In life, people often see a variety of film materials, not only fresh-keeping film, but also food packaging, which play a great role, and people can't live without these packaging. Coextrusion film is a common film in modern life. What are its advantages? The following is about "Introduction to the advantages and application scope of coextrusion film".

All layers of coextrusion film are extruded at the same time, so there will be no aluminum foil, paper and other non plastic materials.

The combination forms of product materials are relatively few, and the scope of application is also small. However, the health and safety of food packaging coextrusion film should be relatively reliable because the winter lamination layer is combined by hot melting without adhesive.

Difference: coextrusion membrane: there is no glue between membranes

Microporous membrane or ultrafiltration membrane is used as the support layer, and its surface is covered with a thickness of only 0.1 ~ 0.25 μ The dense homogeneous membrane of M is used as the separation membrane composed of barrier layer. It greatly increases the transmission of matter.

The film produced by single-layer LDPE or blending LDPE with other resins has single performance and can not meet the packaging requirements of modern article development. Therefore, the comprehensive performance of coextrusion film produced by coextrusion blowing film or coextrusion tape casting equipment is improved. For example, the mechanical strength, heat sealing performance, heat sealing temperature, barrier, opening and pollution resistance of the membrane are improved, and its processing cost is reduced, so it is widely used.

Such as hot melt adhesive film of H-layer coextrusion blown film: PE / hm, cable film PE / EAA, low temperature heat sealing film of mLLDPE, cover film of EVA, antistatic film and smooth film. Coextrusion CPP of H-layer coextrusion casting, unmodified PP / heat sealable PP, etc. Three layer coextrusion film blowing machine, nylon coextrusion film with five layer coextrusion film blowing machine structure, five layer and seven layer EVOH and PVDC high resistance diaphragm are also developing and widely used.

Heat sealing strength refers to the peel strength achieved after two layers of the same or different plastic materials are thermally bonded together under a certain melting temperature and pressure. According to relevant standards, heat sealing is the strength measured after 2 ~ 3 seconds of heat sealing time at a temperature of 130 ℃ ~ 140 ℃ and a pressure of 1kgf / cm2. There are many factors affecting the heat seal strength, mainly including:

(1) Properties of resin;

(2) The composition and amount of additives in the resin;

(3) The conditions of processing and forming, especially the oxidation degree of the surface during extrusion coating processing;

(4) When the film is compounded, the properties of other materials compounded with heat sealing resin are different, and the heat sealing strength and heat sealing temperature are also different;

(5) The degree of surface treatment during compound operation, such as the size of corona treatment, etc.

The heat sealing strength of polyethylene is related to the thickness of polyethylene. With the increase of the thickness of heat sealing resin, such as PE, the heat sealing strength increases. For example, when the thickness of LDPE heat sealing layer is 20 μ M, i.e. the heat sealing strength is 1.0kgf/15mm wide, while 30 μ 1.5kgf/15mm in thickness, 40 μ 2.5kgf/15mm wide for 60 m thick μ M thick, the peel strength can reach 4.2kgf/15mm wide. This is why the inner sealing material PE or PP film of high-temperature cooking bag should be 60 ~ 70 μ The reason for the thickness of M.

The performance of resin for heat sealing is also closely related to the heat sealing strength: for a composite film with a certain thickness, under the pressure of 2kgf / cm2 and the heat sealing condition of 0.5 seconds, the heat sealing strength is the highest at 150 ℃, MI = 3.7g/10min, d = 0.923g/cm3, and the heat sealing strength is 1.25kgf/15mm wide; Mi = 3.0g/10min, d = 0.921g/cm3, heat sealing strength: 1.4kgf/15mm wide; Mi = 7.0g/10min, d = 0.917g/cm3, heat sealing strength: 1.75kgf/15mm wide; Mi = 9.5g/10min, d = 0.917g/cm3, heat sealing strength: 1.9kgf/15mm wide. It shows that the heat sealing strength increases with the increase of MI.