Maybe you will confuse about this question for years. Here we share you some following reasons:
a. Adding too much silicone oil into silicone rubber. Silicone oil is an additive which will destroy the molecular weight of silicone rubber and reduce the tension and tear strength.
b. Adding too much catalyst into the silicone rubber when you make the molds. For the condensation cure(tin catalyst) silicone rubber. we suggest you add no more than 2% of catalyst. If you 1add too much catalyst, the operation time will be too fast to operate ,which will also reduce the tension and tear strength.
c. Using the silicon rubber with a high hardness to make molds for small sized products with delicate and intricate designs and the silicon rubber with a low hardness to makes molds for large sized products with simple designs.
(Notes: we should choose the silicon rubber specifically according to the requirements of our products to avoid this problem.