![]() ![]() ![]() In addition, today’s lighter preforms are often blown into high strength carbonated soft drink bottles at filling plants. While distributing the optimal amount of material into all regions of the bottle has always been important, today’s light-weight designs make accurate and consistent material distribution even more critical. PET preform and resulting bottle after reheat stretch blow molding. Figure 1 shows example images of the two stages.įigure 1. This 2-step bottle production process is known as reheat stretch blow molding, as the injection molded PET preform bodies are heated again (“reheated”) and stretched they are blown into bottles. In the second step of the bottle production process, the preform bodies are heated, stretched, and blown into the final bottle shape. Preforms can be stored in bulk boxes or totes containing several thousand pieces and later blown into bottles at the same site or shipped to a filling plant to be blown into bottles immediately before filling. In the first stage, PET pellets are injection molded into preforms, which consist of thick bodies that resemble laboratory test tubes, with threaded neck finishes onto which closures (bottle caps) will be applied after product filling. Large scale production of PET bottles for beverages are produced by a 2-step process. With less margin for error, correct bottle design and manufacturing processes to consistently meet design intent have never been more critical than they are today. Regions of the bottle that do not have sufficient wall thickness will be weak points that can lead to bottle damage or even failure as the filled package makes its way from the filling plant to the consumer. With less PET available to make up the walls of today’s bottles, distribution of the material throughout the bottle walls is critical. This internal pressure subjects the walls of PET bottles to a significant degree of tensile stress. Carbonated soft drinks are typically pressurized to the 4 – 5 atmosphere/bar pressure range. While it is less noticeable for water bottle applications, carbonated soft drink applications have also become much lighter since the year 2000. Bottle designs have been light-weighted to such an extent that today’s utility water bottles are approaching a “bag with a bottle cap.” Lighter weight bottles reduce cost and help to make PET a more sustainable packaging option. The average weight of a 500 ml PET bottle used to package bottled water has been reduced by approximately 50% since the year 2000. Plastic bottles used for beverages are typically made from a polymer called PET (Polyethylene terephthalate). ![]()
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