Defects in extusion

Question 1

What are cracks and laminations caused by? How are they prevented?

Answer 1

~ non-uniform shrinkage during drying

~ controlled humidity dryers may be used

Question 2

What are the effects of excessive extrusion pressures?

Answer 2

~ can result in liquid migration, causing drying effects

Question 3

What effect can anisotrpic particles have?

Answer 3

~ if they align with they extrusion direction, they can cause differential shrinkage

Question 4

What happens to air during extrusion?

Answer 4

~ air may be forced to dissolve in the liquid under extruding pressures

~ exsolved air during decompression can form surface craters and blisters

Question 5

What causes surface laminations?

Answer 5

~ slip-stick wall friction