The manufacturing processes for PET plastic bottles primarily consist of injection stretch blow molding (ISBM) and extrusion stretch blow molding (ESBM). Among these, the ISBM process is more widely adopted due to its ease of control, high production efficiency, and minimal generation of waste and defective products.
Key factors influencing the blow molding process include the preform, heating, pre-blowing, the mold, and environmental conditions. Preforms require the use of PET material with a molecular weight ranging from 31,000 to 50,000 and an intrinsic viscosity between 0.78 and 0.85 cm³/g. The proportion of secondary recycled material used must not be excessive (typically below 5%), and injection-molded preforms must be conditioned for at least 48 hours prior to use.
Based on their contents, PET bottles can be categorized into pressurized bottles (e.g., for carbonated beverages) and non-pressurized bottles (e.g., for water, tea, oil, etc.). Bottles intended for tea beverages are typically modified PET bottles-blended with polyethylene naphthalate (PEN)-or composite bottles combining PET with thermoplastic polyarylates; these variants are capable of withstanding temperatures exceeding 80°C. Relevant production equipment-such as the ISBM machinery manufactured by companies like SIDEL (France) and KRONES (Germany)-generally comprises five main components: a preform feeding system, a heating system, a bottle blowing system, a control system, and auxiliary units. In the quality control phase, pressurized bottles must simultaneously satisfy the requirements for both stress testing and pressure resistance testing. Through the integration of techniques such as feed-forward correction combined with closed-loop feedback, 3D optical measurement, and adaptive feedback mechanisms, the precision of wall thickness control and overall product consistency have been significantly enhanced.