Unidirectional Stretching Film Principle
DATE：2019/9/2 9:05:28 / READ： / SOURCE：This station
Unidirectional stretching film principle
(1) Conventional uniaxial stretching method The stretching and crystallization of a polymer material has been widely used in the fiber industry. The stretched polymer has more molecular chains oriented in the direction of stretching than in other directions. The unidirectional stretching system stretches the plastic sheet or film in one direction in a viscoelastic state, and the polymer chains or portions are arranged in parallel with the stretching direction. The biaxially stretched plastic film is elongated in two directions perpendicular to each other, and as a result, the area of the sheet is enlarged, the thickness is decreased, and the molecular chain is parallel to the sheet surface, and the in-plane is still in an irregular state.
Usually uniaxial stretching. The film has a tensile strength that is inferior to the direction of stretching. The polyolefin film is easily torn under the action of an external force. One way to avoid this tendency is to stretch in both directions. The second method is a special one-way stretching.
(2) Stretching temperature and molecular orientation Generally speaking, the plastic is in a viscoelastic state, and under the action of stress, the deformation speed is slow, which is called relaxation phenomenon. During the relaxation time of the plastic film, on the one hand, the stretching process produces crystals, and on the other hand, the molecular chains are relatively moved, and the orientation is irregular. That is, the portion having a short relaxation time is oriented earlier than the portion having a longer relaxation time, and then most of the orientation is to increase the temperature in order to orient the portion having a long relaxation time.
(3) Near-width stretching method Figure 2-3-7 shows the necking of the film. Usually, the unstretched portion A, that is, the low-speed roller group on the apparatus, and the stretched portion B, that is, the high-speed roller group on the apparatus. As shown in the figure, in the order of a>b>c>d>e between AB, the width is reduced and the thickness is simultaneously reduced. If the heating roller is stretched and then stretched, the position of A moves toward a, and the position of B moves toward b. Stretching between ab, the film is reduced little in the direction of the web, and the wide film is almost unreduced in the direction of the web, so it is also called the stretching method. The characteristics of the stretching method: A is close to the neck of the width-stretching film, and is formed in a space between a pair of stretching rolls, in which the thickness of the film is drastically reduced, and the width is inversely proportional to the stretching ratio. The film web has a small reduction in the upward direction. The tensile strength in the B direction is high, and is 10% to 30% in the stretching direction.
(1) Conventional uniaxial stretching method The stretching and crystallization of a polymer material has been widely used in the fiber industry. The stretched polymer has more molecular chains oriented in the direction of stretching than in other directions. The unidirectional stretching system stretches the plastic sheet or film in one direction in a viscoelastic state, and the polymer chains or portions are arranged in parallel with the stretching direction. The biaxially stretched plastic film is elongated in two directions perpendicular to each other, and as a result, the area of the sheet is enlarged, the thickness is decreased, and the molecular chain is parallel to the sheet surface, and the in-plane is still in an irregular state.
Usually uniaxial stretching. The film has a tensile strength that is inferior to the direction of stretching. The polyolefin film is easily torn under the action of an external force. One way to avoid this tendency is to stretch in both directions. The second method is a special one-way stretching.
(2) Stretching temperature and molecular orientation Generally speaking, the plastic is in a viscoelastic state, and under the action of stress, the deformation speed is slow, which is called relaxation phenomenon. During the relaxation time of the plastic film, on the one hand, the stretching process produces crystals, and on the other hand, the molecular chains are relatively moved, and the orientation is irregular. That is, the portion having a short relaxation time is oriented earlier than the portion having a longer relaxation time, and then most of the orientation is to increase the temperature in order to orient the portion having a long relaxation time.
(3) Near-width stretching method Figure 2-3-7 shows the necking of the film. Usually, the unstretched portion A, that is, the low-speed roller group on the apparatus, and the stretched portion B, that is, the high-speed roller group on the apparatus. As shown in the figure, in the order of a>b>c>d>e between AB, the width is reduced and the thickness is simultaneously reduced. If the heating roller is stretched and then stretched, the position of A moves toward a, and the position of B moves toward b. Stretching between ab, the film is reduced little in the direction of the web, and the wide film is almost unreduced in the direction of the web, so it is also called the stretching method. The characteristics of the stretching method: A is close to the neck of the width-stretching film, and is formed in a space between a pair of stretching rolls, in which the thickness of the film is drastically reduced, and the width is inversely proportional to the stretching ratio. The film web has a small reduction in the upward direction. The tensile strength in the B direction is high, and is 10% to 30% in the stretching direction.
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