Why do almost all the bottom of the plastic bottles is concave?

(1) bottle manufacturing process is simple - — As a result of the bottle inside the pentagon hollow, make the bottle blowing more simple ( Specific reasons is due to the Coca-Cola company's trade secrets, we don't know) 。 2 material savings - — If make it flat, as to bear the pressure of liquid, the bottom must be upset, leading to the waste of materials. Using concave type, on the surface seems to be wasted materials, but in fact it by an average of five Angle to share in the liquid pressure, can make the bottom more thin, saves material instead. (3) to increase the strength of the bottle - — The pentagon inside concave type design, make its can be reduced through appropriate deformation damage degree. Please focus on us! ! ! !