Ceramic silicone rubber develops new fields, serves new energy vehicles, and solves the fire and flame retardant requirements of cables and harnesses of new energy vehicles

With the rapid growth of urban population, there is an increasing demand for public service places such as large supermarkets, hospitals and airports, and the construction of urban transportation such as subways and tunnels is also being gradually accelerated to provide convenient services for people to a great extent. Because these areas are densely populated areas, special attention will be paid to safety issues in all aspects, especially fire safety.

How to ensure smooth power and communication within a certain period of time in case of fire, so as to reduce casualties? Tracing back to the source can eliminate the occurrence of fire from the root. Cable fire is usually the inducing cause of fire. Therefore, the fire prevention and flame retardancy of cables can be improved to reduce the occurrence of fire.

At present, magnesium oxide mineral insulated fire-resistant cable and mica tape wound fire-resistant cable are mostly used at home and abroad, but these two kinds of cables have obvious disadvantages. The external protection of magnesium oxide mineral cable is all copper, the cost of raw materials is high, it is difficult to use on a large scale, and it is difficult to lay and install; The fire-resistant cable wound with mica tape is prone to defects because it needs multi-layer winding, and the fire-resistant effect is poor.

Different from the above two cable materials, the cable made of silicone rubber has lower cost and superior fire resistance effect, which is more suitable for building cables. Especially in recent years, a new type of fire-retardant composite material, ceramic silicone rubber, has gradually come into our view. It has far more properties than ordinary silicone rubber, so it is more widely used in the direction of wires and cables.

1、 Composition of ceramic silicone rubber

The components of ceramic silicone rubber mainly include silicone rubber matrix, ceramic filler, flux, reinforcing agent and vulcanizing agent.

1. Silicone rubber matrix

Silicone rubber is a linear organosiloxane polymer with a relative molecular weight of hundreds of thousands or even millions. It has good insulation performance, aging resistance, arc resistance, ablation resistance, high and low temperature resistance, and can maintain elasticity at -65 ~ 250 ℃. The main chain is Si-O-Si structure, and the side group (R) is methyl, ethyl, phenyl, vinyl and other organic groups. The structural formula is shown in Figure 1.

The residue of silicone rubber after high-temperature decomposition or combustion is amorphous SiO2 powder, which can prevent the melting and dripping of combustibles, expand the flame range, prevent the diffusion of internal decomposition products and the entry of external oxygen, and play a certain flame retardant effect.

2. Porcelain filler

Ceramic filler is an important component of ceramic silicone rubber, which is generally inorganic silicate or other inorganic powder, with high hardness, strength and thermal stability. It can react with the residue of silicone rubber decomposition and the liquid substances produced by the melting of flux to form ceramic body.

3. Flux

Flux is a kind of inorganic substance with low melting point (below 1000 ℃), which can reduce the porcelain forming temperature of vitrified silicone rubber. The most commonly used flux is low melting point glass powder.

4. Reinforcing agent

Silica is the most commonly used reinforcing agent in silicone rubber. It is an amorphous SiO2 spherical powder. Adding an appropriate amount of silica can greatly improve the tensile strength of silicone rubber.

There are hydroxyl groups on the surface of white carbon black, which form hydrogen bonds with the oxygen atoms on the main chain of silicone rubber at room temperature, making the compound hard and the viscosity increase, and the processability becomes poor. This phenomenon is called "structurization". In order to improve the structural problems caused by silica, it is necessary to add a structural control agent to inhibit the structural effect of silica and silicone rubber by combining with the active hydroxyl group of silica.

5. Vulcanizing agent

Vulcanization refers to cross-linking, which refers to the process of changing linear macromolecules into three-dimensional network macromolecules through the action of vulcanizing agent at a certain temperature and pressure. The vulcanized silicone rubber has high elasticity.

2、 Advantages of ceramic silicone rubber

As a new fire retardant material, ceramic silicone rubber has many excellent characteristics different from traditional flame retardant materials. These characteristics make ceramic silicone rubber have excellent performance in flame retardant performance.

1. Comparison at room temperature

Ceramic silicone rubber is basically the same as ordinary silicone rubber at room temperature, and has good insulation performance, aging resistance, arc resistance, ablation resistance, high and low temperature resistance, etc.

2. Comparison at high temperature

Traditional flame retardant materials with flame retardants will decompose when exposed to high temperature or flame, thus losing their fire resistance. The ceramic silicone rubber will undergo ceramic transformation at high temperature or flame combustion to prevent the spread of flame.

3. Function of ceramic body

After the ceramic body is formed, it has a certain flexural strength and compressive strength, good thermal stability and dimensional stability, and can maintain the original structural integrity of power equipment in a fire and maintain the normal operation of the equipment. The bending strength of ceramic silicone rubber is much higher than that of ordinary silicone rubber, and it increases obviously with the increase of temperature.

4. Environmentally friendly rubber

The decomposition products of vitrified silicone rubber in the combustion process are water, CO2 and SiO2, which are non-toxic and harmless substances. In addition, during the combustion process, smoke will only be generated at the initial stage of combustion. During the continuous vitrification process, smoke will not be generated during combustion, which will not cause harm to human body.

5. Production conditions

The preparation process of ceramic silicone rubber is basically the same as that of ordinary silicone rubber. The production requirements can be met by using conventional molding or extrusion processing equipment. The production conditions are simple and no extra cost is required.