Increasing inorganic nanoparticle impregnation efficiency by external pressure for natural fibers

•We developed a novel inorganic nanoparticle impregnation process for nature fibers.•An external pressure was introduced to this process.•The impregnation of nanoparticle content was significantly increased.•The impregnation efficiency for reducing the fiber porosity increased dramatically.•The mechanical properties of the polyester composites were highly enhanced.

The effect of external pressure during the inorganic nanoparticle impregnation (INI) process on the content of impregnated calcium carbonate nanoparticles in kenaf fibers was investigated. The in situ INI process was used to introduce the calcium carbonate nanoparticles into the fibers. The retted kenaf fibers were immersed into calcium chloride solution with various pressures and then treated by sodium carbonate solution to produce calcium carbonate nanoparticles impregnated kenaf fibers. It was found that the calcium carbonate content increased by 76.7% when a 13.8 MPa external pressure was applied during the calcium chloride immersing process. The impregnation efficiency for reducing the fiber porosity was increased by 70.1%. The mechanical properties, including modulus of elasticity, modulus of rupture and tensile strength of the INI-treated fiber/polyester composites were enhanced by 43%, 79% and 86% compared with the un-treated fiber/polyester composites.