Morphology of Polyethylene-Carbon Black Composites
G Beaucage, Daniel A. Fischer, Gabrielle G. Long, S Rane, D W. Schaefer
Carbon black is a common polymer additive that is used for reforcement and for its ability to enhance physical properties such as conductivity. This paper pertains to a small-angle x-ray scattering [SAXS] study of a conductive grade of carbon black and carbon black/polymer composites. The scattering pattern for such blacks displays a surface-fractal-like power-law decay over many decades in scattering vector, q. It is often assumed that small-angle scattering from carbon black aggregrates can be described in terms of surface-fractal models, related to particles with fractally rough surfaces. Such self-similar surface roughness is usually easy to identify by microscopic techniques. However, scanning electron microscopy from these blacks fails to support clearly this assumption. It is proposed here that an apparent surface-fractal scattering actually represents a more complicated morphology including overlapping structural features and a power-law scaling of polydispersity. One use of conductive black compositive black composites with polyethylene is in circuit protection devices where resistive heating leads to a reversible association of carbon black aggregates that controls switching between a conductive and a non-conductive state. Scattering can be used as an in-situ tool to observe the morphological signature of this reversible structural change. Scattering patterns support a model for this switching based on local enhancement of concentration and the formation of linear agglomerates associated with the matrix polymer's semi-crystalline morphology.
, Fischer, D.
, Long, G.
, Rane, S.
and Schaefer, D.
Morphology of Polyethylene-Carbon Black Composites, Journal of Polymer Science Part B-Polymer Physics
(Accessed October 4, 2023)