Annealing induced electrical conductivity jump of multi‐walled carbon nanotube/polypropylene composites and influence of molecular weight of polypropylene

Abstract

Multi-walled carbon nanotube (MWCNT)/polypropylene (PP) composites were prepared by a micro melt mixing process. As-prepared composites had relatively low electrical conductivity due to the disruption of MWCNT network by strong shear. The electrical conductivity jumped to high values throughout an annealing process above the melting temperature of PP. The significant enhancement of electrical conductivity was influenced by annealing time, temperature, and content of MWCNTs. In particular, molecular weight of PP played an important role in affecting the conductivity enhancement. The molecular weight of PP was varied from 190,000 to 340,000 to examine its effect on the electrical conductivity. By comparing the conductivity enhancement behavior of composites with different molecular weight PPs and observing the morphology evolution during annealing, it was found that reaggregation of MWCNTs and the subsequent formation of MWCNT network during annealing are the main reasons for the jump of electrical conductivity.

Determination of percolation threshold and electrical conductivity of polyvinylidene fluoride (PVDF)/short carbon fiber (SCF) composites: effect of SCF aspect ratio

“…Excessive filler loading (region 3, the upper plateau region of the plot) may lead to increase in the aggregation and agglomeration of conducting filler, which may adversely affect the mechanical properties of the polymer/conducting filler composites due to improper filler distribution. The percolation threshold of the composites depends markedly on several dependent or independent factors such as the kind, dispersion, distribution, aspect ratio, orientation, agglomeration, surface treatment of fillers and polymer, type of polymer, phase structure, surface energies, mixing method etc …”

Dielectric and Electromagnetic Behavior of Conductive Nanocomposites Polymers: PP/MWCNT Investigations for EMI Applications

“…A lot of studies were made on this nanocomposite material types in general for developing mechanical and electrical properties [5][6][7].…”

“…This paper purpose a composite material that consist in a mixture of polypropylene with multi-walled carbon nanotubes, which would result in a material with better mechanical and physical properties. These properties can be improved by varying the percentage of the conductive inclusions (MWCNT's) in the base polymer (PP) matrix [1,5].…”

“…PP is a semi-crystalline polymer that is extensively used due to its good thermic and plastic modeling properties, cost and for the easy processing [5]. Manufacturing techniques that polypropylene can be processed are varied: injection molding, blow molding, extrusion, multifilament, micro-oven or different profile extrusion [4].…”

Micro‐contact reconstruction of adjacent carbon nanotubes in polymer matrix through annealing‐Induced relaxation of interfacial residual stress and strain

“…Secondary agglomeration which is derived from thermodynamic driving forces (e.g ., heating induced forces) or external forces (e.g., shear deformation) can lead to inhomogeneous CNT distribution with CNT aggregation, and thus the electrical conductivity improves for CNT/polymer composites. Pan et al . found that for microinjection molded 5 wt % MWCNT/PP composites, the electrical conductivity was increased from 10 −9 to 10 −3 S/cm under 230°C for 30 min, they observed the morphology evolution of annealed samples and confirmed that reaggregation of MWCNT (transition from individual CNT to loosely packed agglomerate) induced the jump of electrical conductivity.…”