Spinnability and Characteristics of Polyvinylidene Fluoride (PVDF)-based Bicomponent Fibers with a Carbon Nanotube (CNT) Modified Polypropylene Core for Piezoelectric Applications.

Benjamin Glauß,Georg Roth,Stephan Walter,Markus Beckers,Gunnar Seide,Thomas Gries,Wilhelm Steinmann

doi:10.3390/ma6072642

Benjamin Glauß, Georg Roth + Show 5 more

Open Access

https://doi.org/10.3390/ma6072642

Copy DOI

Journal: Materials	Publication Date: Jul 3, 2013
Citations: 55	License type: CC BY 3.0

Affiliation: FEG Textiltechnik (Germany), RWTH Aachen University

Abstract

This research explains the melt spinning of bicomponent fibers, consisting of a conductive polypropylene (PP) core and a piezoelectric sheath (polyvinylidene fluoride). Previously analyzed piezoelectric capabilities of polyvinylidene fluoride (PVDF) are to be exploited in sensor filaments. The PP compound contains a 10 wt % carbon nanotubes (CNTs) and 2 wt % sodium stearate (NaSt). The sodium stearate is added to lower the viscosity of the melt. The compound constitutes the fiber core that is conductive due to a percolation CNT network. The PVDF sheath’s piezoelectric effect is based on the formation of an all-trans conformation β phase, caused by draw-winding of the fibers. The core and sheath materials, as well as the bicomponent fibers, are characterized through different analytical methods. These include wide-angle X-ray diffraction (WAXD) to analyze crucial parameters for the development of a crystalline β phase. The distribution of CNTs in the polymer matrix, which affects the conductivity of the core, was investigated by transmission electron microscopy (TEM). Thermal characterization is carried out by conventional differential scanning calorimetry (DSC). Optical microscopy is used to determine the fibers’ diameter regularity (core and sheath). The materials’ viscosity is determined by rheometry. Eventually, an LCR tester is used to determine the core’s specific resistance.

Highlights

The results shown will primarily explain the spinnability and the bicomponent fibers’ mechanical and physical properties, determined via different analytical methods
The material used as a sheath is the Poly(vinylidene fluoride) (PVDF) homopolymer SOLEF 1008 by Solvay Solexis
A comparison between the 10 wt % carbon nanotubes (CNTs) plus 2 wt % sodium stearate PP and the standard PP without any modification shows, that equal viscosities are reached for shear rates of 48,808 L/s for the former, and 50,930 L/s for the latter, that is only a 4% drop in applicable shear rates resulting in the same viscosity

Summary

Introduction

Poly(vinylidene fluoride) (PVDF) is a fluoropolymer consisting of the monomer unit CF2–CH2 It is a polymorphic, semi-crystalline polymer showing at least four crystal phases at different processing conditions [1,2]. It has an excellent chemical stability and a large dipole moment of 9.8 × 10−30 cm, perpendicular to the polymer chain [3,4]. This results in piezo-, pyro-, and ferroelectric characteristics due to a polar crystal phase it can build.

Methods

Results

Conclusion