Melt Spun Electro-Conductive Polymer Composite Fibers
Doktorsavhandling, 2011

One interesting approach is the development of conductive polymer composite fibers for innovative textile applications such as in sensors, actuators and electrostatic discharge. In this study, conductive polymer composite fibers were prepared using several different blends containing conductive components: a conjugated polymer (polyaniline-complex) and/or carbon nanotubes. Different factors such as processing parameters, the morphology of the initial blends and the final fibers, fiber draw ratio and material selection were studied separately to characterize their effects on the fiber properties. In binary blends of PP/polyaniline-complex, the processing conditions, the matrix viscosity and the fiber draw ratio had substantial effects on the electrical conductivity of the fibers and linearity of resistance-voltage dependence. These factors were associated with each other to create conductive pathways through maintaining an appropriate balance of fibril formation and breakage along the fiber. The blend morphology was defined as the initial size of the dispersed conductive phase (polyaniline-phase), which depended on the melt blending conditions as well as the PP matrix viscosity. Depending on the initial droplet phase size, an optimum draw ratio was necessary to obtain maximum conductivity by promoting fibril formation (sufficient stress) and preventing fibril breakage (no excess stress) to create continuous pathways of conductive phase. Ternary blend fibers of PP/PA6/polyaniline-complex illustrated at least three-phase morphology with matrix/core-shell dispersed phase style. When ternary fibers were compared to binary fibers, the former could combine better mechanical and electrical properties only at a specific draw ratio; this showed that draw ratio was a more determinant factor for the ternary fibers, as both conductivity and tensile strength depended on the formation of fibrils from the core-shell droplets of the PA6/polyaniline-complex through the polypropylene matrix. The achieved maximum conductivity so far was in the range of 10 S/cm to 10 S/cm, which for different samples were observed at different fiber draw ratios depending on the mixing conditions, the matrix viscosity or whether the fiber was a binary or ternary blend. To improve the properties, PP/polyaniline-complex blends were filled with CNTs. The CNTs and the polyaniline-complex both had an increasing effect on the crystallization temperature and the thermal stability of PP. Furthermore, the maximum conductivity was observed in samples containing both CNTs and polyaniline-complex rather than the PP with either one of the fillers. Although increasing the content of CNTs improved the conductivity in PP/CNT fibers, the ease of melt spinning, diameter uniformity and mechanical properties of fibers were adversely affected. Diameter variation of PP/CNT as-spun fibers was shown to be an indication of hidden melt-drawings that had occurred during the fiber extrusion; this could lead to variations in morphology such as increases in the insulating microcracks and the distance between the conductive agglomerates in the drawn parts of the fiber. Variations in morphology result in variations in the electrical conductivity; consequently, the conductivity of such inhomogeneous fiber is no longer its physical property, as this varies with varying size.

composite

blending

conductivity

polyamide

polyaniline

morphology

draw-ratio

conductive fiber

melt spinning

carbon nanotubes

polypropylene

KC-salen, Chalmers, Kemigården 4, Göteborg.
Opponent: Professor Mikael Hedenqvist

Författare

Azadeh Soroudi

Chalmers, Kemi- och bioteknik

The discovery of conjugated polymers received the Nobel Prize in Chemistry 2000. Conjugated polymers have unique properties, particularly electro-conductivity, and are finding their way into a wide range of new technologies. Carbon nanotubes are another conductive material with unique structures and properties, with diameters in the range of one to tens of nanometers, and lengths of microns to several centimeters. Both conjugated polymers and carbon nanotubes are interesting candidates for making conductive textile fibers for novel applications. In this thesis, textile polymers are mixed with a conjugated polymer, polyaniline, and/or carbon nanotubes in the molten state. The blends are then shaped into fibers using melt spinning method which is the most favored way of fiber manufacturing in the industry. However, preparation of these conductive composite fibers is challenging, because improving a property like conductivity, may result in destroying the other properties like mechanical strength. In this work, apart from the fiber preparation, there were attempts to find out the advantages and limitations of the materials and the process as well as the effects of different process parameters on the fiber properties. Furthermore, the prepared textile fibers are now investigated by other research groups in order to be embedded in a textile structure for applications in the innovative and smart textiles, such as in flexible sensors and high efficiency filtration.

Styrkeområden

Nanovetenskap och nanoteknik

Materialvetenskap

Ämneskategorier

Kemiteknik

Drivkrafter

Innovation och entreprenörskap

ISBN

9789173855303

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 3211

KC-salen, Chalmers, Kemigården 4, Göteborg.

Opponent: Professor Mikael Hedenqvist

Mer information

Skapat

2017-10-07