Question

The resin mainly used in shell moulding is

• A. Phenol formaldehyde
• B. Ethanol formaldehyde
• C. Phenol
• D. Ethanol

Hint:

Shell moulding always uses a {thermosetting resin}, most commonly phenol formaldehyde.

Answer 1

The Correct Option is A

Shell moulding coats sand with a resin, drops it onto a metal pattern heated to roughly \( 230\text{-}260^\circ\text{C} \), and needs that resin to cure into a rigid shell within seconds.

1. Phenol formaldehyde: a genuine thermosetting resin that cross-links rapidly under this heat, forming the strong shell used in the process.
2. Ethanol formaldehyde: not a real cross-linking binder system used in foundries.
3. Phenol: just one raw ingredient, not a cured resin on its own.
4. Ethanol: a solvent, incapable of binding sand at all.

So the resin used in shell moulding is phenol formaldehyde.

Answer 2

Shell moulding (the Croning process) was specifically developed around a resin that could be pre-coated onto sand and then rapidly hardened by contact heat alone, and comparing the options against that specific requirement is informative.

1. Phenol formaldehyde: resin-coated sand using phenol formaldehyde was the material choice that made the Croning shell process practical, since it could be dry-coated onto sand grains in advance and then cured almost instantly by the heat of the pattern alone, with no separate catalyst step needed for the shell to set.
2. Ethanol formaldehyde: no established industrial pre-coated sand system uses this combination for shell moulding.
3. Phenol: lacking formaldehyde to react with, phenol alone cannot form the cured film needed to coat sand grains.
4. Ethanol: being a volatile solvent, it would simply evaporate under the pattern's heat rather than forming any binding film.

The historical and practical basis of the Croning shell process confirms phenol formaldehyde as the resin used.

Therefore, the correct answer is Phenol formaldehyde.