Fire resistance for rubber

Imerys minerals, such as talc, mica and kaolin, act in synergy with flame retardant fillers and additives.

Flame retardant fillers and additives for cost-effective barriers 

Acting in synergy with flame retardant fillers and additives, Imerys minerals create a physical barrier to fire, reducing combustion rate, improving char strength and decreasing both smoke quantity and rate of emission.

With MDH and ATH in EVA rubber sheathing

Talc* and hydrous kaolin are particularly effective partial replacements for Magnesium Hydroxide (MDH) and Aluminum Trihydrate (ATH) reducing compound costs without affecting fire retardant properties. These minerals create a mass transfer barrier restricting the transfer of combustible materials and oxygen and imparting a cohesive foam structure to the polymer.

Talc and hydrous kaolin:

  • Limit the diffusion of oxygen and combustion products and slow down combustion
  • Create a physical barrier effect limiting heat and mass transfer
  • Provide excellent char performance
  • Improve ash cohesion
  • Generate less smoke

High aspect ratio talcs

For more stringent requirements, high aspect ratio ImerFlex HAR® talc provides an outstanding intumescent effect which retards fire ignition and protects the EVA from combustion. This intumescence is mainly due to the combination of heterogeneous bubble nucleation, barrier effect, increased viscosity and char promotion.

With APP

Mica can also partially replace ammonium polyphosphate (APP) in flame retardant polyolefins, while improving mechanical properties without affecting overall fire resistance. Loading levels of around 30% APP are commonly used to meet UL94 V-0 ratings. However, APP is expensive and diminishes physical properties such as tensile strength. Replacing up to one third of APP flame retardant by Imerys mica not only improves fire resistance, char promotion and afterglow time, it boosts the mechanical properties of the material.

We recommend our Suzorite® range for this application.

Hydrous and calcined clays

Imerys hydrous clays are suitable char promoters in fire retardant wire and cables.

Calcined clays are excellent solutions for improving insulation, dielectric properties and dissipation factors in wire and cable applications.

  • Polestar™ product range imparts excellent electrical insulation properties to low and medium voltage power cables
  • Polarite™ products have been specifically developed for use in high and very high voltage power cable insulations based on EPR and EPDM rubbers
  • Suprex™ and Barrisurf™ HX are good solutions for char promotion in FR cables

*Talc products are not available in the USA and Canada. Contact us for an alternative range.