In situ melt grafting in carbon black/polyolefin composites and its influence on conductive performance

Abstract

To improve the conductive properties of carbon‐black‐filled low‐density polyethylene, in situ grafting of certain monomers was applied during the melt compounding process. The experimental data obtained demonstrated that chemical bonding could thus be established between the fillers and the matrix polymer. The degree of enhancement of the filler/matrix interfacial interactions in the composites prepared in this way depends on the species of the grafting monomers being employed. When compared with the untreated carbon black composites, the composites manufactured through in situ melt grafting exhibited reduced room temperature resistivities and greatly increased positive temperature coefficient intensities, as well as favorable performance reproducibility. This proposed technical route has several advantages, including simplicity, low cost and easy control. Copyright © 2004 Society of Chemical Industry

Time–temperature dependence of the electrical resistivity of high‐density polyethylene/carbon black composites

“…This behavior has been observed for all the conductive HDPE–CB composites here investigated, the characteristic temperatures being independent of the filler content or type. As previously proposed for several polymer/CB composites,10–15, 17, 22–24, 26, 27 the resistivity–temperature behavior can be directly correlated to the melting temperature of the polymeric matrix. In fact, DSC analysis carried out on the HDPE matrix shows the onset of the melting at 124°C, the melting peak at 135°C, and the endpoint at 147°C; the crystallinity was about 80%.…”

“…These parameters are reported in Figure 5 as a function of the CB content of the HDPE–CB composites. According to the existing literature,10, 11, 13, 15, 17 as the filler content increases, the intensities of the PTC and NTC parameters decrease. Moreover, as the surface area of the CB increases, the intensities of the PTC and NTC effects markedly decrease.…”

“…PTC and NTC effects can be analyzed in different ways. A simple approach refers to a parameter called the PTC intensity,10, 11, 13, 15, 17 which is defined as the ratio of the maximum observed resistivity to the corresponding room‐temperature value. Similarly, the NTC intensity is usually defined as the ratio of the maximum resistivity value to the resistivity observed in the molten state (200°C in our case).…”

“…For the conductive composites based on crystalline polymers, the resistivity increases as the temperature increases. In fact, for these materials, a positive temperature coefficient (PTC) effect has been reported 8, 10–26. This phenomenon is generally ascribed to differences in the coefficient of thermal expansion between the host matrix and the filler particles.…”

Influence of In-situ Grafting on the Dispersion of Carbon Black in Solvents and Natural Rubber

“…In addition, CB aggregates cluster together under the influence of surface forces in collections of aggregates, referred to as agglomerates, which are 10-100 µm. [4][5][6] Generally it is thought that an ideal dispersion of CB would be one in which all agglomerates are broken down into aggregates, which would be separated from all other aggregates, and the surface of each aggregate would be completely covered by polymer. [7] It is important to note that aggregates are thought to be the characteristic units of CB and are not broken down further under normal dispersion condition.…”