Construction of dendritic structure by nano-SiO2 derivate grafted with hyperbranched polyamide in aramid fiber to simultaneously improve its mechanical and compressive properties

Weak transverse interaction of aramid fiber leads to low compressive strength, which is a prominent problem for its further application. In this study, a novel strategy by constructing dendritic structure in aramid fiber was conducted to solve the problem. Hyperbranched aromatic polyamide and linear aromatic polyamide are grafted on nano-SiO2 respectively, which will present absolutely different conformations. Structure of the SiO2 derivates was analyzed in detail by Fourier transform infrared spectroscopy (FTIR), dynamic laser scattering (DLS) and X-ray photoelectron spectroscopy (XPS). Compared with linear polyamide, hyperbranched polyamide tends to grow in multiple directions during polymerization due to significant steric effect, which can be confirmed by molecular simulation. When the SiO2 derivates were blended in aramid fiber, three-dimensional dendritic structure will be constructed by utilizing distinctive conformation of the hyperbranched polyamide. When loading content of nano-SiO2 derivate modified by hyperbranched polyamide in aramid fiber is 0.5 wt%, compressive strength of the fiber is improved by nearly 114%. Moreover, tensile strength and modulus are improved by nearly 13% and 9% respectively. Therefore, comprehensive performance of the aramid fiber can be remarkably improved by utilizing unique conformation of the hyperbranched polyamide, even if loading content of the SiO2 derivate is relatively low.