再生POM聚甲醛:齿轮滑轨的耐磨件,为什么再生料很少见

塑料知识科普 发布时间: 2026-09-14 1584 阅读

Have you ever taken apart a printer, a coffee machine, or a car seat adjustment handle? That ring of gears inside, which is hard and smooth and turns almost silently, is mostly made of POM. For a material this resilient, why is it that recycled POM pellets are hardly seen on the market like PP or ABS? The answer isn't that it doesn't deserve to be, it's that it's too picky. Today, let's thoroughly explain this issue.

Let's spend two minutes getting to know the main character. POM, scientifically known as polyoxymethylene and nicknamed 'super steel' in the industry, has a main chain made up of a series of regular –CH2O– units. It has high crystallinity, sufficient rigidity, low dry friction coefficient, self-lubricating properties, and low water absorption. Gears, slides, sliders, cams, and fasteners made from it have stable dimensions and fatigue resistance. The vending machine dispensing gears, roller door pulleys, and zipper teeth in your hands all bear its mark. Ningbo Kolon New Materials Co., Ltd. supplies plastic raw materials, integrating industry and trade, and keeps common recycled plastic categories in stock year-round. Among them, POM is one that is relatively selective with customers and usage scenarios.

The source of recycled POM is somewhat different from other materials. The vast majority of recycled POM circulating in the market does not come from old gears picked out of the trash, but from clean sprues, regrind, and scrap generated in injection molding and extrusion factories—same grade, single source, and known before being reprocessed. POM recovered from post-consumer products is very rare because POM components are small, have mixed colors, and are mixed with other plastics, making sorting costly. This also explains why recycled POM "appears scarce": its recycling is mostly confined within factory boundaries and rarely reaches the open market. Ningbo Kolon New Materials Co., Ltd., when sourcing this type of material, prioritizes clean sprues of the same grade from the same factory rather than unknown mixed scraps.

Recycled POM is rare; it's not that it's worthless, but it can't withstand rough handling.

Many people think that regenerated POM is rare because the usage of this material is small. Wrong, completely wrong. The usage of POM in engineering plastics is not small; it is everywhere, from gears and slides to zippers. The reason regenerated material is rare lies in its molecular structure — this material is an 'impatient type' and wants to break down as soon as it is heated.

PP and PE can be remelted and granulated; at most, the molecular weight drops a little, and the color turns slightly yellow, but it's still essentially the same material. POM is different. Its main chain consists of carbon-oxygen single bonds, which are not very strong, and once the hemiacetal structures at the ends of the molecular chains get overheated and out of control, they start to unzip from the chain ends like a zipper, releasing formaldehyde monomers along the way. The industry calls this a 'depolymerization avalanche.' The released formaldehyde has a pungent smell, detectable in the workshop, and what's even worse is that the molecular weight drops sharply—when the material's molecular weight falls, properties like wear resistance, impact resistance, and toughness all collapse with it.

There is a piece of data that really illustrates the issue: even if the temperature is strictly controlled between 180 and 210°C and air exposure is minimized, after conventional melting and one round of recycling, the intrinsic viscosity of POM usually decreases by 15% to 30%, which is relatively large among engineering plastics. What’s more troublesome is that stabilizers are consumed with each processing—studies have shown that each time POM is repeatedly processed, its thermal stability drops, and the more times it is processed, the less protection remains, making it more prone to degradation the next time it is heated. In other words, it's not that POM cannot be recycled, but the 'number of times' it can be reprocessed is very limited; each recycling reduces its inherent quality.

By the way, let me answer a frequently asked question: Why do gears have to use POM? Nylon is also wear-resistant. The difference is: Nylon absorbs moisture, which changes its dimensions, and once the gear clearance changes, tooth meshing occurs; POM has a very low water absorption rate, so its dimensions hardly change with humidity, its dry friction coefficient is low, it doesn't need frequent lubrication, and it operates quietly and lasts long under low speed and low load. Because of this, most of its parts are 'moving pairs'—they need to rotate, slide, and wear. Once the material's molecular weight drops and its wear resistance declines, problems occur in batches, unlike housing parts where a crack might still be tolerable. This also means that recycled POM has a much lower tolerance for defects compared to PP or ABS used for housings—customers can tolerate cracks in housings, but messed-up gear teeth require a full batch recall.

Figure 1 POM gears and slide rail components of Saigang

Reheating steel is like zipping a zipper; if a tooth is missing, it has to be filled back in.

Since POM is so delicate, how is clean sprue material recycled? It relies on pressing the 'zipper' chain back as much as possible. The standard method is far more precise than ordinary material production.

The first step is low temperature and rapid processing. Ordinary granulation prefers to allow the material to melt for a longer time, but POM is the opposite — the longer it stays in the barrel, the more it degrades. Sophisticated factories use a twin-screw extruder, with the front section delivering at low temperature with gentle shear, and the rear section having a short compression segment for instantaneous melting, keeping the material's residence time in the high-temperature zone to within tens of seconds to cut depolymerization off in terms of time. The second step is to supplement the stabilization system. Some of the original stabilizers are consumed during reprocessing, so when recycling, it’s necessary to add hindered phenolic antioxidants and auxiliary stabilizers, along with some formaldehyde scavengers, to lock down the cleaved end groups and free formaldehyde, preventing them from slowly releasing in the final product. The third step is sorting, washing, and drying — POM is sensitive to water, and excess moisture can cause hydrolytic degradation, so the drying step cannot be skipped.

After going through such a process, how much of the performance of recycled POM can be restored? Clean water-gate scrap, used only once, with a properly replenished stabilizer system, retains performance relatively well; if the source is mixed, no stabilizer was added, and it has been recycled many times, don't expect it to still serve as a main wear-resistant material. Homopolymer and copolymer also need to be discussed separately: copolymer POM has relatively better thermal stability and releases formaldehyde more gently; homopolymer POM is more rigid and firm, but also more brittle and heat-sensitive, so extra care is needed during recycling. The grade table below classifies them according to source and treatment level.

This explains another strange phenomenon of recycled POM: most of its recycled material 'never leaves the factory.' The manufacturers' own sprue material is collected separately, clean and uniform; by simply adding some stabilizer and mixing it back into their production line at about ten to twenty percent, the performance can still be maintained. This kind of closed-loop reuse saves material without waste and is the cost-effective, reliable mainstream practice in recycled POM. The recycled POM that actually reaches the open market and is freely traded by merchants, on the other hand, tends to be from unclear sources and mixed batches. Although the price looks low, the risk is equally high. So the reason why you see few recycled POM pellets on the market is not that nobody recycles it, but that the good material is all absorbed within the factory's closed loop.

LevelMain sourceKey indicatorsTypical uses
Natural Watergate Recycled POM (Single Use)Injection molding factory, same grade clean gates, cold materialLow loss of intrinsic viscosity, low odor, and relatively good mechanical retentionOrdinary low-load gears, sliders, structural components
Black wear-resistant modified recycled POMWater gate material compounded with carbon black PTFE or MoS2Low coefficient of friction, good weather resistanceWear-resistant gears, slide rails, bushings
Copolymer Recycled POMCopolymer POM Factory NozzleGood thermal stability, relatively mild formaldehyde releaseGeneral transmission parts, parts that need hydrolysis resistance
Random Copolymer POMHomopolymer POM Factory NozzleHigh rigidity, slightly higher temperature resistance, greater degradation riskHigh-rigidity gears (require supplementary stabilization system)
Filled Enhanced Regenerative POMRecycled material modified with glass fiber or mineral powderImproved rigidity and dimensional stabilitySize-sensitive structural components
Blended Grade Recycled POMMulti-source hybrid granulationPerformance fluctuations are relatively large, and the odor is relatively strongNon-wear-resistant, non-load-bearing, low-requirement internal components

Note: POM recycling currently mainly refers to GB/T 40006.1 "Plastics - Recycled Plastics Part 1: General Rules" and the corporate standards of various manufacturers. Specialized recycling standards for different types of POM are still being developed; the indicators in the table are summarized from publicly available industry information and manufacturers' technical data. For more grades and physical property parameters, refer to the manufacturers' official TDS.

Gears grind the material, accounting calculates the lifespan.

Is recycled POM cheap? Let me be honest with you: recycled POM that can really be used for wear-resistant parts isn't actually much cheaper than virgin material—it still needs stabilizers, low-temperature rapid processing, and strict odor control, so the processing cost isn't saved at all. As for the cheap mixed materials, you can afford to buy them, but you can't afford to use them. You have to account for this in the lifespan of the gears, not just focus on the small price difference up front.

Let me add a few words about the current situation and standards in the market. Compared with mature recycled categories like PP and ABS, recycled POM has always been a niche business: first, there is very little clean material available for recycling, most of it remains in closed loops within factories; second, processing it is very demanding, and ordinary pelletizing plants dare not handle it, fearing that even a slight rise in temperature would cause smoke and odor; third, national standards for recycled POM specifically classified by type are still being improved, and downstream users lack a unified 'reference guide' for selection, so they can only rely on manufacturers’ own enterprise standards and TDS to judge. When these factors combine, the result is: there are few factories that are willing and able to produce recycled POM, and even fewer that make high-quality material suitable for wear-resistant moving parts. But conversely, precisely because the threshold is high, using the right material in the right scenario makes this cost-saving more valuable—the areas others dare not touch are your opportunities.

Cost itemsVirgin POMRecycled POMDifference Explanation
Price per ton of materialHigherGood ingredients are a bit lower, miscellaneous ingredients are even lowerRecycled materials from clean water sources are not cheap; mixed materials are cheap.
Thermal stabilitySufficient stabilizer, wide processing windowThe stabilizer has been depleted, and the window is narrowIf the material temperature exceeds 200°C, it easily emits formaldehyde smoke
Wear-resistant and self-lubricatingHigh molecular weight, wear-resistant and stableMolecular weight decreases, wear resistance is discountedThe service life of wear-resistant parts is directly affected
Odor/VOCLowSlightly high, residual odorSealed household appliances and in-car parts need to be tested
Batch ConsistencyTallThe same factory's nozzle is stable, but miscellaneous materials fluctuate greatly.Fluctuations in miscellaneous material batches will affect machine adjustments.
Comprehensive costBenchmarkClean water-grade material is cost-effective, mixed material carries high riskNot all parts dare to be replaced with recycled ones.

Based on this account, the boundary list below helps you determine whether the gears and sliders you have can be used with recycled materials.

Suitable for using recycled POM: the factory directly reuses clean runners of the same grade; ordinary gears and sliders with low load, low speed, and non-enclosed; wear-resistant modified parts with restored stability and lubrication system.

High-load, high-speed precision transmission gears, as well as components around car engines that are subjected to long-term high temperatures: don't gamble with recycled materials.

For parts that come into contact with food, sealed home appliances, or vehicle interiors with odor/VOC requirements: test them first, as the odor of ordinary recycled materials tends to be strong.

Unknown-source miscellaneous POM: Do not touch, the base is unstable and will gradually 'zip up' during service.

Materials that have been remelted several times and are brittle but flavorful: no matter how cheap, don't use them for load-bearing parts.

Whether a gear lasts three years or three months, it was already determined when the material was made.

The following incident is a typical case handled by Ningbo Cologne New Materials Co., Ltd. The details are presented according to common situations, and the names of people and the company have been altered.

There is a factory in East China that makes small transmission gears, supplying coffee machines and office equipment. The boss saw that new POM material was expensive, and after hearing that recycled material was cheaper, he bought a batch of black recycled POM that was priced lower than the market rate and used it to produce a batch of gears for assembly. The first two months went fine, but once the machines reached the customers, several months later, repair requests started to come in one after another: gearboxes making abnormal noises, rough rotation. Upon inspection, the gear teeth were found to be worn and frayed, with an indescribable smell. A batch of machines had to be reworked and replaced, and the after-sales cost far exceeded the money saved on the material.

The factory owner, with a try-it-out attitude, dialed the phone number of Kolon New Materials. Kolon New Materials didn’t quote a price right away; instead, they first asked about the operating conditions: under what conditions the gears would run, the load and speed, and whether they would be in a closed or open environment. After understanding this, their advice was to stop using unknown, unclear-history scrap material: for ordinary low-load gears, one can use the factory’s same-grade, single-use, stabilized natural-color recycled material from sprues, which performs well and is more cost-effective than new material; for critical gears that require wear resistance and long life, either use black wear-resistant modified recycled POM with added PTFE or MoS2, or continue to use new material in certain areas. They also stipulated that for each batch, viscosity and odor reports must be checked, the material temperature must be strictly kept within the processing window, and one shouldn’t raise the temperature just to fill the cycle.

COLON New Materials also set a rule for this factory: before running recycled POM on the machine, first adjust the material temperature, drying, and cycle to match the new material process—don’t just use the parameters for new material as-is. POM absorbs moisture, so it must be fully dried before injection molding; don’t leave material in the barrel overnight, and clean out the machine when stopping, otherwise leftover material will sit in high heat overnight and next time the machine runs, it could produce a bad smell and brittle batches. These details may seem trivial, but they are the watershed for whether recycled POM can be used reliably.

After the adjustment, the material cost of that batch of low-load gears decreased, and after-sales complaints also reduced; the key gears no longer had batch problems. Having worked with POM for a long time, there is a personal insight: the more attentive you are to its thermal history, the more it will repay you in gear lifespan. This is also why Ningbo Cologne New Materials Co., Ltd., when promoting recycled POM, prefers to recommend clean sprues from the same factory rather than mixing random materials—the source of the material is unclear, and no matter how cheap it is, it’s just setting off after-sales time bombs.

Replace wear parts with recycled material, smell it first before putting it on the machine

The reasoning has all been explained. The table below is for you to follow to choose, use, avoid pitfalls, and place orders accordingly. One more thing: if you get close to smell the material and it smells strong or sour, it's likely to have a problematic heat treatment history, so no matter how cheap it is, don't use it in load-bearing parts.

Application scenarioRecommendation LevelPrecautionsWhen not to use
Standard low-load gearNatural Color Water Gate Recycled POMReinforce the stabilizing system, check the viscosityDo not use under high load and high speed
Wear-resistant slide rail/shaft bushingBlack wear-resistant modified recycled POMCheck the friction coefficient and wear amountDo not use without a lubrication system
Low-stress automotive interior componentsCopolymer Recycled POMOdor/VOC ControlDo not use when the engine compartment is hot
dimension-sensitive structural componentsFilled Enhanced Regenerative POMCheck shrinkage rate and sizeExtremely high precision, do not use
Shell/Non-load-bearing componentBlended Grade Recycled POMLow costDo not use under wear and stress
Food contact/sealed partsAssess carefullyMust comply with food contact regulationsDon't touch ordinary recycled material

With this POM material, you saved money in the wrong place; all the money saved turned into downtime and after-sales costs.

Recycled POM, the scenarios where it can save money are actually more valuable

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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