Fire resistance Imerys minerals act in synergy with flame retardant fillers and additives
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 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 tri-hydrates (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 burnable gas emissions and oxygen diffusion by foaming effect, resulting in delayed combustion
- Create a physical barrier effect limiting heat and mass transfer
- Are excellent char promoters
- Improves ash cohesion
- Generate less smoke
Effect of talc in EVA systems
High aspect ratio talcs
For more stringent requirements, Imerys high aspect ratio Mistron HAR® talc provides an outstanding intumescent effect which retards fire ignition and protects the EVA from combustion. This intumescence is mainly due to the conjunction of heterogeneous bubble nucleation, barrier effect, increased viscosity and char promotion.
Mica can also partially replace ammonium polyphosphate (APP) systems in polyolefins, while improving mechanical properties without affecting overall fire resistance. Loading levels of around 30% APP are commonly used to meet UL94 requirements such as 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 FR wire and cables.
Calcined clays are excellent solutions for improving insulation, dielectric properties and dissipation factor in wire and cable applications.
- Polestar™ imparts excellent electrical insulation properties to low and medium voltage power cables
- Polarite™ has 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
We offer a full range of bespoke formulation and technical and process support services to help you match the right mineral grade to your application requirement.