Abstract:

With the rapid development of the global economy and the continuous strengthening of human awareness of environmental protection and fire safety, green environmental protection, low-carbon energy conservation and fire safety have become the focus of the construction industry.

With the rapid development of the global economy and the continuous strengthening of human awareness of environmental protection and fire safety, green environmental protection, low-carbon energy conservation and fire safety have become the focus of attention in the construction industry. With the development of cities, the density of high-rise buildings on the ground has increased, and even the development and progress of underground rail transit and urban pipe gallery projects have emerged. The demand for wires and cables is increasing, and the radiation intensity is getting higher and higher. At the same time, fire safety disaster accidents caused by the quality problems of wires and cables occur frequently. How to reduce the occurrence rate of fires and the mortality rate of fires, low smoke, halogen-free, flame-retardant, fire-resistant, environmentally friendly and safe have become the common research and development directions in the field of wires and cables.

With the enhancement of fire safety awareness in the construction industry and public safety consciousness, for public safety-related building sites such as hotels, shopping malls, stations, and airports, the requirements for low smoke, halogen-free, flame-retardant, fire-resistant, environmentally friendly, and safe wires and cables have become an important performance indicator for use. The BV wires of the traditional home decoration JB/T 8734-2017 can no longer meet the market demand. The new type JB/T 10491-2004 WDZ-BYJ wires, namely low smoke zero halogen flame retardant cross-linked polyethylene insulated copper core wires.

WD: Halogen-free and low smoke, which refers to the toxic smoke produced by the burning of insulating and protective layer materials in flames being below the required value. It is used for power distribution in large public places (such as large shopping malls). Z stands for flame-retardant. BYJ is a cross-linked polyethylene insulated wire. WDZ-BYJ(F) stands for copper core irradiated cross-linked low smoke zero halogen flame-retardant polyethylene insulated wire and cable

WDZ-BYJ wire is an updated product of the environmentally friendly new generation of flame-retardant cross-linked low smoke zero halogen polyolefin insulation. It has excellent flame-retardant, low smoke and low toxicity performance, and overcomes the defect of traditional halogen-containing polymers that produce a large amount of smoke when burning, causing suffocation and corrosion of instruments and equipment. It represents the current development trend of wires and cables.

After cross-linking low smoke zero halogen polyolefins as insulating materials, the mechanical properties, heat resistance, and resistance to environmental stress cracking of the materials can be improved, broadening the application range of the materials and enhancing their reliability and service life. At present, the commonly used cross-linked low smoke zero halogen flame-retardant polyolefin cable materials in China mainly include irradiation cross-linking, ultraviolet light cross-linking and silane cross-linking.

Irradiation cross-linked material

Irradiation cross-linked materials are the earliest and currently the most widely used cross-linked low smoke zero halogen flame-retardant polyolefin insulating materials in China. However, as most domestic cable factories do not have irradiation equipment, the installation and ancillary costs of irradiation equipment are currently too high. Therefore, if these manufacturers use irradiation cross-linked materials, they must complete the irradiation cross-linking by outsourcing the processing. This not only increases the costs (irradiation costs and transportation costs), but also makes it impossible to control the product quality and delivery time by oneself. Therefore, considering the overall situation comprehensively, the irradiation cross-linked material method has the most reliable and stable product performance, but its cost (equipment cost) is relatively high, and the domestic cable market competitiveness is too low.

Ultraviolet cross-linked material

Although ultraviolet cross-linking technology overcomes the drawbacks of irradiation cross-linking mentioned above and can be cross-linked online in one go, it is also a material that has been widely applied in recent years. However, since it uses the online cross-linking method of ultraviolet light, its production efficiency is relatively low. If the extrusion speed is too fast, it is prone to non-cross-linking, and if it is too slow, it is prone to over-cross-linking. Moreover, the ultraviolet lamp tubes need to be replaced frequently. If they are not replaced in time, the products will also have non-cross-linking, and it is difficult to determine when to replace the lamp tubes. Once the wires that have undergone ultraviolet light cross-linking are not cross-linked well, they cannot be cross-linked again. Moreover, the color of the cross-linked material will also affect the degree of cross-linking.

In conclusion, ultraviolet cross-linked materials, as a new type of material developed and researched after irradiation cross-linked materials, are affected by their material properties and equipment. If this material is adopted, the supporting equipment still needs to be further developed and researched. Therefore, the application of this material is somewhat limited by the equipment and the material itself.

Silane cross-linked material

Silane cross-linked low smoke zero halogen flame retardant polyolefin insulation material is a new type of cable material formed by organically combining silane cross-linking technology and halogen flame retardant technology and applying them to cable materials. It not only has a high production efficiency (some manufacturers can achieve a production speed of up to 95 meters per minute), but also is convenient for crosslinking. Crosslinking can be done with warm water or steam, or naturally. Meanwhile, its crosslinking quality is stable and the degree of crosslinking is basically not affected by color.

Silane natural crosslinking material

Silane natural cross-linked low smoke zero halogen flame-retardant polyolefin insulating material is a new type of cable material formed by changing the proportion and content of its initiator and oxidant on the basis of silane cross-linked low smoke zero halogen flame-retardant polyolefin insulating material and applying it to cable materials. It not only has high production efficiency but also is convenient for cross-linking. Compared with the warm water and steam cross-linking of silane cross-linked materials, the most important option is natural cross-linking. Meanwhile, its cross-linking quality is stable and it has high operational flexibility when applied in the production of cable products.

The production process of silane natural cross-linked low smoke zero halogen flame-retardant polyolefin insulation material is rather complex and technically challenging, so it has not been widely used in China up to now. Even some manufacturers are still in the experimental research stage, and the engineering and technical personnel in the cable industry have a relatively shallow understanding of the production and usage of this product. This material has a relatively high cost performance in overall use and will be the direction of research and development in the future.

The research and application prospects of silane natural cross-linked low smoke zero halogen polyolefin insulation materials

Silane cross-linked low smoke zero halogen materials have long been a hot topic in the field of materials research and development. Professor Jiang Pingkai from Shanghai Jiao Tong University guided his students to study silane cross-linked polyolefin elastomer zero halogen flame retardant composite materials [1] in 2007, which used magnesium hydroxide as the flame retardant. The effects of flame retardant dosage, silane dosage, DCP dosage, etc. on the flame retardancy, crosslinking and other properties of polyolefin materials in POE and EVA systems were studied. Liu Xu [2] et al. from Dalian Polytechnic University also used magnesium hydroxide as a flame retardant and a single-screw extruder as the reactor to study the effects of crosslinking degree, magnesium hydroxide and EVA dosage on the flame retardant performance and mechanical properties of the composite system, as well as the influence of EVA on the micro-light-level structure of silane-crosslinked magnesium hydroxide composites. In conclusion, when developing this material, the selection of the following key materials is of vital importance: the selection of the matrix resin, the selection of the initiator, the selection of the flame retardant, the selection of the silane crosslinking agent, the selection of the catalyst, the selection of the antioxidant and other materials. At the same time, it is also advocated that various production and research institutions in the industry provide high-performance materials for joint development and utilization.

The production method of 2-silane natural cross-linked low smoke zero halogen polyolefin insulating material

Although silane natural cross-linked low smoke zero halogen polyolefin insulating material is developed on the basis of silane cross-linked low smoke zero halogen flame-retardant polyolefin insulating material, its production process has stricter requirements and more complex production control than the former. When producing silane cross-naturally linked low smoke zero halogen flame-retardant polyolefin insulation materials, always be vigilant against the entry of moisture during the production process. Therefore, when choosing the production process, one must be cautious. During production, even stricter management is necessary. Automated or semi-automated processes should be adopted as much as possible to reduce errors caused by human factors.

3. Application of Silane Natural Cross-linked Low Smoke Zero halogen Polyolefin insulation materials

At present, the cross-linked low smoke zero halogen flame-retardant polyolefin insulating materials used in China are mainly applied in wire distribution. Foreign products can also be used in solar energy, automotive wires and even nuclear power plant cables.

When using silane naturally cross-linked low smoke zero halogen polyolefin insulating materials, the A and B materials should be mixed evenly first and then extruded in a dedicated low smoke zero halogen screw extruder. The extrusion speed may be determined according to the specific equipment and product specifications. The cross-linking of the product after extrusion can be achieved through natural cross-linking. Generally speaking, when the temperature is relatively high in summer, natural crosslinking can be adopted, with a crosslinking time of 3 to 5 days. Due to the lower temperature and humidity in winter, steam crosslinking equipment can be used to create the temperature and humidity environment required for natural crosslinking and accelerate the crosslinking speed. The production operation is more convenient and the production cost is lower by adopting this method.

4. Conclusion

Silane natural cross-linked low smoke zero halogen flame-retardant polyolefin insulation materials offer a more convenient manufacturing cost than irradiation cross-linked materials, a more energy-efficient cross-linking method, and low production costs with simple and easy-to-operate processes. At the same time, when applied to products, the production cost is even lower. Compared with ultraviolet cross-linked materials, the material performance is more stable. When applied to products, the product performance is also more stable. The production efficiency and production methods are more convenient. Compared with silane cross-linked low smoke zero halogen flame-retardant polyolefin insulating materials, the production process of the product is simpler and the product performance is more stable and reliable. It has received more and more favorable comments from cable manufacturers, and the usage volume is steadily rising. If the price of this material is further adjusted and reduced, there is a trend of irradiation cross-linked insulation.

The production of wires using silane natural cross-linked low smoke zero halogen flame retardant polyolefin insulating materials has its outstanding advantages, especially suitable for the situation of China's cable industry. It is hoped that producers and users of silane natural cross-linked low smoke zero halogen flame-retardant polyolefin insulation materials should continuously strengthen the research, improvement and performance of this product, so as to make its performance more excellent and expand its application in more products of wires and cables.