This set of Food Packaging Technology Multiple Choice Questions & Answers (MCQs) focuses on “Coating and Laminating in Thermoplastics”.
1. A single laminate layer is thicker than _____
a) 15 μm
b) 6 μm
c) 1 μm
d) 10 μm
View Answer
Explanation: A single laminate layer is thicker than 6µm. A laminate is made up of two or more layers which can be plastic or non-plastic. But at least one layer must be a plastic. All layers to make a laminate must be thicker than 6 μm. However, there is no upper limit for this.
2. Coating is the bonding of two or more layers.
a) False
b) True
View Answer
Explanation: The above statement is false. Coating is the process of applying one or more layers of a fluid or melt to the surface of a material, while laminating is the bonding of two or more webs/layers.
3. Materials other than a thermoplastic can be used in a laminate.
a) True
b) False
View Answer
Explanation: The given statement is true. Materials other than a thermoplastic can be used in a laminate. A laminate is defined as any combination of distinctly different plastic film materials or plastic plus non plastic materials (typically paper and aluminium foil).
4. In the process of surface treatment before lamination or coating, the surface energy is ______
a) Constant
b) Decreased 10 fold
c) Increased
d) Decreased
View Answer
Explanation: In the process of surface treatment before lamination or coating, the surface energy is increased. This is done to improve wet-out and adhesion of coatings, inks and adhesives used. Improved wet-out maximises the contact area and attractive forces between the films.
5. Which of the following treatments increases the surface energy by using electricity?
a) Chemical Treatment
b) Priming
c) Flame Treatment
d) Corona Treatment
View Answer
Explanation: Corona treatment involves the application of a high voltage (10–40 kV) low frequency (10–20 kHz) discharge across a fixed air gap between an electrode and an earthed conductive roller which carries the film. The corona treatment cleans, oxidizes and activates the surface by converting it from a nonpolar to a polar state by bombarding it with ozone, O2 and free radicals of O2. This increases the surface energy and results in the substrate surface being more compatible with a freshly oxidized thermoplastic surface, thus promoting adhesion between the two.
6. For Flame Treatment prior to laminating and coating, the temperature time combination is _____
a) 2000-4000°C, 5s
b) 1000-2800°C, 1s
c) 3000-5000°C,10s
d) 1000-2800°C, 15s
View Answer
Explanation: For Flame Treatment prior to laminating and coating, the temperature time combination is 1000-2800°C, 1s. If the temperature or time increases, the film degrades and becomes weak. If the temperature or time is less than required, the film would have a lower surface energy than required.
7. Optimum primer weight for priming films is defined in _____
a) mg/m2
b) μg/m2
c) mg/cm2
d) mg/mm2
View Answer
Explanation: Optimum primer weight for priming films is defined in mg/m2. The quantity of primer is a critical aspect because thicker primer results in lesser cohesive forces and hence loss of adhesiveness. Thinner primer wouldn’t result in required adhesion.
8. Which of the following processes is done to remove surface contaminants?
a) Priming
b) Chemical Treatment
c) Corona Treatment
d) Flame Treatment
View Answer
Explanation: Chemical treatment is an essential step in surface treatment to remove surface contaminants. Rest of the treatments- priming, corona treatment and flame treatment are mainly done for increasing surface energy. Chemical treatment has mainly three steps- cleaning, etching and rinsing.
9. Which of the following plastics is used in the lamination of paperboards?
a) LDPE
b) PS
c) PVC
d) HDPE
View Answer
Explanation: LDPE is used in the lamination of paperboards. Compares to other thermoplastics, LDPE- Low Density Polyethylene offers a greater strength, seal integrity and resistance to cracking and flaking off. It also provides a greater resistance to moisture and has greater flexibility.
10. Which of the following materials is used for solventless laminating?
a) Sodium silicate
b) Polyester isocyanate
c) Rubber latex
d) Dextrin
View Answer
Explanation: Polyester isocyanate is used for solventless laminating. Solventless laminating is the process of bonding together two webs by curing in absence of solvents. Polyester isocyanates is used for curing the laminate.
11. Which of the following lamination methods doesn’t require an adhesive for lamination?
a) Dry bonding lamination
b) Solventless lamination
c) Extrusion lamination
d) Wet bonding lamination
View Answer
Explanation: Extrusion lamination doesn’t require an adhesive for lamination. It causes adhesion by heat and pressure during the process of extrusion. Dry and wet bonding lamination used aqueous or solvent based adhesives. Solventless lamination uses a curing agent for adhesion.
12. ASTM stands for _____
a) American Society for Testing Machines
b) American Society for Tempering Machines
c) American Society for Testing and Measurements
d) American Society for Testing Materials
View Answer
Explanation: ASTM stands for American Society for Testing Materials. ASTM is an international standards organisation which sets up standards for various miscellaneous materials including metals and plastics.
13. Lacquering and lamination are the same terms.
a) True
b) False
View Answer
Explanation: The given statement is false. Lacquering is a term used for coatings on can, mainly to provide it a resistance against discoloration and corrosion. Whereas, lamination is a term used for combination of two or more materials into a single homogeneous packaging webs using adhesive, solvent or heat.
14. Which of the following materials is the outermost lamination layer in tetrapacks?
a) Polyester
b) Polypropylene
c) Polyethylene
d) Polystyrene
View Answer
Explanation: Polyester is the outermost lamination layer in tetrapacks. Polyester provides strength to the tetrapack. It also acts as an excellent printable surface. Polypropylene is the innermost layer, the food contact layer. Polyethylene and polystyrene is not used in tetrapacks.
15. Polymers used for packaging films must have a surface energy – _______
a) 5-25 mNm-1
b) 29-45 mNm-1
c) 45-55 mNm-1
d) 10-25 mNm-1
View Answer
Explanation: Polymers used for packaging films must have a surface energy- 29-45 mNm-1. The standard is set by ASTM. Also, the surface energy of the substrate should be 7-10 mNm-1 higher than the surface tension of coating being applied.
Sanfoundry Global Education & Learning Series – Food Packaging Technology.
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