1. 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.
2. 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.
3. Which catalyst is used in the production of electrical grade laminates from m-f resin?
a) triethanolamine
b) sodium carbonate
c) sodium hydroxide
d) ethanamine
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.
4. Which of the following monomer molecule does cumarone and indene resemble to?
a) ethylene
b) styrene
c) butadiene
d) cumene
Explanation: Cumarone and Indene are aromatic in nature and bear a vinylic kind of structure attached to aromatic ring, that’s why the closely resemble s to styrene.
5. Which catalyst is used in the resinification reaction of cumarone and indene?
a) nitric acid
b) sulphuric acid
c) stearic acid
d) boron trifluoride
Explanation:In the resinification reaction of cumarone and indene, they are polymerized in the crude naptha without separation using sulphuric acid as the ionic catalyst.
6. How should the temperature be kept to prevent premature gelation of of polyimides?
a) 30-40 C
b) 60-80 C
c) 55-65 C
d) 50-55 C
Explanation:The second stage reaction or premature gelation of polyimides can be prevented by using dry reactants in an anhydrous system free from pyromellitic acid and keeping the temperature low i.e. below 50 C.
7. Which of the following diamines is not used to prepare useful polyimides?
a) m-phenylene diamine
b) benzidine
c) m-benzylene diamine
d) 4,4-diaminodiphenylether
Explanation: The diamines that are used to make useful polyimides are m-phenylene diamine, benzidine and 4,4-diaminodiphenylether. M-benzylene diamine cannot be used to prepare polyimides.
8. Which of the following monomer pairs polymerize to give Perlon U?
a) hexamethylene diamine and adipic acid
b) hexamethylene diisocyanate and 1,4-butanediol
c) hexamethylene diamine and 1,4-butanediol
d) hexamethylene diisocyanate and adipic acid
Explanation: Perlon U is chemically known as polyurethane and is prepared by the rearrangement polymerization of hexamethylene diisocyanate and 1,4-butanediol by a step-growth mechanism.
9. Which of the following properties of polyurethane rubbers is incorrect as compared to other rubbers?
a) higher tensile strength
b) excellent abrasion resistance
c) excellent resistance to oxygen
d) excellent resistance to acids
Explanation:The polyurethane rubbers have higher tensile strength than any other rubber, excellent abrasion resistance and resistance to oxygen and ozone. However they are less resistant to acids and alkalies than other conventional rubbers.
10. Where is the polyurethane foams extensively used as?
a) adhesive
b) paint rollers
c) printing rollers
d) fabric coatings
Explanation:Polyurethane foams are extensively used as paint rollers, cushioning materials, soft backing or padding, etc. polyurethane rubbers are used as printing rollers and fabric coatings.