Reinforcement agent and related mechanism

The strength of silicone rubber vulcanized rubber without reinforcement is very low, only about 0.3Mpa, and has no actual use value. Adding appropriate reinforcing agent can make the strength of silicone rubber vulcanized rubber up to 3.9 ~ 9.8MPa, which is very important to improve the performance of silicone rubber and prolong the service life of products. The selection of silicone rubber reinforcing filler should take into account the adverse effects of the high temperature use of silicone rubber and the use of peroxide vulcanization (especially the use of acid and alkaline substances) on silicone rubber. Silicone rubber with reinforcing filler according to its reinforcing effect can be divided into reinforcing filler and weak reinforcing filler, the former particle size of 10 ~ 50nm, specific surface area of 70 ~ 400 square meters /g, reinforcing effect is better; The latter particle size is 300 ~ 1000nm, the specific surface area is below 30㎡/g, the reinforcing effect is poor.

Reinforcing filler

The reinforcing filler of silicone rubber mainly refers to synthetic silica, also known as white carbon black. White carbon black can be divided into gas phase method and precipitation method white carbon black. Gas phase method white carbon black is one of the most commonly used reinforcing agents for silicone rubber. The rubber reinforced by it has high mechanical strength and good electrical properties, and can be used with other reinforcing agents or weak reinforcing agents to prepare rubber with different use requirements. Compared with the silica rubber reinforced by gas phase method, the silica rubber reinforced by precipitation method is slightly lower in mechanical strength, and the dielectric property (especially the dielectric property after dampness) is poor, but the heat resistance aging property is better, and the cost of mixing rubber is low. When the mechanical strength of the products is not high, the precipitation method of silica can be used alone or with the gaseous method of silica.

additives

(1) structure control agent

Silicone rubber reinforced by gaseous silica will become hard, its plasticity will decrease and its processing performance will be gradually lost during storage, which is called "structural" effect. Complexes added to prevent and weaken this "structural" tendency are called "structural control agents". Structure control agents are usually low molecular organosilicon compounds containing hydroxyl or boron atoms, commonly used adiphenylsilanediol, methylphenyldiethoxy silane, tetramethyldioxy dimethylsilane, low molecular hydroxyl silicone oil and silazane, etc.

(2) heat resistant additives
The hot air aging performance of silicone rubber can be greatly improved by adding some metal oxides or their salts and some organic compounds of elements. The most commonly used is ferric oxide, and the general dosage is 3 ~ 5. Other metal oxides such as manganese, zinc, nickel and copper have similar effects. A small amount (less than 1 part) of spray carbon black can also be added to improve the heat resistance. The effect of these additives is usually demonstrated by hot air aging in the temperature range of 250 ~ 300 ° C.

(3) the colorant
Silicone rubber commonly used colorants are as follows: iron oxide (iron oxide) red, cadmium yellow (cadmium dioxide) yellow, chromium green (chromium oxide) green, carbon black (black), titanium dioxide (titanium dioxide) white, group green (blue).