Preliminary Distinction Based on Appearance and Touch
PET: Transparent and sturdy bottle, not easily deformed when squeezed.
PE (No. 2, No. 4): Soft and resilient, does not easily make a brittle sound when rubbed.
PVC: Relatively hard to the touch; some non-food grade products may have a pungent odor.
PP: Relatively hard and elastic; has a good gloss when semi-transparent.
PS: High transparency; makes a crisp sound when gently tapped.
Simple Auxiliary Identification
Density Test: PE and PP have a density less than water and float in water; PET and PVC have a density greater than water and sink.
Burning Test (Caution): PE burns with a paraffin-like smell; PP burns with a petroleum-like smell; PVC is difficult to ignite and extinguishes immediately upon removal from the flame, with a pungent hydrogen chloride odor; PS burns with black smoke.
