Johannes Wulfhorst of the Institut für Textiltechnik (ITA) der RWTH Aachen, Aachen (Germany) reported on the ways of checking the orientation of carbon nanotubes in polymers used to make electroconductive fibres. An FEI Tecnai F20 electron microscope is used to create a series of 2D views as the sample is tilted through 120 degrees. Tomographic imaging software compiles these into a 3D model to allow exact nanotube orientation analysis to be carried out. The work shows that nanotubes do indeed get oriented in the axial direction during fibre extrusion. ITA has also observed that carbon nanotube inclusion alters the bimodal melting character of polyester.
Roland Scholz of Kelheim Fibres GmbH, Kelheim (Germany) reviewed fibre types and their effect on the dispersibility of wet wipes made by carding and hydroentanglement. 0.9 and 1.7 dtex round fibres were compared with 1.7 dtex “gel-surface” fibre, solid flat fibres with a 5:1 aspect ratio, inflated-collapsed fibres with a 20:1 aspect ratio and a new fibre of undisclosed dimensions in lengths of 12, 16 and 20mm. The shorter the fibre the easier was the dispersion in the tube test, similar results being obtained from the Netherlands sewer pump test. The round fibres and the “new shape” fibres dispersed best at these lengths. Standard 40mm fibres formed ropes.
Peng Chen of the Ningbo Institute of Materials Technology and Engineering, Ningbo (China) has discovered that polyhydroxy butyrate valerate fibres (PHBV) are too brittle and rigid to make good nonwovens. Surprisingly blends of PHBV with PLA – which is also brittle and rigid – are soft and give nonwovens with reduced shrinkage. The mixture of polymers is extruded with additives to promote “reactive blending”, at speeds up to 3000m/min. The resulting yarn can be stretched up to 3 times off-line to make the final soft but glossy yarn. The unexpected softness is thought to arise from the oriented fine lamellae structure induced by extensional flow during spinning and drawing. It feels like rayon or silk but is naturally hydrophobic.