Effect of liquid resol on the mechanical and thermal properties of EPDM/Kynol elastomeric heat shielding materials

The state of the art of heat shielding materials is represented by a rubber matrix reinforced with aramid (Kevlar®/Twaron®) or phenolic (Kynol®) pulp or fibers that exhibit excellent thermal stability and mechanical properties. In this work, Kynol® short fibers were used as reinforcement for an EPDM matrix modified with liquid phenolic resin and the heat shielding materials were studied in terms of mechanical, thermal, and ablative properties. A chemical coupling agent was used to improve the adhesion of the polar phenolic matrix with non‐polar EPDM phase. It was found that the thermal stability of the heat shielding materials was not affected by the presence of phenolic that, on the other hand, increased the deformability of rubber. In oxy‐acetylene torch tests, EPDM/Kynol formulation, with no addition of liquid phenolic, was characterized by a carbonaceous residue with the smaller dimensional change and the higher adhesion on the virgin material while the presence of the phenolic reduced the structural integrity of char and its adhesion to the substrate. The value of the heat capacity of composites increased with the increase of the phenolic content