Maleic anhydride grafted polyolefins: PP-g-MA coupling agents, PE-g-MA tie resins and grafted elastomers

What maleic anhydride grafting does

PP and PE are non-polar. They do not bond to glass, wood, nylon, EVOH or metal on their own, so a filled compound pulls apart at the fiber surface and a blend separates into weak layers. Producers graft maleic anhydride onto the chain, most often by reactive extrusion with a peroxide. The grafted polymer then works as a bridge: its polyolefin backbone blends into the matrix, and its anhydride groups react with or bond to the other material.

• Coupling. In glass-filled PP, the anhydride reacts with the aminosilane sizing on glass made for PP, so load passes from the polymer into the fiber. In wood and natural fiber composites, it bonds to the hydroxyl groups on the fiber and cuts water uptake. Coupled grades are much stronger than uncoupled ones. See glass-filled PP vs. nylon.
• Compatibilizing. In nylon/PP and PE/EVOH blends, the anhydride reacts with nylon amine end groups or EVOH hydroxyl groups at the interface. That gives a finer, stable blend instead of coarse layers. It also helps when recycled streams mix a known pair of resins.
• Adhesion. As a tie layer, a grafted PE or PP bonds a polyolefin layer to EVOH, nylon or metal in coextruded film, sheet, bottles and pipe.
• Impact modification. A grafted elastomer such as POE-g-MA or EPR-g-MA disperses as fine rubber particles in nylon and bonds to it, which is how toughened and supertough nylons are made.
• Why PP-g-MA runs so fluid. Peroxide grafting breaks PP chains as it adds anhydride, so PP coupling agents often have a far higher melt flow than the base PP. PE tends to crosslink instead, so PE-g-MA grades keep a melt index closer to film and molding resins.
• A close relative. Some coupling agents are grafted with acrylic acid instead of maleic anhydride, mainly for adhesion to metal and for glass or mica in PP. Say which one your formula uses.

PP-g-MA vs. PE-g-MA vs. grafted EVA and elastomers

Examples from published producer and distributor data. Match the backbone to the matrix: PP-g-MA in PP, PE-g-MA in PE. A PE-based grade in PP, or the reverse, often couples poorly because its backbone does not mix well into the matrix.

Graft level: how much MAH, and how it is measured

Graft level is the weight percent of maleic anhydride bonded to the polymer. Producers label grades in bands, but the bands differ. One producer’s sheets call 0.15–0.30% low, 0.4–0.6% medium, 0.8–1.2% high and 1.3–1.7% very high. Other producers draw the lines in different places and use different words. So ask for the number, not the word. Higher graft gives more reactive sites per pound, so you can use less, but it often comes with lower molecular weight, higher melt flow and more risk of color and odor. Coupling agents for glass and wood tend to sit at about 0.8% and above, and one producer markets its highest-graft PP grade for long-glass PP and pultrusion. Nylon tougheners and tie resins often sit lower.

• How it is measured. Producers use titration or infrared (FTIR) against their own calibration. FTIR reads the anhydride band near 1790 cm⁻¹ and the acid band near 1712 cm⁻¹, because anhydride picks up moisture in air and opens to acid.
• Why numbers differ. Free, ungrafted maleic anhydride and its by-products can inflate a result unless the sample is purified or heated first. Two producers can test the same polymer and report different values. Compare graft level only by the same method, and ask whether the value is total or bonded MAH.
• On the COA. Ask whether graft level and melt flow are reported lot by lot or are typical values only. For a coupling agent in a structural compound, a lot-to-lot graft range on the COA is worth asking for.

Melt flow conditions, free MAH and odor

• Read the test condition first. PP is normally tested at 230°C / 446°F and 2.16 kg, but many PP-g-MA grades are reported at 190°C / 374°F and 2.16 kg, and some very high-flow grades at a lighter load, such as 0.325 kg, or a lower temperature, because they run too fast to measure well at the standard load. One producer lists its high-graft PP-g-MA at 115 g/10 min (190°C / 374°F, 2.16 kg) and its low-graft PP-g-MA at 9 g/10 min (230°C / 446°F, 2.16 kg). Numbers at different conditions cannot be compared directly.
• Why flow matters. In a compound, a high-flow coupling agent spreads to the fiber surface quickly. In a tie layer, the melt flow must suit the layers on either side so the coextrusion runs without layer instability. Ask for MFR with the load and temperature, and test both grades at the same condition when you compare.
• Free MAH and odor. Grafting never reacts all of the maleic anhydride. Leftover free MAH and low molecular weight by-products cause a sharp odor, can add color and can affect emissions in automotive interior parts. Maleic anhydride itself is an irritant and a skin and respiratory sensitizer, so check the SDS and ventilate the feed area. Ask for the producer’s free or residual MAH value and test method, and for a low-odor or devolatilized grade where the part goes into a car interior or food packaging.
• Storage. Keep bags and liners closed. Anhydride groups pick up moisture and turn to acid. Much of that closes back up at melt temperature, but damp material can still change results and cause splay. Follow the producer’s storage and drying advice.

Typical loadings and uses

Starting ranges from producer literature and published studies, not recommendations. The right level depends on graft level, filler type and amount, and the properties you need, so confirm it with a lab compound.

Tie layers in multilayer film, bottles and pipe

EVOH and nylon give oxygen and aroma barrier, but they do not bond to PE or PP. A coextruded structure such as PE / tie / EVOH / tie / PE, or PP / tie / EVOH / tie / PP for trays and retort cups, needs a tie resin on each side of the barrier. Anhydride-modified tie resins bond to EVOH, nylon and, for some grades, PET and aluminum. For foil and metal in coating and lamination, acid copolymers such as EAA are the usual choice; see acid copolymers and ionomers.

• Match the tie to its neighbors. LLDPE-based ties for PE film, HDPE-based ties for blow-molded bottles, and PP-based ties for PP sheet, cups and retort pouches. The tie’s melting point and melt flow should suit the adjacent layers.
• Bond strength. Ask for peel strength to EVOH or nylon in a structure close to yours, and test after aging and contact with the product. Bonds can weaken with oils, solvents or heat in use.
• Barrier pipe. Oxygen-barrier PEX and PE-RT heating pipe carries a thin EVOH layer held to the pipe by an anhydride-modified PE adhesive layer. Multilayer pipe with an aluminum layer also uses adhesive layers. The pipe standard and the system maker’s approval set what can change. See pipe resin.
• Film and bottles. See film resin for converters and delamination for layer-bond troubleshooting.

Food contact: which rules apply

• Grafted PP in coatings. 21 CFR 175.300(b)(3)(xix) lists the maleic anhydride adduct of polypropylene for resinous and polymeric coatings, with a maximum combined maleic anhydride content of 0.8% and a minimum intrinsic viscosity of 0.9, made from PP homopolymer that meets 21 CFR 177.1520(c) item 1.1. 21 CFR 177.1390 lists the same adduct as an adhesive in laminates used at 121°C / 250°F and above.
• Grafted EVA. 21 CFR 177.1350 allows maleic anhydride grafted EVA with no more than 11% VA before grafting, no more than 2% grafted MAH and a melt flow index of no more than 2.1 g/10 min (190°C / 374°F, 2.16 kg). It may be used at no more than 17% of a polymer blend, with limits on some food types.
• Ethylene-maleic anhydride copolymers. 21 CFR 177.1520(a)(6) covers ethylene-maleic anhydride copolymers (made by copolymerization, not grafting) with up to 2% maleic anhydride, for use as the adhesive component in multilaminate structures or as the sealant layer in flexible packaging, in contact with food at up to 49°C / 120°F. It does not cover grafted PE, so ask what a grafted tie resin’s letter relies on.
• Anhydride-grafted HDPE. 21 CFR 177.1520(a)(5) lists polyethylene (density 0.94 or higher) grafted with a different anhydride (methyl nadic anhydride) at no more than 1.7%, with a melt index of no more than 2 and limits on film thickness times concentration for some food types. It is not a maleic anhydride graft, so it does not cover PE-g-MA either.
• Tie resins. Producers’ letters for tie resins often rely on 21 CFR 175.105 (adhesives), a section of 177, or a food contact notification (FCN). Ask for the letter for the exact grade and its conditions of use.
• Coupling agents for glass-filled PP are often not sold for food contact at all. If the compound touches food, check every component. See what FDA compliance means.

Producer families, supply and price drivers

We name these only so you can recognize them on a formula sheet. The names belong to their owners. We source by spec through our supply partners, case by case, and do not imply we sell any brand. Some coupling agents are sold mainly through additive distributors; if we can’t source a grade, we tell you.

Ownership checked against producer, distributor and SK annual report pages in October 2026. Confirm the producer on your current sheet.

• We do not post prices. Every quote is for a specific grade, quantity, package and ship-to city. See how resin is priced and the resin market notes.
• What moves price. The base PP or PE, maleic anhydride and peroxide, graft level, low-odor treatment, and the small number of producers. Grafted polyolefins cost more per pound than the base resin, which is why the loading matters.
• Lead time. Many grades are made in campaigns, and some come from one plant. Keep a qualified second grade for a structural compound or an approved tie layer. See qualifying a second source.
• Packaging. Coupling agents and tie resins often ship in 55 lb (25 kg) bags, about 40–55 per pallet, or gaylords (about 1,000–1,600 lb). Large film and pipe lines may take bulk.

What to put on the RFQ

• Backbone. PP homopolymer or copolymer, HDPE, LLDPE, LDPE, EVA, or POE, EPR or EPDM elastomer.
• Graft type and level. Maleic anhydride or acrylic acid, the graft level in weight percent with its range, and the producer’s method.
• Melt flow with conditions. Temperature and load (for example 190°C / 374°F and 2.16 kg, or 230°C / 446°F and 2.16 kg), nominal and range.
• Use and partner material. Glass (short or long, and its sizing), talc, wood or natural fiber, nylon, EVOH, or metal, and your matrix resin.
• Loading you run now. And the properties it must hold: tensile, flexural, notched Izod, heat aging, water uptake or peel strength.
• Odor and free MAH. Any limit on free MAH, odor or emissions, such as automotive interior specs.
• Food contact. The FDA letter and the section it relies on, if the part or package touches food.
• Form. Pellets, powder or a tie concentrate, and whether it is pre-blended.
• Quantity and package. This order, yearly use, and bags, gaylords or bulk. Send your ship-to city.
• COA values to check. Melt flow at the stated condition on every lot, and graft level where the producer reports it. See the RFQ package page.

Common questions

If your grade is not listed, tell us what you run. We source commodity, engineering and specialty resins.