Preparation and characterization of hemp hurd powder filled SBR and EPDM elastomers

The effect of HP loading on the curing characteristics and mechanical properties of filled SBR and EPDM composites was investigated using bis-(3-triethoxysilylpropyl) tetrasulfide (Si69) as coupling agent. For all composites, 20 phr (part per one hundred parts of rubber) silica was used. The addition of HP enhances the vulcanization process of composites filled with silica. The hybrid reinforcement of HP and silica imparts good stiffness and toughness to filled rubber composites. An excess of HP will tend to form agglomerates in the rubber matrix, which adversely affects the silica-rubber matrix interfacial interaction, and consequently lowers the overall mechanical properties. The HP distribution and filler-rubber matrix interaction, which were analyzed by scanning electron microscopy and equilibrium swelling, explained well the changes in mechanical properties of composites filled with hybrid fillers. Dynamic mechanical analysis indicated that the composites exhibited higher Payne effect and storage modulus, and lower tanδ_max value with an increase of HP loading.