Fibre melt-spun

The HDT differs greatly depending on the type of elastane fibre and often lies between 170 and 190 °C with melt-spun fibres it can be lower. In order to avoid damage the setting temperature should not noticeably exceed the HDT of the respective elastane fibre type. ... 

Fig. 1.13 Wide-angle X-ray pattern of a melt spun fibre of poly e-caprolactone. The fibre axis is vertical. The intense spots on the equator correspond to Q 1.5 A f...

Brody, H. Process of melt spinning of a blend of a fibre-forming polymer and an immiscible polymer and melt spun fibres produced by such process, U.S. Patent 4,518,744, May 21, 1985. 

Melt spun fibres from PA6-grafted SWNTs in a PA6 matrix were produced by Gao et al. The fibres were stiffened from 440 MPa to 1200 MPa on the addition of 1.5 wt% tubes (dT/dFf 120 GPa). The strength was doubled from 41 to 86 MPa. Both strength and toughness were maximised at mass fractions of 0.2%. 

Typical orientation diagram plots obtained by X-ray diffraction for hot drawn film melt spun fibres, and cold drawn films of iso tactic polypropylene are shown in Fig. 50. It is noted that the crystal orientation change is... 

A. Soroudi, M. Skrifvars, H. Liu, Polyaniline-polypropylene melt-spun fibre filaments the collaborative effects of blending conditions and fibre draw ratios on the electrical properties of fibre filaments, J. Appl. Polym. Sci. 119 (2011) 558—564. 

Confirmation of this idea comes from the observation that the natural draw ratio observed for melt-spun fibres is sensitive to the degree of molecular orientation introduced during the spinning process. It appears that the molecular network is formed as the polymer freezes from the melt, is subsequently stretched in the rubber-like state before the polymer cools below Tg and is eventually collected as a frozen stretched rubber. The amount of stretching in the threadline can be measured by shrinking these spun fibres back to a state of zero strain, i.e. isotropy. These results then can be combined with measurements of the natural draw ratio to give the limiting extensibility of the network [33]. 

The most common orientation process is used to produce fibres and is described in research disclosures from ICI, academic literature and manufacturer processing guidelines. Melt spun fibres of PEKEKK have exhibited moduli as high as 13 GPa [33]. There are also a number of academic references to oriented material which, as expected, shows enhanced mechanical performance. Techniques such as solid-state extrusion [34] and die drawing have been applied to PEEK and a modulus of 11 GPa has been obtained [35]. Orientation processes are similar to those used for polyethylene terephthalate but there are some key differences in terms of orientation-induced crystallisation [36, 37]. 

The surface of melt spun fibres consists of many large spherulites, as indicated by SEM observations." After drawing to DR = 6, the fibres have a fibrillar structure and their surface is fairly smooth. This fibrillar stmcture is formed mainly in surface areas of the fibres as indicated by the appearance... 

Overall, there is considerable variability in the published mechanical data due to the largely different systems and experimental approaches. Nevertheless, a tentative comparison of data for melt-spun fibres to the typical data for bulk systems processed in the melt (see Section indicates a more... 

Studies of propylene random copolymers have recently gained importance over isotactic polypropylene in applications requiring high clarity, flexibility and low-temperature performance (Maier and Calafut, 1998). Traditionally, the enhancement in mechanical performance of melt-spun fibres relies primarily on the control of molecular chain orientation and crystalline structure development through take-up speed, drawing ratio and quenching conditions. Heterogeneous particulate reinforcement of polymers often leads to phase separation, increases the melt viscosity and creates hydrodynamic instabilities. 

In structural studies, fibres are generally considered to be transversely isotropic. However, it is sometimes found that commercial fibres have a distinct radial differentiation of structure. This is most pronounced in fibres spun from solutions, which show a distinct skin-core effect. A radial nonuniformity has been also found in some melt-spun fibres, e.g. in polyester fibres produced at very high spinning speeds.It should also be noted that in some fibres e.g. aramids" ) there is a preferential radial orientation of certain crystal planes, in contrast to a random radial orientation normally exhibited by conventional commercial fibres. 

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