Food Packaging Technology Multiple Choice Questions & Answers (MCQs) on “ Extrusion and Calendering in Thermoplastics”.
1. Which of the following is not a type of calender?
a) I type
b) L type
c) Z type
d) M type
Answer: d
Clarification: M type is not a type of calender. In I type of roller setup, the rollers are placed horizontally. In L type arrangement of roller setup, is I type setup mirrored vertically. In Z type arrangement of rollers, each pair of rollers is placed at right angles to the next pair in chain.
2. Calendering and extrusion are similar processes.
a) True
b) False
Answer: b
Clarification: This is a false statement. Calendering and extrusion are different processes. Extrusion is a process of passing the molten plastic through a shaping device, to give it any form. Whereas, calendering is a complementary process to film and sheet extrusion, which involves the formation of continuous sheets of controlled thickness by passing plastic materials through rollers.
3. As defined by ASTM, the thickness of a plastic film (after single extrusion) should be not more than ________
a) 0.25mm
b) 0.50mm
c) 0.01cm
d) 1mm
Answer: a
Clarification: As defined by ASTM, the thickness of a plastic film (after single extrusion) should be not more than 0.25mm. ASTM, American Society for testing materials is an international standards organisation which functions to set standards for miscellaneous materials.
4. Which of the following is not used for conversion of extruded plastic into sheets?
a) Cast Film Extrusion
b) Slit Die Extrusion
c) Blown Film Extrusion
d) Micro Extrusion
Answer: d
Clarification: Micro Extrusion is not used for conversion of extruded plastic into sheets. Micro extrusion is the process to create comparatively smaller sized objects. Whereas, Cast Film Extrusion, Slit Die Extrusion and Blown Film Extrusion are used for conversion of extruded plastic into sheets.
5. Tubular Extrusion is also known as _______
a) Flat Film Extrusion
b) Blown Film Extrusion
c) Slit Die Extrusion
d) Cast Film Extrusion
Answer: b
Clarification: Tubular Extrusion is also known as Blown Film Extrusion. Flat Film extrusion is also known as Cast Film and Slit Die Extrusion. Like Flat Film Extrusion, Tubular extrusion is also used to convert extruded plastic into sheets. It is done by blowing air through the center of tubular die, due to which the thin tube from extruder is inflated into a thin bubble and cooled, after which it is flattened and wound up.
6. Compression ratios for single screw extrusion should lie between ____ and ____
a) 2:1, 3:1
b) 1:2, 4:1
c) 2:1, 4:1
d) 1:2, 1:3
Answer: c
Clarification: Compression ratios for single screw extrusion should lie between 2:1 and 4:1. Compression ratio is an important parameter for any extrusion process. Compression ratio is the ratio of the volume of one flight of the screw at the in-fees end to the volume of one flight at the die end.
7. The term BUR in extrusion and calendering of thermoplastics refers to _______
a) Blow Up Ratio
b) Bauxime Up Ratio
c) Bottom Upper Ratio
d) Bottom Up Ratio
Answer: a
Clarification: The term BUR in extrusion and calendering of thermoplastics refers to Blow Up Ratio. It is the ratio of bubble diameter to die diameter. BUR for most blown films in packaging generally lies between 2:1 and 4:1.
8. Flexibility of plastic packaging films increases with increasing density.
a) True
b) False
Answer: b
Clarification: The statement is false. Flexibility of packaging films increases with decreasing density. As the density increases, the forces amongst the monomers increases and the rigidity increases. Hence, flexibility decreases.
9. ________ is a process which combines layers of two or more plastics together at the point of extrusion.
a) Lamination
b) Plating
c) Co-extrusion
d) Calendering
Answer: c
Clarification: Co-extrusion is a process which combines layers of two or more plastics together at the point of extrusion. Lamination is the process of packaging via combination of two or more materials by a solvent, adhesive or heat. Calendering is a complementary process to film and sheet extrusion, which involves the formation of continuous sheets of controlled thickness by passing plastic materials through rollers. Plating is the process of coating any surface (especially metal) by other metal, mostly by electrochemical cell.
10. Co-extrusion uses adhesives for binding between two layers.
a) True
b) False
Answer: b
Clarification: The statement is false. Co-extrusion doesn’t use adhesives for binding between two layers. Co-extrusion uses solely heat for binding different layers of plastics. Lamination used adhesives for binding between two layers. Hence, co-extruded films are generally thicker than laminated films.