The interlayer material of heat shrinkable film is usually used to enhance a certain characteristic of the composite structure, such as barrier properties, light-shielding properties, fragrance retention, strength and other properties. Today, the most commonly used are aluminum foil (AL), aluminized film (VMCPP, VMPET) , polyester (PET), nylon (NY), polyvinylidene chloride coated film (KBOPP, KPET, KONY), EVOH and other materials.
The function of the adhesive layer is to bond the adjacent two layers of materials together to form a composite structure. According to the characteristics of the adjacent materials and the composite process, an adhesive or an adhesive resin can be selected as the adhesive layer material, and the adhesive layer is bonded. The bonding strength between materials is an important purpose to evaluate the intrinsic function of composite packaging materials, and different packaging requirements have different requirements for this purpose.
From the perspective of functional requirements, a combination of five polymers is sufficient, but co-extruded composite films with seven, nine, eleven or more layers have been used in the market, making it a trend , and has been developed flexibly, the structural design of co-extruded film is gradually required to systematically reach an ideal situation that integrates function, technology, cost, environmental protection, safety, and secondary processing.
