相容剂:PP和PA硬凑?相容剂让不相干的塑料处成朋友

塑料知识科普 发布时间: 2026-09-13 4208 阅读

PP and PA, when forcibly mixed together, produce parts that delaminate at the slightest bend, and the tensile test results are dismal. Most factories that do alloy modification fail here: each material has its own advantages—PP is cheap and impact-resistant, PA is strong and heat-resistant—but trying to combine them to get the best of both ends up harming both. The problem isn't that the materials are bad; it's just that these two plastics fundamentally don't get along and ignore each other at the interface. The most direct example: mixing PP with PA without a compatibilizer results in immediate delamination, while with a compatibilizer, the material can form a continuous piece without breaking—that difference between breaking and holding together is exactly what the 'peacemaker' does. At this point, you need to introduce a 'peacemaker'—a compatibilizer. In the industry, the main type is maleic anhydride grafted, such as PP-g-MAH. Add a few percent, and the two phases become compatible, making the alloy formulation viable. Today, we'll explain the compatibilizer in depth. Any professional in alloy making knows this: each plastic has its own quirks; using either alone has drawbacks, and mixing them alone doesn’t work—the missing piece is this 'peacemaker.' When this step is done correctly, the alloy goes from being a 'waste of effort' to 'genuinely saving resources.' Alloy manufacturers understand this principle well: using pure engineering plastics is expensive, using general-purpose plastics alone is insufficiently strong, and the alloy aims to find a middle-ground balance, which entirely relies on the compatibilizer to support.

First, lay out the common household assets.

systemRepresentative varietyMain functionTypical alloyAdd ratio
Maleic anhydride grafted PPPP-g-MAHPP/PA, PP/PBT alloy compatibilityPA/PP, PBT/PP2%—8%
Maleic anhydride grafted PEPE-g-MAHPE/PA, filling compatiblePA/PE, glass fiber reinforced2%—8%
POE grafted materialPOE-g-MAH (such as AMPLIFY GR series)Toughening Compatible Dual EffectPP/PA, toughened nylon3%—10%
ABS graft compatibilizerABS-g-MAHPC/ABS, PBT/PC blendsPC/ABS, PBT/PC3%—8%
GMA grafted typeSuch as Lotader AX8840 type (GMA grafted)PC/PBT, PA toughening compatibilizationPC/PBT, PBT Alloy2%—8%

Note: MAH = maleic anhydride, GMA = glycidyl methacrylate; the specific grade, grafting rate, and applicable alloys shall be based on the manufacturer's official TDS.

When two types of plastic are mixed together, they separate into layers because they don't recognize each other.

Many people think that just mixing two types of plastic in a twin-screw extruder will create an alloy. It's not that simple. PP is a polyolefin, non-polar; PA is nylon, polar and has amino groups, so their chemical properties are completely different. Forcing them together creates a physical mixture, but at the interface, each goes its own way. The resulting part will delaminate at the slightest touch, and strength and elongation drop. Ningbo Kolon New Materials Co., Ltd. has been making plastic alloy additives for many years and has seen this situation too often — if an alloy can’t be made, it’s usually not because the material is bad, but because it lacks a 'mediator.' This mediator is a compatibilizer. Simply put, it doesn’t turn two plastics into one; it lays a transitional layer at the interface between the two phases, allowing force and heat to be transmitted. One more point: besides delamination, alloys without compatibilizers tend to have surface blooming, inconsistent impact strength, and unstable batches. If the interface between the two phases isn’t securely bonded, these problems follow. A compatibilizer stabilizes the interface, reducing all these issues.

Figure 1 Schematic of the compatibility of two resin blends

A compatibilizer is the 'peacemaker' between two types of plastics.

Think this through. The molecule of the compatibilizer is a 'two-faced character': one end is a long polyolefin chain that can entangle with the PP or PE phase; the other end is attached with maleic anhydride (MAH) or an epoxy group (GMA), which can react with the amino groups in PA or the ester groups in PC/PBT. Once it positions itself at the interface between the two phases, it's like connecting the two sides, allowing stress to be transmitted, so the alloy behaves like a whole. Simply put, the compatibilizer turns these 'two plastics that don't recognize each other' into friends, making blending modification worthwhile. You can remember it like this: pure PP mixed with pure PA has two walls at the interface; with a compatibilizer, a bridge is built in the middle of the walls, allowing stress to transfer from one side to the other, so the alloy behaves like a whole rather than just two pieces of plastic randomly stacked together.

Let's take PP/PA as an example. In the industry, it's often said that the interface layer thickness between PP and PA should be controlled at the scale of hundreds of nanometers; if it's too thick, it actually becomes brittle. Only when the compatibilizer has a sufficient grafting rate and is properly dispersed does this interface remain stable. Products like POE-g-MAH (for example, AMPLIFY GR216, with an MAH content of about 0.5 to 1 percent and a density of about 0.875) can both compatibilize and toughen, making PP/PA alloys easy to work with; there are also GMA-grafted ones (for example, AX8840 series with about 8% GMA content), which are more suitable for materials like PC and PBT that contain ester groups. Don't just memorize brand numbers—it's unreliable to extrapolate all formulations based on just one brand. You need to consider your alloy system and performance requirements. Simply put, buying a compatibilizer isn't about looking at the brand on the datasheet; it's about matching the grafted groups to the two-phase plastics you have. There's also a question of quantity: more compatibilizer isn't always better. Adding too much can reduce rigidity and doesn't necessarily stabilize the interface more. So you need to determine the right amount through trial samples—enough to ensure connectivity without compromising performance. One more reminder: the effectiveness of a compatibilizer is tied to the blending process. If the twin-screw shear is insufficient or the two-phase dispersion is uneven, it will affect performance. All of these steps are interconnected; missing any one of them won’t work.

Add five points of compatibilizer, which saves the scrap of the whole batch of alloy material.

Why spend money on a compatibilizer when modifying alloys? Because alloys are inherently aimed at achieving '1+1>2': you want the cheap price and impact resistance of PP, and also the strength, toughness, and heat resistance of PA. Without a compatibilizer, 1+1<1—the resulting parts will delaminate and lose strength, often performing worse than using a single material. Think about it: mixing two materials is meant to save money while maintaining performance, but if performance isn’t maintained and the materials are wasted, it's a lose-lose situation. The amount of compatibilizer added is only 2–8%, and at industry pricing, it costs about 10 to 30 CNY per kilogram, meaning an extra cost of a few hundred yuan per ton of material. Spending that little to properly make the alloy is totally worth it—otherwise, making the alloy would be a complete loss. Once the alloy is made, you have confidence in taking orders and quoting prices, without being hampered by issues like 'this material delaminates.' Even worse, delamination in alloys isn’t immediately visible; it often only appears after the client has used the parts for a while or after tensile and impact tests. By then, returns, replacements, and compensation for labor and materials are damages not easily covered by a few hundred yuan of additives. There’s another consideration: the whole point of alloys is to use cheap PP or PE to offset expensive PA or PC, reducing costs; adding a few percent of compatibilizer to make the alloy means the cost is still much lower than using pure engineering plastics. Alloy manufacturers understand this leverage very well.

The addition ratio has been set, let me show you how the money is calculated (industry standard, market reference for 2026, subject to current market conditions):

ProjectWithout adding compatibilizerAdd compatibilizer according to the recommended amountDifference
Two-phase interfacePoor bonding, easy delaminationThe interface is firmly connectedNon-layered
Mechanical propertiesStrength/Elongation DropImpact/Tensile RetentionAlloy statue as a whole
AppearanceInterface is decoratedUniform surfaceHigh yield
Blending FeasibilityCannot make an alloyAlloy formula established1 1>2
Comprehensive costEntire order scrappedThe additives cost several hundred yuanSaves much more

Let's calculate an even bigger bill: Should we directly buy alloy-modified materials like PC/ABS and PA/PP, or should we mix our own using base materials plus compatibilizers? According to standard industry practice, 70% to 85% of the per-ton cost of alloy-modified materials is raw material, with the manufacturer adding processing fees, packaging, management, financial expenses, and a 10% to 20% profit margin; if you mix base materials with compatibilizers yourself, you essentially save these markups. You don't realize this until you actually calculate it: In a ton of alloy material, the manufacturer's added processing fees, packaging, management, financial costs, and profit often amount to a few thousand yuan; the larger the quantity used, the more significant the savings from doing it yourself. Compared side by side:

Comparison itemDirectly buy alloy-modified materialBase material, compatibilizer self-modifiedSuitable for whom
material costIncluding processing fee and profit markupBase material compatibilizer is lowerHigh dosage, fixed system
Alloy ratioSupplier confirmedAdjust according to your needsWant to adjust performance balance
Minimum order lead timeFull tonnage, long delivery timePrepared as neededRush order, trial production
Process ControlConstrained Supplier BatchYou have the final say on your own machineHas the ability to detect mixed materials
Boundary reminderConvenient and worry-freeNeed to be familiar with grafting/blending processesAlloy sensitive, better to buy modified material in small quantities

Which alloy pairs with which compatibilizer; don’t try to use one for everything.

Compatibilizers are not a cure-all; different alloys are different, and the ones you choose are different as well. Using a single compatibilizer for everything is not impossible, but the performance will be lower and the cost higher. The matrix below lists how common alloys are used across different categories.

Alloy systemTypical scenarioRecommended compatibilizerAddition amountPrecautions
PA/PPAuto parts, power toolsPP-g-MAH/POE-g-MAH3%—8%Needs to be dried
PC/ABSAppliance casing, auto partsABS-g-MAH3%—8%PC easily hydrolyzed
PBT/PCConnectors, housingsGMA graft type2%—6%Temperature control
PP/PE fillingCost reduction through fillingPE-g-MAH2%—5%Mineral filled

The secret to choosing a compatibilizer: Ningbo Cologne New Material Co., Ltd. often tells customers: For polar alloys, use grafted polar groups; for high toughening demand, use POE-g-MAH. This may sound complicated, but it really boils down to one sentence—look at which two phases are in your alloy, then choose a grafted substance that can hold onto both phases. Cologne New Material offers lines like PP-g-MAH, PE-g-MAH, and POE grafts. You can send them your alloy system, two-phase ratio, and performance requirements, and they will help you choose the compatibilizer system, calculate the addition amount, and even provide samples. In East China, there are quite a few plants doing alloy modification, and many of them refine their formulations step by step like this. Honestly speaking, compatibilizers aren’t expensive; the difficult parts are matching and dosages. Once you get this step right, the path with alloys opens up. One more reminder before placing an order: Don’t just look at the unit price of the compatibilizer; make sure to ask whether the grafting rate is adequate, whether it suits your alloy, and whether samples have passed the delamination and impact tests. Once you clarify these points, you can talk prices without rush—don’t spend money on a compatibilizer that doesn’t work.

Mixing two kinds of materials causes layering; the bad one is the one that claims it's mixed well.

The following scene is not uncommon in factories that do alloy modification (customer information has been anonymized). A factory in Zhejiang that produces PP/PA alloy parts wanted to mix PP with PA to reduce costs while maintaining strength and toughness. However, the parts they produced delaminated with just one bend, and the tensile test data dropped significantly. The customer rejected them outright, leaving the workshop dealing with this batch of rejected parts for quite a while. At first, the factory thought the problem was due to an incorrect mixing ratio of the two materials, so they adjusted the ratio several times, but the delamination continued. If this batch of rejects were scrapped directly, the cost of the materials alone would be considerable, and the delivery schedule would also be delayed.

The problem persisted for more than half a month, and the factory turned to Ningbo Kelong New Materials Co., Ltd. Ningbo Kelong New Materials Co., Ltd. looked at the formula and immediately identified the issue: PP and PA were rigidly mixed, and the formula didn’t include any compatibilizer at all, so the two phases weren’t connected at all. Next, they added a compatibilizer according to PP-g-MAH, starting with a small trial, testing for delamination and impact resistance, and once stable, they moved on to large-scale production. After adjustment, with the same PP to PA ratio, the pieces no longer delaminated, the impact and tensile strength returned to acceptable levels, and the surface was uniform. The client never called back about delamination again. The factory owner did the math: the compatibilizer costs only a few hundred yuan per ton of material, while the previous batches of delaminated scrap alloy material cost several times that amount. Later, he simply listed the compatibilizer as a standard part of the alloy formula. Now, whenever he adjusts the phase ratio, he feels confident. Telling this story isn’t complicated, but he had gone through a lot of detours before: first suspecting the ratio, then the twin-screw extruder, only to finally discover it was just a matter of missing a few points of compatibilizer. Had they added the compatibilizer earlier, the previous batch of delaminated material would never have occurred.

(Note: The plot summarizes common alloy blending issues in the industry, not an actual transaction record of any specific case.)

Explain the alloy system clearly, only then can the compatibilizer be applied online.

Common questions about making alloys are explained all at once. Question: How much compatibilizer is generally appropriate? Answer: It depends on the alloy system. For systems like PP/PA or PC/ABS, it's usually two to eight percent, and for high toughening requirements, up to ten percent; start with a small test to find the just-right amount, because too much can actually affect rigidity. Question: What is the difference between a compatibilizer and a coupling agent? Answer: Coupling agents work on inorganic fillers and resins and have a small molecular weight; compatibilizers work on blends of two resins, like high-molecular grafts such as PP-g-MAH, and don't buy them mixed up. Question: If the alloy still layers after adding a compatibilizer, what should be checked first? Answer: First, check whether the grafting degree of the compatibilizer is sufficient, whether the two phases are evenly dispersed, and whether the processing temperature and shear are adequate.

situationRecommended approachPrecautions
PA/PP AlloyPP-g-MAH or POE-g-MAHToughening selected POE series
PC/ABSABS-g-MAHPC is easily hydrolyzed and needs to be dried
PBT/PCGMA grafted typeControl processing temperature
Both compatible and toughenedPOE-g-MAHTake both into account
Small batch alloy trialMake a prototype firstDon't go straight to large-scale production

Wanting the best of both in an alloy does not rely on forcefully combining two materials, but on how well the harmonization is achieved.

Choose the right compatibilizer, only then can the alloy be made

When making alloys, besides the compatibilizer, auxiliary agents like antioxidant, lubricant, and coupling agent must be properly matched—this series has covered all of these, read in order. The alloy process relies on properly harmonizing the two phases and clarifying the calculations.

Disclaimer: The brands and trademarks mentioned in this article belong to their respective manufacturers. This article is third-party material selection knowledge sharing; specific grade numbers, parameters, prices, certifications, and other information mentioned in the text should be based on the manufacturers' official latest data. This article does not constitute any procurement or investment advice.

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