Factors affecting the output of plastic (PVC) extrusion

September 30, 2019

Factors affecting the output of plastic (PVC) extrusion
 

1 The effect of mechanics—the amount of extrusion increases linearly as the head pressure increases.

 

1). For an extruder with a deep groove and a short screw, the extrusion pressure drops sharply with an increase in the random head pressure.
2). Increasing the temperature of the die, the extrusion volume is slowed by the influence of the head pressure.
3). When the die resistance is high (the effective load area is small), the extrusion amount is more affected by the pressure of the head.
4). When the screw speed is high, the extrusion amount is high, but the increase of the head pressure is proportional to the decrease of the extrusion amount.
5). The larger the aspect ratio of the screw, the smaller the extrusion volume is affected by the pressure of the head.
6). Uncooled screw, the amount of extrusion is much more affected by the pressure of the head than the cooled screw.
7. The larger the gap between the screw and the barrel, the greater the proportion of the extrusion head with an increase in the random head pressure.

 

2 Effect of screw speed - The amount of extrusion increases with increasing screw speed, but it is not linear.

1). With the increase of the screw speed, the increase of the extrusion amount is related to the material. HDPE>LDPE>PP.
2). The extrusion amount of low-viscosity molten material is more affected by the screw rotation speed.
3). At high melting temperatures, the amount of extrusion increases with increasing screw speed. However, at low melting temperatures, the increase is minimal.
4). The amount of uncooled screw is slightly larger than the cooled screw due to the screw speed.
5). When the die resistance is low, the extrusion amount increases with the increase of the screw rotation speed; on the contrary, the increase ratio is small.

 

3 The amount of extrusion increases rapidly as the melt index of the material increases.

 

4 The amount of extrusion increases as the length of the homogenization section increases.

 

5 When the head pressure is low, the extrusion amount increases as the depth of the homogenization section becomes deeper; however, if the head pressure is high, the extrusion amount decreases as the depth of the homogenization section becomes deeper.

 

6 The amount of extrusion decreases as the gap between the screw and the barrel increases. However, when the gap is larger than 1 mm, the amount of extrusion is remarkably reduced.

 

7 The amount of extrusion decreases as the temperature of the feed section increases.

 

8 As the melting temperature increases, there is no change in the amount of extrusion at the beginning. When the temperature continues to increase to a certain extent, the viscosity of the material decreases and the amount of extrusion decreases rapidly.

 

9 When the temperature of the barrel is increased to a certain limit, the amount of extrusion is also drastically reduced due to the rapid decrease in the viscosity of the material.

 

10 The amount of extrusion decreases as the amount of volatiles in the material increases.

 

11 As the screw temperature increases, the amount of extrusion sharply decreases.

 

12 As the depth of the groove deepens, the amount of extrusion increases rapidly at the beginning, and when a certain limit is reached, the amount of extrusion is drastically reduced. This is because the degree of plasticization of the material in the screw is deteriorated after the depth of the groove is increased.

 

13 The amount of extrusion increases proportionally with an increase in the area of ​​the die-forming hole.

 

14 The amount of extrusion decreases proportionally with the increase in the length of the advection portion of the die.

 

15 Materials with different melt flow rates cannot be compared to the amount of extrusion depending on the screw speed.

 

16 The amount of extrusion is not proportional to the screw speed.

 

17 Even the same type of extruder (same screw structure, the same temperature setting), due to the length of the adapter, the die area, the resistance of the filter, the degree of screw cooling, the preheating temperature of the material, and the extruder itself The slight difference in the gap between the screw and the barrel, etc., the amount of extrusion when the same material is extruded is not the same.

 

18 For fixed extruders, the amount of extrusion will vary depending on melt pressure, screw temperature, and material stability at different times.

 

19 The influence of the formula of pvc compound, the same equipment, different formula system, different extrusion amount, the faster the plasticization, the larger the extrusion amount, the plasticized ingredients on the formula are 316A, internal lubricant, processing aid ACR and so on.
 

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