The effect of sulfate half-ester groups on the mechanical performance of cellulose nanocrystal-natural rubber composites

Cellulose nanocrystals (CNCs) are commercially produced via hydrolysis by sulfuric acid, resulting in the formation of sulfate half-ester groups on the surface of the nanoparticles. The sulfate half-esters promote good colloidal stability but could affect other properties of the CNCs. To study the impact of the sulfate half-ester groups on the mechanical properties of CNC-natural rubber composites, sodium hydroxide was used as a desulfation agent to partially remove this chemical functionality. Mechanical characterizations revealed that CNCs conferred outstanding mechanical properties to the composites. At the same time, differences in the amounts of sulfate half-ester groups had remarkable consequences for the tensile strength and the dynamic mechanical properties, while the vulcanization properties of the composites were less influenced.