再生PBT:接插件线圈骨架都在用,水口料回炉能省多少

塑料知识科普 发布时间: 2026-09-14 2762 阅读

The sprue material that falls off the assembly line in an electronics factory is piled in the corner with no one paying attention, but it's actually money. This is referring to PBT — polybutylene terephthalate, a common material for electronic connectors, coil bobbins, and automotive parts. A ton of new material isn't cheap; the sprue material from injection molding can be reprocessed into pellets and mixed back into your own products, saving real money. This article clarifies the accounting for recycled PBT.

Let's spend two minutes getting to know the main subject. Ningbo Kelon New Materials Co., Ltd. has long been handling PBT raw materials, with recycled PBT being one of their areas. PBT is a crystalline engineering plastic: it crystallizes quickly, has a short molding cycle, maintains stable dimensions, and is chemically resistant. It is used in electronic and electrical connectors, coil frames, switches, as well as automotive sensor housings and lamp holders. It has a characteristic: it crystallizes quickly and solidifies once cooled, making injection molding cycles short, which is particularly suitable for mass-produced connectors. The sources of recycled PBT mainly come from two areas: sprues and defective products from injection molding in electronics factories, and offcuts from home appliance components and automotive parts factories. A large portion of it is glass fiber reinforced and flame-retardant.

Scraps piled in the corner; those who know value them as treasures, those who don't see them as trash.

Factories that do PBT injection molding all have an experience in common: when a connector mold produces a dozen or so parts at once, it comes with a big pile of sprues, which account for 20-30% of the total injection volume. The composition of these sprues is the same as the actual products, and when they come out of the mold, they are clean and uniform. Skilled factories crush the sprues on the spot and mix them back into the new batch according to proportion, using them internally; those who are not as knowledgeable pile them in a corner and sell them as waste, making only a few cents per pound.

There is a key premise here: PBT sprue material must be 'reblended with the same grade.' Material with glass fiber should be reblended with material that also has glass fiber, flame-retardant material with flame-retardant material, black material with black material. If different grades are mixed, the glass fiber content changes, the flame-retardant level changes, and the connectors produced will not have the correct dimensions or flame-retardant properties. Therefore, in electronics factories, when recycling sprue material, the first step is not crushing it, but sorting the grades clearly.

Why is PBT used so extensively in electronic components? Because it crystallizes quickly, has a short molding cycle, and a single mold can produce connectors in just tens of seconds. Its dimensions are stable, and it is resistant to solder and chemicals, which are exactly the characteristics required for mass production in electronics factories. The new material is easy to use, but it can't withstand the sheer volume—hundreds of thousands of connectors per month, and the sprue material piles up into a mountain. Making good use of this sprue material can save more than just a little.

Also, distinguish PBT from a few other similar materials nearby, so you don’t get confused. PBT crystallizes quickly and is chemically resistant, used for connectors; PET crystallizes a bit more slowly and is mostly used for bottles and films; POM is used for gears and bearings. Recycled PBT mainly comes from the sprues of electronics factories, which is not the same stream as PET bottle scrap. When collecting materials, keep PBT sprues and PET bottle chips separate; don’t mix them—once mixed, the crystallization behavior becomes erratic, and the manufactured parts won’t have stable dimensions.

The small amount of money for PBT material in the province can't compare to a batch of mixed scrap connectors made from sprue material.

Figure 1 Recycled PBT granules and electronic connectors (schematic)

PBT crystallizes quickly, and there are considerations when recycling it back into the furnace

When breaking down recycled PBT by reinforcement and flame retardant levels, it roughly looks like the table below (the indicators are a generalization of the industry's common range, and specific values should refer to the manufacturer's TDS). For PBT, the glass fiber content and flame retardant level are hard specifications: the amount of glass fiber added directly determines stiffness and dimensional stability; whether the flame retardant level is sufficient determines if it can be used in electronic components.

LevelTypical sourceKey indicatorsTypical applications
Pure Resin Recycled PBTSprue material, defective productsNo fiberglass, natural colorOrdinary structural components, modified base materials
15% Glass Fiber Recycled PBTConnector sprue15% fiber-reinforced, enhancedGeneral connectors and housings
30% glass fiber recycled PBTskeleton, shell gate30% fiber reinforced, high rigidityCoil skeleton, structural components
Flame-retardant recycled PBTElectronic component casing sprueFlame retardant V0 gradeElectronic connectors and switches
Black fiber-reinforced flame-retardant recycled PBTMixed black material water outlet10-40% fiber reinforced, fire-resistantBlack electronic components, internal parts of home appliances
Mineral-filled recycled PBTFilling-level sprueStable dimensions, low warpingPrecision parts, appearance parts

Market Reference: Recently, recycled PBT materials with 10-40% fiber reinforcement and V0 flame retardant grade are priced at just over nine yuan per kilogram, which is lower than brand new reinforced grades. When Ningbo Kolon New Materials Co., Ltd. quotes PBT materials, they usually first ask whether the downstream application is for connectors or structural parts, how much glass fiber is needed, and whether flame retardant is required, then recommend based on the grade—because in the PBT business, if you ask the wrong questions about glass fiber or flame retardant, the cheaper material won't pass safety regulations.

One more word about the process of recycled PBT. PBT crystallizes quickly, so the temperature cannot be too high during regranulation of recycled material; if it's too high, the material will degrade and its molecular weight will drop, making the final parts brittle. When sprue material with glass fiber is recycled, the glass fibers will be sheared again, shortening their length and slightly reducing the reinforcing effect — so PBT that is mixed multiple times will have rigidity that decreases generation by generation. Experienced manufacturers will send repeatedly recycled material to lower-end products, reserving fresh sprue material for parts with higher requirements.

Why is it said that PBT crystallizes quickly, yet recycling and reprocessing it require careful handling? Because it crystallizes quickly, if the material stays in the barrel for too long, it easily degrades. After degradation, the molecular weight drops, making the produced parts brittle. Therefore, when recycling PBT into pellets, both the temperature and residence time must be tightly controlled and cannot be handled as loosely as with PP. At recycling plants, processing PBT requires adjusting the screw L/D ratio and the heating zone temperatures; it's not something that can be done with just any pelletizing machine.

There is one more easily overlooked point: PBT absorbs moisture. Recycled material must be dried to a sufficiently low moisture content before granulation, otherwise there will be bubbles and silver streaks during injection molding, and the surface of the connectors will be blemished. This drying step may seem trivial, but without it, the entire batch could be scrapped.

Let me mention another new approach in the industry. Besides physical blending, some manufacturers use chemical recycling—for example, chemically depolymerizing PET bottles and then synthesizing PBT, creating new PBT material with PCR content. This type of material is suitable for orders that require recycled content, but it is more expensive than ordinary sprue recycling. For regular electronics factories making connectors, physical blending is sufficient; if you want to fulfill export orders or need proof of recycled content, then consider the chemical recycling route.

PBT with glass fiber has another trouble: the glass fiber is hard, and repeated reprocessing can wear down the screw and barrel. If the equipment wears out quickly, maintenance costs go up, and this has to be accounted for. So, when old factories recycle glass fiber reinforced PBT, they regularly check screw wear and don’t maximize the reprocessing ratio, allowing the equipment some breathing room. In the long run, this actually saves on maintenance costs.

Let me talk about something related to appearance. Most recycled PBT is black, which is perfect for black appliance internal parts since the color difference is small and not noticeable. If you make natural light-colored parts, material that has been recycled multiple times tends to yellow and darken, and any flaws in appearance are easily revealed. Therefore, light-colored appearance parts should be prioritized for new material or clean first-use sprues, while black parts can be made from recycled material. Thinking through this color issue in advance can save a lot of rework.

The cost of recycled PBT lies in the watermarks, the value lies in stability.

The cost of recycled PBT cannot be judged solely by the price per kilogram of the material. Consider the material price, fiberglass, flame retardant, and yield together:

Cost itemBrand new PBTRecycled PBTDifference Explanation
Raw material purchase priceBenchmark priceA bit lowerThe price difference for flame-retardant fiber-filled grade is significant
Glass fiber contentStableDepends on the number of times it is recycledMulti-generation material glass fiber shorter
Flame retardant ratingStableReturning to the same level is the only way to be stable.Mixed material flame retardancy does not meet the standard
Dimensional stabilityGoodObserve the crystals and dryMoisture absorption will cause silver streaks
Appearance ColorconsistentBlack is more stableLight-colored natural parts are prone to discoloration
Annual Comprehensivesuperficially expensiveSignificant drop in electronic component costsPrecision exterior parts first to verify

If you thoroughly understand this table, you will find that the real cost-effectiveness of recycled PBT is not in hard-touch exterior parts, but in mastering parts like connectors, frameworks, and internal components of home appliances—these are 'single-grade and not color-sensitive' parts. These parts are originally made with black fiber-reinforced materials, and mixing in runner material results in small color differences and matches the grade, ensuring stable yield. Conversely, high-gloss exterior parts or precision tolerance parts, if their dimensions are out of spec, can lead to the whole batch being scrapped. Don't gamble to save on material costs.

A few more words about the market. The price of recycled PBT follows that of new PBT and fiberglass—when the price of new material rises, reclaimed material also becomes sought after. Factories making connectors naturally have a stable source of reclaimed material, and managing it well is like having an on-demand material warehouse. The key is not to mix reclaimed materials of different grades—once mixed, the whole batch will have to be downgraded.

Let me give a practical example. When sourcing recycled PBT externally, don’t just look at the price; first ask where the material comes from. Our factory mixes in sprue material, which has a single grade and stable batches; the mixed black material collected from outside has its glass fiber and flame retardant adjusted, making the batches inconsistent. Using our own sprue material as the main source and supplementing with externally sourced material is a more stable combination. When using external material, start with a small batch, and only scale up after it passes safety regulations and dimensional checks.

Boundary List — Which Items Are Safe to Use and Which to Avoid:

Safe to use: connectors, coil skeletons, switches, internal appliance components, automotive structural parts.

Use with caution: flame-retardant parts, make sure to use the same flame-retardant grade, pass safety regulations before mass production.

First verify: for long-term loaded components, observe the rigidity retention after multiple remixes.

Do not touch: components subjected to long-term high humidity, long-term stress, precision optical parts, and high-gloss appearance parts.

Procurement actions: you need the fiberglass content, you need the flame retardant report, you need to check the moisture content, don't just ask how much it costs per kilogram.

The comings and goings of a pile of black sprue material: from the corner of the workshop to the connectors

The following situation is probably familiar to many in injection molding (just making an example, don’t look for the original case). There is an electronics connector factory in Ningbo that used to add fully enhanced PBT for injection molding. After crushing the sprue material, they would mix it and sell it. The grades were mixed and the prices were low, while new material was expensive. The boss always felt that the connector business only earned hard-earned money.

Later, they matched the two ends of the process: they separated the workshop sprue material by grade—30% glass fiber reinforced sprues, flame-retardant connector sprues, and black casing sprues—then crushed, dried, and granulated them separately, and finally blended them back into corresponding grades of new machines according to proportion. Ningbo Kolon New Materials Co., Ltd. helped streamline this step—ensuring the drying moisture content was precise, starting the blending ratio with a small amount, and increasing it after measuring the dimensions and flame retardancy of the connectors. After the process was streamlined, the amount of purchased new material dropped significantly, the sprue material was no longer sold cheaply, and the yield of the connectors remained stable.

They also ran into pitfalls. The first time they mixed different grades of sprues together for crushing, the resulting batch of connectors failed the flame-retardant random inspection, and the entire batch had to be reworked. Later, they started storing sprue materials separately based on fiberglass content and flame retardancy, and the crushers were separated as well, and the problem disappeared. This case shows: recycling PBT saves material costs, provided you don't take shortcuts in grade separation.

Running the numbers: after handling the sprue material internally, the cost per ton of material dropped significantly, and the samples still passed safety inspections, usable by downstream users. What this case illustrates isn't complicated: the profit in PBT recycling lies in taking the sprue material from the corners of the workshop and feeding it back into the machines according to grade. Ningbo Kolon New Materials Co., Ltd. provides PBT recycling supply; what they do isn't just selling a bag of pellets, but helping downstream users smoothly handle grading, drying, and blending back.

The boss calculated a detailed account: previously, sprue material was sold cheaply by the ton. Now, by pelletizing it himself and mixing it back in, the annual tonnage of externally purchased new PBT has been reduced significantly, and the yield of connectors is even more stable than before—because the sprue material comes from his own factory, he knows the grade of each batch. This account is about connecting both the waste and the new material.

When selecting recycled PBT, first look at the glass fiber, then look at the flame retardancy.

Below is a comparison table of application scenarios and recommendation levels, which you can directly refer to when using it:

Application scenarioRecommendation LevelPrecautionsWhen to stop using
electronic connectorGlass fiber reinforced/flame-retardant recycled PBTPassed flame retardant safety regulationsHigh-gloss exterior parts caution
coil skeleton30% glass fiber recycled PBTCheck dimensional stabilityPrecision tolerance parts must be verified first
Switches and buttonsFlame-retardant recycled PBTEnsure the flame-retardant gradeBe cautious with long-term high temperatures
Home appliance internal componentsBlack reinforced recycled PBTPrice PriorityDo not use exposed exterior parts
Ordinary structural componentsPure resin recycled PBTModified base materialDon't use load-bearing structural parts

Another common misconception. Some people worry about inaccurate dimensions or flame retardant as soon as they hear 'recycled PBT.' Actually, PBT sprue material comes from the same grade from our factory. As long as it's properly dried and the re-doping ratio is stable, it's more than enough for connectors. The real pitfall isn't 'regeneration'—it's mixing different grades of sprue nozzles, over-maximizing re-doping, or slacking off on drying. If you lock these three points, recycled PBT becomes a cost-reducing material ready for electronics factories.

How much recycled PBT is suitable for new material? It depends on what kind of part you're making. For black home appliance components and ordinary connectors, the blending ratio can be increased; When making flame-retardant safety parts, start with a small quantity, pass flame-retardant spot checks for each batch, then add more. Don't rush in on large quantities right away—repeated remixing of PBT will make it brittle, too many will crack easily. Mixing is related to your mold and screw wear. If you copy other factories' proportions directly, you'll probably need to rework.

Buying recycled PBT Here's another practical action: For your first collaboration, start with a sample, measure glass fiber content, flame retardant rating, moisture content, install a few connectors on the machine to check size and appearance, and only negotiate batch size if it passes. The trick with PBT recycling isn't about single batches, but about whether the fiberglass and flame-retardant are floating between two batches—clearly state the acceptance scope and include data with each batch—it's more effective than verbal assurance.

Finally, to put it bluntly: recycled PBT isn't some advanced technology; what it earns is the money from "not delivering from the factory's shuikou." No matter how good the new material is, piling up sprue material in the corner is still waste; If you classify it, dry, and connect it to the machine according to the proportions, the cost of electronic components can drop by a whole chunk. Whoever doesn't slack off on grading and drying can truly reap this profit. Remember these three rules: don't mix the sprue nozzle, don't crystallize too quickly, don't slack off during inspection. Follow them and you're less likely to fall into pitfalls. Electronics factories should post these three on the workshop wall to remind themselves not to stumble over these small matters every day. Only then can you save on material costs and secure orders. This is what experienced buyers often say: save money in the open, not in the visible places. This is the way to maintain long-term business and the old rule in this industry. New factories must follow suit, don't start from scratch. Just follow the old rules, and you won't make major mistakes. Don't worry.

Shuikou material is not waste, but raw material that hasn't been properly aligned—if you get it to the right grade, it's your own cost-reducing material.

Use the right grade of recycled PBT to ensure connectors are worthwhile .

Ningbo Kelong New Materials Co., Ltd. has long supplied recycled PBT raw materials, covering pure resin, 15%/30% glass fiber, flame-retardant V0, black fiber-reinforced materials, and multiple grades, used in connectors, coil frames, switches, and home appliance internal components. Can't tell the difference between glass fiber and flame retardant grade? Worried that mixing materials won't meet safety standards?

Statement: 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 mentioned are subject to the latest official information from each manufacturer. This article does not constitute any procurement or investment advice

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