Question

In shell moulding sand preparation, the resin is combined with a catalyst (hexa) to develop the_____

(a) thermoplastic characteristics

(b) toughness of the resin

(c) thermosetting characteristics

(d) viscosity of the resin

This question was addressed to me at a job interview.

My doubt is from Shell Moulding in division Special Casting Techniques of Casting-Forming-Welding I

Answer 1

Correct option is (c) thermosetting characteristics

The explanation is: The phenolic resins used in shell moulding have excess of phenol and acts like a thermoplastic material. During coating with sand the resin is mixed with a catalyst such as hexa methylene tetramine (hexa) in a proportion of 14 to 16 % so as to develop the thermosetting characteristics.