PE coating is used primarily to make paper products liquid-proof and durable, transforming them from simple paper into functional packaging. Here's a breakdown of its key functions:

• Waterproofing: Plain paper is porous and absorbs water, causing it to become weak and leak almost immediately. PE forms a thin, continuous plastic film that is impermeable to water and other liquids, preventing leaks and maintaining the cup's structural integrity.
• Grease Resistance: It also provides an excellent barrier against oils and greases, which is essential for cups containing dairy products, soups, or fried foods.

PE has a low melting point. This allows the seams and bottoms of paper cups to be sealed quickly and securely using heat and pressure during the manufacturing process. This creates a strong, leak-proof seal that is crucial for the cup's functionality.