1.Foreword
With the rapid development of power, electronics, communication and other industries, China has become the largest cable manufacturer in the world. The popularization and application of physical foaming technology in communication cable has played a huge role in promoting the development of communication industry. In the communication cable, there are two kinds of foaming modes of insulating materials: chemical foaming and physical foaming. Because the foaming degree of chemical foaming is low, and the residual of foaming agent has a certain degree of negative impact on the electrical indicators of the cable. Therefore, the current application is not as wide as physical foaming. Physical Foaming Insulation Materials is mainly used in the manufacturing of RF coaxial cable in the field of mobile communication, CATV coaxial cable in radio and television system and railway digital signal cable developed in recent years. The application fields of the above three types of cables are different, and the requirements for various performance indexes are different, so the corresponding requirements for foamed insulation materials are also different. In this paper, the brand, performance, characteristics, defects and future development trend of foamed insulating materials used for these three types of cables are briefly introduced.
2.Polyethylene insulating material for RF cable of mobile communication
The typical standard for the application of RF radio frequency coaxial cable is “YD/T 1092-2004 communication cable — 50 foam polyethylene insulated corrugated copper conductor external conductor coaxial cable for wireless communication”. The applicable test frequency of this series of cables can reach 3000MHz. The test frequency is very high, so the attenuation requirement of the cable under the high frequency condition is correspondingly high. At the same time, the attenuation index is one of the most important electrical performance indexes in the production process control of this kind of cable. It is also the biggest challenge for foamed insulating materials to achieve high attenuation index.
