Processing Matters of Halogen-free Flame Retardant Wire and Cable Material

In order to meet the requirement of low smoke and halogen-free flame retardant for wire and cable materials, a large number of inorganic flame retardants must be added. When extruded, the melt has high viscosity, poor fluidity and is prone to friction heating, which leads to excessive local temperature of the melt, decomposition of the material in the fuselage for a long time, and pore formation of the decomposed gas in the product. When extruding low smoke halogen-free flame retardant wire and cable materials, the following points should be paid attention to.

1,Before material extrusion processing, drying treatment should be carried out to avoid air holes in the cross section of the product.

2,Selection of processing technology. In addition to selecting suitable extruders, the processing technology should also be reasonable. If the temperature is too high, the additives will decompose, resulting in the products with stomata; if the temperature is too low, it will produce poor plasticization. The fuselage pressure should be reduced as far as possible. The screw speed should not be too high. Under the condition of ensuring full plasticization of materials, the extrusion temperature should be reduced appropriately. Processing technology should be adjusted according to different materials and formulations.

3,Due to poor fluidity of materials and high friction resistance with equipment, silicone can be added to improve the dispersion of inorganic flame retardants and reduce processing torque. The addition of organosilicon can improve the flame retardancy of wire and cable materials, and it is a good processing aid.

4,Selection of extruder. Because there are many additives in low smoke halogen-free flame retardant wire and cable materials and the melt viscosity is high, the extruder with low screw compression ratio should be adopted. Ordinary single screw extruder has low shear rate and poor mixing ability; twin screw extruder has high mixing ability, but processing high filling low smoke halogen-free flame retardant wire and cable materials often causes material decomposition and discoloration due to excessive shear, so it is better to choose a two-stage mixing extruder combined with single screw and twin screw. Reciprocating single screw mixer is an ideal equipment for processing low smoke halogen-free flame retardant wire and cable materials.

In short, low smoke halogen-free flame-retardant wire and cable materials have stricter requirements on processing equipment and process conditions, and suitable extrusion equipment and process conditions must be selected according to the characteristics of raw materials, product properties and extrusion characteristics.