Injection-molded lightweight and high electrical conductivity composites with microcellular structure and hybrid fillers

Abstract

Polypropylene/carbon black (PP/CB) and PP/CB/multiwalled carbon nanotube (PP/CB/MWCNT) composites were fabricated by solid and foam injection molding, with the goal of enhancing the electrical conductivity of the composites while decreasing the cost of the final product. The foaming behavior and through-plane (T-P) electrical conductivity of the composites were characterized and analyzed. Cell growth increased the interconnection of the conductive fillers, changed the filler orientation, and enhanced the T-P electrical conductivity of the composites. Under appropriate processing conditions (200°C melt temperature, 70 cm3/s injection flow rate, and 5% void fraction), the T-P electrical conductivity of the foam PP/CB composites was 5 orders of magnitude higher than that of the solid composites (from 5.877 × 10−12 S/m to 1.010 × 10−7 S/m). Moreover, the T-P electrical conductivity values of the PP/CB and PP/CB/MWCNT were compared at the same conductive fillers content (15 wt%). The results showed that the T-P electrical conductivity of the PP/CB/MWCNT composites was far higher than that of the PP/CB composites by almost five orders of magnitude because the MWCNT acted as a bridge between CB particles, and a unique geometric shape was formed in the system. The T-P electrical conductivity of the foam PP/CB/MWCNT composites with 15 wt% carbon fillers was higher than that of the solid PP/CB composites with 20 wt% carbon fillers. This study reveals that the effect of foaming and the addition of hybrid fillers can improve the T-P electrical conductivity of plastic products, which is very important for the development of lightweight conductive plastics.

Improvement of the dispersity of micro‐nano particles for PP/PVC composites using gas‐assisted dispersion in a controlled foaming process

“…a, an expected imperfect foam structure of neat PP resin with a cell density of 5.7 × 10 5 cells/cm 3 and an average cell size of 51.9 μm can be observed from the SEM micrographs. It is not easy to manufacture a foamed neat PP sample with a cell density of 10 6 cells/cm 3 using a conventional injection molding machine . The cell size and cell density of neat PP resin, as shown in Fig.…”

The Cellular Structure and Mechanical Properties of Polypropylene/Nano-CaCO3/Ethylene-propylene-diene-monomer Composites Prepared by an In-Mold-Decoration/Microcellular-Injection-Molding Process

“…Figure 10 shows the density and expansion ratio of PP-composite foams. As the EPDM content increased from 0 wt% to 15 wt%, the expansion ratio of PP-composite foams increased from 123.4% to 134.8%, and the density decreased from 0.777 g/cm 3 to 0.698 g/cm 3 . When the EPDM content increased to 20 wt%, the expansion ratio of the composite foams decreased significantly, and the density increased.…”

“…The development of lightweight automotives has increased the demand for foamed plastics. PP materials have been widely applied in the automobile industry [1][2][3]. However, the brittleness and poor cellular structure of foamed PP materials result in insufficient mechanical properties, and cannot meet the requirements of engineering applications.…”

Microwave‐assisted foaming of polystyrene filled with carbon black; effect of filler content on foamability

“…Polymeric foams are used in numerous research areas and industrial fields, such as automotive, insulation, packaging, and so forth [1,2] due to their low weight, high impact resistance, sound absorption, and low heat and electrical conductivity. [3][4][5][6] Several techniques have been utilized to produce polymeric foams using chemical and physical foaming agents. [7][8][9] Physical foaming agents are typically applied in extrusion and solid-state batch foaming processes.…”