Engineering Chemistry S Datta

336 ENGINEERING CHEMISTRY
SHORT QUESTIONS AND ANSWERS
Q. 1. What is an adhesive?
Ans. Adhesive is defined as a substance capable of joining bodies together by surface
attachments.
Q. 2. What are the different theories that explain the mechanism of adhesion?
Ans. The theories explaining the mechanism of adhesion are:
(a) Mechanical theory
(b) Electrostatic theory
(c) Adsorption theory
(d) Diffusion theory
3. Mention the types of adhesives used for joining
(i) Wooden surfaces (ii) Glass and cloth (iii) Metals
(iv) Papers
(v) Plastics and rubbers
Ans. (i) Urea-formaldehyde and phenol-formaldehyde resins are used for joining wooden
surfaces.
(ii) Polyesters dissolved in styrene etc. are used for joining glass and cloth.
(iii) Epoxy resins are used for joining metals in aircraft industry.
(iv) Cellulose ethers, esters and also acrylics are used for binding paper.
(v) Silicon resins are used for bonding of plastics, rubber etc.
EXERCISES
1. What are adhesives?
2. Explain the different mechanisms of adhesive action.
3. Discuss the physical and chemical factors that influence adhesive action.
4. Write a brief note on natural and synthetic adhesives.
5. Mention a few important advantages and limitations of adhesives.
6. Describe the different steps of the bonding processes of adhesives.
7. (i) Adhesive action of a polymeric adhesive is influenced by
(a) Polar character
(b) Degree of polymerization
(c) Complexity of molecule
(d) All these
(ii) Adhesive used for bonding metals is
(a) Epoxy resin
(b) Polyesters
(c) Acrylics
(d) All these
(iii) Adhesive used for bonding leather for shoes
(a) Phenol formaldehyde resin
(b) Acrylics
(c) Polyvinyls
(d) Polyesters
(iv) Adhesives used for manufacturing furnitures of wood
(a) Urea-formaldehyde resin
(b) Polyesters
(c) Silicon resins