Constructing a gradient modulus interfacial layer on the surface of hydrotalcite enhances the interfacial properties of hydrotalcite/benzoxazine composites

Abstract The gradient modulus interface layer between hydrotalcite (LDH) and benzoxazine (Bz) polymer matrix was designed by grafting silane coupling agent KH560. The effect of varying proportions of LDH on the mechanical properties of the poly(LDH/Bz) was analyzed. When the LDH content was at 6 wt%, the mechanical properties of the poly(KH560‐LDH/Bz) exhibited enhancements of 78.31%, 68.58%, and 117.91% in tensile strength, flexural strength, and impact strength, respectively, compared to the poly(LDH/Bz). This improvement is attributed to the interfacial phase of KH560, which enhances the surface roughness and polarity of LDH, effectively buffering and equilibrating the modulus disparity between LDH and the polymer matrix. The surface tension between functionalized LDH and the matrix was calculated using the Harmonic Mean formula. Upon the incorporation of KH560, the surface energy difference between LDH and the matrix was reduced, thereby enhancing the interfacial compatibility between the two materials. The interfacial layer thickness of the functionalized LDH and benzoxazine polymer matrix was investigated using atomic force microscopy (AFM), which confirmed the presence of a graded modulus interfacial layer within the poly(KH560‐LDH/Bz). Highlights The mechanical properties of the poly(KH560‐LDH/BZ) were improved the most when the addition of KH560‐LDH was 6 wt%. KH560‐LDH has a low surface free energy, which is conducive to dispersion in the matrix. The composite with the addition of 6 wt% KH560‐LDH showed excellent thermal and thermomechanical properties. The interface layer thickness of the composite with 6 wt% KH560‐LDH was increased by 41.27%. The gradient modulus interface layer promotes stress transfer and dispersion in the matrix.