Film properties of three-layer co-extrusion blown film machine?

Films produced by three-layer co-extrusion blown film machines are manufactured by plasticizing and melting three types of plastic materials with distinct functions via three extruders. The melts pass through a composite die head to form an integrated outer layer-functional layer-inner layer structure, followed by blowing, cooling and winding. These films deliver far superior performance to single-layer or two-layer blown films and serve as a core manufacturing method for certain functional films.

Their primary advantage lies in outstanding multi-barrier properties. Materials can be selected purposely for the three layers: high-density polyethylene (HDPE) with weather resistance and anti-aging properties for the outer layer; high-barrier materials such as ethylene vinyl alcohol copolymer (EVOH) or polyamide (PA) for the middle layer; and linear low-density polyethylene (LLDPE) with excellent heat-seal performance for the inner layer. This layered structure endows the film with oxygen barrier, water vapor barrier and UV resistance simultaneously, which cannot be achieved by single-layer films. For instance, fresh food vacuum bags made of three-layer films have an oxygen transmission rate only one-tenth that of single-layer PE films, extending food shelf life by 2 to 3 times. Medical infusion bags block bacteria and liquid molecules to prevent deterioration and leakage, complying with medical safety standards.

Secondly, mechanical properties are precisely balanced and optimized. Materials for each layer meet respective mechanical requirements: high-strength polypropylene (PP) or low-density polyethylene (LDPE) for the outer layer ensures tensile and puncture resistance; toughened polybutene (PB) added to the middle layer improves impact toughness; LLDPE for the inner layer guarantees heat seal strength. The structure balances rigidity and toughness. Heavy-duty courier films boast 1.5 times higher tear resistance than single-layer films and resist punctures by sharp objects during transportation. Agricultural mulch films utilize outer-layer tensile strength and middle-layer puncture resistance to withstand mechanical damage in farmlands, extending service life by over 60%.

Thirdly, integrated functions and low residue reduce overall industrial costs. The three-layer co-extrusion process forms multilayer structures directly without extra lamination procedures, eliminating solvent residue from dry lamination. It meets food contact safety standards while cutting costs on lamination equipment, labor and energy consumption. Snack packaging films integrate inner-layer heat sealing, middle-layer oxygen barrier and outer-layer printability. The integrally formed films can be directly printed and converted into bags, boosting processing efficiency by 30%. Free of odor residue from adhesives, they greatly enhance food safety.

Fourthly, the films feature customizable adaptability for diverse scenarios. The thickness and functions of each layer can be flexibly adjusted to satisfy special requirements across industries. Agricultural greenhouse films can incorporate UV stabilizers in the outer layer, thermal-insulating fumed silica in the middle layer and anti-dripping agents in the inner layer to achieve combined weather resistance, heat preservation and anti-dripping functions. Medical dialysis bags adopt biocompatible inner materials, bacteria-barrier middle layers and disinfection-resistant outer layers to meet strict medical specifications.

In summary, three-layer co-extrusion blown films, featuring integrated multifunctions, superior performance and customizable adaptability, have become key materials for packaging, agriculture, medical and other sectors. Their performance will keep improving with advances in material technology, offering vital support for industrial upgrading.

Dalian Longyao Plastic Machinery specializes in the R&D and production of blown film equipment. We supply machinery across Shandong Province and serve plastic processing factories in Qingdao, Yantai, Weifang, Linyi, Zibo and other regions. We provide Shandong customers with complete blown film production lines, auxiliary spare parts and technical commissioning services.