High transparency facilitates the identification of goods; High longitudinal elongation facilitates pre-stretching and saves material consumption; Good puncture performance and transverse tear strength allow the film to encounter sharp corners or edges of the goods without breaking at high tensile ratios; The high yield point makes the packaged goods tighter.
The film produced by the cast method has high transparency, which is not discussed here. With the increase of the number of C atoms of the comonomer of the material, the length of the branch chain increases, the crystallinity decreases, and the "winding or kinking" effect of the copolymer increases, so the elongation increases, and the puncture strength and tear strength also increase. MPE is a high-dimensional structured polymer with a narrow molecular weight distribution, which can accurately control the physical properties of the polymer, so the performance is further improved. Due to the narrow molecular weight distribution of MPE and the narrow processing range, the processing conditions are difficult to control, and 5% LDPE is usually added to reduce the melt viscosity and increase the flatness of the film.
The price of MPE is also high, and in order to reduce costs, MPE is usually used with C4-LLDPE, but not all C4-LLDPE can be paired with it, so you should have a choice. The machine stretch film is mostly made of C6 and C8 materials, which is easy to process and can meet various packaging requirements. Due to the low stretch rate of manual packaging, C4 material is mostly used.
The density of the material also affects the properties of the film. With the increase of density, the orientation degree is improved, the flatness is good, the longitudinal elongation is improved, and the yield strength is improved, but the transverse tear strength, puncture strength and light transmittance are reduced. The addition of LMPE can also reduce the coefficient of friction of the non-adhesive layer and avoid the adhesion of the packaged tray to the pallet.
Effect of cooling roll temperature. The temperature of the cooling roller increases, the yield strength increases, but the rest of the performance decreases, so the temperature of the cooling I roller is generally controlled at 20 °C ~ 30 °C. The tension of the cast line affects the flatness and tightness of the film, and if PIB or its masterbatch is used as the adhesive layer, it also affects the migration of PIB and reduces the final viscosity of the film. The tension is generally not more than 10kg, and the stress remains in the film roll if it is too large, which reduces the elongation and other properties, and is easy to cause film breakage. Application form of stretch film.
Stretch film has a wide range of applications, mainly used in conjunction with pallets, to package loose goods in a single set, instead of small containers. Because it can reduce the cost of bulk cargo transportation and packaging by more than 30%, it is widely used in the whole package of hardware, minerals, chemicals, medicine, food, machinery and other products; In the field of warehouse storage, foreign countries also use stretch film pallet packaging for three-dimensional storage and transportation to save space and land occupation
