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 1415 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

Description: Thermosetting plastics (phenolic form, epoxy, thermosetting PU, etc.) form a three-dimensional cross-linked network after curing and cannot be melted and repelled. Currently, recycling mainly uses mechanical and physical grinding powder as filler, referring to GB/T 40006.1 "Plastics—Recycled Plastics Part 1: General Rules" 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; for more specifications and physical properties, please refer to the manufacturer's official TDS.

Grinding waste into powder is not just compromise; it's another way to reduce costs .

Some people look down on grinding powder as filler, thinking it's 'downgraded utilization.' But from another perspective: thermosetting can't be re-boiled to begin with, and mixing in grinding powder already turns 'landfill' waste into material that can be sold for money. That's how you calculate it.

Cost itemWaste disposalMilling reuseDifferential explanation
Disposal costSpending money on landfilling/incinerationCrush and grind into powder to sell for moneyTurn expenditure into income
Filler value——Mix wood-plastic/new material to replace part of the fillerReduce costs for some of the new filler
Processing cost——Crushing, grinding, and classification have costsThe finer the mesh, the higher the cost.
Source ClassificationBuried togetherSeparated by phenolic/epoxy/PUMixing materials affects performance
Environmental pressureLandfilling, incinerationReduce landfilling, reduce incinerationIn line with the circular economy orientation
General accountPure expenditureScrap turns into profitMade the right move and profited on both ends

Why is this called a 'value lowland'? Because thermoset waste has been so despised in the past; whenever people talk about it, they get a headache, and no one really studies how to use it properly. But the more people ignore this material, the more you can grind it into powder and sell it by grade—the less competition, the bigger the room for negotiation. Coupled with the broader trends of carbon neutrality and the circular economy, landfilling is becoming more expensive and increasingly restricted. Factories want to turn waste from a 'cost center' into a 'profit source.' On one hand, landfill fees keep rising every year; on the other hand, there are people eagerly snatching up the powdered material you’ve prepared—the price difference in between is the profit margin in the thermoset recycling business. Industry insiders have already set up collection points near various bakelite and epoxy board factories. If you’re too late, the good material will already be gone.

Based on this account, the boundary list below helps you determine whether thermosetting waste should be ground into powder and how to mix it.

Suitable for grinding and reuse: Phenolic bakelite, epoxy fiberglass boards, and clean factory scraps of thermosetting PU, after being graded and ground into powder, can be used as filler.

Stop fantasizing about melting and re-pelletizing: thermosetting plastics do not melt when heated, and trying to pelletize them will only clog the machine and cause decomposition.

Grind separately according to material: do not mix phenolic, epoxy, and PU in the same batch; mixing them will make the filler properties unstable.

Choose the mesh size based on usage: coarse powder is used for construction materials and wood-plastic, fine powder is used for plastic modification, don't use coarse powder for fine filling.

Those containing impurities, oil stains, or metal scraps: sort and clean them before grinding, otherwise mixing them in will contaminate the downstream process.

The scrap from the bakelite factory, ground into powder, is another cartload of money.

Let me give a typical scenario example. Ningbo Cologne New Materials Co., Ltd. has dealt with some factories in the field of thermosetting recycling. Below is a reconstruction according to common situations in the industry.

In the Yangtze River Delta, there is a factory that produces phenolic bakelite electrical insulation parts. The corners of bakelite sheets cut in the workshop and the flash from injection molding pile up into small hills. Previously, this hard and brittle waste was hauled away for landfill, and they even had to pay fees to dispose of it. The boss had also considered recycling it, but after hearing that thermosetting materials cannot be melted, he gave up, treating it as an unavoidable burden.

A turning point came when they got in touch with Cologne New Materials. Cologne New Materials didn’t start by negotiating the price; they first asked clearly: whether the scraps were clean, what phenolic resin grade it was, and whether any other materials were mixed in. After understanding this, their suggestion was: stop trying to pelletize it, separately crush the clean bakelite scraps, grind them to 60-70 mesh, and sell them as insulating filler to buyers making wood-plastic or modified filler; epoxy board scraps with fiberglass should be separated, ground into coarse powder, and used as building material filler. Different materials should be ground and stored separately, not mixed. In this way, waste that used to cost money to haul away could instead be sold out by the truckload.

The factory later also turned thermoset recycling into a standard procedure: bakelite scraps, fiberglass epoxy boards, and PU waste were sorted into three piles, crushed and ground, then sieved according to mesh size. The coarse powder was sold to construction material and wood-plastic factories, while the fine powder was sold to companies that modify plastics. Over the course of a year, the previous costs for landfilling were saved, selling the powder even brought in some income, and the small mountain of waste in the workshop was gone. The boss said that if he had known grinding thermoset materials could be so profitable, he wouldn’t have treated it as a burdensome waste in the past few years. Ningbo Kolon New Materials Co., Ltd. has been collecting this kind of thermoset scrap for years, precisely because of this transformation from 'being buried to being sold.'

This factory was worried at first: there were bits of other plastics mixed in with the bakelite corners, and the powder ground from them had uneven coloring, which the buyers found impure. Later, Cologne New Materials suggested that they separate different materials right at the first stage in the workshop—bakelite goes with bakelite, fiberglass boards with fiberglass boards, and the edge scraps are picked out separately. With this separation, the color and purity of the powder became clean immediately, and the selling price went up. This shows that in thermosetting powder production, success depends not on how powerful the equipment is, but on how finely the materials are sorted. If sorted well, there’s no problem selling both coarse and fine powder; if not, what comes out is just a pile of unwanted mixed powder.

By doing this, we save on landfill fees, can recover money from the waste, and the workshop is also cleaner. The boss said that he used to think thermosetting plastics were unrecoverable waste, but now he realizes that they are not without value; their value lies in the process of grinding them into powder. After being in this industry for a long time, one realization is that the recovery of thermosetting plastics depends not on who can melt them back, but on who can meticulously handle the crushing and grading process. This is also why Ningbo Cologne New Materials Co., Ltd. insists on grinding thermosetting scraps separately according to material type and selling them graded by mesh size— the money in thermosetting plastics is hidden in the mesh size of the powder.

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. Different downstream clients have very different requirements for powder: for building material wood-plastic, as long as it’s cheap, available in large quantities, and the mesh size is roughly right, it’s fine; for plastic modification, it needs to be fine, clean, and consistent across batches. If you sell powder to the right client, it’s good material; sell it to clients with high-precision requirements, and it becomes a headache. That’s why knowledgeable factories would rather sort the material finely and sell it slowly than mix everything together for a quick, cheap sale. So, those who collect or sell powder must first understand what the client wants, rather than acting on their own assumptions. Anyone in the thermosetting powder business must understand this, or they’ll suffer losses sooner or later.

Thermoset recycling starts with recognizing the premise that it cannot be melted.

In the following boundary comparison, just match it according to its use. Thermosetting cannot be melted and remade into granules; this is the premise. Once you accept this, the subsequent path will be smooth.

Application scenarioRecommendation LevelPrecautionsWhen not to use
Insulation Fill/Composite MaterialPhenolic coarse powderControl Count and PurityDo not use if contaminated
Plastic modified fillerPhenolic fine powderThe number of stitches needs to be fine enoughCoarse powder disperses poorly
WPC/Building Material FillerEpoxy/Fiberglass Board PowderReplace part of the fillerDo not use high-strength structural components
Car seat cushion/paddingThermoset PU Pulverized MaterialControl of Odor and Particle SizeHigh interior standards, do not use
Concrete ModificationNon-metallic powder of circuit boardSorted cleanlyDo 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 reuse

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

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