Control Of Physical And Mechanical Properties Of Wrapping Film

High transparency is beneficial for identifying goods; High longitudinal elongation is beneficial for pre stretching and saves material consumption; Good puncture performance and transverse tear strength allow the film to withstand sharp corners or edges of the cargo at high tensile ratios without breaking; A high yield point makes the packaged goods more secure.
The film produced by the casting method has high transparency, which will not be discussed in detail here. As the number of C atoms in the copolymer monomer of the material increases, the branch length increases, the crystallinity decreases, and the "winding or twisting" effect of the generated copolymer increases, resulting in an increase in elongation, puncture strength, and tear strength. MPE is a highly stereoregular polymer with a narrow molecular weight distribution, which can accurately control the physical properties of the polymer, thus further improving its performance; Due to the narrow molecular weight distribution and processing range of MPE, it is difficult to control the processing conditions. Therefore, 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, it is usually used in combination with C4-LDPE. However, not all C4-LDPE can be paired with it, so it should be chosen accordingly. Machine stretch film often uses C6 and C8 materials, which are easy to process and can meet various packaging requirements. Due to the low stretching ratio, manual packaging often uses C4 materials.
The material density also affects the performance of the film. As the density increases, the orientation degree improves, the flatness improves, the longitudinal elongation rate increases, and the yield strength increases. However, the transverse tear strength, puncture strength, and light transmittance all decrease. Therefore, considering all aspects of performance, an appropriate amount of medium density linear polyethylene (LMDPE) is often added to the non stick layer. Adding LMDPE can also reduce the friction coefficient of the non stick layer and avoid adhesion between packaged trays.
The influence of cooling roller temperature. As the temperature of the cooling roller increases, the yield strength increases, but other properties decrease. Therefore, it is generally advisable to control the temperature of the cooling roller between 20 ℃ and 30 ℃. The tension of the casting line affects the flatness and winding tightness of the film. 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 greater than 10kg. If it is too high, the stress will remain inside the film roll, causing a decrease in elongation and other properties, which can easily lead to film breakage. Application forms of stretch film
Stretch film has a wide range of applications, mainly used in conjunction with pallets to package scattered goods in bulk, replacing small containers. Due to its ability to reduce the packaging cost of bulk goods transportation by more than 30%, it is widely used in the integrated packaging of various products such as hardware, minerals, chemicals, pharmaceuticals, food, machinery, etc; In the field of warehouse storage, foreign countries also commonly use stretch film pallet packaging for three-dimensional storage and transportation to save space and land.