ã€Chinese Packaging Network News】 Biaxially stretched film is widely used because of its tensile properties, biaxially stretched film achieves excellent tensile strength, and its process technology must be very different from other types of protective film. The difference, then, the stretch film strength of biaxially stretched film is how to form it? The following is explained by Shenzhen stretch film manufacturers:
The biaxially stretched film is oriented at a certain temperature, usually above the glass transition temperature of the polymer, and below the melting point, the polymer thick film or sheet is oriented and stretched in both the horizontal and vertical directions in parallel to align the macromolecular chains. The stretching temperature of the amorphous polymer should be between the temperature and melting point of the polymer vitrification, ie, the viscoelastic state of the polymer, and the stretching orientation of the crystalline polymer should generally be performed at an appropriate temperature above the glass transition temperature of the polymer. The process of stretching orientation of the substrate is essentially the deformation process of the spherulites. The orientation of the crystalline polymer is mainly formed by the microfilament structure. As a result of the stretching orientation of the polymer, the number of extended chain segments increases and the pleats increase. The number of stacked segments is reduced, thereby increasing the mechanical strength and toughness of the polymer materials. Therefore, one way to increase the mechanical strength of the oriented polymer is to control the aggregation structure of the polymers produced by the liver during processing, and to make more linear structures.
The general law of plastic film stretching orientation is as follows:
(1) When the degree and the drawing speed are constant, the lower the glass transition temperature of the material is, the greater the orientation effect is.
(2) When the temperature and the drawing speed are constant, the larger the draw ratio, the larger the orientation effect.
(3) When the temperature and the draw ratio are fixed, the faster the drawing speed, the greater the orientation effect.
(4) The higher the cooling rate under the stretching condition, the larger the orientation.