Breathable butyl rubber non-woven mats have been successfully produced by the electrospinning technique, providing a fibrous membrane with controlled porosity and surface area. These properties are directly related to the barrier properties of the product, including water vapor transmission, air flow resistance, aerosol resistance, and the transportation of chemical vapors. Butyl rubber is also known as a highly chemical resistant elastomer material, which can be used for applications requiring high elongation. The use of carbon black filled elastomers provides the ability to tailor the properties, such as processability, mechanical properties, and barrier properties through proper selection of carbon black type and loading. In this work, the structure and mechanical properties of electrospun butyl rubber non-woven mats were investigated using a series of carbon black types with variation in particle size and structure. Fiber diameter decreased. with decreasing particle size and increasing carbon black structure. Mechanical properties can be explained by variation in density and fiber morphology of membranes. Decreasing carbon black particle size and increasing structure decreased the density, and increased tensile strength, ultimate elongation and modulus.