BLOW MOLDING: Lightweight PET Bottle Bases for Demanding Applications

New bases address CSD bottles in hot, humid environments, as well as still water with nitrogen gas dosing.

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Sidel of France (U.S. office in Norcross, Ga.) has enlarged its range of Starlite PET bottle base designs for still and carbonated beverages to include carbonated soft drinks (CSD) bottles produced and distributed in extreme environmental conditions, as well as still beverages using nitrogen dosing. The Starlite family of non-petaloid bases, first introduced in 2013, is designed to provide improved bottle stability through enhanced standing surface, plus greater lightweighting potential. The new base molds can be retrofitted to existing Sidel bottle molds and are said to work with all Sidel stretch-blow machines.

New Sidel Starlite Tropical is a base designed for production and distribution conditions of high heat and humidity. It is available for CSD bottles from 0.25 to 3 L and all standard levels of carbonation. It yields a PET bottle with improved resistance to stress cracking and creep, as well as better stability throughout the supply chain. That means improved resistance to base roll-out, bottle bursting, and deformation, according to Sidel. The Starlite Tropical base has passed testing at more than 72 hr at 38 C (100 F) and 50% humidity. The bottles also resist extreme cold, Sidel says. Starlite Tropical base molds boast enhanced venting and optimized cooling. The base is already in production in the Far East.

Also new is the Starlite Nitro base for still beverages in ultra-lightweight PET bottles of 0. 2 to 2 L that use nitrogen gas dosing to provide rigidity. For example, a 0.5 L bottle with this base weighing 1.8 g can resist an internal pressure of up to 1 bar, depending on the preform and bottle design and grade of PET resin used. Additionally, bottles with the new base reportedly are more resistant to extreme temperatures—e.g., in storage at up to 50 C (122 F), bottles can last up to 25 days or more without deformation. They also can demonstrate 50% less base rollout under frozen conditions. What’s more, the new base is said to be easier to blow than existing bases and to provide a wider process window for stretch-blowing. Air pressure can be reduced by up to 25%, saving energy. A 0.5 or 1 L bottle requires only 18-20 bars (261-290 psi), vs. 25 bars (363 psi) for typical bases.