Structure analysis of electrically conductive polymers filled with agglomerated components

Abstract

An analysis of macrostructure topology of electrically conductive polymer composites with agglomerated fillers is performed. Parameters that allow the value of volume electrostatic resistance and agglomeration of the filler are determined.Structurally heterogeneous (multi-component) materials possess unique consumer properties due to a virtually infinite ability of varying their characteristics. An efficient application of these materials largely depends on an understanding of the fundamentals of their property formation and a feasibility of designing materials with a predetermined set of characteristics in the stage where their formula is developed. Solution of the problems of controlling and predicting the properties of multi-component materials requires that a comprehensive analysis of the process of structure formation be made. Inhomogeneity of the structure at the macro-and microlevels substantially complicates this solution.Currently, the set of tools for investigation of structurally heterogeneous materials is still incomplete. It is, therefore, urgent to develop new approaches to macrostructure studies. Of special concern is the analysis of structurally heterogeneous materials with agglomerated fillers, since in the latter case even minor changes in the macrostructure topology considerably affect the resulting properties. The process of structure formation in highly filled materials is even more difficult to study. Conventional approaches to macrostructure investigation are virtually invalid [1]. On the other hand, in a number of cases it is the high filling that ensures a required set of properties to be obtained. This is the case with, e.g., resistive composite materials.It is well known that with conventional control of properties through variations in filler concentration, a stable electroconductivity in operational modes (action of temperature and deformation, etc.) is observed in low-resistance materials only [1]. In [2], it is shown that a directed influence on the agglomeration -deagglomeration processes at a high filler concentration in the base material makes it possible to produce materials with a wide range of volume electric resistivity values that is virtually unvaried under a variety of operation conditions.Since the "agglomeration -deagglomeration" effect is made manifest through an action on mutual filler -matrix distribution, we formulated a problem to design a technique capable of distinguishing macrostructure topology under variation of the degree of filler agglomeration at a high concentration of the filler. Its solution relies on a hypothesis that macrostructure topology contains information on phase boundary properties. Assuming that the composition and volume of phase boundaries affects macrostructure topology of multi-component media, we may judge about manifestation of the "agglomeration -deagglomeration" effect by geometrical characteristics of the filler -matrix interfaces.The studies were performed using high-filled elastomers (80 wt. fractions of filler per 100 wt. fractions ...

Estimating the stability of electrical conductivity of filled polymers under the influence of negative temperatures

“…In [12] it was shown that for the constant step ε of the squared mesh covering photomicrographs of the structure of different materials, the plots of dependence p i on ln ε are well described by a linear dependence (here p i is the probability to find a fractal point in the ith mesh). The slope angle of the straight line yields information of dimension D 1 .…”

Providing stability of properties of filled polymers under the joint effect of exploitation factors

“…According to [10], the structural parameter D 1b responds to the agglomeration-deagglomeration processes of the filler in the electroconductive grid and hence, to the degree of grid branching. This parameter is determined from an analysis of the texture of photomicrographs of the material structure.…”

“…The parameter works by means of a comparison of photomicrographs of the material with the known properties with those of the material being synthesized. The filler-polymer boundaries are identified from gradations of grey color in the photomicrographs using a specially adjusted texture parameter that allowed the boundaries with minor changes in the grey color to be taken into account [10]. The texture parameter characterizing the autocorrelation of the histogram of joint distribution of the second-order brightness, namely, the interrelation between two neighboring points in photomicrographs turned out to be efficient.…”

Special features of large-size resistors for high-voltage pulsed installations

“…A quantitative description of interphase boundary contours were thus performed using the Renyi fractal dimensions. Then, the fraction numerator dependence plot was made according to formula (1) along the denominator (mesh size) [7,8]:…”

“…It is designated by D 1b . In [7] it was shown that this parameter reflects the character of electroconductive mesh formed during the technological process.…”