Blow out with blow molding machine or hollow blow molding machine.
The blow molding process is a two-way stretching process. During this process, the PET chains extend, orient and align in both directions, improving the mechanical properties of the bottle wall and thus increasing tensile, tensile and impact strength. Good air tightness. While stretching can help build strength, it's not advisable to overstretch. The tensile expansion ratio must be controlled: it should not exceed 3.5 to 4.2 in the radial direction and 2.8 to 3.1 in the axial direction. The wall thickness of the preform should not exceed 4.5mm.
Blowing is carried out between the glass transition temperature and crystallization temperature, usually controlled between 90 and 120 degrees. During this period, PET takes on a highly elastic state and becomes a transparent bottle after rapid blow molding, cooling and solidification. In the single-step method, this temperature is determined by the length of cooling time during the injection molding process (such as Aoki blow molding machine), so the relationship between the injection station and the blow molding station must be connected.
The blow molding process includes: one stretch blow molding and two blow molding. Although these three actions are short, they must be well coordinated, especially the first two steps that determine the overall distribution of the material and the quality of the blow. Therefore, it is necessary to adjust: stretching start time, stretching speed, pre-blow start and end time, pre-blow pressure, pre-blow flow, etc. It is best to control the overall temperature distribution if possible. container. Temperature gradient of precast parts, inner and outer walls of precast parts.
During the rapid blowing and cooling process, induced stresses occur on the bottle walls. For carbonated beverage bottles it can resist internal pressure, which is advantageous, but for hot-fill bottles it must be fully released above the glass transition temperature.
