What are guanidine accelerators?

Guanidine accelerators are the most used alkaline accelerators. This type is a medium-speed accelerator for natural rubber and synthetic rubber. When the guanidine accelerator is used alone, the vulcanization starts late, the operation safety is high, and the storage stability of the mixed rubber is good, but the vulcanization speed is slow (1 times slower than that of the sulfenamide accelerator). The biggest feature of guanidine accelerator vulcanizate is the high degree of vulcanization, resulting in high hardness and high modulus stress.
However, due to the presence of a large number of polysulfide bonds and more cyclized compounds in the vulcanized rubber, the vulcanized rubber has poor heat aging resistance, easy cracking, and large compression deformation. In addition, this type of accelerator has discoloration and pollution, and is not suitable for white products. Due to the slow vulcanization speed and poor heat aging resistance, guanidine accelerators are generally not used alone, but as the second accelerator of thiazoles and sulfenamides. When used together, the activation effect is particularly strong. It is used in the production of rubber sheets, shoe soles, bicycle tires, industrial products, thick products, and hard rubber products. The rubber compound with guanidine as the second accelerator is suitable for all vulcanization methods. However, when it is used as the first accelerator, its vulcanization start is so late that it cannot generally be used for hot air vulcanization.