Phase homogeneity and spinline stability

The cold-fractured surface morphologies of the various fibres, associated with the matrix phase homogeneity are shown by the SEM photomicrographs in Fig. 19.5. The relatively smooth morphology exhibited by PPEX, close to that of the neat PP, is an indication of the presence of significantly exfoliated silicate layers that preserved a homogeneous PP phase. In contrast, PPEZ 

The surface textures of the various melt-spun hsv fibres were associated with their spinline stability. The PPEX fibre featured a smoother circumference than the neat PP fibre, which is usual for a filled polymer system. Given that the development of fibre surface texture is largely dependent on its spinline stability and crystallisation behaviour, this would imply a favourable alteration of the linear viscoelastic response of the PP that had led to better spinning properties and crystallisation attributes. 

It is not uncommon for the presence of bulk nanofiller particles in a conventional polymer system to lead to a reduction in melt spiimability or even provoke the formation of aggregates, owing to instabilities, such as localisation and phase segregation. However, in this work, because the layered-silicate had already been intercalated and partially exfoliated via compounding prior to melt-spinning, the resultant particles would exhibit an improved aspect ratio and anisotropy. This, in effect, should lead to an enhanced mesoscopic reorientation ability of the silicate platelets in the shear flow direction, which, in turn, could promote the realignment of the polymer chain (Giannelis et al., 1999). 

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