What are the advantages and characteristics of co-extrusion vacuum bags

　　For example, the three-layer co-extruded layer structure is: PA/AD/PE (PP). Nylon is on the outer layer and is not protected. Nylon has poor impact resistance, is easy to scratch, leaks, and is hydrophilic, easy to absorb moisture, and reduces oxygen permeability.

　　If it is a five-layer structure, PP (PET)/PE, PA outer/Ad. PA outer/PA, PA outer/Ad, PP/(PE). In this way, the nylon is protected on both sides and prevents the nylon from absorbing moisture.

　　Seven layers and nine layers have been tested. If various resins are arranged properly, the shelf life can reach more than 1 year, almost reaching the effect of tinplate cans, such as PET/Ad/PA/EVOH/PA/Ad/PE (PP). Oxygen barrier layer that is still in multi-layer film, the functions and functions of each layer are different: According to the storage period of the package, determine the corresponding barrier material (PVDC, EVOH) and layer thickness, the thickness of nylon is generally 20% , EVOH is generally 10%~15%, and the thickness deviation should not exceed 10%. Within this range, the impact on packaging storage is very small.

　　Adhesive layer (AD): Although nylon and EVOH have good extrusion moldability, they have no ability to bond with other layers (LDPE, PP, EVA) during co-extrusion. Special junction resin must be used as the junction layer to achieve Higher peel strength between layers.

　　Therefore, the choice of layer material is a very important factor. Appropriate grades should be selected according to the structure, the thickness is generally 5~15g/m2, the inner and outer layers: nylon, EVOH although the oxygen transmission rate is small, but the water vapor transmission rate is very large, therefore, when determining the inner and outer layer materials, should be Fully consider the problem of water vapor barrier, and the inner layer material must take into account the heat sealing performance and heat sealing strength, such as LDPE, MLLDPE, EVA, PPO, etc.;

　　If necessary, it can be modified with Surlyn, PRIMCOR, POP. When used as a composite substrate, the corona on the outer surface reaches 38~42 dynes.

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