How to solve the problems you may meet during plastic granulating modification?

How to solve the problems you may meet during plastic granulating modification?

Posted by Andy

1.Too much black spots in the granules product

  • The quality of raw materials is poor, the black spots are more;
  • The temperature of some barrel sections is too high, resulting in material carbonization aggravating and finally brought into the plastic strand;
  • The shearing of screw is too strong which cause the material carbonization aggravating;
  • The pressure of die-head is too high (including plugging, screen changer is too small, the temperature of die-head is too low), the reflux material is too many, causing the material carbonization aggravating;
  • The extruder machine is too old and the gap between barrel and screw increases, the adhesion of carbonization inner the cylinder increases. And with the extrusion time, it is gradually brought to the plastic strand;
  • It’s too long time without clean up of nature exhaust port and vacuum degassing port, the accumulation of carbonized material increased;
  • The die-head and material discharge ports aren’t clean, accumulated too many carbonized material;
  • Some screw elements is damaged (lack of angle, wear, etc.), resulting in the plastic carbonization increasing in the dead corner;
  • External environment or man-made cause impurity mixing into the extruder;

2.Causes of plastic strands broken

  • The screen filter is not enough: increasing the sieve mesh or number;
  • Decreasing the main extruder rotary speed or increasing the material feeder rotary speed;
  • External environment impurity: decreasing the impurity during material mixing and feeding process; decreasing adding too much the recycled material or adding clean up waste material;
  • Internal impurity: reduce the production of material carbonization;
  • The material plasticizing is not good: the temperature of extruder is too low or the screw shearing is too weak; The low melting point additive in the formula system (including EBS or PETS etc.), in the weak screw shear or screw and barrel gap increase, resulting in poor plasticizing;
  • Too much water steam inside the extruder: Material moisture is serious / Natural exhaust or vacuum exhaust is not good / The processing temperature is too high or the screw shearing is too strong, resulting in some flame retardants and other additives decomposition, release gas, and vacuum system did not degas timely;
  • The material rigidity is too big or the water temperature is too low or too long water cooling time, especially for PBT/PET/PC/AS/ABS with glass fiber reinforcing modification. At this point can be appropriate to improve water temperature or reduce water cooling time;

3.Granules hollow problems

  • The extruder exhaust system is not good, causing the gas(vapor) inside the granules;
  • Material plasticizing is not good:
    1. Low processing temperature, the materials cannot be incomplete plasticizing;
    2. On the premise of screw and barrel gap increase or screw shear is too weak, too much low melting point auxiliaries (including EBS or PETS);
    3. The cooling water temperature is too low, the material meets the water contraction, causes the shrinkage hole. Crystalline plastics (such as PP, PA, PBT, etc.) should be used low water temperature, amorphous plastic (such as ABS, ABS, hips, etc.) using high water temperature;

4.Nature exhaust port / Vacuum degassing port material leaking

  • Nature exhaust port material leaking
    1. Main extruder rotary speed didn’t match the material feeding speed. Appropriate reducing the feeding speed or increasing the extruder rotary speed;
    2. The temperature of material feeding section to nature exhaust section is too low, the material is not plasticizing. Under the action of screw extrusion, the material will leak;
    3. The temperature nearby nature exhaust port is too high, the material viscosity seriously reduced causing the screw skidding. Materials cannot be transported in a timely manner to the front section, in the subsequent extrusion of the material flow, resulting in leaking;
    4. There is no reverse conveying or kneading element in the port, the screw pressure cannot reduce. And in the subsequent flow extrusion, resulting in the material leaking;
  • Vacuum degassing port material leaking
    1. The vacuum pump is too large, the material sucked into the vacuum pipe;
    2. The temperature nearby vacuum degassing port is too high, the material viscosity seriously reduced causing the screw skidding. Materials cannot be transported in a timely manner to the front section, in the subsequent extrusion of the material flow, resulting in leaking;
    3. There is no reverse conveying or kneading element in the port, the screw pressure cannot reduce. And in the subsequent flow extrusion, resulting in the material leaking;
    4. The pressure of die-head is too big, causing the reflux material increasing. Under the vacuum pumping force effect, causes the material leaking;

5.Feeding hopper bridging

  • Too many fillers, moisture absorption, reunion, resulting in the friction of mixed material and hopper wall increased: can be solved by adding white oil etc.  liquid lubricants;
  • Mixed material caking (including high temperature caking and too much liquid additive adding caking): reduce the drying temperature or high mixing time, reduce the amount of liquid additives added, add resin or additives powder which good for to the “oil” material absorption (such as, high rubber powder, AS powder, PP powder, etc.);

6.Material feeding bridging

  • Mainly caused by the low melting point of some processing aids. The temperature of barrel section one and two areas is too high, the material in the feeding bin softening, adhesion in the equipment wall, resulting in material feeding problem. Appropriate reducing the temperature of the barrel section one and two areas are ok.

Any problems you meet, please feel free to contact us:
Mr.Andy, WhatsApp:+86-18550112020, Email: weishunzhou@gmail.com

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