A2 Non-combustible Granules and B1 Flame-retardant Granules: How to Choose, Test and Source Core Materials

A2 Non-combustible Granules vs B1 Flame-retardant Granules: Key Differences at a Glance

The short answer: the two grades differ mainly in how much mineral they carry and, as a result, in how they flow, bend and burn. A2 non-combustible granules are formulated so that the finished panel can be tested toward the A2 class, while B1 flame-retardant granules aim at the B1 class, which sits one step lower in the Chinese system under GB 8624. In the European system the comparable language appears in EN 13501-1, where facade panels targeting a non-combustible class are often written as A2-s1,d0 and flame-retardant products fall in the B to C range. The two systems are not interchangeable, so always check which class your target market actually names.

In day-to-day production the difference shows up in the extruder first. A2 non-combustible granules carry so much filler that the melt is stiff, torque rises and the die needs careful temperature control. B1 flame-retardant granules carry more polymer, so they flow more easily, tolerate small temperature drifts and give a core that bends with less cracking during fabrication. The table summarizes typical differences, using ranges that many plants see in practice.

The weights in the table assume 0.5 mm aluminum skins on both sides and a 3 mm core, which is a common build-up for 4 mm panels. Mineral content is the thread that links most rows, so the chart below shows it directly for three example grades. It is worth reading the chart as a menu of starting points for discussion with your granule supplier and not as a formula.

The three rings show a climb from 70 percent for a standard B1 grade to 90 percent for an A2 grade, with a high-filler B1 grade sitting in between at 75 percent. Each step upward adds fire performance margin but removes polymer, and polymer is what gives the melt its flow and the finished core its flexibility. A buyer who compares A2 non-combustible granules and B1 flame-retardant granules should therefore look at the whole package of processing and fabrication behavior and not at the filler number alone. A production line manufacturer can then size the extruder, die and laminating section for the grade you plan to run most often.

Match the grade to the fire class in your project specification first, then check that your line can process it with a stable window.

What Is Inside A2 Non-combustible Granules and B1 Flame-retardant Granules

The short answer: both grades are mineral-filled polymer compounds, and the formulation is built from four groups of ingredients. Understanding these groups makes data sheets easier to read and makes supplier conversations more specific.

Mineral filler

Metal hydroxides carry most of the fire performance. Aluminum hydroxide starts to release water at roughly 180 to 200 degrees Celsius, while magnesium hydroxide holds until roughly 330 degrees Celsius. That difference matters in the extruder: a compound built mainly on aluminum hydroxide limits how hot the melt can run, while a magnesium hydroxide rich compound leaves more room for temperature adjustment. Many halogen-free flame-retardant granules use blends of both, and the blend ratio is part of how a supplier tunes the processing window. Particle size and surface treatment also count, because fine, well-coated particles disperse better and give a smoother core surface.

Polymer binder

The binder is usually a polyethylene or a copolymer such as ethylene vinyl acetate, chosen for melt flow, flexibility and adhesion to the film that bonds the core to the aluminum skins. In B1 flame-retardant granules the binder share is large enough to give a forgiving melt. In A2 non-combustible granules the binder share is small, so the choice of binder and the way it wets the filler have an outsized effect on flow and on core strength.

Compatibilizers and processing additives

Grafted polymers, coupling agents and lubricants help the filler and the binder stay together and help the compound leave the die cleanly. They make up only a few percent of the weight, but they influence bubble formation, surface finish and the bond to the adhesive film. Stabilizers protect the polymer during the heat history of compounding, extrusion and lamination.

Granule form

Granules are commonly cut to a few millimeters in size, with consistent shape so that feeders meter them evenly. Fines and dust make feeding irregular and can carry moisture, so a clean granule with a tight size distribution usually runs better than a mixed one. When you review samples from a granule manufacturer, look at the pellets under good light and check for fines, fused clusters and discoloration before any lab test is run.

• Halogen-free route: most panel cores today use metal hydroxide systems because they release water and not corrosive gases.
• Surface-treated filler: improves dispersion and reduces moisture pickup compared with untreated powder.
• Custom formulation: an OEM granule supplier can adjust binder type and additive package to suit a particular extruder.

Ask the supplier which hydroxide system and binder family are used, because both shape the processing window.

Fire Classes, Test Methods and What a Granule Data Sheet Should Show

The short answer: a fire class belongs to the finished panel and not to the granules on their own, so the data sheet and the panel test report have to be read together. The same granules can reach different results if the skin thickness, core thickness, adhesive film or fixing method changes, and classification reports normally describe the exact build-up that was tested.

Common test routes

For non-combustible targets, laboratories commonly use a furnace test for non-combustibility under ISO 1182 and a gross calorific value test under ISO 1716, which measures how much heat the material could release if fully burned. The single burning item test under EN 13823 looks at heat release, smoke and burning droplets for building products. Chinese projects refer to GB 8624 and its associated test methods. The limits that apply differ between the product as a whole and its individual components, so check the current text of the standard named in your contract before you finalize a formulation.

Zhangjiagang Hongyang Machinery Equipment Co., Ltd. took part as a drafting unit of the standard for non-combustible metal composite panels for architectural decoration, which gives its engineers a practical view of how line settings, core material and test outcomes connect.

Data sheet items worth asking for

Request a panel-level test report that names the exact build-up, and treat the granule data sheet as supporting evidence.

Filler Content, Melt Flow and Processing Behavior of A2 Non-combustible Granules

The short answer: every extra point of mineral filler reduces ease of processing, and the loss becomes steeper once the filler passes about 80 percent. That is the reason A2 non-combustible granules need more careful extruder setup than B1 flame-retardant granules, and it is why a supplier that offers several filler levels can help a plant find a workable balance.

Operators describe the change in practical terms. At 65 to 75 percent filler, the melt fills the die evenly and the barrel runs at moderate pressure. At 85 percent and above, die pressure climbs, screw and barrel wear increases because the mineral particles are abrasive, and small temperature changes show up as thickness variation across the sheet. The scatter chart below places eight example grades on a plot of filler share against a processing ease score.

The B1 grades cluster in the upper left, where scores stay between about 65 and 90, while the A2 grades sit lower right and fall from about 50 to 26 as the filler share rises from 84 to 92 percent. The gap between the two clusters, between roughly 74 and 84 percent filler, is where many high-filler B1 grades and low-filler A2 candidates are discussed. Scores in this chart are planning values and not measurements, but the shape reflects a real pattern: processing ease drops faster as filler approaches the upper end of the range. When a plant is deciding between a high-filler B1 grade and a low-filler A2 candidate, a joint extruder trial with the granule supplier shows the actual trade-off for that line.

Practical settings that change with filler content

• Barrel temperature profile: keep the peak below the decomposition onset of the hydroxide system in use.
• Screw design: a screw with good mixing and moderate shear helps dispersion without overheating the melt.
• Die lip and sizing: narrower gaps and tighter temperature control matter more as the core becomes stiffer.
• Output rate: a lower rate often gives a more even core on A2 grades, so compare qualified output and not nominal speed.

Run a joint trial at your own extruder settings before locking in a filler level, because the processing trade-off is specific to each line.

Side-by-Side Property Profile of B1 Flame-retardant Granules and A2 Non-combustible Granules

The short answer: A2 non-combustible granules lead on fire performance margin and mineral share, while B1 flame-retardant granules lead on flow, flexibility and processing tolerance. Neither profile is better in general; each suits a different project and a different production setup.

Plant teams often want to see the contrast on one picture before they talk to suppliers. The dumbbell chart below plots five properties on a relative index from 0 to 100, with a light dot for B1 flame-retardant granules and a dark dot for A2 non-combustible granules.

The first two rows show A2 non-combustible granules ahead on fire margin and mineral share, with indexes of 90 against 60 and 72 for the B1 example. The last three rows reverse the picture: B1 flame-retardant granules score 80, 78 and 75 on flow, flexibility and processing window, while the A2 example scores 35, 45 and 40. The long lines in the lower rows mean that choosing A2 asks more from the extruder, the die and the operators. A balanced plan is to select the grade by fire class, then use the chart as a checklist of the areas where extra control will be needed.

What the flexibility row means in fabrication

Panel fabricators route, groove and fold panels to make cassettes, corners and curved details. A B1 core usually tolerates tighter fold radii and deeper grooves before cracking, while an A2 core asks for a larger radius and more careful groove depth. If your customers order a lot of folded cassettes, tell the granule supplier and the line manufacturer early, because the core formulation, the skin thickness and the adhesive film all influence fold quality.

Use the property profile to plan extra process control where the chosen grade is weaker, instead of treating the grades as interchangeable.

Moisture, Storage and Handling of Flame-retardant Granules

The short answer: moisture is one of the most common and most preventable causes of bubbles in a mineral-filled core. Hydroxide fillers and some additives pick up water from humid air, and that water turns to steam in the hot zone of the extruder or the laminating press, leaving voids that weaken the bond and spoil the surface.

Plants in humid regions feel this most, particularly during rainy seasons and when bags stay open between shifts. A2 non-combustible granules tend to show the problem more strongly because the stiff melt traps vapor instead of letting it escape. The column chart below compares an illustrative bubble defect rate for both grades at four moisture levels.

At the driest level both grades stay near one percent in this example, but the curves separate as moisture rises, reaching 7.0 percent for the B1 example and 11.0 percent for the A2 example at 0.40 percent moisture. The A2 columns grow faster because the stiff melt traps steam more easily, which is why many plants set a tighter moisture target for A2 non-combustible granules than for B1 flame-retardant granules. A moisture analyzer at the hopper takes only minutes and gives an early warning before a long run produces scrap. The numbers are illustrative, so each plant should build its own curve from trial data and record it in the process sheet.

Handling rules that keep moisture down

• Store bags on pallets in a dry, cool room and keep the liner closed after each use.
• Use a hopper dryer when the humidity is high, with drying time and temperature set according to the supplier advice, often in the range of 70 to 90 degrees Celsius for a few hours.
• Cover the feeding path between the dryer and the extruder so that dried granules do not pick up moisture again.
• Use older lots first and label each opened bag with the date and lot number.
• Sieve out fines and dust before feeding, since they carry moisture and disturb metering.

Set a written moisture target for each grade, and measure at the hopper before every long production run.

Matching A2 Non-combustible Granules and B1 Flame-retardant Granules to Extruders and Panel Lines

The short answer: the granules and the line should be specified together, because a good compound on the wrong screw or die still produces an uneven core. A fireproof composite panel line has to feed the granules evenly, melt and mix them without overheating, shape them into a uniform sheet, bond that sheet to the aluminum skins and cool the panel flat.

Equipment areas that depend on the granule grade

Why the line builder matters

A production line manufacturer that builds fire-resistant panel lines for both A2 and B1 targets has seen how different granules behave across many installations. Hongyang organizes its equipment into fire-resistant aluminum composite panel lines, aluminum honeycomb core machines with honeycomb panel lines, and multifunctional customized lines, covering twelve categories that include A2 and B1 grade fire-resistant materials. For a buyer, this breadth means that questions about granule behavior, die design and cooling length can be raised in a single technical discussion and written into one agreement.

Auxiliary equipment completes the picture. Metal detectors and magnets protect the screw from tramp metal, dryers and sealed conveying protect the granules from moisture, and crushers return trim to the process. A basic package can run, but a full package reduces manual handling and keeps conditions steadier across shifts.

Write the granule grade into the technical agreement of the line, so that screw, die and cooling are sized for the material you will run.

Material Yield and Scrap Recycling When Running Fireproof Granules

The short answer: a well-run line returns most of the granule mass to qualified panels, and the difference between a good and a poor plant often lies in startup scrap and in how trim is reused. Because mineral-filled compounds carry a high material weight, every kilogram of avoidable waste is visible in the stock room and in the daily report.

A waterfall view helps teams see where mass leaves the process and where it comes back. The chart below follows 100 kilograms of granules fed into an example line, with losses at startup, edge trimming, cutting and inspection, and a recovery step where ground trim returns to the extruder.

The example starts with 100 kilograms and loses 13 kilograms across four steps, with edge trim as the largest single loss at 5 kilograms. Regrinding trim and returning it to the extruder brings back 6 kilograms, so the net usable core mass reaches 93 kilograms in this planning case. Recovery matters most on A2 non-combustible granules, where the filler share is high and unused trim carries a large amount of material. Since regrind changes the effective formulation, it should be validated against the fire test and the mechanical tests before a fixed regrind ratio is allowed in regular production.

Practical ways to improve yield

• Shorten startup scrap with a written warm-up routine and a standard purge procedure when changing grades.
• Keep trim clean, dry and separated by grade so that A2 and B1 regrind never share a bin by accident.
• Record the regrind ratio on every batch sheet so the fire test sample can be linked to the actual recipe.
• Review rejected panels weekly and trace them to lot numbers to see whether a granule lot or a process setting is involved.

Track mass loss by step, and validate any regrind ratio against fire and mechanical tests before using it in production.

Troubleshooting Panel Defects Linked to Flame-retardant Granules

The short answer: separate material causes from process causes before changing any setting. Operators often adjust temperatures first because it is quick, but a defect that follows a particular lot number points toward the granules, while a defect that follows a shift or a machine point toward the process.

A simple habit that speeds up diagnosis is to keep a retained sample from every granule lot and to write the lot number on the panel batch sheet. When a customer reports a question months later, the plant can compare the retained granules with the production record and answer from evidence. This habit is also what many specifiers look for when they evaluate a panel manufacturer for a facade project.

Link every defect to a lot number and a shift before changing settings, so the real cause can be found.

How to Choose a Flame-retardant Granules Manufacturer, Supplier or Wholesaler

The short answer: look for a partner that can show batch records, share samples for a joint trial and explain how a formulation was chosen. A factory-direct granule manufacturer can usually adjust the formulation, while a wholesaler or trading supplier may offer a wider range of grades but pass technical questions back to the source. Both routes can work, so it helps to know early which one you are dealing with.

Questions to ask before a bulk order

1. Which hydroxide system and binder family does each grade use, and what melt temperature limit applies?
2. Can the supplier provide panel-level fire test reports for a build-up similar to ours?
3. What is the lot-to-lot variation in filler content, melt flow and moisture, and how is it measured?
4. How are granules packed for export, and what protects them from moisture during sea freight?
5. Is OEM customization available for color, additive package or private-label packaging?
6. How will the supplier notify us if the formulation or the raw material source changes?
7. What is the minimum order quantity for each grade, and are trial samples available before a bulk order?

Export buyers add a few items of their own. Ask about palletizing, shrink wrapping, humidity protection in containers and the documents needed for customs. For long-term supply, a bulk supply agreement with a defined sampling plan keeps the quality conversation factual, because both sides compare the same measurements.

• Technical support: a supplier who joins the first trial run learns how the granules behave on your line and can adjust the formulation.
• Grade range: access to both A2 non-combustible granules and B1 flame-retardant granules lets a plant serve different projects from one source.
• Documentation: clear batch certificates and safety data sheets reduce delays at the border and in the plant.

Choose a granule supplier that shares batch data, supports a joint trial and tells you before any formulation change.

Incoming Inspection and Trial Plan for New Granule Lots

The short answer: a short, repeatable inspection routine catches most granule problems before they reach the extruder. The routine does not need an expensive laboratory; a moisture analyzer, a balance, a sieve set and a simple melt flow check cover the main risks.

A practical sequence for every new lot

1. Check bag labels, lot numbers and the batch certificate against the purchase order.
2. Inspect the packaging for punctures, wet patches and damaged liners.
3. Sample from several bags and look at the granules for fines, fused clusters and color variation.
4. Measure moisture, bulk density and granule size, and compare the results with the data sheet.
5. Run a melt flow check on a retained sample and record the value for trend tracking.
6. Run a short extruder trial and make test panels, then check thickness, peel strength and surface appearance.
7. Keep a retained sample from the lot, labeled and sealed, for later comparison.

For a new grade or a new supplier, add a laboratory fire test on panels made from the trial run, using the same build-up that will go to market. Panels from a trial are also the right material for fabrication checks such as grooving and folding, so that sales teams know what the product can do before they quote a project. Many plants run a short comparison between the new lot and the previous lot on the same line, which shows lot-to-lot change in a way a data sheet cannot.

Common planning mistakes

• Reading the filler number alone. Two granules with the same mineral share can behave differently because of binder type and particle treatment.
• Changing supplier without a new trial. A different source changes flow and bonding, so earlier test results may no longer apply.
• Mixing regrind between grades. A2 and B1 trim should be stored and tracked separately.
• Skipping moisture control in the dry season. Granules can pick up moisture in storage at any time of year, so measurement belongs in the routine.
• Sizing the line for B1 and planning to add A2 later. The screw, die and cooling length should be specified for the stiffest material you expect to run.

Make inspection a short written routine for every lot, and add a fire test whenever the grade or the supplier changes.

About Zhangjiagang Hongyang Machinery Equipment Co., Ltd.

Zhangjiagang Hongyang Machinery Equipment Co., Ltd. is a national enterprise specializing in the R&D and manufacturing of intelligent equipment for metal composite materials, providing systematic solutions for the global construction materials industry. As a drafting unit of the 《Non-Combustible Metal Composite Panels for Architectural Decoration》 and a standing council member of the Metal Branch of China Building Materials Federation, the company's core products encompass three major technological systems: Fire-resistant aluminum composite panel production lines, aluminum honeycomb core machine and aluminum honeycomb core metal composite panel production lines, and multifunctional customized metal composite panel production lines. These cover 12 categories of high-end production lines, including A2/B1-grade fire-resistant materials, 3D aluminum-core metal composite panels, and aluminum honeycomb series products.

Planning a fireproof panel project with A2 non-combustible granules or B1 flame-retardant granules? Prepare your target fire class, granule grade, panel thickness and width range, daily output goal and available utilities, and share them with the Hongyang engineering team through the official company website. A clear brief at the first conversation shortens the path to a line layout and a technical agreement.

A line builder with experience in both A2 and B1 fire-resistant lines can help match equipment to the granule grade you plan to run.

FAQ About A2 Non-combustible Granules and B1 Flame-retardant Granules

Q1: What are A2 non-combustible granules?

They are mineral-filled polymer granules with a very high filler share, used to form the core of aluminum composite panels intended for A2 non-combustible testing. The class a panel reaches depends on the formulation, the build-up and the test results.

Q2: What are B1 flame-retardant granules used for?

They form the core of panels aimed at the B1 flame-retardant class, which suits interior walls, ceilings, signage and cladding where B1 is accepted. Their lower filler share gives a wider processing window and a more flexible core.

Q3: Can one line run both A2 and B1 granules?

Often yes, with changes to the temperature profile, die settings and a purge between grades. The line should be specified for the stiffer A2 material, and the changeover procedure should be tested during the trial run.

Q4: Why do bubbles appear in the panel core?

Moisture in the granules is a frequent cause, followed by melt temperatures above the stability onset of the hydroxide filler. Measuring moisture at the hopper and drying when needed addresses the most common case.

Q5: Which documents should a granule supplier provide?

Ask for a data sheet, a batch certificate for each lot, a safety data sheet and panel-level test reports for a comparable build-up. A change notification process for formulation updates is also useful.

Q6: Can trim and offcuts be reused?

Many plants regrind clean trim and return a controlled share to the extruder. The ratio should be validated with fire and mechanical tests, and A2 and B1 regrind should be kept separate.

Q7: How should flame-retardant granules be stored?

Keep them in sealed bags on pallets in a dry, cool room, close the liner after each use and use older lots first. Label opened bags with the date and lot number.

Q8: What should I prepare before talking to a line manufacturer?

Prepare the target fire class, granule grade, panel thickness and width range, daily output goal, skin material and available utilities. These details let the manufacturer propose a layout and a technical agreement that fit your plant.

Bring your fire class, granule grade and panel range to the first discussion so the answers match your plant.