Influence of polymer particle size on the percolation threshold of electrically conductive latex‐based composites

Abstract

Monodispersed copolymer emulsions, each with a different polymer particle size, were used to investigate the effect of particle size on the electrical and thermomechanical properties of carbon black (CB)‐filled segregated network composites. These emulsions were synthesized with equal moles of methyl methacrylate and butyl acrylate, with latex particle size ranging from 83 to 771 nm. The electrical percolation threshold was found to decrease from 2.7 to 1.1 vol % CB as the latex particle size was increased. Microstructural images reveal diminished latex coalescence, and improved CB segregation, with increasing latex particle size. In general, coalescence is shown to increase for all systems with increasing CB concentration. Furthermore, all systems exhibited a similar maximum electrical conductivity plateau of 0.7 S cm−1, albeit at lower concentration for larger latex particle size. This ability to tailor percolation threshold with latex particle size provides an important tool for manipulating electrical and mechanical properties of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1547–1554, 2011

Formation of Conductive Networks with Both Segregated and Double-Percolated Characteristic in Conductive Polymer Composites with Balanced Properties

“…In this case, the constants A and B are 0.33 and 0.2775, which correspond to hexagonal packing of PENT conductive coatings to produce the smallest threshold values. 16 Figure 3d shows the decreasing trend of percolation threshold with increasing polymer particle size. LPP/PENT5 composites has almost a quarter the threshold (0.08 wt %) of SPP/PENT5 composites (0.33 wt %).…”

“…This behavior can be explained by the greater amount of surface area associated with smaller polymer particles, which creates a random, less segregated microstructure. 16 In theory, polymer particle size can be used to tailor percolation threshold. For a compacted mixture of polymer and conductive particles, the percolation threshold is expected to decrease with increasing ratio of polymer to conductive particle size according to Malliaris and Turner: 44…”

“…13,23−25 It has been widely demonstrated that these morphological control methods are crucial for their p c and final electrical properties. 26 Among these methods, double-percolated network through using polymer blends 27−29 and segregated network through using latex particles 16,30 have been shown to be prominently effective at allowing the formation of conductive networks with low filler content. In double-percolated networks, conductive fillers are selectively distributed in one of the polymer matrices or their interface in immiscible polymer blends.…”

“…30,35−41 Due to their tunable particle size and surface functionality, latex particle based composites that possess segregated network characteristic have been intensively investigated in the past decade to achieve ultralow percolation threshold. 15,16,30,40,42 Such low percolation threshold can be achieved thanks to the fact that conductive fillers are constrained at the interface between these polymer domains in such a segregated structure, leading to the formation of conductive networks at relative low filler content. Therefore, the polymer domain size of such structure is thought as very important issue as the amount of interface in the system increases with decreasing domain size.…”

Influence of the Compaction Temperature on the Electrical and Mechanical Properties of the Segregated Conductive Ultrahigh Molecular Weight Polyethylene/Carbon Nanotube Composite

“…When the concentration of the conductive grains reaches a critical value, a conductive network in the polymer matrix starts to construct, resulting in composite to transition from insulator to conductor. This critical value of filler loading is known as the percolation threshold [9,10] .…”