Blow molding part thickness

The process of inflating the parison is primarily one of planar extensional flow especially away from the ends of the parsion. Since the ends of the parsion are constrained as the parison expands, the thickness of the wall decreases as the diameter expands, leading to primarily planar extensional deformation. Eor this reason the blow molded part contains primarily orientation along the circumferential or hoop direction and hence exhibits mechanical anisotropy. 

Parison cooling significantly impacts the cycle time only when the final parison thickness is large. In thin blown articles the mold is opened when the pinched-off parts have solidified so that they can be easily stripped off thus they are the rate-controlling element in the cooling process. For fast blow molding of even very thin articles, the crystallization rate must be fast. For this reason, HDPF, which crystallizes rapidly, is ideally suited for blow molding, as are amorphous polymers that do not crystallize at all. 

Blow Molding Can make hollow parts (such as bottles) stretching action improves mechanical properties, fast cycle requires low labor. No direct control over wall thickness cannot mold small details with high precision requires a polymer with high melt strength. —... 

---