Which of the following statements about melamine, a common thermosetting plastic used in kitchenware and laminates, are correct?

Introduction / Context:
Melamine is a widely used synthetic material that appears in tableware, kitchen utensils, electrical fittings, and decorative laminates. It belongs to the family of thermosetting plastics, which means that once moulded and set, the material cannot be remelted and reshaped by heating. The question gives three statements about melamine and asks which combination of them is correct, testing your knowledge about thermal behaviour, fire resistance, and heat conduction properties of plastics.

Given Data / Assumptions:

• Statement I: Melamine is a thermosetting plastic.
• Statement II: Melamine resists fire.
• Statement III: Melamine is a poor conductor of heat.
• We assume that the question refers to typical melamine formaldehyde resin used in household products.

Concept / Approach:
Thermosetting plastics, unlike thermoplastics, harden permanently when heated and shaped during manufacturing. They form extensive cross linked polymer networks that do not soften again on reheating. Melamine formaldehyde resins are classic examples of thermosetting plastics; they are heat resistant, hard, and used where durability and fire resistance are desired, for example in kitchenware and electrical switch covers. Plastics in general, including melamine, are poor conductors of heat, which is why they often serve as insulators and handles on hot cookware. Therefore all three statements about melamine are consistent with its known properties.

Step-by-Step Solution:
Step 1: Evaluate Statement I: Melamine is a thermosetting plastic. This is correct because melamine formaldehyde resin, once set, does not melt again on heating and keeps its shape. Step 2: Evaluate Statement II: It resists fire. Melamine based materials have good heat and flame resistance, which is why they are used for kitchen plates, cups, and electrical fittings. So this statement is also correct. Step 3: Evaluate Statement III: It is a poor conductor of heat. Plastics generally conduct heat poorly compared to metals, and melamine is used as an insulating material, so this statement is also correct. Step 4: Combine the evaluations. Since Statements I, II, and III are all correct, any option that omits one of them is incomplete. Step 5: Choose the option that states that all I, II, and III are correct, which is "All I, II and III".

Verification / Alternative check:
Practical observations support these conclusions. Melamine dinner plates hold hot food without softening, and their surface remains hard under normal kitchen temperatures, which indicates thermosetting behaviour. When exposed briefly to flames or high heat, melamine exhibits better fire resistance than many thermoplastics that may melt or deform. Additionally, melamine switch boards and handles on cookware remain comfortable to touch when metal parts next to them become very hot, demonstrating poor heat conduction. Technical literature on polymer science also lists melamine formaldehyde as a thermosetting resin used for heat resistant and flame retardant applications.

Why Other Options Are Wrong:
- Only I and II: This option accepts thermosetting nature and fire resistance but wrongly excludes the poor heat conduction property, which is also correct.
- Only I and III: This option omits fire resistance, even though melamine is indeed valued for this feature.
- Only II and III: This option suggests melamine is not a thermosetting plastic, which contradicts its well known classification.
- Only II: This recognises only the fire resistance and ignores both the thermosetting nature and poor heat conduction property, so it is incomplete.

Common Pitfalls:
Students sometimes confuse thermosetting plastics with thermoplastics and assume that all plastics soften on heating. Another common mistake is to believe that if a material is fire resistant, it must conduct heat well, but these are separate properties. Fire resistance concerns flammability and thermal degradation, whereas thermal conductivity deals with how quickly heat is transmitted. Remember that melamine is both a thermosetting plastic and a poor conductor of heat that shows good fire resistance, so all the given statements are correct.

Final Answer:
All three statements about melamine are correct, so the right choice is All I, II and III.