The rubber compound made by blending raw rubber with hydrophilic silica will gradually harden and lose its processability during storage. This phenomenon is called "structuring". The main reason for the formation of a structured structure is that silica forms a three-dimensional network structure through hydrogen bonds between the Si-H groups on its surface. To prevent the structuring phenomenon of silicone rubber, a structure control agent needs to be added to the rubber compound. The function of the structure control agent is to inhibit the formation of hydrogen bonds between particles by interacting with the Si-OH groups on the surface of silica.
Commonly used structure control agents include diphenylsilanediol, low molar mass hydroxyl silicone oil, cyclosilamane, hexamethylsilazane, etc. At present, the most commonly used, effective and convenient one is low-viscosity hydroxyl silicone oil. The effect of low-viscosity hydroxyl silicone oil is related to the degree of polymerization and the content of hydroxyl groups. Experiments show that when the degree of polymerization x=6 to 10 and the content of hydroxyl groups is 6.5% to 8%, it can better control the structure of the rubber compound. The dosage for structural control varies depending on the type of filler, the dosage, processing technology and climate changes, and should be adjusted according to the actual production situation.