Endothermic reactions with polymers

Aug 2016
I am currently working at a Bowden cable manufacturing firm in India over the summer. Some of our cables, which were used with the gearboxes in trucks were rejected and sent back to the plant. The sheathing of these cables, when cut open, revealed nearly ice cold steel fibers (~5 degrees Celsius). I will now describe the features and materials used in the outer cable. The innermost layer is made of PTFE, upon which there is a layer of HDPE. Then come the high carbon steel fibers which were cold (around four percent carbon) and then the outermost sheathing of LDPE. All these layers are stuck tightly, with very little or no space for fluid dispersion. The hollow inner part of the cable is the only space were a fluid can move freely. This cable took two months to return to the factory, yet the fibers were cold. The insulation provided by the LDPE is being tested currently, yet it can be assumed that the insulation isn't the primary factor and the cooling of the steel fibers was because of some kind of endothermic reaction. I am new to this kind of testing and haven't studied much chemistry beyond high school and have been using google to try and figure out the chemicals that could have reacted with the LDPE/HDPE or the steel fibers. The chemical could have permeated through the PTFE membrane (?). Here are the pictures of the cross section and the length of the Bowden cable:



Please let me know of an online resource of some kind where I could possibly filter through the reactants that react with LDPE/HDPE/steel endothermically and are likely to be found in the fluids used in trucks and other vehicles. Otherwise any ideas that seem applicable here are of course welcome. Thank you.