UltraCarb products are hydromagnesite - huntite fire retardants, for a wide range of polymers and rubbers.

LCA covering a variety of environmental factors.

30 Years of Experience

Fire-Resistant Filler



Own European Source

UltraCarb - Halogen Free Fire Retardant Filler

Product information

Nature’s own fire retardant

This unique natural mixture of minerals is also known as HMH. It is a proven fire retardant filler in a wide range of polymers and rubbers such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), ethylene-propylene diene monomer (EPDM) and nitrile rubber (NBR).

The combination gives a unique product in which specific properties can be optimised by selected mining and processing to fit a variety of applications.

Unique fire retardant properties

UltraCarb has a unique 3-stage fire-retardant mechanism. Whereas the classical endothermic flame retardant fillers act by releasing water in a single action process, our premium product works as follows:

  • Water is released at temperatures of ~220°C (thermal decomposition)
  • CO 2  release at temperatures of ~330°C
  • At temperatures of ~560°C, particles accumulate at the surface of the burning polymer to form a stable cementitious char. This char inhibits the combustion process and thus the propagation of the fire through burning droplets.
Three stage fire retardant mechanism

The platy, high surface area particles of our halogen-free mineral provide excellent properties when you use these as a functional filler in polymers. The products’ high heat absorption protects polymers from rapid thermal degradation and the formation of combustible products.

UltraCarb standard grades

Primary HydromagnesitePrimary Huntite
LH151251 (stearate surface treated)
LH15C (stearate surface treated)1253 (proprietary surface treated)
LH15X (proprietary surface treated)1290
1291 (proprietary surface treated)

UltraCarb packaging

Our UltraCarb product range is available in paper sacks, big bags or in bulk.

Stearate surface treatment improves wetting and reduces the agglomeration in the compound; proprietary surface treatments are beneficial as an external lubricant, act as a processing aid for extrusion and improve the LOI in EVA.

Mineral information

The typical properties of UltraCarb are:

Physical properties of UltraCarb

Specific gravity [g/cm3]2.4
Refractive index1.56
Hardness (Mohs)2.5
Surface area [m2/g]11 – 17
Loose bulk density [kg/l]0.4

Chemical properties of UltraCarb

MgO [%]36 – 39
CaO [%]6 – 9
SiO2 [%]0.2 – 1
Loss on ignition at 1,000°C51 – 54

UltraCarb origin

The naturally occurring mixtures of Hydromagnesite and Huntite mineral deposits are formed by near surface geochemical processes. The formation of our Turkish deposits is the result of three specific conditions:

  • a depositional area of magnesium rich ultramafic basement rocks;
  • a lake environment which evolved into a basin;
  • tectonic activity: This allowed magnesium rich ground water to reach the surface.

The precipitation of HMH  is related to the mixing of ground water with fresh water from the lake environment.

HMH toxicology

Our UltraCarb is a non-toxic, non-hazardous stable mineral.

Industry use

Our customers use industrial minerals to improve constructions, increase safety and reduce costs.

Frequently asked questions

Here are the most common questions and answers for this product.

Surface treatments change the interactions between the individual UltraCarb particles and between UltraCarb and the polymer matrix it is mixed into. This can lead to improvements in dispersion quality and fire retardancy. 

No. LKAB Minerals supplies UltraCarb to many compounding companies worldwide. 

UltraCarb starts releasing water and carbon dioxide at 220°C, and the reaction continues up to 550°C. The loss in mass is 52%. The process is endothermic and absorbs approximately 1000 J of energy per gram. 

Yes. UltraCarb is a natural, halogen-free, fire-retardant mineral filler. 

No. UltraCarb is a halogen-free fire-retardant filler. 

UltraCarb is also used to promote char formation. UltraCarb particles accumulate at the retreating molten polymer surface to form a stable cementitious char. This char further inhibits the combustion process and propagation of fire from burning droplets. 

UltraCarb is a halogen-free fire-retardant filler for polymers and rubbers. 

LKAB Minerals has a deep and detailed understanding of its hydromagnesite and huntite mineral deposits. This means the mineral composition of the raw material feeds used for UltraCarb can be precisely controlled as part of the manufacturing process. 

UltraCarb products are differentiated by three physical characteristics: 

  • Mineral composition 
  • Particle size 
  • Surface modification 

The amount of huntite and hydromagnesite is fixed at two levels for the UltraCarb LH and UltraCarb 1200 series, respectively. The LH series has more than 60% hydromagnesite, while huntite is the main mineral fraction in the 1200 series. Internal production specifications define the amount of hydromagnesite and huntite in each product series. 

There are currently four primary UltraCarb products available, and they are also available with two different surface treatments. Please contact your nearest sales manager through the UltraCarb product page. 

The product has no measurable changes if stored in dry conditions. 

UltraCarb is available globally and sold through our local offices; please visit the product page on our website to get your nearest contact

HMH is an acronym for HydroMagnesite-Huntite often used to describe products like UltraCarb made with huntite. 

LKAB Minerals´ huntite deposits are situated in the southwestern region of the Republic of Türkiye (Turkey) near the city of Denizli. Processing plants are found near the ports of Izmir in the Republic of Türkiye (Turkey) and Hull in the United Kingdom. 

UltraCarb is the brand name for our range of huntite fire retardant fillers for the polymer industry. UltraCarb fire retardant fillers are made from rock deposits rich in huntite and hydromagnesite. 

Huntite has the formula Mg3Ca(CO3)4 and can be described as magnesium calcium carbonate. Huntite-bearing rock is an aggregate which also has hydromagnesite associated with it. Hydromagnesite has the formula Mg5(CO3)4(OH)2 ·4H2O and can be characterised as hydrated magnesium carbonate. 

Huntite-bearing rock is an aggregate which also includes some hydromagnesite. Large, commercially practical deposits of huntite are only found in the Republic of Türkiye (Turkey) and Greece. Thermo-chemical processes below the earth’s surface formed the world’s largest deposits in the Republic of Türkiye several million years ago from hydrothermal magnesium-rich solutions. The industrial value of a huntite deposit flows from quarrying and processing rock to carefully defined combinations of huntite and hydromagnesite mineral fractions.