This set of Food Packaging Technology Questions and Answers for Freshers focuses on “Optical, Mechanical Properties of Thermoplastic Polymers”.
1. Which of the following optical properties cannot be measured by spectrophotometer?
a) Gloss
b) Haze
c) Optical Distortion
d) Yellowness Index
View Answer
Explanation: Gloss cannot be measured by spectrophotometer. It is measured by a glossmeter. Gloss is an inherent property of any material. It is a measure of light reflected by the surface of a material. Rest of the optical properties is measured by spectrophotometer. Haze is produced by scattering of light when passed through a material. Optical Distort is the ability to distort light. Yellowness Index is the parameter to check the deviation of color of the material towards yellow or white.
2. Which of the following materials is used for Grease Resistance Testing?
a) Quinone
b) Azo dye
c) Sudan Dye
d) Malachite green
View Answer
Explanation: For plastics, Grease resistance can be performed directly in pouches using groundnut oil colored with Sudan dye. Grease resistance is conducted to measure the resistance of a plastic towards grease, by exposing it to grease containing dye and measuring the time it takes to show at the unexposed side.
3. What is the correct order of their tensile strength?
a) PSU < PC < PVC < PS
b) PC < PSU < PS < PVC
c) PC < PS < PSU < PVC
d) PVC < PS < PC < PSU
View Answer
Explanation: The correct order of tensile strength of given plastics is – PVC<PS<PC<PSU. The tensile of the mentioned plastics is – Polyvinyl Chloride:40-50 N/mm2, Polystyrene:50-65 N/mm2, Polycarbonate:65-70 N/mm2, Polysulfone:70-80 N/mm2.
4. Thermoplastics have crosslinking of monomers.
a) True
b) False
View Answer
Explanation: The statement is false. Thermoplastics do not have crosslinking of monomers. Because of the absence of this chemical reaction, the processing cycles are comparatively short. Thermoplastics are made by linear chain polymerization of monomers.
5. Arrange the following in correct order of modulus of elasticity.
a) PVC < Teflon < PET < Polyimide
b) Polyimide < PET < Teflon < PVC
c) PVC < PET < Teflon < Polyimide
d) Polyimide < Teflon < PET < PVC
View Answer
Explanation: Modulus of elasticity is a term which measures a substance’s resistance to being deformed when a stress is applied on it. The modulus of elasticity is in the order –Polyimide:510MPa, Polyethylene Terephthalate (PET):450MPa, Teflon:217MPa, Polyvinyl Chloride (PVC):110MPa.
6. Which of the following thermoplastics is transparent?
a) Polyphenylene Sulfide (PPS)
b) Polystyrene (PS)
c) Polyaryletheretherketone(PEEK)
d) Polypropylene (PP)
View Answer
Explanation: Transparency is related to the degree of regularity in the arrangement of molecules. This is due to the amorphous arrangement of the macromolecules. Opaque plastics have more of a semi-crystalline to crystalline arrangement.
7. Which of the following plastics is opaque?
a) Polyethylene Terephthalate (PET)
b) Polycarbonate (PE)
c) Polyphenylene Sulfide (PPS)
d) Polyvinyl Chloride (PC)
View Answer
Explanation: Opaque plastics are those which block all lights and doesn’t let light to pass through it. Some plastics like Polyphenylene Sulfide are naturally opaque in nature. Other plastics can be made opaque by using additives. However, using some techniques, even opaque plastics can be made transparent.
8. __________ is the measure of ease with which one layer slides over another layer of plastic.
a) Flex Resistance
b) Blocking
c) Coefficient of friction
d) Crease Resistance
View Answer
Explanation: Coefficient of friction is the measure of ease with which one layer slides over another layer of plastic. Blocking is the ability of two films to be in such a contact, so as to eliminate any air present in between the layers. Crease or flex resistance is the resistance of a plastic against crease of flexing by repeatedly folding the film forward and backward at a given rate.
9. Which of the following test is used to measure tensile strength of plastic?
a) Blocking
b) WVTR
c) Creep Test
d) OTR
View Answer
Explanation: Creep Test is used to measure tensile strength of plastics. In this the specimen is subjected to a static load. The results are noted accordingly for long term behavior of plastics. Blocking is the ability of two films to be in such a contact, so as to eliminate any air present in between the layers. WVTR and OTR are Water Vapour and Oxygen Transmission Rates.
10. Which of the following is not a term used for defining optical property?
a) Birefringence
b) Yellowness Index
c) Grammage
d) Refractive Index
View Answer
Explanation: Grammage is not used to define optical property. Grammage is expressed as grams per square meter and is used to express paper density. The terms used for defining optical property include – Birefringence, clarity, transmittance, reflectance, refractive index, haze, gloss and yellowness index.
Sanfoundry Global Education & Learning Series – Food Packaging Technology.
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