Hybrid multiwalled-carbon nanotube/nanosilica/polypropylene nanocomposites: Morphology, rheology, and mechanical properties

Polymer composite are very interesting materials in automotive industry. Nanocomposites play a crucial role in the automotive parts and cars weight reduction fields. Hybridization of polymer nanocomposites is appeared as a process of choice in obtaining the required property/weight ration. Simple and hybrid nanocomposites of polypropylene (PP) blend with carbon nanotubes (CNTs) having different aspect ratios and nanosilica at different nanosilica contents were prepared in molten state in an internal mixer. Scanning electron microscopic images along with rheological and tensile properties revealed that only 0.2 wt% CNT is high enough to finely disperse nanosilica particles in PP matrix in the absence of any chemical compatibilizer. Differential scanning calorimetric thermograms showed that none of nanoparticles has any effect on crystallinity of PP. Mechanical characterizations showed that hybrid composites are superior to PP-S3 composite. Due to its more intensive hydrodynamic motions it was also observed that the longer CNT showed a higher ability to disintegrate nanosilica particles aggregates. Transmission electron microscopic images well portrayed the nanosilica particles in the vicinity of CNTs' surfaces which accounts for electrostatic adsorption of fine nanosilica particles. At such a low CNT content (say 0.2 wt%) in the absence of any chemical compatibilizer, elongation at break of the tensiled nanocomposites raised from 13.23% to 35.41% and fracture energy was mounted from 1253 to 2750 J. This divulges the effectiveness of CNTs to disperse nanosilica in PP matrix but a poor adhesion between the particles and PP matrix is an overwhelming drawback yet. Under these conditions a maleic anhydride grafted PP (PP-g-MA) was added to the composite in molten state. The tensile strength of these chemically compatibilized nanocomposites increased with respect of that of their counterpart physically mixed nanocomposites. For example, in the presence of this chemical compatibilizer, the tensile strength of PP-S3 nanocomposite raised from 21 to 28 MPa.

Automated summary

Polymer composites are interesting materials in the automotive industry. Nanocomposites are crucial for reducing weight in automotive parts and cars. Hybridization of polymer nanocomposites is an effective way to achieve the desired property/weight ratio. Adding a chemical compatibilizer can enhance the tensile strength of nanocomposites.