It can be due to the following reasons:
A. Adding too much silicone oil in to silicon rubber. Silicon oil is an additive which destroies the molecular weight of silicone rubber and reduce the tension and tear strength.
B. Adding too much catalyst(curing agent).Too much catalyst can make the silicone cure very fast and and reduce the mold life.
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.)
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