Extrusion

Question 1

What is extrusion?

Answer 1

A continuous process of forcing molten materials (thermoplastic) through a
shaped die by means of pressure. In this process, screws are used to progress the
polymer in the molten or rubbery state along the barrel of the machine, shearing
and mixing the material along the barrel to make a homogenously mixed polymer
output.

Question 2

What are the main parts of an extruder:

Answer 2

feeding system, mixing and shearing, die or tool, cooling, puller and removal.

Question 3

What are the three zones on a single screw extruder?

Answer 3

Feed, Compression, Metering

Question 4

Which screw type provides better mixing, Single screw and double screw?

Answer 4

Double screw is for better mixing.

Question 5

What temperature do you have to set the extruder at?

Answer 5

The barrel temperature should be just below the crystalline melt temperature

Question 6

What are extruders used for?

Answer 6

Extruders mix polymers with other polymers, additives, and reinforcements. They
also can make plastic parts.

Question 7

What is the single most important parameter that determine extruder capacity

Answer 7

The size of the screw

Question 8

What does the screw do in the extruder?

Answer 8

The screw pushes the materials toward the die while mixing them. It adds
mechanical energy to aid the melting of the materials.

Question 9

What is die swell?

Answer 9

Because the polymer material is under a significant stress tensor, an unique
phenomenon occur where the extrudates swells in size as it exits the barrel. The
cross-sectional area increase compared to the die diameter. Geometry of the die
can effect this parameter.

Question 10

. Name several defects that can occur if the polymer exits the die unstable.

Answer 10

Shark Skin, Orange Peel, Bambooing, Discolorations, Contamination!!!

Question 11

What torque should you not exceed on our Brabender to not ruin the screw?

Answer 11

2000 N-m

Question 12

How can you change the size of the extruded pellets?

Answer 12

Regulate speed/torque on the keypad and increase or decrease pelletizer speed.

Question 13

When adjusting pelletizer speed, turning the dial which direction increases speed?

Answer 13

Clockwise

Question 14

Can multiple runs through an extruder be harmful to a polymer compound?

Answer 14

Yes, depending on the shearing stress and temperature, a polymer compound can
experience degradation due to this process.

Question 15

. How can an operator increase the diameter of an extruded pellets

Answer 15

Increase the screw RPM, slow the chopper feed puller, or change the die on the
extruder