Filler Loading in HFFR Cable

Halogen-free flame-retardant (HFFR) cable compounds protect against fire without halogen chemistry. They work by loading the polymer with mineral fillers that release water when heated. The challenge is fitting a very high filler content into a polymer while keeping the compound processable.

The Role of Polarity

Mineral fillers such as aluminium trihydrate (ATH) and magnesium dihydroxide (MDH) are polar and hydrophilic. A polar EVA matrix — higher in vinyl acetate — wets and bonds to these particles better than a low-VA, polyethylene-like matrix. That improves dispersion and lets formulators push filler levels higher before the compound becomes brittle or hard to extrude.

Why 33% VA Is a Sweet Spot

• High enough polarity to wet ATH/MDH and hold high filler loadings.
• MFI around 45 keeps the filled compound flowing in extrusion.
• Still enough crystallinity for mechanical strength in the cable.

Grades like Evatane 33-45 are widely used as the EVA base in LSZH and HFFR cable jacketing for this reason.