The difference between HDPE (high density polyethylene) and LDPE (low density polyethylene) films

LDPE is a flexible and transparent non-toxic and odorless, with a thickness of generally 20-100 microns, with good water resistance, moisture resistance, drought resistance and chemical stability. It is widely used in general moisture-proof packaging and frozen food packaging of food, medicine, daily necessities and metal products. However, for items with high hygroscopicity and high moisture resistance requirements, films and composite film packaging with better moisture resistance are required. LDPE film has high air permeability, no aroma retention and poor oil resistance, so it cannot be used for the packaging of easily oxidized food and oily food. However, the good air permeability makes it suitable for fresh packaging of fruits and vegetables. LDPE film has good thermal adhesion and low temperature heat sealing, so it is often used as the adhesive layer and heat sealing layer of composite films. However, due to its poor heat resistance, it cannot be used as a heat sealing layer for retort pouches. LDPE (low density polyethylene) is polymerized under high pressure of 100~200Mpa, with a density of 0.92 g/cm3. Among high, medium and low polyethylene, LDPE has the best transparency. HDPE is a tough, translucent film with a milky white appearance and poor surface gloss. The tensile strength, moisture resistance, heat resistance, oil resistance and chemical stability of HDPE are better than LDPE, and it can also be heat sealed, but the transparency is not as good as LDPE. HDPE can be made into a thin film with a thickness of 0.01mm, which is similar in appearance to tissue paper and feels comfortable, also known as paper-like film. It has good strength, toughness and openness. HDPE paper film is mainly used to make various shopping bags, garbage bags, fruit packaging bags and various food packaging bags. Because of its poor air tightness and no aroma retention, the storage period of packaged food is not long. In addition, because of its good heat resistance, HDPE can be used as a heat sealing layer for retort bags. HDPE (High Density Polyethylene), polymerized under normal pressure, has a density of 0.94~0.985 g/cm3, and HDPE has poor transparency.