Bicomponent melt spinning

Figvire 19.2. 600 polypropylene islands-in-arsea of PVA with a PVA/PP ratio of 30/70 [8] 

To date, multicomponent fibers have been used much less in micro-filtration than melt blown fibers, and they are far less well known for their small size than electrospun fibers. 

However, modern melt spinning distribution system technology has clearly demonstrated the capability to produce fibers with smaller size and better consistency than either of the two aforementioned techniques. Multicomponent fiber sizes as low as -0.04 pm (-40 nm) have now been demonstrated commercially at attractive production rates [22]. In addition, micro-sized (1-10 pm) and nano-sized ( 1 pm) multicomponent fibers can be produced with improved production rates, economics and physical properties over the other systems, and with an even broader choice of polymers [22]. Multicomponent fiber production can be used to create fibers in staple or continuous filament form using the spunbond and melt blowing processes. 

Polymer materials in fiber form possess superior mechanical properties compared to the same material in bulk polymer form. The reason for this is clear, the alignment and straightening of the polymer chains make better and better use of the bond stiffnesses and strengths that exist between the individual atoms from which a single polymer molecule is comprised. As the fibers become thinner, this effect is amplified until finally a theoretical maximum is reached. In order to assess the applicability and potential of various SPCs, it is useful to compare both the measured and theoretically achievable (theoretical calculation based on atomic forces) values of tensile strengths and stiffness for various polymer fibers. Table 19.1 presents a selection of thermoplastic polymers, summarizing their mechanical properties in terms of both measured and theoretically achievable fiber properties in comparison with its bulk state [24]. 

Little work has been done on the modeling and simulation of the mechanical properties of nanofiber composites, although many micromechanic models have been developed for fiber composites, it remains to be seen whether they are still applicable to composites at 

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The physical properties of flashspun fabrics are unique and not attainable via the melt-spun spunbond process. Even bicomponent melt spinning cannot produce similar structures. As a result the profitability of a fiashspun operation is very high when the capacity of a line is fully utilized. 

Polylactic acid also has many potential uses in fibres and non-wovens. It is easily converted into a variety of fibre forms using conventional melt-spinning processes. Spunbound and meltblown non-wovens as well as monocomponent, bicomponent, continuous (flat and textured) and stable fibres are all easily produced. 

Figure 9.4. Results of melt-spinning a simple bicomponent fiber. Light and dark portions represent different polymer materials. Note the ballooning effect (the die-swell phenomenon) as the blend leaves the common capillary. Since the pressure drop in the common capillary must be the same for each component, careful regulation of the homopolymer capillary diameters is necessary to obtain the desired result.

What are known as bicomponent fibers can additionally be made by wet, dry, and emulsion spinning, as well as by melt spinning, but more rarely... 

For the triplication in medical products, tte PVDF is spun by a melt spinning process. In addition to multi- and numofilament also bicomponent fibres can be produced. Multifilaments are subject of currendy carried out studies at the ITA. 

The polymer material used for the artificial cornea was Solef 1008/0001 and for the cell tests 1006/0001 produced by Solvay-Solexis S.A., Tavaux, France. The melt spinning trials were performed at a bicomponent plant (Foumd Polymertechnik GbmH, Alfter-Impekoven, Germany, Figure 1). 

Melt spinning from supercooled fluoride melts affords optical single and bicomponent glass fibers [7]. The latter have a concentric fluoride core and a fluoride sheath or clad with a slightly different composition. 

The double crucible apparatus, which yields concentric bicomponent fluoride fibers, is a generic melt spinning process except that the dual melt is separately maintained under carefully controlled conditions in a supercooled state well below the llquidus temperature of the fluoride glasses [6-7]. The inner and outer crucibles form the concentric tip system through which the glass melts flow. 

Keywords Biotextile Fibers and filaments Melt spinning Bicomponent spinning Textile structures Braids Knits Nonwovens Spacer fabric... 

T.Kitukani,J.Radhakrishnan,S.Arikawa,A.Takaku,N.Okui,X.Jin,F.Niwaand Y. Kudo (1996), High-speed melt spinning of bicomponent fibers Mechanism of fiber structure development in poly(ethylene terephthalate)/polypropylene system,/. Appl. Polym. Sci.,62,1913-1924. 

T. H. Oh (2006a), Melt spinning and drawing process of PET side-by-side bicomponent fibers,/. Appl. Polym. Sci., 101,1362-1367. 

N., Niwa, F., and Kudo, Y, High-Speed Melt Spinning of Bicomponent Fibers Mechanism of Fiber Structure Development in Polyfethylene tere-phthalate)/Propylene System , Journal of Applied Polymer Science, 62, 1913-1924, 1996. 

The diameter of natural and synthetic fibres usually ranges from 7 to 20 xm. Microfibres and bicomponent split fibres allow a range of 3-7 pm and finer. Tightly woven textiles made of fine microfibres are watertight, but are permeable to water vapour. Melt-blow and flash spinning fibres have a 1 pm diameter. With electro-spinning, a diameter of 100 nanometres or lower can be produced. These fine fibres are very suitable for the filtering of small particles. 

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