PET Chips Hot-filling Grade

1. What are hot-filling grade polyester chips?

Hot-fill grade polyester chips are a high-performance PET material specifically designed for high-temperature filling processes. Ordinary PET bottles deform significantly above 85℃, while bottles made with these special chips can be filled with beverages such as tea, juice, and herbal tea at temperatures of 85℃-95℃ while maintaining their shape.

2. What are the differences between general water bottle grade and hot-fill grade PET chips?

The core differences lie in “heat resistance” and “crystallinity control.”

Compared with water bottle garde pet chips, hot-fill grade PET chips, through special formulation and process design, form a uniform, fine crystalline structure during the heat treatment after blow molding. This crystalline structure prevents softening and deformation at high temperatures. Simultaneously, the process requires precise control of crystallinity to balance heat resistance and transparency.

3. How do PET hot-filling bottles achieve heat resistance?

Bottle design: The bottle body typically features a special vacuum decompression ring design. When the contents cool after hot filling, the volume shrinks, creating negative pressure. The reinforcing rings deform inward, absorbing stress and preventing the bottle body from twisting.

Reinforcing ribs: The bottle body may have vertical reinforcing ribs to further enhance its resistance to pressure and deformation.

Base design: The bottle bottom is often petal-shaped or has a crystallized base for better stability.

Blow molding process: Utilizes “heat setting” technology. After blow molding, the bottle is placed in a specific high-temperature mold for a period of time to promote crystallization, significantly improving overall heat resistance and dimensional stability.

4. What properties must hot-fill grade PET resin possess?

Low acetaldehyde formation and release: PET easily produces acetaldehyde (AA) during high-temperature processing and heating, severely affecting the flavor of beverages. Hot-fill grade chips significantly reduce AA formation and migration during high-temperature processing and filling by optimizing polymerization catalysts, using AA inhibitors, and copolymerization modification.

Excellent thermal stability and processing window: During blow molding and heat setting, the material needs to undergo longer high-temperature treatment. Therefore, hot-filling bottle grade PET chips must possess higher thermal oxidation stability to prevent yellowing, viscosity reduction, or off-odors during processing.

A good balance of mechanical strength: While pursuing high heat resistance, it is essential to consider the bottle’s impact toughness and top pressure strength at room temperature. This requires precise control of crystal morphology to avoid excessive crystal growth leading to brittleness.

5. What are the technical challenges of polyester chipsfor hot-filling bottles?

Balance between heat resistance and transparency: Higher crystallinity results in greater heat resistance but less transparency.

Control of processing stability: Precise temperature and time control are required to ensure uniform crystallization and prevent bottle defects or insufficient strength due to uneven crystallization.

Balance between impact resistance and rigidity: Rigidity must be maintained at high temperatures without deformation, while good drop resistance must be maintained at room temperature.

6. Why are PET hot-fill beverage bottles not completely transparent?

This slight “haze” or “crystalline appearance” is a visual manifestation of crystallization in the bottle. Crystallization improves heat resistance but slightly reduces optical transparency. High-quality hot-fill PET resin and processes strive to keep haze to a minimum while ensuring heat resistance.