PSE 322 QUIZ 4 QUESTIONS AND ANSWERS
What is a distinctive feature of the charged-patch mechanism of agglomeration (in
contrast to the polymer bridging mechanism)? - Answers :Reversibility (formation again
after being broken by hydrodynamic shear)
Which of the following occurrences will tend to increase the efficiency of the sieving
mechanism of retaining mineral fillers during paper formation? - Answers
:Agglomeration of fines, fillers, etc.
What type of polyelectrolyte has a tendency to adsorb as a "patch" on a negatively
charged surface, bringing about strong coagulation? - Answers :High-charge cationic,
relatively high mass (e.g. 1 million g/mole) branched polyelectrolyte (such as PEI)
Which condition is most likely to result in highly variable white water solids over a period
of many days in a typical paper machine system? - Answers :Steady feeding of
retention aid at a relatively low level
What type of papermaking fibers has few pores larger than about 2 nm (mesopores) in
its cell wall? - Answers :Thermomechanical pulp (TMP)
Which type of mineral filler will tend to be retained more efficiently in a system where
there is no effective retention aid system? - Answers :Larger particle size
What is able to pass through the screen of Britt's "Dynamic Drainage / Retention Jar"? -
Answers :Cellulosic fines and mineral filler particles
Goossens and Luner (1976) reported that a greater amount of cationic polymer was
required to maximize settling in a suspension of papermaking fines when the stirring
time was increased from 30 seconds to 1 hour. Why? - Answers :Much of the added
cationic polymer had diffused into mesopores in the cellulose fiber walls.
What happens to the white water solids when the flow of retention aid is changed? -
Answers :A change in white water solids takes place over several minutes until a new
dynamic equilibrium is established.
Adding either cationic starch or alum to papermaking furnish often can increase the
effectiveness of subsequent addition of a cationic retention aid polymer (cPAM). Why? -
Answers :Neutralization of dissolved and colloidal anionic substances
What type of polyethyleneimine (PEI) is expected to be more effective for improving
drainage rates (lower Schopper Riegler degrees)? - Answers :Higher molecular mass
PEI
What is a likely cause, if the time-distribution of white water solids levels is very narrow?
- Answers :Online control of retention is active on the paper machine.
What is a distinctive feature of the charged-patch mechanism of agglomeration (in
contrast to the polymer bridging mechanism)? - Answers :Reversibility (formation again
after being broken by hydrodynamic shear)
Which of the following occurrences will tend to increase the efficiency of the sieving
mechanism of retaining mineral fillers during paper formation? - Answers
:Agglomeration of fines, fillers, etc.
What type of polyelectrolyte has a tendency to adsorb as a "patch" on a negatively
charged surface, bringing about strong coagulation? - Answers :High-charge cationic,
relatively high mass (e.g. 1 million g/mole) branched polyelectrolyte (such as PEI)
Which condition is most likely to result in highly variable white water solids over a period
of many days in a typical paper machine system? - Answers :Steady feeding of
retention aid at a relatively low level
What type of papermaking fibers has few pores larger than about 2 nm (mesopores) in
its cell wall? - Answers :Thermomechanical pulp (TMP)
Which type of mineral filler will tend to be retained more efficiently in a system where
there is no effective retention aid system? - Answers :Larger particle size
What is able to pass through the screen of Britt's "Dynamic Drainage / Retention Jar"? -
Answers :Cellulosic fines and mineral filler particles
Goossens and Luner (1976) reported that a greater amount of cationic polymer was
required to maximize settling in a suspension of papermaking fines when the stirring
time was increased from 30 seconds to 1 hour. Why? - Answers :Much of the added
cationic polymer had diffused into mesopores in the cellulose fiber walls.
What happens to the white water solids when the flow of retention aid is changed? -
Answers :A change in white water solids takes place over several minutes until a new
dynamic equilibrium is established.
Adding either cationic starch or alum to papermaking furnish often can increase the
effectiveness of subsequent addition of a cationic retention aid polymer (cPAM). Why? -
Answers :Neutralization of dissolved and colloidal anionic substances
What type of polyethyleneimine (PEI) is expected to be more effective for improving
drainage rates (lower Schopper Riegler degrees)? - Answers :Higher molecular mass
PEI
What is a likely cause, if the time-distribution of white water solids levels is very narrow?
- Answers :Online control of retention is active on the paper machine.
