FROM MASTER CURVES FOR THE MECHANICAL REINFORCEMENT OF RUBBER BASED NANOCOMPOSITES TO LIGHTWEIGHT MATERIALS

sp2 carbon allotropes are efficient reinforcing fillers for rubber materials. CB is made by primary nanometric particles, fused together to form micron-size aggregates. Nanofillers bring individual nanometric particles into the polymer matrix: they have large surface area and hence large interfacial area with the polymer matrix. Nanofillers such as graphene related materials (GRM) and carbon nanotubes (CNT) have anisometric nature. Nanoplatelets and nanofibers achieve the largest values of interfacial area and can exhibit preferential orientation inside a matrix, leading to anisotropic properties. In this work, the reinforcing ability and the anisotropy of mechanical reinforcement of CB, CNT and GRM1 in rubber matrices such as poly(1,4-cis-isoprene) and poly(styrene-co-butadiene) was investigated. Correlation was studied between mechanical reinforcement and filler-polymer interfacial area (i.a.), defined as the product Ai·ρ·φ, where Ai is the surface area (assumed to be equal to BET surface area), ρ is the filler density and φ is the filler volume fraction2. Samples based on nanofillers were transversally isotropic: properties were very similar inside the sheet plane and very different in the orthogonal direction. The initial modulus in the direction orthogonal to the sheet plane, was taken as the index of mechanical reinforcement. It was observed that for i.a. value up to about 27 μm-1, experimental points due to CNT, CB, as well as to hybrid filler systems, lie on a sort of master curve. Thanks to the above mentioned master curves, composites were designed and prepared with lower density.