Electrical and morphological properties of microinjection molded polypropylene/carbon nanocomposites

Abstract

A series of different carbon (carbon black, carbon nanotubes, and graphite nanoplatelets) filled polypropylene nanocomposites were prepared by melt blending, then followed by compression molding or microinjection molding (µIM). Direct current electrical conductivity measurements and melt rheology tests were utilized to detect the percolated structure for compression molded polypropylene/carbon nanocomposites. For µIM, a rectangular mold insert which has a three‐step decrease in thickness along the flow direction was adopted to study the effect of abrupt changes in mold geometry on the electrical and morphological properties of subsequent micromoldings (µ‐moldings). Results indicated that the µ‐moldings exhibited a higher percolation threshold when compared with their compression molded counterparts. This is largely due to the severe shearing conditions that prevail in the µIM process. The morphology of µ‐moldings containing different carbon fillers was examined using scanning electron microscopy. The development of corresponding microstructure is found to be strongly dependent on the types of carbon fillers used in µIM, which is crucial to the enhancement of electrical conductivity for the resulting µ‐moldings. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45462.

Properties of microinjection‐molded polypropylene/graphite composites

“…, the percolation threshold ( p c ) for compression‐molded PP/SG composites is about 30 wt% (i.e., 14.8 vol%). However, the p c for microinjection‐molded samples shifted to higher filler concentrations when compared with the samples prepared with compression molding . Abbasi et al reported that the p c for compression‐molded PP/CNT and PC/CNT composites is 1 wt% and 3 wt%, respectively.…”

“…Many studies have been carried out regarding the micromolding of unfilled thermoplastics . However, applications that require microparts having specified electrical, thermal, and mechanical properties can be accommodated by using polymeric composites with multifunctional fillers . To date, a few studies have been performed with the μIM of multiwalled carbon nanotube (CNT)‐loaded polymer composites .…”

“…However, applications that require microparts having specified electrical, thermal, and mechanical properties can be accommodated by using polymeric composites with multifunctional fillers . To date, a few studies have been performed with the μIM of multiwalled carbon nanotube (CNT)‐loaded polymer composites . For example, Abbasi et al reported that the percolation threshold ( p c ) for polycarbonate (PC)/CNT microparts shifted to higher filler concentrations when compared with their compression‐molded counterparts, which was attributed to the preferential orientation of CNT along the melt flow direction (FD) arising from the predominant shearing effect in this specific direction.…”

“…Therefore, the employed processing parameters are crucial to the development of microstructure in subsequent moldings. Moreover, we also reported that the morphology and intrinsic properties of carbon fillers can significantly affect the electrical and morphological properties of subsequent moldings. Aside from the above‐mentioned factors, the selection of host polymers also played a significant role in determining the microstructure of subsequent microparts, thereby affecting their electrical and morphological properties .…”

Microinjection molding of multiwalled carbon nanotubes (CNT)–filled polycarbonate nanocomposites and comparison with electrical and morphological properties of various other CNT‐filled thermoplastic micromoldings

“…To compare the electrical and morphological properties of various other CNT‐filled thermoplastic micromoldings, another set of PP, PS, and polyamide 6 (PA6) masterbatches obtained from the Hyperion Catalysis International Inc was diluted with corresponding pure components. The properties of PP/CNT, PS/CNT, and PA6/CNT masterbatches as well as corresponding pure polymers are available in the previous studies …”