ETL is a fully woven reflective liner that is hung into a general purpose ISO shipping containers and allows for forklift, hand or slip sheet loading. Once loaded, it is completely sealed providing a closed off temperature controlled environment for the goods inside the container.
The effectiveness of ETL preventing heat transfer is by taking care off all major heat transfer factors which contribute more than 96% of the total heat transfer in the structure. To understand how ETL liner works, we must first understand the fundamentals of heat transfer, which contributed by 3 major factors: -
1. Radiation Heat Transfer
Radiation heat is the heat transfer from warm surface to cooler surface through air space. E.g. sunlight
2. Conduction Heat Transfer
Conduction heat is the heat transfer through solid or fluid materials by physical contact. E.g. boiling water
3. Convection Heat Transfer
Convection heat transfer is the heat transfer by physical movement of air or liquid. E.g. warm air
In all 3 factors, radiation heat is the major contributor of the total heat transfer for a close structure (e.g. building, container), which is about 80%; conduction and convection with a total about 20%.
ETL Is effective against radiant heat transfer as the liner is made out of high reflective aluminum materials which reflect 97% of radiant heat. This special installation method also creates air gap in between the container wall and roof to prevent conductive heat transfer. A total seal environment created by the ETL prevents movement of air and thus preventing convection heat transfer.
On the other hand, a 5 layers lamination provide maximum moisture vapor and oxygen barrier as the WVTR (Water Vapor Transmission Rate) for ETL is<0.09g/sqm/day. The ability to prevent major temperature fluctuation will prevent container from reaching the dew point (100% RH), resulting condensation during shipment.
In order to prevent condensation, we must first understand “RELATIVE HUMIDITY (RH %)”.
RH% - The amount of water vapor in the air at a given temperature
When the amount of water vapor increases, RH% increases. Until the point where air can no longer hold anymore water vapor, the air has reached its saturation point or 100% RH. Since the air is now holding all the water it can, any increase in water vapor will start to condense on local surfaces cooler than the air temperature, as a result, CONDENSATION HAPPENS!
The point where air reached it 100% RH, the air is said to reach its DEW POINT TEMPERATURE – The temperature where condensation happens.
Factors that caused condensation: -
• Increase in RH% due to increase in water vapor in the air
- Products releasing water vapor (Evaporation Rate)
- Infiltration, uncontrolled air leakage into the container
• Reduce in container temperature
- When the temperature goes down, RH% inside the container increase, until it reached 100% RH (dew point temperature)
ETL is an effective agent against condensation as it: -
√ Perform as a air barrier – prevent uncontrolled air leakage inside the container
√ Perform as a vapor barrier, very low WVTR, less then 0.09g/sqm/day
√ Prevent major temperature fluctuation happen inside the container during shipment. Avoid reaching of dew point temperature
√ Prevent over heated inside the container thus reducing vapor evaporation rate
√ For products which releasing moisture during shipment, desiccant have to use together with ETL liner, which creating the envelopment where temperature and RH% is under control
Besides it's effectiveness against heat & moisture, ETL is also tough, lightweight and easy to handle.
ETL provides excellence tensile strength and tear resistance with lower material grammage. Hence, ETL have excellence advantages in handling as describe as below: -
√The product is light in weight and thickness which easy to handle and improve installation efficiency.
√ The product provides maximum tear resistance which manage to withstand rough handling
√ Allows for rough loading using forklift without damaging the liner
√Light in weight and low in thickness which do not affect the container loading capacity