Rubber insulation of cables

1. Preparation of raw materials
The preparation of raw materials requires warm glue and glue cutting. The weighing of raw materials is a crucial process of preparation.
2. Plasticizing
Rubber has high elasticity at room temperature and is not easy to process. Therefore, it is necessary to change its high elasticity to make it have a certain degree of plasticity. The process of converting rubber from a highly elastic state to a plastic state is called plasticizing.
Factors affecting mastication; roll distance, temperature, mastication time, speed ratio and number of revolutions
Natural rubber must be masticated, while synthetic rubber may not be masticated.
Three, mixing
Mixing is to scoop all kinds of compounding agents into the rubber to make 2 rubber materials with a certain degree of plasticity. One strand is divided into open mixer mixing, internal mixer mixing, and continuous mixing.

Fourth, filter rubber
The requirements for the mixed rubber materials used for insulation and thin sheath products are relatively high. In the actual production process, various rubber materials inevitably contain impurities, and impurities will also be mixed in the transportation and mixing processes. The purpose is to eliminate the above-mentioned various impurities.
There are two methods for filtering rubber: raw rubber after plastic refining and rubber filtering during mixing. Under normal circumstances, raw rubber does not need to be filtered.
l Extrusion process and equipment
Extrusion is a process that uses a rubber extrusion machine to squeeze the insulation layer on the conductor or squeeze the rubber jacket layer on the cable core.
Extrusion process: warm glue, selection and adjustment of molds, control of extruding temperature, cold feed extrusion process
The equipment used to squeeze insulating rubber or sheath rubber has become the main extruder and is divided into eight types: 30.45, 60.90, 120, 150, 200, and 250.
The squeezing machine is composed of a main engine, a traction device, a take-up device, a meter counter, a cooling device and a transmission system, etc.
Main technical parameters: screw, outer diameter, screw length-to-diameter ratio, screw speed range, glue output per hour, main motor model power, equipment center height and overall dimensions

l Vulcanization process
Under heating conditions, the raw rubber in the rubber compound chemically reacts with the vulcanizing agent, so that the rubber is cross-linked from linear structure macromolecules into three-dimensional network structure macromolecules, resulting in a significant improvement in the physical and mechanical properties and other properties of the rubber compound. This process is called vulcanization.
The entire vulcanization process is divided into four stages: vulcanization induction stage (scorch), pre-vulcanization stage (low sulfur), normal vulcanization stage (normal sulfur), and over-bowling stage (over)
The scorch time refers to the time when the rubber begins to harden and the Men’s viscosity increases, and the thermoplastic flow cannot be carried out from then on. The stage between the scorch time and the positive vulcanization is called under-sulfur, which seriously affects the aging performance. Rubber should strictly control the lack of sulfur phenomenon: normal sulfur means that the degree of vulcanization cross-linking meets the process requirements, and the physical and mechanical properties meet the vulcanization time required by the use. The positive vulcanization time is called the vulcanization flat zone, and the vulcanization flatness refers to the wide area in the positive vulcanization zone. Flat vulcanization curve: Excessive sulfur indicates that the vulcanization crosslinking temperature is too high, at this time the tensile strength and fixed extension are reduced.
Vulcanization process: fixed vulcanization of vulcanized tube, continuous vulcanization
Vulcanization conditions include vulcanization temperature, vulcanization time, and vulcanization pressure. Correctly setting vulcanization conditions is a decisive factor to ensure quality.
The most basic principle of continuous vulcanization: use the method of increasing the temperature to speed up the vulcanization rate. According to the relationship between the vulcanization speed and the vulcanization temperature, it can be seen that for every 10 degrees increase in the vulcanization temperature, the vulcanization speed can be doubled on average, that is, the vulcanization time can be reduced by half.
According to the position of the vulcanizing tube, it can be divided into four types: horizontal, inclined, catenary and vertical. In addition to saturated steam, there are superheated steam, low melting point metal salts and infrared rays.
Continuous vulcanization has many advantages compared with tank line vulcanization: high production efficiency, good product quality, product length is not limited by equipment, easy to operate, continuous vulcanization has become the most important vulcanization method in the wire and cable industry, vulcanization tube vulcanization Be in a secondary position.