Polymer-based materials face increasing limitations imposed by European legislation due to their environmental impact, namely carbon footprint and recycling capabilities. Radome antennas often use these materials due to their electrical and mechanical properties and, therefore, there is a search for alternative dielectrics. Here, we evaluate the performance of cork + nitrile rubber and cork + chloroprene rubber composites to be used in radomes at E-band for 5G backhaul communications. Both materials present a dielectric constant of around 1.6 and a loss tangent of 5×10-2 at 50 GHz. We fabricated a 1-ft reflector antenna which we covered with a cork-rubber radome. We measured the radiation pattern and isotropic gain across the 71-86 GHz frequency band. Results indicate that the cross-polarization slightly deteriorates with the use of cork+rubber and the gain drops by around 1 dB, when compared to an ABS radome used by Radio Frequency Systems.