The effects of carbon nanotubes, blend composition and glycidyl methacrylate-grafted polypropylene compatibilizer on the morphology, mechanical and electrical properties of polypropylene-polyamide 6 blends

Abstract

The effect of multi-walled carbon nanotubes (MWCNTs) and a glycidyl methacrylate grafted polypropylene (PP-g-GMA) on the morphology, electrical and mechanical properties of polypropylene (PP), polyamide 6 (PA6) and their respective blends (PP/PA6), prepared by melt mixing, was investigated. The study of MWCNT nanocomposites from PP/PA6 blends is of significant interest, given that they combine the thermomechanical properties of PA6 with the processability of PP, resulting in materials with a wide range of mechanical and electrical properties. In this work, it was demonstrated that the addition of the same amount of MWCNTs to immiscible PP/PA6 blends produced nanocomposites with different morphologies, mechanical and electrical properties depending on the polymer proportion, and that the PP-g-GMA improved mechanical properties while preserving the electrical properties. SEM and TEM images showed that MWCNTs were comparatively better dispersed in PA6 than in PP; however, the addition of PP-g-GMA to PP matrix improved MWCNT dispersion. On the other hand, SEM micrographs showed different morphologies of PP/PA6 blends, depending on the composition of the polymers in the blend. The addition of PP-g-GMA to PP/PA6 blends and PP/PA6/MWCNT nanocomposites reduced significantly the domain size in both dispersed and continuous phases. Regardless of compatibilization, MWCNTs were located preferentially in the PA6 phase. The electrical characterization showed that PP/PA6/MWCNT nanocomposites exhibited lower volume resistivity values (108 Ω cm) compared to PA6/MWCNT nanocomposites (1011 Ω cm), at the carbon nanotube load employed, as a result of the confinement of the MWCNTs in the PA6 phase. The incorporation of PP-g-GMA to the PP/PA6 blends and PP/PA6/MWCNT nanocomposites did not cause a significant change in the volume resistivity of the blends; moreover, PP-g-GMA considerably improved the modulus and tensile strength of the PP/PA blends (i.e. up to 90 and 97 %, respectively for PP/PA 80/20 blend).