This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Thermosetting Polymers”.
1. The neighbouring polymeric chains in thermosets are held together by
a) Vander Waal’s force
b) Hydrogen bond
c) Covalent bond
d) Electrovalent bond
Explanation: The neighbouring polymeric chains in thermosets are held together by covalent bonds. A covalent bond is bond by the sharing of electrons and has good strength.
2. Select the incorrect statement from the following option.
a) Thermosets have 3-dimensional, cross-linked network structure
b) Thermosets cannot be remoulded, reused or reclaimed
c) Thermosets are hard, strong and brittle
d) Thermosets are soluble in suitable solvents
Explanation: Thermosets are insoluble in any solvent. They have 3-D cross-linked network structure and cannot be remoulded, reused or reclaimed. They are hard, strong and brittle.
3. Which of the following is not an example of thermosets?
c) Vulcanised rubber
Explanation: Epoxy, vulcanised rubber, Bakelite are some of the examples of thermosets. Teflon is not an example of thermosets. PTFE (Teflon) is best known for its use in coating non-stick frying pans and other cookware.
4. The condensation product of phenol and formaldehyde is known as
a) Phenolic resins
b) Urea formaldehyde resins
c) Polyvinyl chloride
Explanation: The condensation product of phenol and formaldehyde is known as phenolic resins or phenoplasts or PF resins. Phenoplasts include the expanded plastics obtained by introducing a blowing agent (foaming agent).
5. Which of the following condition is not true for the formation of Bakelite?
a) Excess of phenol
b) Excess of formaldehyde
c) Acid catalyst
d) Heat and curing agent
Explanation: Excess of formaldehyde is not required for the formation of Bakelite. Excess of phenol is required in the formation of Bakelite and it also requires an acid catalyst and heat and curing agent.
6. Which of the following condition is not true for the formation of Resite?
a) Excess of formaldehyde
b) Base catalyst
c) Acid catalyst
d) Neutral or acidic conditions and heat
Explanation: Acid catalyst is not used for the formation of Resite. It requires a base catalyst and excess of formaldehyde. It also requires neutral or acidic conditions of heat.
7. Select the incorrect statement from the following option.
a) Phenolic resins are hard, rigid and strong
b) Phenolic resins have good abrasion resistance
c) Phenolic resins are usually dark coloured, pinkish brown
d) Phenolic resins have poor chemical resistance
Explanation: Phenolic resins have good chemical resistance. All the other options are correct. Phenolic resins are hard, rigid and strong and have good abrasion resistance. They are usually dark coloured, pinkish brown.
8. Which of the following is not an application of phenolic resins?
a) Finishing of cotton textiles
b) Distributor heads of car
c) Domestic plugs and switches
d) Adhesives for grinding wheels
Explanation: Distributor heads of car, domestic plugs and switches, adhesives for grinding wheels, etc are some of the applications of phenolic resins. It also includes the expanded plastics obtained by introducing a blowing agent (foaming agent).
9. Urea formaldehyde resins are used as adhesives for plywood and furniture.
Explanation: Urea formaldehyde resins are used as adhesives for plywood and furniture. These resins are used in adhesives, finishes, particle board, MDF, and molded objects. UF and related amino resins are considered a class of thermosetting resins of which urea-formaldehyde resins make up 80% produced globally.
10. Select the incorrect statement about the Urea formaldehyde resins from the following option.
a) They are clear and colorless
b) They have good adhesive characteristics
c) They have low hardness and tensile strength than PF resins
d) They have excellent abrasion resistance
Explanation: Urea formaldehyde resins have better hardness and tensile strength than PF resins. All the other options are correct. They are colorless, clear and have good adhesive characteristics and excellent abrasion resistance.
Sanfoundry Global Education & Learning Series – Engineering Chemistry.
To practice all areas of Engineering Chemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.