HFFR calcium carbonate is an indispensable mineral filler in halogen-free flame-retardant cable compounds, working alongside aluminium trihydroxide (ATH) and magnesium dihydroxide (MDH) to preserve mechanical integrity while optimising total compound cost.
This comprehensive technical guide covers the chemistry of HFFR (Halogen-Free Flame Retardant) cable compound production, the synergistic role of calcium carbonate with ATH and MDH, the EU Construction Products Regulation (CPR) and EN 50575 fire classification framework, IEC 60332 and IEC 61034 test protocols, and concrete recommendations for formulation optimisation. The content is written for both R&D and compound engineers, and for procurement managers at European cable manufacturers exporting CPR-classified products.
Quick definition: HFFR calcium carbonate is a micronised natural CaCO₃ filler used in halogen-free, low-smoke (LSZH) cable compound formulations alongside ATH/MDH primary flame retardants. Typically loaded at 5–15 wt%, it reduces the ATH/MDH demand while protecting mechanical strength, stabilising extrusion rheology and supporting EU CPR EN 50575 fire-class compliance.
What Is HFFR? The Strategic Importance of Halogen-Free, Low-Smoke Cables
HFFR (Halogen-Free Flame Retardant) is a modern family of cable jacketing and insulation compounds in which halogen-containing plastics — primarily PVC and chlorinated polyethylene — are eliminated. The same technology is commonly marketed under the term LSZH (Low Smoke Zero Halogen). Three core performance attributes define the category:
- Flame retardancy — the cable does not propagate the flame and is self-extinguishing.
- Low smoke density — combustion produces a translucent smoke that does not obstruct visibility.
- Zero halogen — no corrosive or toxic gases such as HCl or HBr are released during a fire event.
The dense black smoke and corrosive HCl gas generated by burning PVC cables are recognised root causes of fatalities in enclosed environments — tunnels, metro stations, hospitals, data centres, shopping centres and ships. After the 1987 King’s Cross underground fire in London and the 2009 Lyon Croix-Rousse tunnel fire, Europe progressively mandated halogen-free cables in public buildings.
Typical HFFR Cable Applications
- Underground infrastructure: metro, rail tunnels, mainline railways
- High-occupancy buildings: hospitals, schools, shopping centres, airports
- Data centres and telecom infrastructure
- Marine and shipbuilding: yachts, cruise ships, offshore platforms
- Industrial plants and renewable energy (e.g. internal cabling of wind turbines)
LSZH Standards and the European Market Trend
Since the EU Construction Products Regulation (CPR) took effect in 2017, the European HFFR market has grown at an average rate of 8–10 % per year. In Germany, Italy, the Netherlands, France, the Nordic countries and the United Kingdom, HFFR cables are effectively the only option in new public infrastructure projects. The same trend is accelerating in Poland, the Czech Republic and Türkiye on the OEM and private-sector side.
For a Türkiye-based cable manufacturer exporting to Europe, CPR-classified HFFR cables are no longer optional — they are a competitive threshold. Aydın Madencilik’s calcium carbonate product range for the cable industry is developed in line with these standards.
Composition of an HFFR Cable Compound
A typical HFFR compound formulation consists of five main material groups:
| Component Group | Typical Loading (wt %) | Function |
|---|---|---|
| Base polymer (EVA, EBA, POE, LLDPE) | 25 – 35 | Mechanical matrix, flexibility |
| Primary flame retardant (ATH or MDH) | 50 – 65 | Endothermic decomposition, water-vapour release |
| Supporting filler (CaCO₃) | 5 – 15 | Mechanical support, cost, rheology |
| Coupling agent (silane, MAH-g-PE) | 0.5 – 2 | Polymer–mineral interfacial compatibility |
| Antioxidant, slip and process aids | 0.5 – 2 | Thermal stability, extrusion performance |
In this formulation, total mineral filler (ATH + MDH + CaCO₃) sits at 65–75 wt%. Using ATH or MDH alone at these loadings collapses the mechanical properties and inflates cost. HFFR calcium carbonate is the supporting filler that economically substitutes part of the ATH/MDH while preserving performance.
The Multi-Functional Role of Calcium Carbonate in HFFR
Calcium carbonate in HFFR is not merely a filler — it delivers five distinct functions:
- Cost optimisation — ATH and MDH are 5–10× more expensive per tonne. Partial substitution with CaCO₃ reduces the net compound cost by 15–25 %.
- Mechanical support — At high mineral loadings ATH/MDH alone cannot preserve tensile strength and elongation; CaCO₃ balances the matrix–filler interface.
- Rheological control — Stabilises low-viscosity extrusion behaviour and ensures homogeneous melt flow.
- Dimensional stability and surface quality — Balances shrinkage and yields a smooth jacket surface.
- Colour and appearance — High whiteness enables uniform brightness on the cable jacket.
For this multi-functional reason, CaCO₃ is regarded as an indispensable supporting filler in HFFR compounds.
Synergy with ATH (Aluminium Trihydroxide)
ATH — chemical formula Al(OH)₃ — is the most widely used primary flame retardant in HFFR formulations. Its decomposition mechanism is:
2 Al(OH)₃ → Al₂O₃ + 3 H₂O ↑ (180–200 °C, endothermic, ΔH ≈ +298 kJ/mol)
This reaction delivers three critical effects: endothermic decomposition reduces flame temperature; released water vapour dilutes oxygen and combustible gases at the flame front; the residual Al₂O₃ layer forms a protective char on the polymer surface.
CaCO₃ in Synergy with ATH
ATH alone at filler loadings above 65 % renders the compound brittle. This is where HFFR calcium carbonate makes the difference:
- Adding CaCO₃ at 10–15 wt% allows the ATH content to be reduced by 5–10 %.
- Elongation-at-break is preserved.
- ATH’s tendency to retain water is buffered by CaCO₃, which reduces voids and bubble formation during extrusion.
- Tensile strength typically improves by 15–20 %.
Aydın Madencilik’s AY 108 (8 µm) and AY 210 (10 µm) natural micronised calcite grades deliver this performance profile in ATH-based HFFR compounds.
Synergy with MDH and High-Temperature Applications
MDH — formula Mg(OH)₂ — operates through a similar endothermic mechanism but with a higher decomposition temperature (~330 °C). That property makes it the preferred choice for XLPE insulation and high-temperature cable applications.
Mg(OH)₂ → MgO + H₂O ↑ (330–350 °C, endothermic, ΔH ≈ +328 kJ/mol)
MDH is approximately 30–40 % more expensive than ATH, which makes the combination with CaCO₃ critical for economic formulation. With CaCO₃ in the mix, MDH loading can be reduced by 5–10 %; high-temperature performance is preserved (XLPE process temperatures up to 280 °C) and the compound cost is reduced by €0.30–0.50 per kg.
Flame Retardant Mechanism: Endothermic Decomposition and Char Formation
HFFR compounds protect the cable through four simultaneous mechanisms during combustion:
- Endothermic decomposition (ATH/MDH) — reduces flame temperature and slows combustion.
- Water-vapour release — dilutes flammable-gas concentration at the flame front.
- Protective ash layer (Al₂O₃ / MgO) — forms a char on the polymer surface and limits oxygen ingress.
- CaCO₃ bonus effect — above 800 °C, CaCO₃ decomposes into CaO + CO₂; the CO₂ acts as an inert diluent in the flame zone.
This multi-layered protection enables HFFR cables to reach EU CPR classes B2ca, Cca and Dca.
EU CPR (Construction Products Regulation) and EN 50575 Fire Classes
The CPR, operationalised through EN 50575:2014+A1:2016, defines fire-performance classes for all permanently installed cables placed on the EU market. Cables are split into seven main classes:
| CPR Class | Performance Level | Typical Use Case |
|---|---|---|
| Aca | Highest (non-combustible) | Mineral-insulated cables (MICC) |
| B1ca | Very high | Tunnels, metro, hospital critical circuits |
| B2ca | High HFFR (premium) | Data centres, airports, shopping centres |
| Cca | Standard HFFR | Offices, commercial buildings, schools |
| Dca | Low HFFR / improved PVC | Residential, low-risk interiors |
| Eca | Minimum | Industrial environments, temporary installations |
| Fca | Not classified | Untested cables |
Three complementary parameters are appended to the main class: s (smoke density — s1, s2, s3 / s1a best), d (flaming droplets — d0, d1, d2 / d0 best), and a (acidity / pH — a1, a2, a3 / a1 best, halogen indicator). A typical HFFR target classification is Cca-s1b,d1,a1.
IEC 60332 and IEC 61034 Fire Resistance Tests
To achieve a CPR class, cables must pass the following international tests:
- IEC 60332-1-2 — single-conductor vertical flame propagation (baseline HFFR certification)
- IEC 60332-3-22 / -23 / -24 / -25 — bunched cable vertical propagation (Categories A, B, C, D)
- IEC 61034-2 — smoke density in a 3 m³ chamber (HFFR target: light transmittance above 60 %)
- IEC 60754-1 — halogen content (HCl evolution below 0.5 %)
- IEC 60754-2 — acidity and conductivity of combustion gases (pH above 4.3, conductivity under 10 µS/mm)
To clear these tests, the purity of the calcium carbonate is critical — particularly low halogen content (Cl⁻ below 100 ppm) and low SO₃ residuals. Calcium carbonate produced from Aydın Madencilik’s wholly-owned quarries is supplied with analytics matching these specifications.
Micron Size and HFFR Dispersion Performance
The median particle size (d50) and particle-size distribution (PSD) of calcium carbonate directly affect HFFR formulation performance:
| Median (d50) | Advantage | Disadvantage |
|---|---|---|
| 3–5 µm | Good surface quality, fine film | High viscosity, dispersion difficulty |
| 8–12 µm | Optimal balance — HFFR standard | — |
| 15–20 µm | Lower cost, easier extrusion | Slight loss of mechanical properties |
| 25+ µm | Most economical | Surface roughness, mechanical weakness |
The ideal range for HFFR formulations is 8–15 µm. The Aydın Madencilik grades recommended for HFFR are:
- AY 108 (8 µm) — premium HFFR formulations, critical-infrastructure cables
- AY 210 (10 µm) — standard all-purpose HFFR
- AY 215 (15 µm) — economical HFFR, high-filler-loading applications
Cost Optimisation Strategy with CaCO₃ in HFFR Compounds
A typical HFFR compound has the following raw-material cost distribution:
| Component | Cost Share |
|---|---|
| ATH or MDH | 55 – 65 % |
| Base polymer (EVA, EBA) | 20 – 25 % |
| Calcium carbonate | 3 – 7 % |
| Coupling agent + additives | 8 – 12 % |
ATH or MDH alone makes up roughly two-thirds of the compound cost. Replacing 10–15 % of the primary flame retardant with CaCO₃ cuts the total compound cost by 8–12 %. For a cable plant producing 5,000 t/year of HFFR, that translates to €300,000–€500,000 in annual savings — without raising fire-test failure risk, because CaCO₃ compensates for the mechanical drawbacks of ATH/MDH at high loadings.
Common Extrusion Issues and Their Solutions
| Issue | Likely Cause | Solution |
|---|---|---|
| Surface roughness | CaCO₃ d97 too high (above 50 µm) | Use a narrower-PSD grade (AY 108, AY 210) |
| Die drool / die build-up | Poor dispersion, insufficient coupling | Raise silane / MAH-g-PE to about 1.5 % |
| Compound yellowing | Inadequate AO; ATH impurities | Reinforce AO system, audit ATH specs |
| Extruder torque spike | Total mineral loading above 70 % | Partially substitute ATH with CaCO₃ |
| “Blooming” on cable surface | Coupling agent / mineral mismatch | Revise coupling-agent grade and dosage |
Sample and Audit Workflow for European Cable Manufacturers
When a European cable manufacturer approves a new CaCO₃ supplier, the typical workflow is:
- NDA and technical scoping — formulation need, micron range, purity targets
- Sample request — typically 5–25 kg for extrusion trials
- Laboratory analysis — CaCO₃ %, MgO, Fe₂O₃, halogens, sulphur, moisture, PSD
- Pilot extrusion — small-scale HFFR compound run with mechanical testing
- Fire testing — IEC 60332, IEC 61034, IEC 60754
- Supplier audit — ISO 9001, ISO 14001, ISO 45001, REACH dossier
- First commercial order — usually 1–3 containers as a trial batch
- Approved Vendor List (AVL) — regular shipments
At every stage, Aydın Madencilik provides technical datasheets, batch-level CoA, REACH documentation and laboratory support. For detailed supplier credentials, see our About Us page.
Aydın Madencilik AY 108, AY 210 and AY 215 for HFFR
From its 15,000 m² covered facility in Bursa Gemlik, Aydın Madencilik produces natural micronised calcium carbonate using German Hosokawa Alpine classifier mill technology. Three product codes are optimised for HFFR applications:
- AY 108 (8 µm) — premium HFFR compounds, CPR B2ca–Cca critical-infrastructure cables
- AY 210 (10 µm) — all-purpose HFFR, standard Cca-class building and commercial cables
- AY 215 (15 µm) — economical HFFR, high-loading compound applications
Every grade meets a specification of CaCO₃ above 98 %, Fe₂O₃ below 0.1 %, halogens below 100 ppm and moisture below 0.3 %. Direct sea access through Gemlik Port enables 3–5 day deliveries to Germany, Italy, the Netherlands, the Czech Republic, Poland and the Nordics.
Frequently Asked Questions
What is the difference between HFFR and LSZH?
Both terms describe the same technology. HFFR (Halogen-Free Flame Retardant) is the dominant term in continental Europe, while LSZH (Low Smoke Zero Halogen) is the more common term in the UK, North America and Asia. The underlying standards (IEC 60332, IEC 60754, IEC 61034) are identical.
Why can’t ATH be used alone in an HFFR formulation?
Loading ATH alone above 65 wt% degrades mechanical properties significantly: elongation-at-break falls below 50 %, extrusion becomes more difficult, and compound cost increases. Substituting 10–15 % with HFFR calcium carbonate protects mechanical performance and optimises cost.
Why is the purity of calcium carbonate so important in HFFR?
Fire testing of HFFR cables measures halogen (Cl⁻) content under IEC 60754-2. If the calcium carbonate carries high chloride impurities, the cable cannot achieve halogen-free certification. Aydın Madencilik’s calcite, sourced from its wholly-owned licensed quarries, naturally has below 100 ppm halogen content and is supplied with certified batch analyses.
What is the optimal calcium carbonate micron size for HFFR?
HFFR formulations generally favour a d50 of 8–15 µm. Particles finer than 5 µm complicate dispersion and increase viscosity; particles coarser than 20 µm degrade surface quality and mechanical properties. Aydın Madencilik’s AY 108 (8 µm), AY 210 (10 µm) and AY 215 (15 µm) grades are optimised for HFFR.
Can ATH replace MDH in every application?
For PE- and EVA-based HFFR, ATH is the standard choice. However, in XLPE insulation and any application above 250 °C process temperature, MDH is mandatory — ATH starts to decompose around 180 °C and becomes unstable at XLPE cross-linking temperatures. The MDH + CaCO₃ combination is the standard for high-temperature cables.
Can a cable that does not comply with EU CPR EN 50575 be sold in Europe?
All permanently installed cables classified as construction products are subject to the CPR across EU Member States, with a mandatory Declaration of Performance (DoP). Cables without a CPR class (Fca) or with no test data cannot be lawfully placed on the EU market. For Türkiye-based exporters, CPR-classified HFFR production is a competitive requirement.
What is the fundamental difference between HFFR and PVC cables?
When burning, PVC releases HCl gas and dense black smoke that obstructs visibility and impairs breathing. HFFR is halogen-free, burns with low smoke and emits no toxic acidic gases. For tunnels, hospitals, data centres and crowded buildings, HFFR is mandatory under EU CPR standards for life-safety reasons.
Does Aydın Madencilik provide samples and technical support for HFFR projects?
Yes. For the AY 108, AY 210 and AY 215 grades intended for HFFR applications, we provide complimentary 5–25 kg samples, batch-level Certificate of Analysis (CoA), Technical Data Sheets (TDS), REACH documentation and laboratory support. To request samples, please use our Get a Quote page or contact our technical sales team.
Optimise Your HFFR Compound with the Right CaCO₃
HFFR cable production is a strategic technology for any manufacturer exporting to Europe or supplying critical-infrastructure cables. The right HFFR calcium carbonate — at the correct purity, micron and PSD — is a decisive factor in both performance and cost.
Work with Aydın Madencilik’s HFFR-grade product range and technical team to optimise your compound formulation: Request a sample | Explore our Cable Industry page
