Polystyrene Box Insulation Test: How Well Does EPS Perform?

Test Overview

This insulation test compared the thermal performance of three common types of temperature-controlled packaging: - Expanded polystyrene (EPS) boxes - Waxed cardboard boxes - Plastic corrugated boxes Each box was evaluated on how long it could maintain an internal temperature below 5°C over a 72-hour period under two different ambient temperature conditions: 5°C (cold) and 15°C (warm). 

Test Method

All boxes were packed with:

• 3.3kg of rainbow trout (as the perishable product)
• 1.8kg of frozen ice sheets (as the cooling medium)

The packing method was consistent:

1. A base layer of fish
2. A layer of ice sheets
3. Another layer of fish
4. A final top layer of ice sheets
5. Lid sealed securely

Before the test began, all boxes were conditioned in 0°C cold storage for 24 hours to stabilise the internal temperature.

Two controlled tests were then conducted:

Test One: Cold Ambient – chamber held at 5°C
Test Two: Warm Ambient – chamber held at 15°C

Each box was fitted with three thermocouple sensors (top, centre, bottom) to record internal temperatures across the box. The test duration for both conditions was 72 hours. 

Test Results Summary

Cold Test (5°C ambient): The 6kg long EPS polystyrene box maintained an internal temperature below 5°C for the full 72 hours. It significantly outperformed both the waxed cardboard and plastic corrugated alternatives, which failed to sustain temperatures below 5°C for the full duration.

Warm Test (15°C ambient): While the EPS box did not maintain sub-5°C temperatures for the entire 72 hours under warm conditions, it still outperformed the cardboard and plastic options by over 12 hours. 

Additionally, the results showed that EPS boxes are capable of maintaining internal temperatures below 0°C, depending on the ambient temperature and configuration of cooling media. 

Conclusion: Why EPS Is Still the Best

This test demonstrates that EPS polystyrene boxes are the most effective solution for transporting fresh foods in both cold and warm shipping environments. EPS provided superior thermal performance across both tests, offering longer-lasting temperature control compared to waxed cardboard and plastic corrugated boxes. For cold chain logistics and chilled food shipping, EPS remains the most reliable and resource-efficient packaging option. 

Where to Buy Polystyrene Boxes

EPS polystyrene fish boxes are available to purchase online from JB Packaging. We also offer sample boxes if you would like to test them for your specific shipping application. Browse Polystyrene Boxes