再生酚醛环氧热固性PU:废料磨粉当填料,热固性回收的价值洼地

塑料知识科普 发布时间: 2026-09-15 3887 阅读

If you lay out the recycling chain for thermosetting plastics, you'll find a value pit that has been overlooked. Waste that others see as unburnable, unburied, or reused waste can be ground into powder and mixed in as filler, and a ton of waste still becomes money. In today's article, we'll explain the three types of 'can't be changed once welded': why they can't be melted and pelletized like PP, how can they be ground into powder and reused, how much can be saved, and what pitfalls exist.

First, let's clarify the root of thermosetting issues. What we usually talk about—PP, PE, and ABS are all thermoplastics—they soften when heated, melt, and can be repeatedly pelletized. Thermosetting is the opposite: phenolic (bakelite), epoxy resin, thermosetting PU, etc. Once cured, the molecules form a three-dimensional mesh of "dead lumps," which do not melt when heated; they only burn and burn first. If you want to recycle them into pellets, before the machine heats them up to the temperature where they can flow, they decompose on their own. Therefore, thermosetting recycling naturally cannot follow the old path of "washing clean and then pelletizing." Ningbo Kelong New Materials Co., Ltd. supplies plastic raw materials, integrating industry and trade, with common recycled plastic categories stocked year-round. Thermosetting grinding powder is one of the specialized fillers and taking a different path.

So how can it be collected? The mainstream approach is the mechanical physics method: the cured scraps and scrap parts are crushed, crushed, and ground into powder, then graded by mesh number. When ground finer, the chemical structure remains unchanged, but the form changes from "one board" to "a pile of powder," which can be used as filler to mix into wood-plastic, building materials, and new plastics. Another method is chemical methods—pyrolysis or solvent decomposition, which breaks down resin back into chemical raw materials, with a high threshold and small quantity. Another method is incineration as fuel, but that is too wasteful. Today, we will focus on the widely used grinding powder reuse.

Bakelite, epoxy, PU were all materials that were "welded shut "

Thermosetting is actually everywhere around you. The brown 'bakelite' on old TV back covers and switches is phenol, also called bakelite, which became famous a hundred years ago—hard, insulating, and cheap. The green board on your epoxy countertop or circuit board is epoxy; The soft foam in sofas, mattresses, and car seats is mostly PU. These materials are heat-resistant, don't deform, and have good insulation, making them especially handy for appliances and structural parts. But once cured, they can no longer return to a flowable granular state—this is the fate of thermosetting: good to use, but stubborn, once set, they don't change it.

Because of this "stubbornness," recycling thermosetting has always been an environmental challenge. Landfill it; it won't decompose in the natural environment for decades; Burning it is troublesome to handle flue gas; Trying to recycle it into pellets like plastic, but it doesn't melt. In the past, many factories had to pay to send it to landfill, and the more it piled up, the more headaches it became. Only in recent years have people gradually figured it out: since it can't melt, don't fight it—grind it into powder and use it as 'filler' for other materials. This way, waste edges become powder that can be sold, landfills are relieved, and thermosetting has finally found its own way to recycle.

Figure 1 Crushing and grinding thermosetting scraps for reuse

The welded three-dimensional network can't melt back even when heated

Many people hear about thermosetting recycling for the first time, and their first reaction is: If it can't melt, what's the point? This brings us back to its structure. During thermosetting curing, linear molecules form a chemical "hand-in-hand," forming an unbreakable web. This net gives it high temperature resistance, rigidity, and insulation, but it also sentences it to "never melt for life." When you heat it, the mesh won't loosen, only carbonizes.

So when it comes to thermosetting, don't use the thermoplastic "re-oven granulation" system as a pretext. Its value isn't in "making an identical piece again," but in "breaking it up as filler." A piece of phenolic bakelite board edge, ground into 60 to 80 mesh powder, mixed into wood-plastic or other plastics, still strengthens and reduces costs; A piece of epoxy fiberglass board edge, if ground up as building material filler, is better than burying it. This is the core idea of thermosetting recycling: if you can't make a new piece, treat it as someone else's "material."

Grinding powder sounds simple, but it actually involves quite a few details. The first step is coarse crushing—first crushing the entire scrap into pieces with a heavy-duty crusher; then grinding finely, using wear-resistant blades to the specified mesh size. Thermosetting is hard and brittle, and the blades wear out quickly, so wear-resistant knives are needed. Mesh size is the lifeline of this business: coarse powder with 60 to 70 grit is enough for wood-plastic and building materials, with low processing costs; To mix in new plastic as modified fillers, it must be ground to a finer mesh size for even dispersion; otherwise, a large powder particle will leave the product surface full of lumps. After grinding, it must be screened and graded; coarse pieces are ground back, fine pieces are sold separately. Epoxy boards containing glass fiber must be cleaned out during grinding, otherwise mixing into downstream products affects appearance.

Chemical recycling is another path, with a higher threshold. It uses pyrolysis or solvents to "tear apart" the cured resin mesh, recover oil, gas, or chemical raw materials, and then use them to make new resin. This path is theoretically more thorough, but the equipment is expensive, batch sizes are small, and the process is still being explored, so few factories have succeeded at present. For most small and medium-sized factories, grinding powder as a filler is the main way to make money immediately and effectively. So don't just hear "thermosetting recycling" and assume fancy chemical decomposition; what the workshop really does is crush, grind, classify, and sell fillers.

The three common types of thermosetting materials each have their own uses. Phenolic (bakelite) is hard, brittle, and highly insulating. After grinding scraps into powder, they are often used as insulation fillers and composite materials, and are widely used in electrical insulation components. Epoxy resin boards, especially fiberglass epoxy boards and circuit board substrates, are ground into non-metallic powders to make wood-plastic, concrete modification, and composite fillers. Thermosetting PU comes in both hard and soft foams, and after crushing, they are often made into car seat cushions and cushioning fillers. The following grade table categorizes these three categories, by mesh count and usage.

GradeMain sourceKey indicatorsTypical uses
Phenolic (bakelite) crushed coarse powderBakelite , bakelite, electrical insulation edges60-80 mesh, good insulation performanceinsulation filler, composite raw materials
Phenolic fine/modified powderPhenolic grinding powderHigh mesh count, well-dispersedPlastic modified filler
Epoxy/fiberglass board shredded materialEpoxy board, fiberglass board edges and cornersContains glass fiber, high rigiditywood-plastic, building material filler
Non-metallic powderPCB non-metallic component sorting of circuit boardsClean sorting with stable compositionBuilding materials and composite material fillers
Thermosetting PU shredded materialHard foam/soft waste PU edges and cornersCrushing classificationCar seat cushions and cushioning fillers
wood-plastic/building material-grade thermosetting powdermulti-source mixed crushinglow cost, low requirementswood-plastic profiles, concrete modification

Explanation: Thermosetting plastics (phenolic aldehyde, epoxy, thermosetting PU, etc.) form a three-dimensional cross-linked network after curing and cannot melt and re-pelletize. Currently, recycling mainly uses mechanical and physical grinding powder as filler, referring to GB/T 40006.1 "Plastics—Recycled Plastics Part 1: General Principles" and enterprise standards; Chemical recovery (pyrolysis/solvent decomposition) and incineration energy recovery are auxiliary routes. The mesh counts and uses in the table are summarized from publicly available industry data; further specifications and physical properties are subject to the manufacturer's official TDS.

Grinding waste into powder is not about settling; it is another way to reduce costs .

Some people look down on grinding powder as a filler, thinking it is "downgrade utilization." But from another perspective: thermosetting can't be returned to the furnace, and grinding powder can be mixed in, turning "landfill" waste into material that can be sold for money. That's how the accounts should be calculated.

Cost itemWaste disposalMilling powder reuseDifferential explanation
Disposal costLandfill/incineration costSelling after crushing and grinding powderFrom expense to income
Packing value——Wood-plastic/new material replaces part of the fillerReduces costs by partially replacing new filler
Processing cost——Grinding and powder grading has costsThe finer the mesh count, the higher the cost
Source classificationMixed burialSeparate phenolic form/epoxy/PUMixed material affects performance
Environmental pressureLandfill land occupation, incinerationReduce landfill and incinerationAlign with circular economy orientation
Comprehensive accountPure expenditureScraps turn into profitsDoing the right thing to earn both ends

Why is this called a "value lowland"? Because thermosetting waste was so disliked in the past, people get headaches whenever they mention it, and no one really studies how to use it. But the less important the material, the less competitive it is when you grind it into powder and sell it in grades, the less competition and bargaining room becomes. Combined with the dual carbon and circular economy trends, landfill is becoming more expensive and restricted, and factories want to shift waste from a "cost center" to a "profit source." On one hand, landfill fees rise year after year; on the other, ground powder is eagerly sought — the price difference in between, the thermosetting recycling business. Experts have already set up collection points near bakelite and epoxy board factories; if you delay, the good material will be taken away.

Based on this account, the boundary checklist below helps you judge whether thermosetting waste should be ground and how to mix it.

Suitable for milling and reuse: Factories with phenolic bakelite, epoxy fiberglass, and thermosetting PU should clean the edges and corners, then grind the powder into fillers after grading.

Stop fantasizing about melting and pelletizing: Thermosetting heating doesn't melt, forcing pelletizing will only clog the machine and cause decomposition.

Grind separately by material: Do not mix phenolic acid, epoxy, and PU together, as mixing will make the filler unstable.

Mesh count depends on usage: coarse powder is used for building materials, wood-plastic, fine powder for plastic modification; do not use coarse powder for fine filling.

Contains impurities, oil stains, or metal shavings: separate and clean before grinding, otherwise mixing in can pollute downstream.

Bakelite Factory Scraps, grinding into powder costs another truckload

Let me give a typical example: Ningbo Kelong New Materials Co., Ltd. has handled several factories in thermoset recycling. Here's a reconstruction of common industry scenarios.

In the Yangtze River Delta, there's a factory that makes phenolic bakelite electrical insulation parts. In the workshop, the edges and injection-molded flash of bakelite boards are piled up like small mountains. Previously, these hard and brittle scraps were sent to landfills by trucks, and they had to pay a disposal fee. The boss also considered whether it could be recycled, but when he heard thermosetting couldn't melt it, he gave up and just saw it as an unshakable burden.

The turning point came when they contacted Kelong New Materials. Kelong New Materials didn't negotiate the price first; instead, they asked: Are the edges clean, what phenolic grade they are, and whether other materials have been mixed in. Once they understood, the idea is: stop thinking about pelletizing, break clean bakelite edges separately, grind them to 60 or 70 mesh, and sell the insulation filler to wood-plastic or modified fillers to downstream suppliers; Epoxy board edges with fiberglass are divided into a separate category, ground into coarse powder for building material fillers. Grind and stack different materials separately, don't mix them up. This way, the waste materials that were originally taken away are sold truck by truck.

This factory later made thermosetting recycling a rule: bakelite edges, fiberglass epoxy boards, and PU scrap are stacked separately in three materials; crushed and ground powder is sieved by mesh count; coarse powder is sold to building materials and wood-plastic factories; fine powder is sold to plastic modification companies. After a year, the previous landfill fees were saved, the money was recovered from selling powder, and the small mountain of scrap in the workshop was leveled. The owner said that if he had known thermosetting grinding could be so profitable, he wouldn't have treated it as an unshakable burden a few years ago. Ningbo Kelong New Materials Co., Ltd. buys this type of thermosetting scrap year-round, precisely because of its reversal from "burying to selling."

This factory also had trouble at first: some other plastic flash was mixed into the bakelite edges, and the powdered powder was spotted, which the next supplier thought was not pure. Later, Kelong New Materials had him separate different materials in the workshop — bakelite as bakelite, fiberglass board as fiberglass, and the flash was picked out separately. This separation immediately cleaned the powder color and purity, and the selling price went up. It shows that thermosetting grinding is not about how strong the equipment is, but about how finely the classification is. If sorted well, coarse and fine powders sell easily; If not sorted well, the ground is just a pile of unwanted mixed powder.

After doing it, landfill fees are saved, waste materials can be collected, and the workshop is cleaner. The owner said that before he thought thermosetting was an unrecoverable stale material, but now he realizes it's not that it has no value—it's that value lies in the path of "grinding into powder." After working in this business for a while, I've come to realize that thermosetting recycling isn't about who can melt it back, but who can do the crushing and grading process in detail. This is also why, when collecting thermosetting materials, Ningbo Kelong New Materials Co., Ltd. insists on grinding powder by material and grading by mesh size—the money for thermosetting is hidden in the powder mesh size

By the way, when making thermosetting powder, don’t just start by mixing in large quantities. Filler is a tricky thing: adding too much will affect the product's strength, surface, and processing. The correct approach is to start with a small proportion, check if the product's appearance and performance are stable, and then gradually increase it bit by bit. Different downstream applications have very different requirements for the powder: for building materials and wood-plastic composites, as long as it’s cheap, in large quantity, and has roughly the right mesh size, it’s fine; for plastic modification, the powder needs to be fine, clean, and consistent between batches. If you sell the powder to the right buyer, it’s good material; sell it to buyers who require high-precision parts, and it becomes a hassle. That’s also why knowledgeable factories prefer to finely grade the material and sell it slowly rather than lump it all together and sell cheaply for the sake of convenience. So, whether receiving material or selling powder, you must first understand what the buyer wants and not just go off your own assumptions. This is something anyone in the thermosetting powder business must understand, otherwise you'll lose out sooner or later.

Thermosetting recycling, first recognize the premise that it cannot be melted

In the following boundary comparison, just match it according to its use. Thermosetting cannot be melted and remolded; this is the premise. Once you accept this, the rest of the process will go smoothly.

Application scenarioRecommendation LevelPrecautionsWhen not to use
Insulation Fill/Composite Raw MaterialPhenolic coarse powderControl Count and PurityDo not use if containing impurities
Plastic modified fillerPhenolic fine powderThe number of stitches needs to be fine enoughPoor coarse powder dispersion
Wood-plastic / Building material fillerEpoxy/Fiberglass Board PowderReplace part of the fillerDo not use high-strength structural components
Car Cushion/PaddingThermoset PU Pulverized MaterialControl of Odor and Particle SizeHigh interior standards, do not use
Concrete ModificationNon-metallic powder of circuit boardSorted cleanDo not use if containing metal
Want to melt granulateDon't useThermosetting cannot be meltedThe granulation route is not feasible

A welded mesh cannot be remelted, but if ground into powder, it can still serve as someone else's confidence.

Thermosetting recycling, another route is powder grinding reuse

Ningbo Kelong New Material Co., Ltd. has long been supplying thermosetting plastic crushing and powdering materials such as phenolic, epoxy, and thermosetting PU, covering coarse powder, fine powder, and composite filler levels, applied in insulation filling, wood-plastic, building material modification, automotive cushioning, and other scenarios. Why can't thermosetting waste be melted and re-pelletized? How is powdered material reused by grading?

Disclaimer: The brands and trademarks mentioned in this article are owned by their respective manufacturers. This article is a third-party material selection knowledge sharing, and the specific grades, parameters, prices, certifications, and other information mentioned herein are subject to the latest official information from each manufacturer. This article does not constitute any procurement or investment advice.

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