Inside the triangular symbol at the bottom of a plastic bottle, you will find the label "PP" (or the number 5)-much like its unique ID number. This material, technically known as polypropylene, is naturally heat-resistant and durable: It does not deform when heated in a microwave, nor does it release odors when filled with boiling water, making it a top performer in the world of food packaging. It is commonly used for yogurt cups and takeout containers; however, it is rarely seen in bottles for carbonated beverages, as PP has relatively high gas permeability, allowing the bubbles to escape easily.
Why Is PP Better Suited for Reuse?
Compared to PET (the material typically used for mineral water bottles), PP offers three major advantages:
High Heat Resistance: It can withstand brief exposure to temperatures of up to 120°C, making it suitable for holding hot beverages.
Resistance to Aging: It is less prone to cracking or deforming after repeated washing.
Excellent Stability: It does not react with acidic or alkaline substances, providing greater peace of mind when used to store fruit juices.
However, a word of caution: prolonged storage of cooking oil in PP containers may cause the plastic to become brittle; therefore, it is recommended to replace the container every three months.
Beyond PP, the numbers found at the bottom of plastic bottles hold further significance:
1 (PET): Disposable mineral water bottles; prone to deformation when exposed to heat.
2 (HDPE): Used for medicine bottles and body wash containers; highly resistant to corrosion.
6 (PS): Used for instant noodle lids; should not be exposed to high temperatures or acidic foods.