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  • How to judge the internal and external in the processing of PVC plastics?

    (1) If internal and external lubrication are both insufficient. It will be high melt viscosity, high plasticizing

    torque, serious melt wall sticking phenomenon and non-smooth inner surface; serious thermal

    decomposition in advance, low mechanical properties of products. If the internal and external lubrication

    are balanced, the melting test material will come down as soon as it touches, and the surface of the rotor

    will not stick to the melt material.


    (2) If internal and external lubricants are both excessive. The plasticizing torque is small and have

    precipitation occurs. Although the product has good smoothness, but its mechanical properties are low ,

    easy broke. When it is serious, the surface of plastics will feel oily when wiped by hand.


    (3) If less internal lubricants and more external lubricants. The plasticizing time is obviously prolonged,

    because the internal lubricant is less, the internal friction of resin is larger, and it is easy to cause

    thermal decomposition. The plasticizing torque increases. Sometimes it feels oily on the surface of the

    sample by hand, and the product  becomes broke


    (4) If more internal lubricants and less external lubricants. The plasticizing time is obviously shortened,

    so that the resin is plasticized ahead of time, resulting in the high viscosity melt being subjected to

    shear force for too long, at the same time, there is a serious adhesion phenomenon, the rotor is not

    easy to clean, also resulting in the shortening of thermal stability time, products have decomposition

    yellow line.


    In a word, if the amount of external lubricant is insufficient, there will be adhesion, short plasticizing

    time and non-smooth surface of the sample; if the amount of external lubricant is excessive, plasticizing

    time will beobviously prolonged, mechanical properties will be reduced, brittle, precipitation may occur,

    and oil-like feeling will be felt when the exterior lubricant is excessive. When the amount of internal

    lubricant is insufficient, the plasticizing torque will be larger and the plasticizing time will be longer;

    when the amount of internal lubricantis excessive, the plasticizing time will be shorter and the

    plasticizing torque will be smaller, but the thermal stability time will also be shorter, and there will be

    thermal decomposition phenomenon, and the inner wall of the sample will not be smooth.


    Usually the tensile strength is the highest when the plasticity is 60%, the impact strength is the highest

    when the plasticity is 65%, and the elongation at break is the highest when the plasticity is 70%.


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