Effect of surface functionalized SiO2 nanoparticles on the physical and mechanical properties of wheat straw/LDPE composites

The scope of the present article is to study the effect of surface-functionalized SiO2 nanoparticles on the physical and mechanical properties of wheat straw flour reinforced by low-density polyethylene composites. The high hydrophilicity of nano-SiO2 originates from their amorphous structure and can induce the particles to be easily agglomerated and hardly dispersible in polymer matrix. Consequently, surface modification of SiO2 nanoparticles is the most effective way to vanquish these problems. Firstly, the SiO2 nanoparticles were modified by 3-aminopropyl-trimethoxysilane (APTMS), and then the wheat straw flour / low-density polyethylene composites containing different percentages of functionalized nano-SiO2 (0, 1, 2, 3 and 5%) were prepared via a melt compounding. Changes in the chemical structure of treated SiO2 were tracked by Fourier transform infrared (FTIR) spectroscopy. Field emission scanning electron microscopy (FESEM) was also investigated to study the distribution of SiO2 nanoparticles in the composites. Finally, the physical and mechanical properties (tensile strength, tensile modulus, bending strength, and bending modulus) of the nanocomposites were evaluated. The appearance of N–H bond at 695 cm−1 and aliphatic C–H bonds at 2841 cm−1 and 2947 cm−1 were indications of successful grafting of APTMS on the functionalized SiO2 nanoparticles. According to the results, using functionalized SiO2 nanoparticles as a reinforcing agent in wood plastic composites resulted in an increase in the tensile and bending strengths and a decrease in the water absorption of the composites.