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On the dazzling array of goods on the shelves, those crystal-clear PET bottles always instantly catch consumers' eyes—whether it's a clear mineral water bottle, a transparent juice bottle, or an exquisite cosmetic bottle, their high aesthetic appeal relies on the precision of the transparent preform mold.
As the core equipment determining the transparency of PET bottles, the technological sophistication of the transparent preform mold directly affects the product's visual quality and market competitiveness.
The "transparency" of clear PET bottles is not naturally occurring, but rather the result of strict control starting from the preform production stage. The transparency of the preform mainly depends on three factors: raw material purity, injection molding process parameters, and mold performance, with the mold having the most critical impact.
High-quality clear preform molds can minimize crystallization, impurity residue, and surface defects in the PET melt during the molding process, allowing the final PET bottle to exhibit a clarity close to that of glass.
When molten PET is injected into the mold cavity, the surface finish and cooling uniformity of the mold directly affect the arrangement of PET molecules. If the mold cavity has scratches or excessive roughness, it will cause micro-depressions on the surface of the preform, which will scatter light and reduce transparency.
Uneven cooling will cause excessive crystallinity in some areas of PET, resulting in "cloudy" white spots. Therefore, the design and manufacturing standards of transparent preform molds are far higher than those of ordinary molds, making it a highly demanding task in the mold industry.
The polishing precision of the cavity surface is a core indicator determining the transparency of the preform. The polishing precision of ordinary preform mold cavities is typically Ra≤0.08μm, while transparent preform molds need to achieve a mirror-like polishing standard (Ra≤0.02μm), and some high-end molds can even reach Ra≤0.01μm. This near-perfect smooth surface allows molten PET to fit evenly into the cavity, replicating a mirror effect after cooling and reducing light reflection loss.
QX Mould has accumulated rich experience in mirror polishing technology, employing multiple precision polishing processes, progressing from rough grinding to fine polishing layer by layer.
Combined with specialized polishing tools and testing equipment, this ensures that the mold cavity surface is free of any scratches, pitting, or orange peel texture. Bottle preforms produced using their molds achieve a surface gloss level of over 95%, laying the foundation for high transparency after subsequent blow molding.
For preforms of different thicknesses (such as 30g small preforms and 100g large-capacity preforms), QX Mould customizes differentiated cooling solutions: thin-walled areas use a dense water channel design, while thick-walled areas have added turbulence structures to avoid crystallization problems caused by localized overheating. This precise temperature control keeps the preform crystallinity below 5%, far lower than the 15%-20% produced by ordinary molds.