The stretch film has good stretchability and can tightly wrap the object. If the stretchability is poor, it will easily cause breakage, which will not only waste resources, but also delay the efficiency of packaging. Today, Zhiteng stretch film manufacturers will introduce to you the factors that affect the stretching function of stretch films.

 

The stretch ratio is a very important performance parameter. The longitudinal and transverse stretch ratios have a significant impact on the energy of the stretched film. At a certain temperature, the greater the stretching ratio, the greater the orientation of the pp molecular chain. The modulus increases, the elongation at break decreases, the impact strength and fold resistance increase, and the air permeability and gloss increase.

 

In the process of longitudinal stretching and transverse stretching of the stretched film, after the longitudinal stretching, the transverse stretching effect becomes worse. After further transverse stretching, the polymer chains tend to be biaxial. With the development of molecular chain orientation, The number of straight chain ends in the film increases, the number of folds gradually decreases, the density and strength of the material are relatively developed, and the elongation at break decreases, so biaxial stretching can be improved.

 

Multiple stretching start and end points are likely to cause uneven thickness of the product. In the process of transverse stretching, there are step stretching and original stretching multiples. In the process of transverse stretching, when it is stretched to a larger multiple, with the stretching, the steps gradually expand to both sides. In the production of stretched film, the stretching level must reach the original stretching multiple.

 

The difference between the longitudinal stretch film ratio and the transverse stretch ratio ultimately determines that the physical effects of the longitudinal and transverse directions and the transverse stretch ratio are not much different, and there is no significant difference in the molecular orientation of the two directions. The stretched film shows that the longitudinal effect is higher than the transverse effect, and the longitudinal and transverse stretch ratios are selected appropriately, usually 5.5, which is lower than the transverse stretch ratio. The transverse stretching of the stretched film is performed in a messy and continuous thermal environment. The transverse stretching process has many starting points and end points, which are caused by some defects, impurities, bubbles and appearance defects in the transverse direction of the film.