Smooth and shiny, LDPE is best for high quality printing with gloss inks. This substrate is softer than HDPE. LDPE has the most excessive branching. This causes the low density to have a less compact molecular structure which is what makes it less dense. The LDPE bags are more flexible but with less tensile strength.
So called because of its high molecular weight, HDPE is very strong. For that reason, it’s the one that’s used most commonly in supermarkets, and is instantly recognisable by its distinctive rustling sound. Although brittle, HDPE is ideal for carrying heavy loads.
Polypropylene (PP) is a thermoplastic of high clarity, high gloss, good tensile strength, excellent chemical and heat resistance. It has a higher melting point than PE which makes it suitable for applications that require sterilization at high temperatures PP is often chosen for food packaging where low permeability, heat sealing and high clarity is advantageous or required like bags for candies, cookies, herbs, nuts and other confectionaries.