High temperature vulcanized silicone rubber sealing strip is a kind of sealing strip made of a new material. It is mainly based on methyl vinyl raw rubber, with reinforcing filler, wetting agent (structure control agent), other additives, crosslinking agent and color masterbatch added to prepare a rubber mixture, which is extruded by a rubber extruder and vulcanized by a high temperature drying channel. The production process is shown in Figure 1. Raw rubber: polymerization degree is 5000-8000, vinyl content is 0.03% - 0.3%; filler: fumed silica, precipitated silica, diatomite, quartz powder, etc.; structure control agent: hydroxy silicone oil, silazane, diphenylsiliol, etc; The Si-O bond energy of the main chain of methyl vinyl siloxane is 444kj / mol, which is larger than the C-C bond energy (356kj / mol) and C-O bond energy (339kj / mol) of the main chain of ordinary organic polymer, making the high temperature vulcanized silicone rubber sealing strip have better aging resistance, high resilience, high and low temperature resistance and other excellent properties than the traditional sealing strips.

Figure 1 production process of silicone rubber sealing strip

Reaction mechanism of high temperature vulcanized silicone rubber

The crosslinking reaction of high temperature vulcanized silicone rubber can be divided into peroxide initiated reaction and hydrosilylation reaction according to the type of crosslinking agent. The peroxide initiated reaction is that the organic peroxides decompose to produce free radicals, which attack the methyl or vinyl groups on the siloxane side to cause chain reaction and cross-linking. The reaction mechanism is as follows:

Hydrosilylation is the crosslinking reaction of vinyl and hydrosilide on the side group of siloxane under the catalysis of platinum complex. The reaction mechanism is as follows:

Excellent characteristics of high temperature vulcanized silicone rubber sealing strip

2.1 excellent weather resistance and aging resistance. The bond energy of silicone rubber is higher than that of ultraviolet radiation (370kj / mol), so the main chain of silicone rubber will not break and its properties will not decline obviously under the long-term sunlight and ozone. The silicone rubber sealing strip has a longer service life.

2.2 excellent high and low temperature resistance. Silicone rubber can be used in - 60 ~ 200 ℃ for a long time. The wide temperature range makes the silicone rubber sealing strip maintain good performance in the cold area of high latitude and hot area of low latitude.

2.3 good resilience. The rotation energy of Si-O bond in silicone rubber is low, and siloxane has a spiral chain structure, so silicone rubber has a good resilience, which makes the silicone rubber sealing strip return to its original shape after being deformed by external force, so as to ensure its sealing performance.

2.4 safety and environmental protection. Silicone rubber is inert, non-toxic and tasteless. It does not release volatile gases in the process of use. It is widely used in food and medicine industry. Up to now, silicone rubber is the most harmless material among all the new environmental protection materials in the FDA certification.

2.5 selective air permeability. According to the research, the oxygen permeability of silicone rubber is 25 times that of natural rubber and 428.6 times that of butyl rubber; the permeability of silicone rubber to sulfur dioxide and other harmful gases is lower than that of other rubber. This kind of performance can make the room keep fresh air, which is most suitable for people's life.

2.6 the surface is smooth and the color is diverse. The surface of silicone rubber is hydrophobic and smooth, adjustable in various colors, with good decorative effect.

Application of high temperature vulcanized silicone rubber sealing strip

In recent years, as a new type of rubber material, silicone rubber has shown unparalleled superior performance in many fields, playing the role of dust-proof, water-proof, fixed, sound insulation, heat insulation, shock absorption, sealing and decoration. It is widely used in construction, automobile, aerospace, medical health, communication power, transportation, home appliances and other fields.

Prospect of high temperature vulcanized silicone rubber sealing strip

Due to price and market recognition, silicone rubber sealing strip has not been widely used. Compared with other rubber sealing strips, the excellent performance index of silicone rubber sealing strip is more suitable for the low-carbon building energy-saving doors and windows vigorously advocated by the state, and more in line with the green and environmental protection requirements of modern life. Other raw materials of plastic rubber sealing strip come from petroleum cracking products, while silicone rubber comes from silicon ore, which is more sustainable. With the development of science and technology and the reduction of cost, it is the general trend to replace other rubber sealing strips with silicone rubber sealing strips.