The cable materials currently used are usually low-smoke halogen-free flame-retardant polyolefin cable materials as the mainstream. This article will analyze the formulation technology and performance of low-smoke halogen-free flame-retardant polyolefin cable materials.
- Formulation technology
Low-smoke halogen-free flame-retardant polyolefin cable material is usually composed of polyolefin blend resin plus flame-retardant filler aluminum hydroxide, magnesium hydroxide, and some antioxidants added in order to improve heat resistance life.
In order to reduce the amount of smoke generated during combustion, some smoke inhibitors, such as vanadium, nickel, molybdenum, iron, silicon, and nitrogen compounds are added.
The flame-retardant mechanism is: when burned, the flame-retardant fillers aluminum hydroxide and magnesium hydroxide will release crystal water and absorb a large amount of heat; at the same time, the dehydration reaction will generate a large amount of water vapor, which can dilute the combustible gas, thereby to prevent combustion. In addition, an infusible and non-combustible oxide hard shell is formed on the surface of the material, which blocks the reaction channel between the polymer and the external hot oxygen, and the final material is flame-retardant and self-extinguishing.
The low-smoke halogen-free flame-retardant polyolefin cable material must have good flame retardancy. The aluminum hydroxide and magnesium hydroxide in the formulation must have a large amount of filling, and a large amount of inorganic flame retardant filling will inevitably lead to lower mechanical properties, electrical properties, and extrusion process performance greatly deteriorate.
In order to solve the balance of flame retardancy and physical and mechanical properties, so that the material can fully meet the technical requirements of the final use, the commonly used methods are: on the one hand, the polyolefin material is modified and grafted to improve the polyolefin material polarity. On the other hand, the surface of inorganic flame retardants is chemically modified, usually treated with coupling agents.
The use of a large number of inorganic flame retardants endows low-smoke halogen-free flame-retardant polyolefin cable materials with flame-retardant, low-smoke, halogen-free, and low-toxicity characteristics. At the same time, it also makes it compatible with physical and mechanical properties, electrical properties, and process properties. There are differences between other non-flame retardant and halogen-containing flame retardant materials.
Due to the different production processes of low-smoke halogen-free wires and cables and their supporting products, the performance requirements are also different, such as tensile strength, elongation at break, aging temperature and indicators, volume resistivity, oil resistance, scratch resistance In terms of performance, flexibility, and flame-retardant requirements, different cables are often biased.
In halogen-free material technology, some of the above indicators are mutually restricted. It is impossible to have an all-around product that can meet the requirements of all the above types of wires and cables. The more prominent one is the elongation at break and the flame retardancy. The contradiction between softness and thermal deformation, and aging properties. What the material manufacturer can do is to balance the advantages and disadvantages between certain performances on the basis of meeting the basic performance requirements, and use different brands of products to adapt to different requirements of wires and cables.