyclate market
• About 3x impact strength and elongation are reported for HDPE/PP 70/30 recyclate dosed with 2-5 wt% polyolefin elastomer
• 30 % recycled content is required in contact-sensitive PET packaging from 1 January 2030 under the PPWR

Why Do Recycled Plastics Need Compatibilizers?#

Recycled plastics need compatibilizers because sorting never separates a waste stream completely, and the polymers that remain mixed are thermodynamically immiscible: long chains gain almost no mixing entropy, so the blend keeps a coarse two-phase structure with a weak interface. Most polymer pairs mix with a positive Gibbs free energy of mixing, because the entropy gained by blending two high-molecular-weight chains is very small, so nothing pulls the phases together once they are melted.

The hub on compatibilizers covers the same chemistries for virgin polymer blends, where a compounder chooses the mix deliberately; recyclate arrives with the mix already made by whatever survived sorting.

How much foreign polymer does mixed recyclate contain?#

Small amounts of the wrong polymer do disproportionate damage: 5 % polypropylene in recycled HDPE can lower slow-crack-growth resistance by up to 40 %, polyethylene in recycled PP block copolymer by up to 70 %, and recycled LDPE carrying up to 7 wt% PP is considerably more brittle than virgin resin. Scholz and co-workers summarise these figures in their 2026 review of additives for recyclate.

Three effects of this residual contamination recur across mechanically recycled polyolefins:

• Loss of slow-crack-growth resistance, the property most sensitive to a foreign phase, since even 5 wt% of a mismatched polymer changes how a crack propagates through the material.
• Embrittlement, visible in recycled LDPE once foreign polypropylene content reaches about 7 wt%, well below the level a visual sort would flag.
• Accelerated thermo-oxidative ageing, because catalyst residues and metals such as titanium, iron, lead and copper that travel with the mixed stream lower the oxidative induction time of the compound.

Compatibilization is one of four strategies in the full package of additives for recycled plastics, the strategy that answers contamination directly. EU plastics production runs at just under 55 Mt/yr, of which 14.5 % is mechanically recycled, 1.1 % bio-based and 0.2 % chemically recycled.

What happens in an uncompatibilized recyclate blend?#

Without a compatibilizer the minor polymer forms coarse droplets that coalesce during mixing, and because nothing crosses the phase boundary, stress is not transferred between the phases: the blend fails at the interface, which shows up first as low impact strength and low elongation at break. During melt mixing, the minor polymer breaks into droplets that immediately start to merge back together, because nothing at the surface of a droplet keeps two droplets apart when they collide; the result is a coarse, unevenly distributed second phase rather than a fine dispersion. Once the part is loaded, the weak boundary between the two phases debonds before either bulk polymer reaches its own failure point, so impact strength and elongation at break drop well below what either resin would show on its own.

What is a compatibilizer in plastic recycling?#

A compatibilizer in plastic recycling is an additive, usually a block or graft copolymer or a reactive polymer, that sits at the boundary between two immiscible polymers in a recyclate and does three things: it lowers interfacial tension, it stops the dispersed droplets from merging again, and it lets the two phases carry load together. Lower interfacial tension means less energy is needed to create new interface, so the dispersed phase breaks into smaller droplets during mixing. Steric stabilization then keeps those droplets from re-coalescing, and interfacial adhesion lets stress cross from one phase into the other instead of concentrating at an unreinforced boundary.

What Are the 5 Types of Compatibilizers Used in Recycled Plastics?#

The 5 types of compatibilizers used in recycled plastics are non-reactive olefin elastomers and block copolymers, maleic anhydride grafted polyolefins, epoxy-functional (GMA) copolymers, acid-functional copolymers and ionomers, and titanate or zirconate compatibilizing agents, with the first two covering most recyclate volume. They are ordered below by how often each is actually used in recyclate rather than by the age of the chemistry.

1. Olefin elastomers and block copolymers (non-reactive)#

Non-reactive compatibilizers are pre-made block or graft copolymers whose segments are each miscible with one phase of the blend, so they anchor at the interface without any chemical reaction during extrusion. A polyolefin elastomer (POE) built from ethylene and octene locates one segment in the polyethylene phase and the other in the polypropylene phase, lowering interfacial tension and suppressing the coalescence that produces coarse domains.

In HDPE/PP 70/30 recyclate, ENGAGE POE dosed at 2-5 wt% (typically 3 wt%) raises impact strength and elongation about threefold while the modulus is maintained, and ExxonMobil's propylene-based elastomer Vistamaxx is used from a 5 wt% starting point in the same blend family. The same elastomers are sold as impact modifiers when the target is toughening a single polymer rather than compatibilizing a blend, which is why the two product families overlap heavily in the supplier catalogue.

Kraton reports that its styrenic block copolymer CirKular+ C2000 works at 3-10 wt% in post-consumer recycled PP, and Dow's propylene-based olefin block copolymer INTUNE at 5 wt% reduces minor-phase domain size in iPP-rich PP/PE blends. SEBS (CAS 66070-58-4) bridges styrenic phases in the same non-reactive family. Density, melt index and comonomer content of a polyolefin elastomer (POE) decide how much stiffness the blend loses at a given dose.

2. Maleic anhydride grafted polyolefins (PP-g-MAH, PE-g-MAH, SEBS-g-MAH)#

Maleic anhydride grafted polyolefins carry a small share of anhydride groups, typically around one percent of the backbone, that react across the phase boundary with amine or hydroxyl end groups and form the compatibilizing copolymer in the extruder itself. In a polyamide-contaminated stream, the anhydride reacts with the amine end group of the polyamide chain to form an imide link, which is why PP-g-MAH is the standard answer for PP/PA recyclate.

The grafting itself is peroxide-initiated radical grafting, carried out in reactive extrusion at 180-190 °C. Beta-scission of the polypropylene backbone competes with the grafting reaction at that temperature, so the melt flow rate of the finished grade rises relative to the base resin, and maleic anhydride does not homopolymerize under these conditions. The full family of maleic anhydride grafted polymers covers PP-g-MAH, PE-g-MAH and SEBS-g-MAH.

The supplier states that POLYBOND 3200 carries 0.8-1.2 % MAH and melts at 157 °C, and in recycled PP/nylon, POLYBOND 3150 and POLYBOND 3002 dosed at 5 % raise notched Izod impact strength about threefold. Grafting levels and identity data for maleic anhydride grafted polypropylene (PP-g-MAH) sit on the substance page.

3. Epoxy-functional (GMA) compatibilizers#

Epoxy-functional compatibilizers carry glycidyl methacrylate units whose epoxide ring opens against the carboxyl and hydroxyl chain ends of polyesters, which makes them the standard answer when PET or PBT is part of the recyclate. The ring-opening reaction forms an ester link at the interface, the same route that anhydride chemistry uses for polyamide, but tuned to the end groups polyesters actually carry.

LOTADER AX8900, an ethylene terpolymer with 24 wt% methyl acrylate and 8 wt% GMA (MFI 6 g/10 min at 190 °C/2.16 kg), and ELVALOY PTW, built from 66.75 wt% ethylene, 28 wt% n-butyl acrylate and 5.25 wt% GMA, are the two reactive ethylene terpolymers most reported for PET-containing recyclate. The full range of glycidyl methacrylate (GMA) functional compatibilizers is set out on its own page, including the grades chosen for PBT, PC/PET and PC/ABS blends.

In rPET reinforced with glass fibre, Monti and co-workers (2021) raised notched Izod impact strength from 5.2 to about 8.1 kJ/m2, a 55 % gain, by adding an ethylene copolymer measured to ISO 180 at 23 °C. Composition and melt index of the ethylene acrylate terpolymer grades are on the substance page. A related molecule, the styrene-acrylic multifunctional epoxide Joncryl ADR-4368, acts as a compatibilizer and a chain extender at the same time. Residual GMA monomer carries a CLP Carc. 1B, Muta. 2 and Repr. 1B classification and an EU food-contact migration limit of 0.02 mg/kg, developed in full in the regulatory section below.

4. Acid-functional compatibilizers and ionomers#

Acid-functional compatibilizers carry free carboxylic acid groups along an ethylene backbone, which lets them hydrogen-bond or react with polyamide and polyester phases without the hazard profile of a glycidyl monomer. The class covers ethylene-acrylic acid (EAA), ethylene-methacrylic acid (EMAA), ionomers and acrylic-acid-grafted polypropylene, and Surlyn 8940, a Dow ionomer, was one of the ethylene copolymers evaluated alongside the epoxy-functional grades in the rPET-with-glass-fibre study. Neutralisation level and metal counter-ion of ionomer resins set their polarity, and therefore which phase they bond to.

On the regulatory side, 21 CFR 177.1330 covers ionomeric resins as ethylene-methacrylic acid copolymers with up to 20 wt% methacrylic acid, and 21 CFR 177.1310 covers ethylene-acrylic acid copolymers directly. Our source library does not hold a published recyclate dosage for EAA, EMAA or ionomer compatibilizers; formulators set the level by trial rather than by a published starting point.

5. Titanate and zirconate compatibilizing agents#

Neoalkoxy titanates and zirconates are the one low-molar-mass class in this group: instead of forming a copolymer, they coordinate to surface protons on fillers, pigments and polymer surfaces and act catalytically at 1.5-1.75 wt% in mixed post-industrial resin. Kenrich Petrochemicals reports that its Ken-React CAPS KPR 12 and KPR 12/LV grades, dosed at 1.5-1.75 wt% in mixed post-industrial resin, let the compound process 20 % faster at a temperature 9 % lower, a supplier claim carried in a trade article rather than an independent test result.

Titanates react with surface protons rather than needing surface hydroxyl groups, which is why they still work on fillers such as calcium carbonate where silane chemistry does not. Chemistry and filler uses of titanate coupling agents are covered on their own page.

Reactive vs Non-Reactive Compatibilization of Recyclate: Which Works Better?#

Reactive compatibilizers work better wherever the blend contains a polymer with reactive chain ends, because the anhydride or epoxide forms a graft copolymer exactly at the interface during extrusion; non-reactive elastomers are preferred in all-polyolefin streams, where there is nothing to react with. The clearest demonstration of reactive chemistry's ceiling comes from a 2024 study of a PA6/PP/ABS/SEBS multi-polymer blend, where 10 wt% POE-g-(MAH-co-St) combined with 10 wt% SEBS-g-(MAH-co-St) raised impact strength by 823 % against the uncompatibilized blend, a gain no non-reactive elastomer alone reaches in a stream this complex.

Reactive chemistry has a narrower process window than non-reactive chemistry. The graft or ester-forming reaction needs enough residence time and melt temperature to run to completion in the extruder, and the same beta-scission that raises polypropylene's melt flow rate during MAH grafting can leave the finished compound softer than intended if the reaction runs too far. Overdosing works against reactive chemistry in a different way: epoxide-functional grades crosslink, and at 3 wt% in rPET the gel content reaches about 32 %, well past the level a converter can tolerate.

Table 1 compares the two approaches directly.

Which Compatibilizer Suits Each Recyclate Blend Pair?#

The right compatibilizer follows the chemistry of the contaminating phase: polyolefin-only streams take an olefin elastomer or block copolymer, polyamide contamination takes a maleic anhydride grafted polyolefin, and polyester contamination takes an epoxy-functional copolymer. Table 2 sets out the reported dosage and effect for each blend pair a recycler is likely to encounter.

Table 2: Recyclate blend-pair compatibilizer selection

Supplier and study values. Every recyclate stream differs in composition, so trials set the final level.

Request quotes for recyclate compatibilizers: send your blend pair, volume, target properties and country through the supplier finder, and download the Recyclate Compatibilizer Selection Chart for the full blend-pair reference in one PDF.

Mixed PE/PP recyclate#

Mixed polyethylene and polypropylene is the largest compatibilizer application in recycling, and because neither polymer has a reactive chain end, the answer is a non-reactive olefin elastomer or block copolymer at roughly 2-5 wt%. Polyethylene and polypropylene arrive mixed whenever sorting residue, film contamination or a rigid-container stream carries both resins, and at that level of contamination the blend needs help regardless of which polymer is the majority phase.

ENGAGE polyolefin elastomer at 2-5 wt% (typically 3 wt%) and Vistamaxx from a 5 wt% starting point are the two grades most reported for this pair, and Dow's PP-based olefin block copolymer INTUNE at 5 wt% works specifically where the blend is rich in polypropylene. The same chemistry applied to virgin engineering blends is on compatibilizers for polymer blends, where polyethylene and polypropylene are compatibilized by design rather than by necessity.

Recycled polyolefins contaminated with PET#

When PET flakes or fibres survive sorting into a polyolefin stream, the two phases have no chemical affinity at all, and either a styrenic block copolymer or an epoxy-functional ethylene copolymer is needed to hold them together. Kraton reports that its CirKular+ C1000 grade in a PCR PP/PET blend at a 72/18 ratio raises notched Izod impact strength by about 50 %, and that CirKular+ C1010 dosed at 5 wt% in PCR HDPE/PET raises notched Izod by about 70 % and yield strength by about 40 %; both figures come from the supplier via a trade article rather than an independent laboratory.

The alternative route uses the same glycidyl methacrylate chemistry described above for polyester-containing streams generally: the epoxide ring opens against PET's carboxyl and hydroxyl chain ends and forms an ester link at the interface. Which route a recycler picks usually comes down to whether the compound also needs the impact toughening a styrenic block copolymer provides.

Recycled PP with polyamide (PP/PA)#

Polyamide in a polypropylene recyclate is the textbook case for reactive compatibilization: the anhydride groups of a maleated polyolefin react with the amine chain ends of the polyamide and build the graft copolymer in the extruder. The imide link that forms is stronger than any physical anchoring a non-reactive elastomer could provide at the same interface.

POLYBOND, the SI Group brand of PP-g-MAH, supplies the grades most often reported for this pair: POLYBOND 3150 and POLYBOND 3002, dosed at 5 wt%, raise notched Izod impact strength about threefold in recycled PP with polyamide. Polybond grades and their MAH content are catalogued in full on the substance page. Where the stream also carries ABS or a styrenic phase, as in the PA6/PP/ABS/SEBS study that reached an 823 % impact-strength gain, the formulation typically pairs a maleated elastomer with a maleated SEBS grade.

Multilayer film recyclate: PE/EVOH and PE/PA#

Barrier films are already built with a maleated polyethylene tie layer between the polyethylene and the EVOH or polyamide, and that tie resin becomes the compatibilizer when the structure is reground. A typical structure layers a PE skin, a PE-g-MAH tie layer and an EVOH or polyamide barrier layer, and the tie layer is still present in the regrind once the film is collected and reprocessed.

The Association of Plastic Recyclers' PE flexible film design guide rates a co-extruded structure with up to 10 wt% EVOH as Design Preferred, provided the PE-g-MAH tie layer carries more than 0.1 wt% MAH; adhesive-laminated structures are rated up to 5 wt% EVOH. These are design-guide ratings, not legal migration limits, so the correct language is that a structure is rated Design Preferred by the Association of Plastic Recyclers, never that it is "allowed." Structure-by-structure guidance is on compatibilizers for multilayer film recycling, including the PE/PA case. Fusabond is one of the anhydride-modified tie resins used in these structures, alongside OREVAC-type grades from SK Functional Polymer.

Styrenic and engineering-plastic recyclate#

Styrenic and engineering-plastic recyclate from electronics and automotive dismantling contains ABS, polycarbonate and polyamide in the same stream, so it usually needs two compatibilizers rather than one. The multi-polymer PA6/PP/ABS/SEBS study is the clearest published example: 10 wt% POE-g-(MAH-co-St) combined with 10 wt% SEBS-g-(MAH-co-St) raised impact strength by 823 % against the uncompatibilized blend, using two maleated elastomers targeted at two different phases.

SEBS and its MAH-grafted version are the standard bridges wherever a styrenic phase is present, because the styrene block anchors into ABS or polystyrene while the rubbery midblock ties into the polyolefin fraction. Styrene content and hydrogenation of SEBS decide which phases it bridges, and no published recyclate dosage exists in our source library for a PC/ABS pair specifically.

Recycled PET: chain extension rather than compatibilization#

A single-polymer rPET stream has no second phase to compatibilize: its problem is lost molar mass, which is repaired with a multifunctional epoxide chain extender at 0.5-1.5 wt%. Intrinsic-viscosity repair is covered under chain extenders for PET and rPET, which is the correct destination whenever a recyclate query is really about a single-resin stream rather than a blend.

Joncryl ADR-4368 (Mw 6,800 g/mol, epoxy equivalent weight 285 g/mol, about 9 epoxy groups per molecule) keeps gel content at or below 2 % when dosed at 0.5-1.5 wt% in rPET, while 3 wt% pushes gel content to about 32 %, well past a usable level. Epoxy equivalent weight and functionality of Joncryl ADR set the gel threshold, and the same molecule saturates its interfacial reaction at about 1.0 wt% when used as a compatibilizer between PLA and PA11 in an 80/20 blend, which shows one grade acting as both a chain extender and a compatibilizer depending on what it is mixed with.

How Much Compatibilizer Does Recycled Plastic Need?#

Recycled plastics need roughly 2-10 wt% compatibilizer, with the level set by how much of the minor polymer is present, whether that polymer offers reactive chain ends, and what impact and elongation the application needs. Four factors drive the final dose:

• Share of the minor phase: a larger foreign-polymer fraction needs more compatibilizer to bring every droplet to the interface.
• Whether the minor phase has reactive chain ends: polyamide or polyester contamination reacts with a small anhydride or epoxide dose, while an all-polyolefin blend needs a larger non-reactive elastomer dose for the same mechanical job.
• Required impact and elongation targets: a part that must pass a drop test needs more compatibilizer than one that only has to hold its shape.
• Cost, since a compatibilizer is usually the most expensive ingredient in a recyclate compound: formulators dose to the property target and no further.

A 25 wt% compatibilizer masterbatch let down at 12 % gives 3 wt% of active compatibilizer in the finished compound (0.25 x 12 % = 3 %), a calculation worth checking against the let-down ratio calculator. More is not always better: epoxide chemistry crosslinks at high doses, reaching about 32 % gel content at 3 wt% in rPET, and every non-reactive elastomer lowers stiffness as its loading rises.

How Are Compatibilizers Added on a Recycling Line?#

Compatibilizers are added at the regranulation or compounding extruder, either as neat pellets blended into the feed or as a masterbatch, because the compatibilizing copolymer has to be formed or positioned while the blend is molten. Three points on the line receive the dose:

• Pellet-blended into the feed of the regranulation extruder, alongside the sorted flake or regrind.
• As a masterbatch let down at the compounding extruder, the most common route because it lets a formulator adjust the active dose without changing the base compatibilizer grade.
• As a tie-layer resin already present in the incoming multilayer film, which needs no separate dosing step because it was built into the structure before the film was collected.

Most recyclers dose the compatibilizer as masterbatch rather than as neat pellets, because a masterbatch is easier to meter accurately at low let-down ratios and to switch between blend pairs without a full line changeover.

Reactive compatibilization has to happen inside the extruder itself, at melt temperature and with enough residence time for the anhydride or epoxide to react with its target end group; a screw design that moves the melt through too quickly leaves unreacted functional groups and a weaker interface. Overdosing works against the process the same way it does in the finished compound, producing gels before the melt leaves the die. Feeding position and screw design are covered under twin-screw compounding.

How Is the Compatibilization of Recyclate Tested?#

Compatibilization is judged on three levels: the mechanical result (notched impact strength, tensile strength and elongation at break), the morphology that produced it (dispersed-phase domain size), and the processing stability of the compound (melt flow rate over repeated passes). Table 3 lists the method and standard behind each measurement.

Table 3: Test methods for compatibilized recyclate

Impact strength, tensile strength and elongation#

Notched impact strength is the sharpest indicator of compatibilization, because a weak interface fails long before the bulk polymer does: the published recyclate gains run from about +50 % to roughly threefold. Specimen preparation and notch geometry for impact strength (Izod, Charpy) follow ISO 180 and ASTM D256 for the Izod method and ISO 179 for Charpy. Every gain reported on this page names the blend it was measured on, since these figures are comparative within one study each, not a general expectation for every compatibilizer at every dose. Elongation at break is measured by tensile testing of plastics and tends to move together with impact strength, because both properties depend on the same interfacial adhesion.

Phase morphology: domain size and interfacial adhesion#

Morphology explains the mechanical numbers: a working compatibilizer makes the dispersed domains smaller during mixing and stops them merging again afterwards, which is why electron micrographs of a compatibilized blend show fine, evenly spread domains that stay bonded to the matrix on a fracture surface. The mechanism is the same one described for every class on this page: lower interfacial tension slows droplet growth during mixing, and steric stabilization at the interface stops the smaller droplets from coalescing back into large ones once mixing stops.

Dow's PP-based olefin block copolymer INTUNE, dosed at 5 wt%, was shown to reduce minor-phase domain size in iPP-rich PP/PE blends. Our source library does not hold a published target domain size for recyclate, so this page does not state a "below one micron" rule; morphology is reported per study, not as a universal specification.

Melt flow rate and multipass stability#

Melt flow rate is measured before and after compounding because compatibilization can move it in both directions: peroxide-initiated grafting chemistry lowers molar mass in polypropylene, while epoxide chemistry raises it and, if overdosed, produces gels. Melt flow rate is measured to ISO 1133 or ASTM D1238, the same standards used across the rest of the additives portfolio, and comparing the value before and after compounding is the fastest way to catch a grafting reaction that went too far.

Beta-scission of polypropylene during peroxide-initiated MAH grafting raises the melt flow rate of the finished grade relative to the base resin, which is expected and part of the specification. Epoxide chemistry works the opposite way, building molar mass rather than cutting it, and produces gels once the dose passes about 3 wt%, the same threshold noted earlier for rPET chain extension.

Which Rules Apply to Compatibilizers in Recycled Plastics?#

No regulation names compatibilizers as a group: the polymers themselves are exempt from REACH registration under Article 2(9) of Regulation (EC) No 1907/2006, so what is regulated is their monomers, the recycling process and the recycled content of the final packaging. A compatibilizer is, chemically, a polymer, and REACH treats polymers as exempt from registration precisely because a polymer's hazard profile is set by its monomers and additives, not by the macromolecule itself. That leaves three separate regulatory layers to track: the monomer-level food-contact limits that apply to the compatibilizer's own building blocks, the recycling-process rules that decide whether a recyclate can touch food at all, and the packaging-level recycled-content targets that create the commercial demand for compatibilization in the first place.

PPWR recycled-content targets that drive compatibilizer demand#

The commercial driver for recyclate compatibilizers is Regulation (EU) 2025/40, the Packaging and Packaging Waste Regulation, which applies from 12 August 2026 and requires 30 % recycled content in contact-sensitive PET packaging and 35 % in other plastic packaging from 1 January 2030. Article 7 sets four separate 2030 targets: 30 % for contact-sensitive PET, 10 % for other contact-sensitive plastic packaging, 30 % for single-use plastic beverage bottles and 35 % for other plastic packaging, each measured as a minimum share of post-consumer recycled content.

Design-for-recycling and substance-of-concern rules of the PPWR are covered on the regulation page in full. The targets step up again from 1 January 2040, to 50 % for contact-sensitive PET, 25 % for other contact-sensitive packaging and 65 % for both single-use beverage bottles and other plastic packaging.

Food-contact recyclate: EU 2022/1616 and the monomer limits of EU 10/2011#

Food-contact recyclate is governed by Regulation (EU) 2022/1616, which splits recycling into suitable technologies such as post-consumer mechanical PET recycling and novel technologies, and lists every authorised recycler, installation and process in a public register. Adopted 15 September 2022, published in the Official Journal on 20 September 2022 and in force from 10 October 2022, it repeals the earlier Regulation (EC) No 282/2008. Suitable technologies cover post-consumer mechanical PET recycling with a maximum 5 % non-food input and output not intended for microwave or oven use; Articles 6(3)(c) and 13(2) apply from 10 October 2024. Process authorisation and the EFSA route are tracked under recycled plastics regulations. EFSA works from a baseline misuse-contamination assumption of 3 mg/kg for PET, and the FDA treats a dietary concentration of 0.5 ppb as negligible.

Compatibilizers themselves enter this picture through their monomers. Table 4 sets out what is regulated for each class.

Table 4: What is regulated, per compatibilizer class

Polymers are exempt from REACH registration under Article 2(9); what is listed and limited are the monomers. Check the grade's own food-contact statement before use.

SML, SML(T) and group restrictions are explained on EU 10/2011. No generic 21 CFR listing was found for PP-g-MAH, so this page states its food-contact status as grade-specific rather than calling it food-contact approved.

Compatibilizers become legacy additives in the next loop#

A compatibilizer does not leave the material: it stays in the compound, and when that compound is recycled again it becomes part of the next stream, which is why Scholz and co-workers describe compatibilizers as future legacy additives in their 2026 review. Every wt% dosed into a recyclate today is a wt% a downstream recycler inherits tomorrow, and measured levels of inherited substances are collected under legacy additives in recycled plastic.

The practical consequence is straightforward: keep the compatibilizer dose as low as the property target allows, and record what was added and at what level, because the next recycler needs that information. Honesty about this trade-off is what separates a technical reference page from a sales page.

Who Supplies Compatibilizers for Recycled Plastics?#

Compatibilizers for recycled plastics come from SI Group (POLYBOND and EVERCYCLE), Dow (FUSABOND, ENGAGE and INTUNE), SK Functional Polymer (OREVAC and LOTADER), ExxonMobil (Vistamaxx and Exxelor), Kraton (CirKular+), BYK (Scona) and Mitsui (ADMER), with neoalkoxy titanates from Kenrich Petrochemicals. SK Functional Polymer's OREVAC and LOTADER lines came from Arkema's functional polyolefins business, acquired by SK Global Chemical in 2020, and several producers, including SI Group and Kraton, sell overlapping chemistry under different brand names for the same underlying MAH-grafted or styrenic backbone. Plants, grades and certifications by company are in the directory of compatibilizer and coupling agent suppliers, alongside the coupling-agent producers that often supply the same customer.

Buyers should compare grades by functional-group content and carrier polymer, not by brand name, since two grades with different names can carry the same anhydride or epoxide level on the same base resin.

Table 5: Producers and brand lines (not a performance-equivalence claim)

Request quotes for recyclate compatibilizers: send your blend pair, volume, target properties and country to the plastic additive supplier finder.

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What Else Does Recyclate Need Besides a Compatibilizer?#

Compatibilization is one of four additive strategies for recyclate, next to restabilization, chain modification and the functional additives that make a recycled compound behave like a virgin one. A compatibilizer fixes the interface between two polymer phases, but a compound that also lost its antioxidant package, its molecular weight or its odour profile in its first life needs each of those addressed separately, usually in the same compounding step.

Restabilization of recycled plastics#

Every recyclate needs its antioxidants replaced before it needs a compatibilizer, because a blend that oxidises during compounding will fail whatever the interface looks like. Recyclate carries less residual antioxidant and more oxidised carbonyl and hydroperoxide groups than virgin resin, so a phenol-plus-phosphite package is added at 0.1-0.3 wt% in recycled PP and HDPE before the compound goes anywhere near a compatibilizer dose. Stabilizer types and 0.1-0.3 wt% dosages are on restabilization of recycled plastics, which covers the full antioxidant package this page only references.

Odor control and moisture control in recyclate#

Odour and residual moisture decide whether compatibilized recyclate can be used in a visible or a food-adjacent part, and both are handled by additives rather than by the compatibilizer. Zeolite dosed at 4 wt% cut the average odour intensity of mixed polyolefin recyclate by 45 % in Garofalo and co-workers' 2023 study, a result gathered under odor removal and odor absorbers for recycled plastics. Moisture in washed flakes is a separate problem, handled with a calcium oxide desiccant masterbatch rather than with any compatibilizer chemistry.

Compatibilizers, coupling agents and impact modifiers compared#

The three families overlap in the catalogue but not in function: a compatibilizer bonds one polymer to another, a coupling agent bonds a polymer to a mineral or natural fibre, and an impact modifier builds a rubber phase inside a single polymer. The same product often carries two labels: PP-g-MAH couples polypropylene to glass fibre, talc and wood flour while it also compatibilizes polypropylene with polyamide, because the anhydride group reacts with whatever hydroxyl or amine group is available.

Silanes, titanates and maleated polyolefins are compared under coupling agents for filled and reinforced plastics, where a silane integral blend typically runs 0.2-1.0 wt% of the total mix and is ineffective on calcium carbonate, where titanates or stearic acid are used instead.

Can PP and PE be recycled together?#

Yes, but only with a compatibilizer: melted together without one, polyethylene and polypropylene form a coarse two-phase blend whose impact strength and elongation fall well below either polymer on its own. With a non-reactive olefin elastomer at 2-5 wt%, the same blend recovers roughly the impact strength and elongation either polymer would show alone.

Does a compatibilizer make recyclate food-contact compliant?#

No: food-contact compliance of a recyclate is decided by the recycling process under Regulation (EU) 2022/1616 and by the limits of Regulation (EU) No 10/2011, and adding a compatibilizer creates one more substance whose monomers have to satisfy those limits. A compatibilizer can only work against compliance, by adding a monomer of its own to the limits that must be met; it never substitutes for the process authorisation itself.

Is a compatibilizer the same as a coupling agent?#

No, although the same product can be both: a compatibilizer works at a polymer-polymer interface while a coupling agent works at a polymer-filler interface, and maleic anhydride grafted polypropylene is sold under both names. Which function a grade performs in a given compound depends on what surface it meets, not on which name is printed on the bag.

Can compatibilized recyclate be recycled again?#

Compatibilized recyclate can be reprocessed, but the compatibilizer stays in the material and joins the additive load of the next stream, which is why design-for-recycling guidance favours single-polymer packaging over blends that need compatibilizing. APR and RecyClass ratings are explained under design for recycling; our source library holds no data on how many loops a compatibilized blend survives, so this page states none.

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