Why is the tear strength of the silicone mold weak...

In order to reduce the viscosity of silicone rubber and pursue a good quality,customers may add a lot of silicone oil into the silicone rubber when making molds.In fact,it might have just the opposite effect.   　　The tension and the tear strength will be reduced badly with the addition of silicon oil.And the silicone molds will be in a weak and flimsy manner.Because silicon oil is an additive which destroies the molecular weight of silicone rubber and reduce the tension and tear strength.   　　In addition,using the silicon rubber with a high hardness to make molds for small sized products with delicate and intricate designs and the silicone rubber with a low hardness to makes molds for large sized products with simple designs can also reduce the the tear strength of the silicone mold weak.   　　When the hardness of silicon rubber is lower than 15 shore A,the tension, the tear strength,the aging resistance,acid and alkali-resistance of silicon rubber will reduce respectively.When the hardness of silicone rubber is higher than 50 shore A,the tension and the tear strength of silicon rubber will reduce, and the solidified silicone mold will be easily broken.We should choose the silicone rubber specifically according to the requirements of our products to avoid this problem.