The first method: silica gel with relatively high hardness and silica gel with relatively low hardness shall be used, and the two shall be mixed in a certain proportion; Generally, in the case of hard silica gel, for example, the hardness of silica gel with 50 degrees (Shore hardness) and 30 degrees is about 40 degrees after mixing.
The second method: we can generally use silicone oil to reduce the hardness of silicone. However, in practical application, if the silicone oil ratio is added to destroy the molecular weight, tear resistance and tensile strength of silica gel, corresponding deterioration will occur, thus affecting the service life of silica gel mold. In addition, a large proportion of silicone oil will also cause the silicone rubber mold to deform easily. Therefore, generally, the ratio of silica gel to silicone oil shall not exceed 5%, and silicone oil with greater viscosity shall be added as much as possible. If the silicone oil content exceeds 5%, please use a small amount to determine whether it can be used.
Finally, some relatively soft silica gel is generally used to make soft silica gel products, such as silica gel kneading music, silica gel facial mask, silica gel Chest Patch / cushion, etc.
Some people will ask, what is the lowest and highest hardness range of silica gel? The minimum hardness of silica gel can reach about 5 degrees (usually liquid silica gel), while the maximum hardness of silica gel products can reach about 80 degrees (it is worth noting that such high hardness silica gel products will be very brittle!). Generally, when the hardness of silica gel is 30 ℃, the fluidity, tear strength and elongation of silica gel are the best degrees; When the hardness of silica gel exceeds 40 ℃, the tear strength and elongation of silica gel products will decrease linearly!