Biaxial oriented films can also be prepared by blowing. As long as the temperature is right and the blowout ratio and the traction ratio are right, the degree of direction in both directions can be roughly the same. If the drawing speed is too fast, the difference between the same blowing ratio is too large, and the difference between the vertical and the horizontal may be too large. The result is low lateral strength and easy to break, just as in the process of producing membrane fibers by uniaxial stretching. The prevention method is to appropriately reduce the traction speed, so that it matches with the blowing ratio; Increase the air volume of the air ring, so that the blowing film cooling quickly, avoid stretching and orientation in the high temperature and high elasticity state.
LLDPE mixture is used for low pressure polyethylene HPPE. Low-pressure materials account for about 80%. The greater the pressure, the greater the tension. The disadvantage is that there is no stiffness, too much will cause blowing film swing back and forth, blowing film edge is not neat, and even finally blowing.
First, it is preheated by the first, second and third zones of the heater. The first area should be low, generally around 170 degrees, and the other areas around 200 degrees. If the temperature is high, the material cannot be transported from the rod and may even be scorched and discolored. Then there are four aspects, or three links. The purpose of placing a 60-mesh -160 screen in the tee is to prevent impurities from entering zone 5. The larger the mesh, the thinner the screen, the thinner the film can be blown, including the transparency, feel, smoothness, tension and so on of the film, but too much thin will prevent the material through, too much will not be blown out. Generally 3-5 pieces is appropriate, and the thickness is determined according to the requirements.
After blowing air through the air hole in the membrane head, air is added to the center of the circular membrane, which is straight up. The size of the bag is controlled by how much air is blown in, and then the film is stabilized with a membrane stabilizer. Thickness is controlled by engine speed and traction. It can be understood that the faster the engine speed, the faster the feed speed, the thicker the oil film; Instead, the faster the traction, the thinner the oil film, which is the most important part.
