Due to the high filling of inorganic flame retardant agent, the rheological property of cable material changes greatly and the viscosity increases obviously. There are mainly two problems in the cable preparation process:
The surface quality of some halogen-free and flame-retardant cables is very rough and lacks luster. The reason is that halogen-free flame retardants are not evenly dispersed in the matrix resin, leading to the formation of agglomeration on the surface of the extruded materials, which is mainly a problem in the process of material composite.
Sharkskin phenomenon on the extruded cable surface is another typical extruding problem, which can sometimes be solved by adjusting extrusion process parameters, such as lower traction speed and higher outlet temperature. However, this solution leads to low production efficiency and no economy.
Second, there is mold head saliva in the process of processing halogen-free flame retardant cable.
This problem may be caused by too much extrusion, or it may be caused by the particle structure of Al(OH)3 and its polarity, which causes melt adhesion to the mold head, delaying the material demulsification. When the saliva accumulates to a certain extent, it will be taken away by the insulated cable, leading to product quality problems.
To solve these problems, it is necessary to improve the rheological properties of cable melt. Lubricant or surfactant can be added into the formula. The low molecular weight polyethylene wax added in the preparation of flame retardant masterbatch is also an effective lubricant, and some surfactants can be added to increase the fluidity of the composite system.