Product | Application of BYK clay additives in halogen-free flame retardant cables

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BYK-MAX CT 4260, a clay additive from BYK Chemicals, is used as a flame retardant synergist (anti-drip and char-forming additive), especially in halogen-free flame retardant wires and cables. It has excellent flame retardant synergy. On the basis of the flame retardant V0 test level, adding BYK-MAX CT 4260 helps wires and cables to reduce the overall usage of mineral-based flame retardants (ATH and MDH). The oxygen index is >36, and the tensile elongation is >250%. At the same time, the The tensile strength, volume resistivity, melt fluidity and water absorption of wires and cables have been significantly improved.


01  Basic features of BYK-MAX CT 4260 clay additive 

BYK-MAX CT 4260 is a surface-treated natural mineral product derived from bentonite (montmorillonite/smectite). Heterogeneous flake minerals (similar to talc/kaolin/mica): approx. 1 nm thick, diameter 300 – 1000 nm (DIN A4).


The clay additive BYK-MAX CT 4260 is produced through the use of a special organic intercalation and peeling process. Good peeling processing can contribute to excellent flame retardant properties and mechanical properties.


02Advantages and processing difficulties of low-smoke halogen-free flame-retardant wires and cables

Compared with traditional PVC or halogen-containing cable materials, halogen-free flame retardant (HFFR) cable materials have multiple advantages:

• High flame retardancy.

• Does not produce toxic or corrosive gases (environmentally friendly and non-toxic).

• Low smoke, halogen-free.

But to pass the V0 level flame retardant test, a typical aluminum hydroxide (ATH) concentration needs to be about 65%. The high ATH content in cables affects the mechanical properties, dispersion and melt flow properties, posing great challenges to cable material manufacturers.


03  BYK-MAX CT 4260 application examples

Halogen-free flame retardant cable material formula:

• Resin (Typical): LLDPE, EVA.

• Flame retardants: ATH, BYK-MAX CT 4260.

• Auxiliaries: antioxidants, processing aids, coupling agents, compatibilizers, etc.

Application: Cable sheathing.


Test Results:

Processing conditions: twin-screw extruder for granulation, tablet press for tableting, tableting thickness is 2 mm.

BYK-MAX CT 4260 can be used as an anti-drip agent in combination with mineral-based flame retardants such as ATH (aluminum hydroxide) and MDH (magnesium hydroxide).

BYK-MAX CT 4260 is used as a char-forming agent in combination with mineral-based flame retardants such as ATH (aluminum hydroxide) and MDH (magnesium hydroxide).


BYK-MAX CT 4260 typical parameters:



Q: How is the clay additive BYK-MAX CT 4260 processed/compounded?
Answer: Since clay is provided in powder form and is composed of agglomerates accumulated in layers, high shear is required during its compounding process in order to achieve the best results. In addition, the shearing time is short, such as in a twin-screw extruder. Therefore, suitable equipment is required, such as a twin-screw extruder with a length-to-diameter ratio of at least 40:1, and side feeding.


Q: In addition to being used as a flame retardant synergist in wires and cables, BYK clay additives have other uses?

Answer: ⑴ Provide barrier function in plastic tanks/containers/films through anisotropy (tortuous path), blocking oxygen, water, solvents, etc.

⑵Lightweight PP, PA and other composite materials/reinforcement functions.

⑶Incompatible blended plastics (as solid compatibilizer).