Rheological behavior of cycloolefin copolymer/graphite composites

Abstract

In this study, morphological and rheological properties of cycloolefin copolymer (COC)/graphite composites prepared in a twin screw extruder by using various amounts of graphite (G) and expanded graphite (EG) were investigated in detail. Rheological behaviors of the samples were measured in a dynamic oscillatory rheometer in the melt state. Rheology data were analyzed in different ways in order to quantify the microstructural features which indicate the solid-state physical properties of the composite materials. In the linear viscoelastic region, increasing of storage modulus (G 0 ) with the filler amount and the van Gurp-Palmen plots were used to determine the percolation threshold which is the critical filler amount for the physical network formation by the G sheets. Percolation threshold values were found to be about 21.5 phr and 3.8 phr for the G-and EG-loaded samples, respectively. Microstructures of the samples which include quite higher amount of filler than the percolation were observed in a scanning electron microscopy. It was found that the sheets of pristine G maintained their original stack form while the EG was successfully dispersed in the COC phase and formed three dimensional house-ofcard structures without a compatibilizer. POLYM. ENG.

Thermal, electrical and rheological behavior of high-density polyethylene/graphite composites

“…Melt rheology is an effective method to probe into the structural change of the matrix caused by the network formation of the introduced inorganic filler [36,37]. The dependence of G′, G″, tanδ and η* on ω for the HDPE/ FG and HDPE/EG composites is shown in log-log plots in Figs.…”

Processing and characterization of conductive composites based on poly(styrene-b-ethylene-ran-butylene-b-styrene) (SEBS) and carbon additives: A comparative study of expanded graphite and carbon black

“…On the other hand, conductive additives such as intercalated graphite and expanded graphite (EG) have been intensively studied for incorporation into polymer matrices because of the possibility of obtaining CPCEs with a low electrical percolation threshold and appropriate physicochemical properties [6,7,9,14,16,17]. Chen et al [17] have demonstrated that polystyrene/expanded graphite (PS/ EG) composites have a lower electrical percolation threshold (1 wt.%) than polystyrene/conventional graphite (PS/G) composites (7 wt.%).…”

High thermally conducting composites obtained via in situ exfoliation process of expandable graphite filled polyamide 6

“…Particularly, starting from 15 wt % LTEG, a plateau was observed at low frequencies in G ′ and a pronounced shear thinning behavior was noticeable in η *. This relationship is a well‐known phenomenon for the composites; it indicates a physical network formation by the inorganic fillers . The in situ exfoliation of LTEG during the sample preparation process is believed to be responsible for the observed structural change in the composites.…”

“…The turning point observed at which concentration of LTEG was deemed as the percolation threshold for the PA6/LTEG composites. It is also a very effective way to determine the structural change in the composites, resulting from the network formation by the organic filler [1]. In combination with the thermal conductivity results, it can be concluded that the thermal conductive networks are formed near the concentration of 15 wt % LTEG, or more specifically, between 10 and 15 wt %, thus enhancing the heat conduction abilities of the composites.…”