Despite the great potential of graphene as a nanofiller, its inhomogeneous dispersion in polymers remains a key challenge for the effective reinforcement of polymer. Herein, we exfoliated worm graphite into graphene by in situ liquidphase exfoliation, and the graphene was coated on the surface of polypropylene (PP) pellets by stirring. Further, we examined several treatment conditions and graphene contents. When graphene was centrifuged at 1000 rpm and the extrusion temperature of the composite was 230 C, the composite achieved optimal overall performance with the addition of only 0.2 wt% graphene. Compared to those of pure PP, the yield strength, bending modulus, and impact strength of the composites increased by 8.71%, 18.32%, and 45.75%, respectively. The thermal conductivity is increased by 29.5%. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) showed that the PP sample exhibited a significant heterogeneous nucleation effect due to graphene addition, improving the crystallization temperature and crystallinity of the composites. Contact angle measurement and scanning electron microscopy (SEM) revealed that the surface energy of graphene and PP are close to each other, and the graphene was well-dispersed in the PP matrix. Thus, this technique can optimize the processing properties and interface structure of graphenepolymer nanocomposites.

Few-layer molybdenum disulfide (MoS 2 ) was prepared by liquid phase exfoliation with in-situ modification as a nanofiller for polypropylene (PP). Scanning and transmission electron microscopies (SEM, TEM) showed uniform dispersion and excellent adhesion of MoS 2 within the PP matrix. When MoS 2 was centrifuged at 1000 rpm, the mechanical properties of the composite were greatly improved by adding only 0.5 wt.% of MoS 2 . The yield strength, bending modulus, and impact strength increased by 2.3%, 8.9%, and 44.03%, respectively. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) showed that the enhanced mechanical properties of the composites were related to PP crystallographic transformation. Thermogravimetric analysis (TGA) showed that the incorporation of 2 wt.% MoS 2 increased the maximum weight-loss temperature of the composites by approximately 30 C. The mechanisms for increasing thermal stability have been thoroughly demonstrated by band energy analysis. MoS 2 nanosheets have high aspect ratios and strong insulation with a change in band gap width compared to bulk MoS 2 , which is resulting in the stronger interactions at the MoS 2 /PP substrate interface. Furthermore, due to the outstanding carrier for rigid and thermally stable materials, MoS 2 composites displayed excellent mechanical and thermal properties. In addition, unlike PP, the melt flow rate (MFR) of composite materials is more conducive to downstream product processing. This will further promote the application scope of MoS 2 /PP composites.