Packaging bag LDPE (low density polyethylene): LDPE is a thermoplastic obtained by free radical polymerization of ethylene under high pressure. It is the oldest member of the polyethylene family and has been produced commercially as wire sheathing since the early 1940s. Its properties include transparency, chemical inertness, good sealing ability, and easy molding and processing. It has excellent cold resistance and low temperature resistance, but is not resistant to high temperatures. Due to its branched structure, it has excellent transparency, flexibility and ease of extrusion.
The application scope of LDPE packaging bags includes food packaging, fiber product packaging, daily chemical product packaging, pharmaceutical packaging, etc. It can also be used as the heat sealing layer of composite flexible packaging materials. For example, mustard can be designed with a BOPP/VMPET/LDPE structure, in which LDPE is used as a non-toxic and odorless heat sealing material.
Packaging bag HDPE (high-density polyethylene): HDPE is a white powder or granular product, non-toxic, odorless, with a crystallinity of 80% to 90%, a softening point of 125 to 135°C, and a service temperature of up to 100°C. Compared with LDPE, HDPE has better hardness, tensile strength and creep properties, as well as better wear resistance, electrical insulation, toughness and cold resistance.
The film has small extensibility but high tensile strength and impact resistance. It has good heat resistance and can show good strength at low temperatures. It has good chemical stability, is insoluble in any organic solvent, and is resistant to corrosion by acids, alkali and various salts. The film has low permeability to water vapor and air and low water absorption.
It is mainly used for moisture-proof bags, convenience bags (vest bags), garbage bags, and its co-extruded film is also used to make packaging for dairy products and frozen foods. For example, the frozen food packaging material is HDPE/EVA, which takes advantage of the advantages of being non-toxic, tasteless, excellent in high and low temperature resistance, and low in price.
Packaging bag
Packaging Bags LLDPE (Linear Low Density Polyethylene): LLDPE has a molecular structure with very short comonomer branches. Its production starts with transition metal catalysts, especially Ziegler or Philips types. Compared with LDPE, LLDPE has a narrower molecular weight distribution and less shear sensitivity. It has good tensile strength and impact strength, is soft and tough, and has better oil resistance and chemical resistance than LDPE. The thermal adhesion is very good, and the heat sealing strength has little relationship with the heat sealing temperature. The heat sealing temperature range is wide and the strength is high.
Its processing properties are similar to LDPE and has excellent rheology or melt flowability.
LLDPE can be made into garbage bags, ice bags, grocery bags, heavy packaging bags, winding packaging bag, etc. It can also be used as the inner sealing layer of composite flexible packaging materials. Compared with LDPE, it makes the bag making more reliable, and the heat sealing strength of the sealing area is higher but The cost is higher than LDPE. For example, the packaging material structure of liquid detergent: BOPA/LLDPE. LLDPE is used as the inner sealing material and has good resistance to sealing contamination.
