A lesser-known factor when it comes to safely using your FIBCs is understanding how product and atmospheric loading temperatures can affect your bulk bags. When discussing product temperatures, it is important to understand that the tapes used to weave FIBC fabric is manufactured through an extrusion process. During extrusion, PP pellets are melted to a liquid that is then forced through a die into a very thin sheet of material and cooled in a water bath.

Due to this manufacturing process, the chemical properties of the polypropylene can become highly susceptible to melting in conditions where the product and/or environmental temperature exceeds the material melting point.

Product Loading Temps and FIBC Melting

The Polypropylene used in your FIBC has a relatively low melting point of 230°F. This means that the material will become more elastic as product temperatures increase and will begin to melt as temperatures approach 230°F. While an FIBC may be able to withstand product temperatures up to 230°F, the material may be adversely affected as product temperatures increase which will reduce the bag’s performance and safe handling. It is recommended that product temperatures be between 50°F – 149°F to ensure the material is not compromised.  Heavier fabric weights and breathable fabrics can help withstand higher temperatures if it’s not possible to fill at a temperature below the recommended 149°F.

Environmental Loading Temperatures

Regarding environmental loading temperatures, it is recommended that bags are stored and filled in an environment where temperatures are between 50°F – 140°F. If it the environmental temps exceeds 176°F there is no escape route for the heat generated inside the bag which will result in dimension instability of the product, leading to a possible bag failure.

Obviously, atmospheric temperatures will not naturally reach 176°F. It is, however, important to consider where your bags are being stored or staged once loaded… i.e. near equipment (possibly a furnace, dryer, or kiln) that may produce radiant heat.

On the negative side, Polypropylene is also a homopolymer, which can become brittle like glass when exposed to extremely low temperatures. This point is defined as the “glass transition point.” This brittle point can be reached when temperatures drop below 14°F. These extremely cold temperatures may result in damage of component or loop breakage which could lead to a catastrophic bag failure.

What To Do if Your Product Temp is Higher than 200°F

There are several products on the market that will help your FIBCs safely support higher loading temperatures. The inclusion of a thick aluminum liner used with a breathable outer bag is an option. You might also consider utilizing bags woven with other materials, like polyester, if the loading temperature exceeds 200°F.

For more information on product or environmental loading temps and how they may affect your FIBCs, please contact your FlexSack sales representative or send your questions to


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