PET bottle blowing process

- Aug 03, 2019-

PET bottle blowing process


When preparing a blow molded bottle, the PET slice is first injection-molded into a preform, which requires that the proportion of the secondary regrind should not be too high (less than 5%), the number of recovery should not exceed two, and the molecular weight and viscosity should not be too low (molecular weight 31000- 50000, intrinsic viscosity 0.78-0.85 cm3/g).


The heating of the preform is done by a heating oven, the temperature of which is manually set and automatically adjusted. In the oven, far infrared rays are emitted from the far-infrared tube to radiate heat to the preform, and the fan at the bottom of the oven performs thermal circulation to make the temperature in the oven uniform.


Pre-blowing is a very important step in the two-step blowing method. It refers to the pre-blowing of the preform while the stretching rod is lowered during the blowing process, so that the preform has a shape. Pre-blowing enthalpy, pre-blowing pressure and blowing flow are three important process factors in this process. The pros and cons of the shape of the pre-blowing bottle determines the difficulty of the blow molding process and the performance of the bottle.


The quality of the production environment also has a greater impact on process adjustment. Constant conditions can maintain process stability and product stability. PET bottle blow molding is generally preferred at room temperature and low humidity. 3 Other requirements Pressure bottles should meet the requirements of stress test and pressure test.