Synthesis and Characterization of CuMoO4/Zn–Al Layered Double Hydroxide Hybrids and Their Application as a Reinforcement in Polypropylene

CuMoO 4 /Zn–Al layered double hydroxide hybrids were synthesized by an ion-exchange and precipitation route. The results of X-ray diffraction (XRD) and transmission electron microscopy–energy-dispersive X-ray spectroscopy (TEM–EDS) analyses demonstrated the successful fabrication of CuMoO 4 /LDH hybrids. Subsequently, CuMoO 4 /LDH hybrids with different loadings were introduced into a polypropylene (PP) matrix by a master-batch-based melt-blending method for properties enhancement. With a CuMoO 4 /LDH hybrid loading of 5.0 wt %, the initial decomposition temperature of the PP composite increased by 61 °C. Differential scanning calorimetry (DSC) showed that the glass transition temperature ( T g ) and the melting temperature ( T m ) were both increased for PP composites. Moreover, according to microcombustion calorimetry (MCC) results, incorporation of CuMoO 4 /LDH hybrids markedly reduced the peak heat release rate (pHRR) and the total heat release (THR). Laser Raman spectroscopy (LRS) and scanning electron microscopy (SEM) images of the char residues of PP composites showed that the addition of CuMoO 4 /LDH hybrids into the PP matrix results in the formation of more stable and continuous char than LDH. The dramatic properties enhancement of PP composites is primarily due to the synergistic effects between CuMoO 4 and LDH nanosheets: the adsorption and barrier effect of LDH nanosheets slowed the thermal degradation of the polymer matrix and inhibited the heat and flammable gas release, whereas CuMoO 4 catalyzed the formation of more stable and graphitized char, which further improved the thermal and flame-retardant properties of PP composites.