This set of Food Packaging Technology Multiple Choice Questions & Answers (MCQs) focuses on “Mechanical Pulping”.
1. The purpose of pulping is to separate the fibers.
a) True
b) False
View Answer
Explanation: The given statement is true. The purpose of pulping is to separate the fibers without damaging them so that they can then be reformed into a paper sheet in the papermaking process. Pulping refers to the process wherein wood or other fibrous raw materials are reduced to a fibrous mass.
2. ______ is the intercellular substance remaining in fiber pulp.
a) Cellulose
b) Pectin
c) Glucose
d) Lignin
View Answer
Explanation: Lignin is the intercellular substance remaining in fiber pulp. Lignin must be softened or dissolved to free individual fibers. Commercial pulping methods take advantage of the differences between the properties of cellulose and lignin in order to separate fibers.
3. If ________ is present in paper, it deteriorates in color and strength quite rapidly.
a) Cellulose
b) Lignin
c) Hemicellulose
d) Pectin
View Answer
Explanation: If lignin is present in paper, it deteriorates in color and strength quite rapidly. Pulps that retain most of the wood lignin consist of stiff fibers that do not produce strong papers.
4. ________ pulp is produced by forcing wood against a rapidly revolving grindstone.
a) Grindwood
b) Groundwood
c) Pinewood
d) Smashwood
View Answer
Explanation: Groundwood pulp is produced by forcing wood against a rapidly revolving grindstone. The heat generated by friction softens the lignin so that the fibers separate with very little damage. In this, practically all the wood fiber (both cellulose and lignin) is utilized.
5. The yield of chemical pulp is more than that of mechanical pulp.
a) True
b) False
View Answer
Explanation: The given statement is false. The yield of chemical pulp is less than that of mechanical pulp. It is about one-half that of the mechanical process. It is because all the wood fiber (both cellulose and lignin) is utilized. This contrasts with several chemical processes where the lignin is dissolved to varying degrees.
6. Which of the following pulping processes was developed in 1950s?
a) Sulphite process
b) Kraft process
c) Refiner mechanical pulping process
d) Screw pulping process
View Answer
Explanation: In the 1950s, the refiner mechanical pulping (RMP) process was developed, which produced a stronger pulp and utilized various supplies of wood chips, sawmill residues and sawdust. RMP results in more long fibers than stone groundwood and subsequently stronger paper. However, the energy requirements of RMP are higher and the pulp does not have the opacity of groundwood fibers.
7. The presteaming temperature for thermochemical pulping is _______
a) 110°C – 150°C
b) 150°C – 200°C
c) 200°C – 250°C
d) 250°C – 300°C
View Answer
Explanation: Thermomechanical pulping (TMP) presteams chips between 110°C and 150°C so that they become malleable and do not fracture readily under the impact of the refiner bars. This material is highly flexible and gives good bonding and surface smoothing to the paper.
8. Chemical pulp fibers have a greater tendency to collapse.
a) True
b) False
View Answer
Explanation: The given statement is true. Groundwood pulp contains a considerable proportion (70%–80%) of fiber bundles, broken fibers and fines in addition to the individual fibers. The fibers are essentially wood with the original cell wall lignin intact. Therefore, they are very stiff and bulky, and does not collapse like the chemical pulp fibers.
9. Paper from mechanical pulp is stronger than that from chemical pulp.
a) True
b) False
View Answer
Explanation: The given statement is true. Paper from chemical pulp is stronger than that from mechanical pulp. It is due to the presence of fiber bundles, broken fibers and fines in addition to the individual fibers.
10. Paper from which pulp is mostly used for newspaper?
a) Groundwood pulp
b) Thermochemical pulp
c) Chemithermomechanical pulp
d) Kraft process pulp
View Answer
Explanation: Most groundwood pulp is used in the manufacture of newsprint and magazine papers because of its low cost and quick ink-absorbing properties (a consequence of the frayed and broken fibers). It is also used as board for folding and molded cartons, tissues and similar products.
11. Which pulping process is suitable for manufacturing of the middle layer of multi-ply boards?
a) Mechanical pupling
b) Kraft pulping
c) Thermomechanical pulping
d) Chemithermomechanical pulping
View Answer
Explanation: Chemithermomechanical pulping – CTMP is suitable for the middle layer of multi-ply boards. It is because CTMP pulps have a greater long fiber fraction and lower fines fraction than comparable thermomechanical pulping -TMP pulps.
12. What is used for pretreatment in Chemithermomechanical pulping?
a) Calcium propionate
b) Calcium carbonate
c) Sodium nitrate
d) Sodium sulfite
View Answer
Explanation: Chemithermomechanical pulping (CTMP) pulps are obtained by a comparatively mild chemical treatment followed by pressurized refining. Sodium sulfite is used for the mild chemical pretreatment. It increases the strength properties of TMP pulps even further.
13. Thermal treatment increases flexibility of mechanical pulps.
a) True
b) False
View Answer
Explanation: The given statement is true. Thermomechanical pulping (TMP) presteams chips between 110°C and 150°C so that they become malleable and do not fracture readily under the impact of the refiner bars. This material is highly flexible and gives good bonding and surface smoothing to the paper.
Sanfoundry Global Education & Learning Series – Food Packaging Technology.
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