Few layer graphene reinforced rubber compounds for tires

In last decade, “Nanofillers” have been explored extensively in rubber compounds to improve dynamic-mechanical properties. Three classes of nanofillers: Clay minerals, Carbon nanoTubes and Graphitic nanofillers have been often used. Most recently, an attention towards “graphene” as nanofiller was reported due to its exceptional mechanical, thermal and electrical properties. In present Ph.D. thesis, different types of commercially available “few layer graphene” were explored in both apolar and polar diene rubbers. These nanofillers were dispersed with melt mixing technique which is most suitable technology for industrial applications, such as for tires. Structural-morphological characteristics of the nanofillers were made with SEM, TEM, XRD and static adsorption isotherms. Features such as shape anisotropy, number of graphene layers in a stack, BET surface area, surface activity and porosity of nanofillers were obtained. Optical microscopy was employed to obtain filler dispersion index and estimation of filler’s aggregates, agglomerates. Dynamic mechanical properties of the rubber compounds were made with rheometric curves for scorch and curing time, rheological properties through RPA (strain sweep and frequency sweep) for viscoelastic properties and filler networking, stress-strain for tensile strength and multi-hysteresis cycles for energy dissipation, dynamic mechanical thermal analysis for high and low temperature properties, hardness of compound for processing features and tear strength tests for compound durability. The electrical properties of rubber compounds were investigated via dielectric AC conductivity and permittivity tests. Epoxidation of diene rubbers (low rate, <10%) was obtained to investigate the effects of presence of epoxy functional groups along polymer chains on filler networking, polymer-filler interactions, filler dispersion and dynamic mechanical properties of rubber compounds. Quantitative analysis of epoxidation, rate of epoxidation and its influence on rubber matrix (such as change in glass transition temperature) was investigated through 1NMR and DSC tests. Under multi-hysteresis stress-strain cycles, it was found that a stable filler networking can reduce hysteresis losses.