PTC effect and structure of polymer composites based on polyethylene/polyoxymethylene blend filled with dispersed iron.(positive temperature ... article from: Polymer Engineering and Science

This digital document is an article from Polymer Engineering and Science, published by Thomson Gale on January 1, 2007. The length of the article is 6707 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.

From the author: The temperature dependence of resistivity, structure, and thermal expansion of composites based on polyethylene/polyoxymethylene (PE/POM) blends filled with dispersed iron (Fe) have been studied. The dependence of conductivity on filler content shows percolation behavior, with the values of the percolation thresholds equal to 21 vol% for PE-Fe, 24 vol% for POM-Fe, and 9 vol% for the filled blend PE/POM-Fe, with two-step character of the conductivity curve. The evolution of structure of the composite PE/POM-Fe demonstrates transition from polymer matrix POM-Fe, with inclusions of PE through cocontinuous phases of both POM-Fe and PE, to PE matrix, with inclusions of POM-Fe. Such a structure occurs due to localization of the filler only in one of the polymer phases, namely in POM. Measurements of the coefficient of thermal expansion [alpha] show the presence of two values of [alpha]: higher value (equal to [alpha] of PE) and lower value (equal to [alpha] of POM-Fe), the transition between them corresponding to the structure with cocontinuous phases. The PE/POM-Fe composites demonstrate double-positive temperature coefficient (PTC) effect, with the presence of two transitions and a plateau between them. In such a system, two contributions to the PTC effect coexist: the first contribution originates from the thermal expansion of the nonconductive PE phase with higher value of the coefficient [alpha], which leads to the break of the continuity of the conductive POM-Fe phase; the second contribution originates from the break of the conductive structure of the filler inside the POM-Fe phase because of the morphological changes in the vicinity of the melting temperature of POM. The double PTC effect is explained in terms of these two processes (thermal expansion and melting). POLYM. ENG. SCI., 47:34-42, 2007. [c] 2006 Society of Plastics Engineers

Citation Details
Title: PTC effect and structure of polymer composites based on polyethylene/polyoxymethylene blend filled with dispersed iron.(positive temperature coefficient)
Author: Y.P. Mamunya
Publication:Polymer Engineering and Science (Magazine/Journal)
Date: January 1, 2007
Publisher: Thomson Gale
Volume: 47 Issue: 1 Page: 34(9)

Distributed by Thomson Gale