Effect of Nano-silicon Nitride on the Mechanical and Electric Properties of Polypropylene Nanocomposite

The nanocomposites of polypropylene (PP) and nano-silicon nitride (chemical formula: Si ₃ N ₄ ) were prepared by a twin-screw extruder with isoactic PP granules, within which a proportion of PP granules were coated by nano-Si ₃ N ₄ modified with a silane coupling agent. The data of mechanical experiments showed that the impact strength of PP nanocomposite materials was improved markedly with up to 25% increasing magnitude while the tensile strength was decreased slightly with less than 10% decreasing magnitude as the content of Si ₃ N ₄ increased within the PP matrix. Electrical properties of PP nanocomposites showed that the average breakdown field strength of the nanocomposite PP materials was increased by 40% and 10% under AC and DC, respectively, compared to those of neat PP. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) spectra showed that the existence of nano-Si ₃ N ₄ within the PP matrix made the crystal phase of PP change to some extent due to the interaction of nano-Si ₃ N ₄ with PP matrix. It was found that the nano-Si ₃ N ₄ that possessed good dispersion into and chemical physical interaction with the PP matrix had a significant influence on the mechanical and electric properties of nanocomposite Polypropylene.