Engineering Questions with Answers - Multiple Choice Questions
Polymer Engineering MCQ’s – Amino Resins
1 - Question
Which of the following is not a characteristic of a cured urea resin?
a) hard and rigid
c) excellent electrical insulation
d) impart colour and odour to food & drinks
Explanation: The cured urea resins do not impart colour and odour to food and drinks with which they may come in contact. They are hard, rigid and non-inflammable but they char around 200 ᵒC. They exhibit excellent insulation properties.
2 - Question
Which of the following is used as a lubricant in the moulding powder from urea-formaldehyde resin?
a) zinc stearate
b) ammonium sulphamate
c) trimethyl phosphate
d) none of the mentioned
Explanation: Metal stearate like zinc stearate, aluminium stearate, etc. (quantity about 1%) is used as a lubricant in the moulding powder.
3 - Question
Which of the following can be used to improve the shelf-life of moulding powders from urea-formaldehyde resin?
a) ammonium sulphamate
b) magnesium stearate
Explanation: To improve the shelf life of moulding powders, it should be stored in cool place. Incorporation of a small amount of a stabilizer such as hexamine further improves shelf-life.
4 - Question
What is the ratio of urea o formaldehyde to produce useful resins?
Explanation: Urea is potentially tetrafunctional and the use of 1.5 to 2 moles of formaldehyde for each mole of urea yields useful resins
5 - Question
What is the pH requirement for the preparation of adhesive resins from urea formaldehyde resin?
Explanation: The adhesive resins are prepared in the water solube form, stabilized by maintaining the pH at 7.5 and a solid content of nearly 50-70%.
6 - Question
Which of the following is commonly used as hardening agent for urea-formaldehyde resins?
a) ammonium chloride
b) sodium hydroxide
c) aluminium chloride
d) sodium carbonate
Explanation: The resins are hardened under acidic conditions and ammonium chloride is used as most common hardening agent for resins which acts as acid donor.
7 - Question
What is the approximate reaction temperature in the formation of melamine, when cyanamide is heated to give dicyandiamide?
a) 300 C
b) 70 C
c) 100 C
d) 180 C
Explanation: Dicyandiamide is produced by heating cyanamide at a temperature of about 70-80 C.
8 - Question
What is the initial molar ratio for melamine to formaldehyde in commercial resinification reaction?
Explanation: An initial molar ratio of 1:3 for melamine to formaldehyde is used in commercial resinification reactions.
9 - Question
What are the temperature and pressure conditions for the compression moulding of m-f resin?
a) 200-250 C and 1000-3000 psi
b) 150-170 C and 2000-8000 psi
c) 150-170 C and 1000-3000 psi
d) 200-250 C and 2000-8000 psi
Explanation: The temperatures in the range of 150-170 C and pressure of the order 2000-8000 psi are employed for compression moulding of m-f resins.
10 - Question
What is the extensive use of melamine-formaldehyde resins?
a) decorative laminates
b) stove enamels
c) air-drying lacquers
d) art and jewellery
Explanation: The exceptional hardness, solvent resistance and heat stability qualities of m-f resin make it suitable to be used as decorative laminates.
11 - Question
Which catalyst is used in the production of electrical grade laminates from m-f resin?
b) sodium carbonate
c) sodium hydroxide
Explanation: The electrical grade laminates are produced by using triethanolamine as condensation catalyst rather than sodium carbonate as catalyst. They are usually made by impregnationg electrical-grade glass cloth with the triethanolamine catalyzed resin.