The compressive strength (N/mm²) of thermocol ranges between ............
🔬 Understanding Thermocol (Expanded Polystyrene - EPS)
Thermocol is the common brand name in some regions for Expanded Polystyrene (EPS). It is a rigid, closed-cell foam plastic made from polystyrene beads. Its structure consists of about 98% trapped air, which makes it extremely lightweight and an excellent thermal and acoustic insulator.
Key Properties:
• Lightweight: Due to its high air content.
• Excellent Insulator: Trapped air prevents heat transfer.
• Moisture Resistant: The closed-cell structure does not readily absorb water.
• Good Compressive Strength: For its low density, it can withstand significant compressive loads, making it suitable for use as a lightweight fill material.
⚖️ Detailed Analysis of Compressive Strength
The question asks for the compressive strength in N/mm². The provided source material gives the range as 110 to 145 kg/cm². To find the correct answer, we must convert these units.
Unit Conversion:
- 1 kgf (kilogram-force) is approximately equal to 9.81 N (Newtons).
- 1 cm² is equal to 100 mm².
- Therefore, 1 kg/cm² = 9.81 N / 100 mm² = 0.0981 N/mm².
Calculating the Range:
- Lower Limit: 110 kg/cm² × 0.0981 N/mm²/kg/cm² = 10.79 N/mm²
- Upper Limit: 145 kg/cm² × 0.0981 N/mm²/kg/cm² = 14.22 N/mm²
Evaluating the Options:
The calculated range is approximately 10.8 N/mm² to 14.2 N/mm².
Let's compare this to the given options:
• (a) 2.0 to 5.5 - Too low.
• (b) 5.5 to 10.6 - The lower end of the range.
• (c) 11.7 to 14.4 - This range aligns almost perfectly with our calculated values.
• (d) 15.0 to 17.5 - Too high.
Therefore, option (c) is the correct choice.
💡 Study Tips for Material Properties
- Master Unit Conversions: This question is a classic example where knowing the material property is not enough; you must also be comfortable converting units (especially kg/cm² to N/mm² or MPa). Remember the factor is approximately 0.1 (or 0.0981 for precision).
- Know the Material's Role: Thermocol is used for insulation and lightweight fill, not for primary structural support. This implies it has moderate, not extremely high, compressive strength.
- Remember Key Values: For common materials like Thermocol, it's useful to remember an approximate strength value. A value around 12-14 N/mm² is a good benchmark.