Properties of microinjection‐molded polypropylene/graphite composites

Abstract

In this study, polypropylene (PP) composites filled with two different types of graphite particles, that is, flake‐shaped synthetic graphite (SG) and low‐temperature expandable graphite (LTEG), were prepared by melt blending, followed by microinjection molding (μIM). The microparts had three consecutive zones with decreasing thickness along the flow direction (FD). Results showed that, in addition to the larger particle size, the in situ exfoliation of LTEG during melt processing is crucial to the overall enhancement of electrical conductivity when compared with their SG‐containing counterparts, as corroborated by morphology observations. Moreover, the preferential alignment of conductive particles favors the construction of conductive pathways along the FD. The melting and crystallization behavior for PP, PP/LTEG, and PP/SG materials, and samples from each section of the corresponding microparts were evaluated by differential scanning calorimetry. Results indicated that both the addition of graphite particles and the typical thermomechanical history of μIM (i.e., high shearing and cooling rates) experienced in different sections of the three‐step microparts influence the melting and crystallization behavior of the composites. POLYM. ENG. SCI., 59:1560–1569 2019. © 2019 Society of Plastics Engineers

A holistic evaluation of the influence of shear rates and matrix viscosity on the properties of polypropylene/multi‐walled carbon nanotubes composites

“…As shown in Table 3, the crystallization behavior was significantly expedited with the presence of CNT, and the values of T c increased with increasing CNTs concentration. The above results suggested that a strong heterogeneous nucleation effect occurred and the crystallization process was dependent on the number of the added fillers, which was consistent with literature 39–41 . Additionally, when compared with pure H‐PP, the χ c of H‐PP/CNT composites from both heating cycles (i.e., Cycle 1 and Cycle 3) decreased with increasing filler concentrations.…”

“…The above results suggested that a strong heterogeneous nucleation effect occurred and the crystallization process was dependent on the number of the added fillers, which was consistent with literature. [39][40][41] Additionally, when compared with pure H-PP, the χ c of H-PP/CNT composites from both heating cycles (i.e., Cycle 1 and…”

Experimental investigation and numerical simulation of the microinjection molding process through an expanding flow configuration

“…Furthermore, the authors accorded special attention to the polymer composite materials because of their large potential for use and commercialization. Therefore, the influence of the machine processing parameters on morphology, electrical, and mechanical properties of microinjection molded parts filled with nanotube composites material was intensively investigated 12‐16 . The special mold insert helps to distinguish the melting behavior when flowing across three part‐steps with decreasing thickness, considering the severe shearing conditions that prevail in the microinjection molding process.…”